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UNIVERSITÉ DE LIÈGEUNIVERSITÉ DE LIÈGEUNIVERSITÉ DE LIÈGEUNIVERSITÉ DE LIÈGE

APPLIED SCIENCES FACULTY

DESIGN AND TESTINGDESIGN AND TESTINGDESIGN AND TESTINGDESIGN AND TESTING

OF THE PRESSURE PAYLOADS AND DATA OF THE PRESSURE PAYLOADS AND DATA OF THE PRESSURE PAYLOADS AND DATA OF THE PRESSURE PAYLOADS AND DATA

ACQUISITION OF ACQUISITION OF ACQUISITION OF ACQUISITION OF QARMANQARMANQARMANQARMAN CUBESATCUBESATCUBESATCUBESAT

Thesis submitted in partial fulfilment of the requirements

for the degree of Master in Aerospace Engineering by:

Roger TORRAS NADAL

Advisor: Prof. Gaëtan Kerschen

Jury composed of: Dell'Elce L., Rochus P., Verly J., Broun V.

Academic Year 2012/2013

i

AcknowledgmentsAcknowledgmentsAcknowledgmentsAcknowledgments

First of all, I wish to thank my parents Jaume and Montserrat for giving me the opportunity to

go abroad to finish my studies. They trusted and helped me a lot all these years allowing me to

achieve my goals, always taking care of my future.

I am greatly indebted to Professor Gaëtan Kerschen for recommending me for this outstanding

thesis. Compared to the ones proposed in my home university, I can consider I have been

really lucky. My special thanks to Lamberto Dell’Elce for his valuable suggestions and very

useful feedbacks.

Particularly, it has been an authentic pleasure to work with Isil Sakraker as supervisor of my

work in Von Karman Institute. Her opinion and guidance throughout this project have been

very helpful to me. I also need to thank Thorsten Scholz for his sincerity and criticism on my

work there.

Last but not least, I am pleased to acknowledge Eray Akyol and Deniz Aksulu. It has been really

gratifying to receive their explanations related to the electronic world, answering all my

questions about it and helping me a lot during the development of the project.

ii

ContentsContentsContentsContents

Acknowledgments ................................................................................................................i

Contents ............................................................................................................................. ii

List of Figures ...................................................................................................................... v

List of Tables ...................................................................................................................... vi

Acronyms .......................................................................................................................... vii

Abstract ........................................................................................................................... viii

1. Introduction ................................................................................................................. 1

1.1. QB50 mission .................................................................................................................. 1

1.2. Thesis outline ................................................................................................................. 2

1.3. CubeSat concept ............................................................................................................ 3

1.4. State of the art ............................................................................................................... 4

1.5. Environmental re-entry conditions ................................................................................ 5

1.6. Data Acquisition System ................................................................................................. 6

1.6.1. What is it? .............................................................................................................. 6

1.6.2. Elements of a DAQS ............................................................................................... 7

1.6.3. Concept definitions ................................................................................................ 8

2. QARMAN design and payload ....................................................................................... 9

2.1. Subsystems ...................................................................................................................... 9

2.1.1. Attitude determination and control subsystem..................................................... 9

2.1.2. Electrical power subsystem .................................................................................. 10

2.1.3. On-board computer and on-board data handling................................................ 11

2.1.4. Telemetry, Tracking and Command Subsystem ................................................... 11

2.1.5. Thermal Protection System .................................................................................. 12

2.1.6. Structure ............................................................................................................... 12

2.2. Aerothermodynamics experiment payload ................................................................. 13

2.2.1. XPL01 ................................................................................................................... 13

2.2.2. Pressure payloads ................................................................................................ 13

2.2.2.1. XPL02 ...................................................................................................... 15

2.2.2.2. XPL03 ...................................................................................................... 15

2.2.3. XPL04 ................................................................................................................... 16

iii

2.2.4. XPL05 ................................................................................................................... 16

2.2.5. XPL06 ................................................................................................................... 16

2.3. Budgets ........................................................................................................................ 17

2.3.1. Mass budget ........................................................................................................ 17

2.3.2. Power budget ...................................................................................................... 18

2.3.3. Data budget ......................................................................................................... 18

3. XPL02 ......................................................................................................................... 19

3.1. Data Acquisition System design .................................................................................. 19

3.1.1. Stating the problem and designing the payload objectives ................................ 19

3.1.2. Subject trades ...................................................................................................... 19

3.1.3. Pressure ports and pressure sensor housing ...................................................... 20

3.1.4. Performance thresholds ...................................................................................... 21

3.1.5. Preliminary configuration .................................................................................... 21

3.1.5.1. Measurement chain ............................................................................... 21

3.1.5.2. Market survey ........................................................................................ 23

a) Pressure sensors................................................................................. 23

b) Amplifiers ........................................................................................... 23

c) Filters .................................................................................................. 24

d) A/D converters ................................................................................... 26

3.1.5.3. Preliminary measurement chain design ................................................ 26

3.1.6. Final configuration ............................................................................................... 29

3.1.6.1. Version A. ............................................................................................... 30

3.1.6.2. Version B ................................................................................................ 31

3.2. Pressure ports design and sensor housing .................................................................. 34

3.2.1. Objectives and main considerations ................................................................... 34

3.2.2. Pressure ports design ......................................................................................... 35

3.2.3. Spool options considered ................................................................................... 38

3.2.3.1. Option 1 ................................................................................................. 39

3.2.3.2. Option 2 ................................................................................................. 40

3.2.3.3. Option 3 ................................................................................................. 41

3.2.4. Spool Final Design ............................................................................................... 42

4. XPL03 ......................................................................................................................... 44

4.1. Data acquisition system design .................................................................................... 44

iv

4.1.1. Stating the problem and designing the payload objectives ................................ 44

4.1.2. Subject trades ...................................................................................................... 45

4.1.3. Pressure ports and pressure sensors housing ..................................................... 46

4.1.4. Performance thresholds ...................................................................................... 47

4.1.5. Measurement chain and final configuration ....................................................... 48

4.2. Ground Testing methodology and Extrapolation to Flight ........................................... 50

4.2.1. Motivation and requirements .............................................................................. 50

4.2.2. Facilities and main testing components .............................................................. 50

4.2.3. Test matrix ........................................................................................................... 54

4.2.4. Test procedure .................................................................................................... 55

4.2.5. The testing circuit and pin connection ................................................................ 57

4.2.6. Testing results ..................................................................................................... 60

4.2.6.1. Test 1 ...................................................................................................... 60

4.2.6.2. Test 2 ...................................................................................................... 61

4.2.6.3. Test 3 ...................................................................................................... 63

4.2.6.4. Test 4 ...................................................................................................... 64

4.2.6.5. Test 5 ...................................................................................................... 66

4.2.6.6. Test 6 ...................................................................................................... 69

5. Conclusions ................................................................................................................ 71

6. Future work ............................................................................................................... 72

7. References ................................................................................................................. 73

APPENDIX 1: Set of sensors ................................................................................................ 75

APPENDIX 2: TPS pressure distribution ............................................................................... 76

APPENDIX 3: XPL03 spool design options ............................................................................ 78

APPENDIX 4: Detailed test matrixes ................................................................................... 80

v

List of FiguresList of FiguresList of FiguresList of Figures

Figure 1. QARMAN flight scenario ................................................................................................. 1

Figure 2. One, two and three unit POD configurations ................................................................. 3

Figure 3. System overview with power and data bus ................................................................... 9

Figure 4. Principle of an absolute pressure sensor ..................................................................... 14

Figure 5. Principle of a differential pressure sensor ................................................................... 14

Figure 6. Principle of differential pressure sensor ...................................................................... 15

Figure 7. Measurement Chain ..................................................................................................... 23

Figure 8. On the left, pressure sensor 101B-a19L; on the right, pressure sensor NPC-1220 ..... 27

Figure 9. Pressure sensor circuitry and components .................................................................. 30

Figure 10. Version A configuration and pin connection .............................................................. 31

Figure 11. Typical instrumental amplifier ................................................................................... 32

Figure 12. Version B configuration and pin connection .............................................................. 33

Figure 13. TPS at 66 km of altitude. a) Pressure distribution; b) Temperature distribution ...... 34

Figure 14. MEADS transducer and tube configuration ............................................................... 35

Figure 15. MEADS pressure ports configuration ......................................................................... 36

Figure 16. TPS pressure distribution at a) 66 km; b) 60 km; c) 53 km; d) 50 km of altitude ....... 37

Figure 17. TPS pressure distribution as a function of altitude .................................................... 38

Figure 18. Option 1 for the spool (in green)................................................................................ 39

Figure 19. Option 2 ...................................................................................................................... 40

Figure 20. Option 3 ...................................................................................................................... 41

Figure 21. Spool final design ....................................................................................................... 42

Figure 22. Final assembly between the spool (green) and the nut (purple) ............................... 43

Figure 23. On the left, front and top drawings of the nut; on the right, front and top drawings

of the bolt .................................................................................................................................... 43

Figure 24. General housing configuration for XPL03 .................................................................. 47

Figure 25. XPL03 configuration and pin connection ................................................................... 48

Figure 26. Induction-Coupled Plasma Minitorch ........................................................................ 51

Figure 27. Plasmatron from Von Karman Institute ..................................................................... 51

Figure 28. Mercury manometer .................................................................................................. 52

Figure 29. Electromagnetic field protection ............................................................................... 52

Figure 30. Digital atmospheric pressure sensor .......................................................................... 53

Figure 31. DAQS of the differential pressure sensor of XPL03 .................................................... 53

Figure 32. On the left, vacuum chamber pressure ports; on the right, vacuum chamber control

panel ............................................................................................................................................ 56

Figure 33. Valve A and B of the vacuum chamber ...................................................................... 56

Figure 34. Valves C, D and E of the vacuum chamber ................................................................. 56

Figure 35. Pressure sensor basic circuit scheme ......................................................................... 57

Figure 36. Current source circuit for pressure sensor ................................................................. 59

Figure 37. Circuit configuration for Test 1 .................................................................................. 60

Figure 38. Differential pressure vs. IN-AMP Output for Test 1 ................................................... 61


Figure 40. IN-AMP gain for Test 2 ............................................................................................... 62

vi

Figure 41. Circuit configuration for Test 4 .................................................................................. 64



Figure 44. Reference voltage generation for Test 5 .................................................................... 66

Figure 45. Test configuration for Test 5 ...................................................................................... 67


Figure 47. IN-AMP gain for Test 5 .............................................................................................. 68



List of TablesList of TablesList of TablesList of Tables

Table 1. Thermosphere main properties ...................................................................................... 6

Table 2. Set of active ADCS instrumentation .............................................................................. 10

Table 3. Mass budget for QARMAN ............................................................................................ 17

Table 4. Power budget for QARMAN .......................................................................................... 18

Table 5. Data budget for QARMAN ............................................................................................. 18

Table 6. Performance thresholds for XPL02 ................................................................................ 21

Table 7. Set of available amplifiers for the pressure sensor ....................................................... 24

Table 8. Filter for pressure sensors ............................................................................................. 24

Table 9. Set of available pressure sensors for QARMAN ............................................................ 25

Table 10. Available A/D converters for pressure sensors ........................................................... 26

Table 11. Preliminary measurement chain for XPL02 ................................................................. 28

Table 12. MSP430 main characterstics ....................................................................................... 29

Table 13. AD8226 main characteristics ....................................................................................... 33

Table 14. Performance thresholds for XPL03 .............................................................................. 47

Table 15. Final measurement chain for XPL03 ............................................................................ 49

Table 16. Test matrix ................................................................................................................... 54

Table 17. Test procedure ............................................................................................................ 55

Table 18. Pin description and connection for pressure sensor ................................................... 58

Table 19. Pin description and connection for AD8226................................................................ 58

Table 20. Pin description and connection for LMP7718 ............................................................. 58

Table 21. Pressure sensor and IN-AMP outputs for Test 5 ......................................................... 66

vii

AcronymsAcronymsAcronymsAcronyms

DAQS Data Acquisition System

VKI Von Karman Institute

TPS Thermal Protection System

QARMAN QubeSat for Aerothermodynamic Research & Measurements on AblatioN

COTS Commercial-of-the shelf

CFD Computational Fluid Dynamics

POD PicoSatellite Orbital Deployer

ELF Extremely Low Frequency

EPS Electrical Power System

AeroSDS Aerodynamic Stabilization De-orbiting System

ADCS Attitude Determination and Control System

OBCS On-Board Computer System

GPS Global Positioning System

COMMS COMMunication System

IN-AMP INstrumental AMPlifier

OP-AMP Operational AMPlifier

MEADS Mars Entry Atmospheric Data System

MSL Mars Science Laboratory

XPL02 Payload number 2

XPL03 Payload number 3

AoA Angle of Attack

viii

AbstractAbstractAbstractAbstract

Von Karman Institute is developing the QARMAN CubeSat, one of the fifty nanosatellites of the

QB50 project. It will have a dedicated aerothermodynamics payload of several sensors which

will be generating data during the mission lifetime. This thesis aims to make its preliminary

design of the Data Acquisition System (DAQS) for the two pressure related payload.

The document explains in detail the background of the QB50 project and also states the main

characteristics of CubeSats, giving some past mission examples in order to justify the current

mission. Once the project frame is defined, the next step will be to focus on the fundamentals

for the DAQS design. It will allow the reader to get an idea of what will be seen in the forward

sections, such as the presentation of the Data Acquisition System components or the software

used.

At this point, it will be very important to know what QARMAN is. For this reason, there is an

entire section explaining the different subsystems forming this CubeSat, as well as presenting

the preliminary configuration with detailed budgets of mass, power and data. In addition,

scientific objectives and main performance thresholds for both payloads will be presented

here, leading to their Data Acquisition System configuration also described in detail

throughout this work.

Another important objective for this thesis is to propose a preliminary housing design for these

payloads. This way, important elements such as pressure ports or spool will be defined,

justifying each decision made and choosing the best configuration possible among the

proposed ones.

Finally, during the development of this thesis it has been possible to build and test the

measurement chain of these pressure sensors. For this reason, there is a last chapter where

the most important results obtained are explained and graphically presented, giving a practical

point of view of what happens when applying the theory in the laboratory. By the end of this

project it is expected to have a preliminary calibrated model of the DAQS for QARMAN

pressure related payloads.

TORRAS NADAL, Roger

Master in Aerospace Engineering

Academic Year 2012/2013

Key words: QB50, QARMAN, re-entry, data acquisition system, pressure sensors, market

survey, spool, vacuum chamber.

1

1.1.1.1. IIIIntroductionntroductionntroductionntroduction

1.1.1.1.1.1.1.1. QB50 missionQB50 missionQB50 missionQB50 mission

Proposed by the European Commission in 2010, QB50 is an approved project involving a

network of 50 CubeSats with the aim of investigating the properties of the lower

Thermosphere (90 - 350 km) and performing in-situ measurements [1]. For space agencies,

building this kind of network under using large satellites would be too costly taking into

account its short orbital lifetime. For this reason, this kind of mission can only be performed by

using very low-cost satellites, which are called CubeSats. This concept will be explained in

detail in 1.3.

Lead by the Von Karman Institute (VKI) in Belgium, the whole network of satellites will be

provided by institutions from all over the world, each one being free to achieve the mission

requirements by developing their own platform and payload. At the end of the day, it is

expected that these 50 CubeSats will be launched together in 2015 into an initial orbit of 350

km of altitude and an inclination of 98º. So far, the launch vehicle and the launch site are not

yet defined.

In order to spread out all nanosatellites around the Earth to form the final network

configuration, they will be deployed at a defined time step. At this point, the orbit will

gradually decay due to atmospheric drag. This way, different layers from the thermosphere

and ionosphere will be studied with no propulsion required. After about three month, all

CubeSats will progressively disintegrate because of the friction with the densest layers of the

atmosphere at about 50-60 km of altitude1..

Among all other CubeSat teams Von Karman Institute presents the QARMAN (QubeSat for

Aerothermodynamic Research & Measurements on AblatioN). It will be designed to collect

scientific data related with aerothermodynamic phenomena during its re-entry to Earth’s

atmosphere. The main phases of QARMAN mission can be seen in Figure 1.

Figure 1. QARMAN flight scenario

This nanosatellite intends to follow the standards of a triple CubeSat. On top of a double

CubeSat structure, an ablative cork based Thermal protection System (TPS) will be

1 Further information related to the deployment strategy in [10]

2

incorporated to protect the CubeSat from extreme heating during re-entry (see section 2.1.5

for further information). Similarly, the side panels will be thermally insulated with appropriate

TPS in order to prolong the functionality of all sub-systems. However, its design is still to be

defined. There must be taken into account that QARMAN will be designed to collect and

transmit data until its end of life, that ideally would be down to 50 km, thus covering the

maximum stagnation heat flux moment of the trajectory. Inside the CubeSat, the sensor suite

will allow aerothermodynamic measurements and validation of aerodynamic stabilization and

de-orbiting system using differential drag, developed by QARMAN team.

Almost the whole CubeSat will be designed using commercial-of-the shelf (COTS) components,

except for the payload data acquisition systems design. They can be bought or licensed instead

of being developed from scratch. Because of this, these components are produced in large

quantities, for a general purpose and with a short design-to-production cycles. Therefore, it

can be translated into being cheaper, more flexible and available than the customized ones.

1.2.1.2.1.2.1.2. Thesis outlinThesis outlinThesis outlinThesis outlineeee

QARMAN CubeSat will have a dedicated aerothermodynamics payload of several sensors like

thermocouples, pressure sensors, etc. The aim of the thesis is to make a preliminary design of

the Data Acquisition System both for ground facilities and for the flight model. This way, by the

end of this study it is expected to have a model ready to be tested in the ground facilities of

Von Karman Institute.

This project is aimed at making a detailed design for XPL02 and XPL032. As starting point, the

conception of the thermocouples located in the TPS as XPL01 is already done [2], which design

strategy will be taken into account to properly develop both payloads. Therefore, data

acquisition system for XPL02 and XPL03 will be designed and described in detail throughout

this thesis, giving a final configuration for the preliminary tests at VKI facilities.

As it will be explained in section 2.2.2.1, XPL02 will be formed by two absolute pressure

sensors located at the front tip of the CubeSat, and its design and housing configuration will be

guided by CFDs developed so far and carefully defined in section 3.2; on the other hand, XPL03

will be composed by two pressure sensors too, but one of them will be measuring in absolute

mode and the other one in differential mode. This thesis also contemplates the building and

testing of the measurement chain for XPL03, even though the housing design for this payload

is considered out of scope of this project due to no CFDs for the side panels have been

developed yet. Therefore, it is expected to be able to validate the measurement chain for this

payload by the end of this study in August, 2013.

Throughout this project, the following software has been used:

• Tecplot, a visualization program for the CFDs performed at the VKI facilities.

• CATIA, a modeling program used for the housing design of the payload.

2 APPENDIX 1 shows the list of the set of sensors for QARMAN

• C coding program, in order to define the payload performances for th

tests.

1.3.1.3.1.3.1.3. CubeSat conceptCubeSat conceptCubeSat conceptCubeSat concept

Before proceeding, there must be answered the following question: what is a CubeSat? Over a

decade ago, Professors Bob Twiggs (from Stanford University) and Jordi Puig

California Polythecnic State Univerist

the development of the first CubeSat. In the beginning, the idea was to provide student

accessibility to space science, giving them the opportunity of improving their skills during their

formation at university. As time passed by, a new economy emerged with the creation of

commercial COTS satellite components.

By the end of 2012, more than 75 CubeSats have been launched. From the first to the last one,

there have appeared some changes and readjustments

overall properties remain pretty the same. This way, a CubeSat can be defined as a small

satellite in the shape of a 10x10x10 centimeter cube and with a weight of about 1.33 kilogram.

However, QB50 will not be applying the last update of the specifications, so each cube is

expected to be less than 1 kg. These cubes can be combined to make larger satellites being

scalable along only one axis depending on the mission; they are called 1U, 2U or

depending on the number of cubes assembled. In the end, CubeSats main advantages can be

summarized as low cost miniaturization and standardization of a design.

These spacecrafts are typically launched and deployed from a mechanism ca

Orbital Deployer (POD). The purpose of the

the CubeSats and the launch vehicle and deployment system. It ensures all CubeSat developers

conform to common physical requirements, which is translate

time reduction. On the other hand, it

in a variety of configurations. In order to

going to be the ISIPOD [4], consisting in

mm3 of hardware, equivalent to a 4 unit CubeSat, and housing a total payload mass of 6 kg.

The general configuration for a one, two and three unit CubeSat can be seen in

Figure

C coding program, in order to define the payload performances for th

CubeSat conceptCubeSat conceptCubeSat conceptCubeSat concept


decade ago, Professors Bob Twiggs (from Stanford University) and Jordi Puig

California Polythecnic State Univeristy) changed completely the idea of space research with



iversity. As time passed by, a new economy emerged with the creation of

commercial COTS satellite components.


there have appeared some changes and readjustments on their specifications



r, QB50 will not be applying the last update of the specifications, so each cube is


scalable along only one axis depending on the mission; they are called 1U, 2U or


summarized as low cost miniaturization and standardization of a design.

These spacecrafts are typically launched and deployed from a mechanism called a Pic

(POD). The purpose of the structure is to standardize the interface between


conform to common physical requirements, which is translated into cost and development

time reduction. On the other hand, its small design enables it to suit different launch vehicles

in a variety of configurations. In order to host the CubeSats for QB50 mission the

, consisting in a tubular design able to hold up to

are, equivalent to a 4 unit CubeSat, and housing a total payload mass of 6 kg.

The general configuration for a one, two and three unit CubeSat can be seen in

Figure 2. One, two and three unit POD configurations

3

C coding program, in order to define the payload performances for the preliminary


decade ago, Professors Bob Twiggs (from Stanford University) and Jordi Puig-Suari (from

y) changed completely the idea of space research with



iversity. As time passed by, a new economy emerged with the creation of


on their specifications [3], but the



r, QB50 will not be applying the last update of the specifications, so each cube is


scalable along only one axis depending on the mission; they are called 1U, 2U or 3U CubeSat


lled a PicoSatellite

to standardize the interface between


d into cost and development

to suit different launch vehicles

host the CubeSats for QB50 mission the POD used is

hold up to 182 x 127 x 414

are, equivalent to a 4 unit CubeSat, and housing a total payload mass of 6 kg.

The general configuration for a one, two and three unit CubeSat can be seen in Figure 2.

4

1.4.1.4.1.4.1.4. State of the art State of the art State of the art State of the art

The increasingly flexibility of CubeSats allow them to fit different type of missions. This way,

this section allows the reader to take a look at some of them. Obviously the list presented

below is not exhaustive, but these nanosatellites have been chosen due to their different

features and science objectives.

• CanX-1: Being launched in 2003 and operated by the University of Toronto, was the

first successful CubeSat launch. It was a one unit CubeSat with the objective of testing

nanoscale devices in orbital space.

• QuakeSat: Also in 2003, the first three unit CubeSat was launched on a Rockot rocket

from Russia. Carried by the Standford University, it is an earth observation

nanosatellite to help scientists improve earthquake detection based on ELF3 signals.

• AAU CubeSat: It was a one unit CubeSat built and operated by students from Aalborg

University in Denmark. Its scientific mission was to take pictures of the surface of the

Earth and particularly of Denmark by using the on-board camera. Once in orbit some

data was received on Earth, but after a couple of months the weak radio signals and

the failure of the batteries stopped its activity.

• OUFTI-1: Made by the University of Liège and I.S.I.L (Haute École de la Province de

Liège), it is a one unite CubeSat with the goal of testing the innovative D-

STAR amateur-radio digital-communication protocol. It is scheduled to be launched on

2013. On the other hand, taking into account the main scientific objective of QARMAN,

it has been done a state of the art related to space re-entry probes. It will give a better

understanding of the Earth re-entry vehicles and will also provide some interesting

ideas for the CubeSat design.

• Mars Science Laboratory: Launched on 2011 the vehicle landed on the Martian

surface on August, 2012. The MSL is part of NASA’s Mars exploration program

including a robotic exploration of the red planet. Concerning the re-entry, data

collected by MEDLI (Mars Science Laboratory Entry Descent and Landing Instrument)

will be very useful to reduce margins on the design of future Mars missions.

• SPRITE (Small Probe Re-entry Investigation for Tps Engineering): This is a probe under

investigation which tries to be a low-cost flight test for next Earth re-entry probes. It

will widely help on the prediction of aerothermal environments and also on the

selection and sizing of the thermal protection systems.

3 Extremely low frequency

5

• Apollo command module: It was a spacecraft used for the United States Apollo

program which landed astronauts on the Moon. It is a cabin which housed a crew of

three and the equipment required for re-entry. In addition, its shape was defined in

order to provide a rotational moment during re-entry giving some lift to the vehicle.

Entry data acquired by this probe is going to be a great help for the thermal protection

system design of QARMAN.

• Space Capsule Recovery Experiment: It is an Indian experimental spacecraft launched

on January, 2007 from India by the Indian Space Research Organization. It remained in

orbit for 12 days before re-entering the Earth's atmosphere. It was mainly designed to

demonstrate the capability to recover an orbiting space capsule and the technology for

performing experiments in microgravity conditions as well as testing reusable thermal

protection systems.

Taking a look at the previous list, it can be stated that simplicity on the design together with

the limited size, power and weight implies focusing on few scientific objective. This will play a

very important role on QARMAN payload design, which will have a large set of sensors for the

aerothermodynamic research. In addition, it is concluded that depending on the re-entry

probe various critical points (i.e. maximum temperature or pressure) will be found, which

leads to a direct impact on the sensors allocation. In the end, it can be stated that QB50

mission offers a great opportunity for low cost investigation compared to larger atmospheric

entry missions.

1.5.1.5.1.5.1.5. Environmental reEnvironmental reEnvironmental reEnvironmental re----entry conditionsentry conditionsentry conditionsentry conditions

When an object enters the Earth’s atmosphere, it experiences the force of gravity, drag and lift

depending on its shape. Therefore, for a spacecraft re-entry it is necessary to meet a set of

requirements which will be the baseline for this phase:

• Deceleration: On the one hand, the vehicle structure and payload will limit the

maximum deceleration it can withstand. The maximum deceleration the vehicle

experiences during re-entry must be low enough to prevent damage to the weakest

part of it.

• Heating: It is the result of friction between the spacecraft and the air. In order to get

an idea of this effect, a real example is proposed:

a) Heating the average house in Catalonia takes about 3·1010 Joules/year.

b) For a CubeSat of 3 kilograms like QARMAN entering the Earth’s atmosphere with

an orbital velocity of 7.7 km/s and an altitude of 300 km, its total mechanical

energy would be 1·107 Joules for only 10 minutes re-entry.

Comparing both results there can be stated that a simple 3 Unit CubeSat has enough

energy during re-entry to heat the average home in Catalonia for about 3 hours. As a

6

result, entering the Earth will be translated to a loss of mechanical energy converted

into heat, what shows the importance of the spacecraft’s thermal protection system.

• Accuracy of landing or impact: Depending on the entering object, these constraints

make designers adjust the trajectory and the general vehicle design. For QARMAN’s

case, the vehicle will burn up at an altitude of about 50 km resulting in the

disintegration of the CubeSat.

There should be noticed that during re-entry there will coexist three different forces: gravity,

drag and lift. On QARMAN, this third force can be neglected because the ADCS will provide an

angle of attack around 0 degrees. This way, drag is going to play the main role related to the

CubeSat heating.

At this point the following question can be stated: why do you want to study the lower

thermosphere? This region is the least explored layer of the atmosphere. Past missions were

able to get some atmospheric data by describing high elliptical orbits with a low perigee, but

their efficiency was not good at all. Hence, QB50 is going to be a great opportunity to provide

in-situ measurements continuously for three months. Finally, for a better understanding of the

region where QARMAN and the whole constellation of satellites will be flying, the atmospheric

conditions for the thermosphere are summarized in Table 1.

Property Information

Thermosphere

situation Above the ionosphere and below the exosphere

Altitude [km] 90 km to 500 km

Temperature range

[ºk] From 200 to 1000/2000

Density [g/cm3] From 1.8 × 10–8 to 1.8 × 10–15

Main species Nitrogen (80%) and oxygen (20%) molecules/atoms. Also hydrogen

and helium.

Sources of energy Electromagnetic radiation, charged particles, gravity waves,

molecules dissociation and own energy dissipation Table 1. Thermosphere main properties

1.6.1.6.1.6.1.6. Data Acquisition SystemData Acquisition SystemData Acquisition SystemData Acquisition System

1.6.1.1.6.1.1.6.1.1.6.1. What is it?What is it?What is it?What is it?

Originally, information was usually presented in analogue form by the position of a pointer on

a dial, and an operator was in charge of reading a number of dials in order to control the

process. One of the first data acquisition systems was developed in 1874, when French

7

engineers built a system of weather and snow-depth sensors on Mont Blanc in order to

transmit real-time information to Paris. However, all these systems have been evolving since

then. Nowadays, even though most sensors are presenting their output as a voltage or current

analogue of the quantity being measured, it is now usual to convert this analogue input into a

digital signal, offering better performances. Besides, the increasing automation of industry as

well as the increasing power of computers have made possible to act and react quickly

achieving almost real-time control.

By definition, the data acquisition system (DAQS) involves the processes used to collect

information to document or analyze some phenomenon. Particularly, throughout this project it

is intended to design the DAQS required for QARMAN in order to get atmospheric information

during its re-entry. Taking this as starting point, next section presents the required

components to design this kind of systems.

1.6.2.1.6.2.1.6.2.1.6.2. Elements of a DAQSElements of a DAQSElements of a DAQSElements of a DAQS

• Sensors: They are in charge of interpreting a physical property in analog form as an

electrical signal such as a voltage or current. The type of sensor varies depending on

the observable data. As examples, QARMAN CubeSat will house a set of

thermocouples and pressure sensors that will be measuring temperature and

pressure, respectively.

• Signal conditioning circuitry: It is used to modify and improve the electrical signal by

performing operations like linearization, amplification or filtering. These steps are

required to make sensor output suitable for the analog-to-digital converter.

• Analog-to-digital converter: It is responsible for converting the electrical analogue

signal into digital data with numeric value that represents the quantity’s amplitude. All

aerothermodynamic payloads of QARMAN will be collecting analog data so, as you will

see in the sections concerning the DAQS design, an analog-to-digital converter will be

required.

• Computer software: Here the main thing is that the software must be compatible with

the operating system of both the computer and the whole system. It will be in charge

of logging data for a further analysis and processing. Once QARMAN will be launched,

this is going to be the only tool to control the data acquisition system, so it must be as

reliable as possible.

8

1.6.3.1.6.3.1.6.3.1.6.3. ConceptConceptConceptConcept definitionsdefinitionsdefinitionsdefinitions

Throughout this project there will be some terminology related to electronics. This section

intends to give a definition for all of them for a better understanding of the forthcoming

sections.

• Sensitivity: It indicates how much the output voltage changes when the measured

quantity changes. For most of pressure sensors working with a linear behavior, it

would be the slope when measuring a defined range of pressures.

• Range: It is the maximum and minimum values of a parameter that can be measured.

For example, if a certain pressure sensor able to measure pressures from 20 Pa to 100

Pa, it would have a range of 80 Pa. However, measuring on the limits of the device

might introduce some errors due to calibration.

• Precision: This concept refers to the repeatability of a measurement. That is to say, if

exactly the same value was measured several times, an ideal sensor would output

exactly the same value every time.

• Resolution: It is the smallest detectable incremental change of input that can be

detected in the output signal. It is commonly expressed either as a proportion of the

full-scale reading or in absolute terms. Throughout this project absolute terms will be

used.

• Accuracy: It can be seen as the maximum difference that exists between the actual

value and the indicated value by the output of the device. In this project this

parameter will be expressed as a percentage of the full scale.

• Offset: This error is just the output that a transducer would have when it should be

zero, i.e. when the input is zero. Due to their simplicity, it is possible to correct these

errors making small modifications on the software.

• Linearity: It is an expression of the extent to which the actual measured curve of a

sensor departs from the ideal curve. Generally, these kinds of errors are considered by

the accuracy. Linearity is often specified as a percentage.

• Response time: It can be defined as the time required for a sensor output to change

from its initial state to a final settled value within a tolerance band (often ±10% of the

correct new value).

• Common-mode rejection ratio: It is a number that describes how well an input or

output will reject noise. A high CMRR is important in applications where the signal of

interest is represented by a small voltage fluctuation, such as in QARMAN payload

case.

2.2.2.2. QARMAN design and payloadQARMAN design and payloadQARMAN design and payloadQARMAN design and payload

The purpose of this section is to be a summary of what QARMAN is. This way, according to the

requirements compliancy table for QB50 mission, it has been developed a preliminary design

for the subsystems of this CubeSat, which are going to be described in the following section.

Following a proper spacecraft design and sizing, next step is going to be t

budgets of mass, power and data. They all will give precious information for the preliminary

design made by QARMAN team, which will be the starting point of an iterative process.

Once the general configuration of the satellite is defi

payload suited in this CubeSat will be also presented. However, the aim of this project is to

specifically design only two of these payloads, which are going to be commented in detail. By

the end of this section, it is exp

properly start with the payload design.

2.1.2.1.2.1.2.1. SubsystemsSubsystemsSubsystemsSubsystems

First of all, a basic frame of the whole configuration and the data and power connections

between the different units is given in

De-orbiting System) is connected by dashed lines due to it will be only necessary during panel

deployment in Phase 2 (from 330 km to 120 km of altitude).

Figure

2.1.1.2.1.1.2.1.1.2.1.1. Attitude determination and control subsystemAttitude determination and control subsystemAttitude determination and control subsystemAttitude determination and control subsystem

This subsystem is tasked with identifying the location and the orientation of the satellite at all

times during the orbit as well as changing the orientation of the satellite. QARMAN will be

stabilized in orbit using the drag force of the

QARMAN design and payloadQARMAN design and payloadQARMAN design and payloadQARMAN design and payload


irements compliancy table for QB50 mission, it has been developed a preliminary design


Following a proper spacecraft design and sizing, next step is going to be the definition of the



Once the general configuration of the satellite is defined, the set of aerothermodynamic



the end of this section, it is expected to understand the basic aspects of QARMAN platform to

properly start with the payload design.


between the different units is given in Figure 3. Note that AeroSDS (Aerodynamic Stabilization

is connected by dashed lines due to it will be only necessary during panel

hase 2 (from 330 km to 120 km of altitude).

Figure 3. System overview with power and data bus [5]

Attitude determination and control subsystemAttitude determination and control subsystemAttitude determination and control subsystemAttitude determination and control subsystem


orbit as well as changing the orientation of the satellite. QARMAN will be

stabilized in orbit using the drag force of the AeroSDS. By controlling the surface exposed to

9


irements compliancy table for QB50 mission, it has been developed a preliminary design


he definition of the



ned, the set of aerothermodynamic



ected to understand the basic aspects of QARMAN platform to


(Aerodynamic Stabilization

is connected by dashed lines due to it will be only necessary during panel


orbit as well as changing the orientation of the satellite. QARMAN will be

. By controlling the surface exposed to

10

the residual atmosphere, it is possible to change the magnitude of the atmospheric drag

affecting the CubeSat and therefore, it is possible to control the trajectory of the spacecraft.

Thus, AeroSDS aims to be an attitude control method in order to provide the required orbital

conditions at 120 km. This system will be located at the end of the CubeSat structure,

displacing the gravity center downstream and leading to a stabilizing moment.

However, AeroSDS is not going to be the only attitude control system. This way, a set of active

ADCS instruments are included in the subsystem. They can be seen in Table 2. At the early

stages of the mission the active ADCS will only be needed for detumbling4 with little

requirements on the pointing accuracy during mission Phase 0. After this, QARMAN should be

stabilized and pointing into flight direction, getting ready for the deployment of the AeroSDS.

Following deployment the ADCS is only needed for attitude and position determination in-orbit

and during re-entry.

Instrument Quantity Definition

Magnetotorquers 3 It generates a magnetic field which interacts with the ambient magnetic field, providing a torque to change

orientation

Reaction wheels 3 This system change the orientation of the CubeSat

around its center of mass thanks to the torques generated with the rotation of these wheels

Star tracker 1 It is an optical device that measures the position of

stars using a small camera

Gyroscope 1 It senses the rotation in the three-dimensional space

without any observation of external objects

Accelerometer 1 This device measures proper acceleration of the

CubeSat

Magnetometer 1 It measures the magnetic field values at the present

point

GPS receiver 1 This device is able to provide accurate position

determination at any time Table 2. Set of active ADCS instrumentation

2.1.2.2.1.2.2.1.2.2.1.2. Electrical power subsystemElectrical power subsystemElectrical power subsystemElectrical power subsystem

It provides conditioned power to all spacecraft and payload subsystems and components. They

are designed and size for the mission end of life. The critical phase for QARMAN is going to be

the re-entry (from 120 km to 50 km of altitude), where the CubeSat will completely run on

battery power. This phase will last around 600 seconds, but in the worst case solar panels will

stop charging batteries half orbit before arriving at 120 km of altitude due to eclipse. Hence, it

is required to the system to provide power at least during 45 minutes (35 minutes the half

orbit + 10 minutes of re-entry). After a market survey, the proposed EPS is NanoPower P31u

with internal battery pack providing 18.7 Wh and a power margin of 136% during Phase 3 [5].

4 It can be defined as the stabilization of the angular rate right after orbital insertion

11

2.1.3.2.1.3.2.1.3.2.1.3. OnOnOnOn----board computer and onboard computer and onboard computer and onboard computer and on----board data handlingboard data handlingboard data handlingboard data handling

This subsystem can be considered as the heart and the brain of the satellite. It is responsible

for controlling the different modes of operation with the following main functions:

• Data handling

• Computation for other subsystems

• Command execution

• Payload operations

• Error handling and diagnosis

• Communication with Ground stations

In QARMAN case, the On-Board Computer (OBC) will acquire raw data from the payloads and

format them for the telecommunication system (packet format for the Iridium system), but it

is important to note that no onboard data processing will be made except data compression

before transmission. After a market survey, the NanoMind A712C (32-bit ARM7 RISC CPU, 2MB

static RAM, 2x4MB data/code storage, optional 2GB MicroSD extension) has been selected [5].

2.1.4.2.1.4.2.1.4.2.1.4. Telemetry, Tracking and Command SubsystemTelemetry, Tracking and Command SubsystemTelemetry, Tracking and Command SubsystemTelemetry, Tracking and Command Subsystem

The system provides the functional interface between the spacecraft and ground stations and

can is divided into three different elements:

• Tracking, to determine the position of the CubeSat and follow its orbit by means of the

ADCS information.

• Telemetry, to monitor the status of the satellite through the collection, processing and

transmission of data from the other subsystems to the ground.

• Commands, which are received from the ground stations for controlling mission

operations.

The configuration of this subsystem for QARMAN mission needs to be carefully studied due to

it is going to be really challenging. In the early phases of the mission, there should not appear

any problem related to the communications aspects, but during re-entry (Phase 3) a plasma

sheet will be formed in front of the vehicle and at some point of the phase the electron density

located there could be able to block any radio signal, preventing communication with the

ground stations. Additionally, there fact of having a compatible ground station at the location

of re-entry could increase the complexity of data transmission.

Thus, considering these aspects, the solution chosen to properly transmit data during Phase 3

is to do it through an antenna located in the lower electron density region, which will be

situated downstream of the CubeSat. On the other hand, in order to have access to the ground

stations at any time during re-entry, data from the spacecraft will be sent to a network of

communication satellites. For this purpose, Iridium constellation formed by 66 satellites at 780

12

km of altitude and an inclination of 86.4º has been chosen. So far, coverage analysis has been

already done demonstrating that QARMAN will be within the communication range of at least

4 Iridium satellites during the entire trajectory [5].

The market survey performed for the communication system ended with the selection of two

systems: the NanoCom U482C UHF transceiver and the IRIDIUM transceiver IR9602, each one

of them covering a different frequency range. For the preliminary design of QARMAN, it will be

assumed that both communication systems will be integrated, even though it is possible that

Iridium system will be chosen as the only one.

2.1.5.2.1.5.2.1.5.2.1.5. Thermal Protection System Thermal Protection System Thermal Protection System Thermal Protection System

The Thermal Protection System (TPS) is in charge to maintain the skin of the CubeSat within

acceptable temperatures, especially during re-entry, where the aggressive environment

conditions could burn up the spacecraft. Note that during this phase, temperature will rise up

to more than 2000 K at the tip and more than 1000 K at the end of side panels. For this reason,

it has been decided to introduce an ablative TPS to protect the front of QARMAN, which by

erosive processes will allow lowering the heat of the entire CubeSat.

QARMAN TPS will be a passive system designed for the critical altitude of 50 km (end-of-life).

Preliminary designs of the system ended up with a total weight of 577 grams (360 g for the

front part and 217 g for the side panels) including margins. Besides, front thermal protection is

foreseen to have a maximum thickness of 50 mm, property that is going to be of importance

for the design of the payload housed there. Additionally, the thermal status of the entire

CubeSat will be monitored during the entire mission by means of thermistors and payload

sensors [5].

2.1.6.2.1.6.2.1.6.2.1.6. StructureStructureStructureStructure

QARMAN will be a custom-built 3 unit structure which is expected to stand maximal structural

loads of 8 g (eight times the gravity force) during re-entry. For the proper design of the

structure and in order to ensure the CubeSat survivability, a finite element method simulation

will be performed in ground facilities by including the expected thermo-mechanical loads on

the structure with a safety factor of one.

Preliminary studies have shown the necessity to design a custom structure, especially for the

bonding with the thermal protection system. This new element on the structure will be really

important for the design of the pressure sensors connected to the TPS. Finally, the

qualification and validation of the global structure configuration will be based on vibration and

thermal vacuum chamber tests.

13

2.2.2.2.2.2.2.2. Aerothermodynamics experiment payloadAerothermodynamics experiment payloadAerothermodynamics experiment payloadAerothermodynamics experiment payload

QB50 mission offers a really good opportunity to investigate the atmospheric re-entry

phenomenon. Besides the restrictive structure, a CubeSat allows to get precious

aerothermodynamic information below 350 km at very low cost compared to bigger space

vehicles. As a result, it is expected that QARMAN will be able to measure the following

parameters: TPS ablation, efficiency and environment; attitude stability; changes in flow

conditions; shear forces; off stagnation temperature evolution and the general

aerothermodynamic environment.

This way, most of these characteristics are foreseen to be measured using temperature and

pressure transducers placed at optimized locations. For this reason, six scientific payloads are

proposed to meet these objectives.

2.2.1.2.2.1.2.2.1.2.2.1. XPL01XPL01XPL01XPL01

This payload will be formed by 12 thermocouples measuring the recession rate of the ablative

TPS and the temperature evolution inside it. After a preliminary design, scientific objectives

have been carefully defined according to the mission objectives and requirements. They are

listed as follows:

• Basic heating of the TPS

• Heat flux in the TPS close to the hot corners

• Stagnation region heating

• TPS recession rate

• TPS total recession

• Subsurface material response

Main requirements for this payload are listed in APPENDIX 1, but detailed information can be

consulted in [2].

2.2.2.2.2.2.2.2.2.2.2.2. Pressure Pressure Pressure Pressure payloadpayloadpayloadpayloadssss

Pressure transducers can be made of many materials for a great variety of conditions and

ranges. For this reason, many different types of pressure sensors are available nowadays in the

market. Often pressure is related to the displacement of some component in the sensor,

allowing the conversion to an electrical output such as voltage or current. To select the right

pressure sensor for a specific application first of all the type of pressure measurement has to

be considered. Pressure sensors measure a certain pressure in comparison to a reference

pressure and can be divided into absolute, gage and differential devices:

• Absolute pressure: This type is referred to an ideally perfect vacuum of free space

(zero pressure). In practice, v

diaphragm the way you can see in

through the pressure intake and the diaphragm is displaced, allowing the senso

convert this amount to an electrical output signal. XPL02 payload design will be based

on this type of sensor.

Figure

• Gauge pressure: In this case pressure is measured relative to

pressure. Note that changes of the atmospheric pressure due to weather conditions or

altitude directly influence the output of this type of sensor. A gage pressure higher

than ambient pressure is referred to as positive pressure. Ot

negative or vacuum gage pressure. Apart from the reference pressure, the basics for

this transducer are the same as the ones for the absolute pressure transducer (see

Figure 5).

Figure

Absolute pressure: This type is referred to an ideally perfect vacuum of free space

(zero pressure). In practice, vacuum reference pressure is sealed behind its sensing

diaphragm the way you can see in Figure 4. Then the target pressure is introduced

through the pressure intake and the diaphragm is displaced, allowing the senso


on this type of sensor.

Figure 4. Principle of an absolute pressure sensor

Gauge pressure: In this case pressure is measured relative to the ambient atmospheric



than ambient pressure is referred to as positive pressure. Otherwise, it is called



Figure 5. Principle of a differential pressure sensor

14

Absolute pressure: This type is referred to an ideally perfect vacuum of free space

acuum reference pressure is sealed behind its sensing

Then the target pressure is introduced

through the pressure intake and the diaphragm is displaced, allowing the sensor to


the ambient atmospheric



herwise, it is called



• Differential pressure: As the name indicates, it is based on the difference between

pressure values from both pressure intakes. For this reason, differential pressure

sensors must offer two separate pressure ports (see

are able to measure positive and negative pressure differences depending on the

inputs. Differential mode will be implemented on one of

XPL03.

Figure

2.2.2.1.2.2.2.1.2.2.2.1.2.2.2.1. XPL02XPL02XPL02XPL02

In this case, two absolute pressure measurements will be taken at the front TPS of the CubeSat

during Phase 3 of the mission. This payload will be d

giving a preliminary configuration for the measurement chain, as well as the housing design of

it. These aspects will be presented in section

APPENDIX 1.

2.2.2.2.2.2.2.2.2.2.2.2.2.2.2.2. XPL03XPL03XPL03XPL03

The main objective of this payload is to determine the stability of QARMAN during Phase 2 of

the mission. This way, it will be giving attitude information additional to sun sensors

accelerometers and the gyroscopes. It will be composed by two pressure sensors, and it has

been decided that for the preliminary design one of them will be operating in absolute mode

and the other one in differential mode.

The design of the whole measur

preliminary configuration for testing. On the other hand, the sensor housing design is out of

scope of this project due to no CFD has been done for the side panels yet. For this reason, only

basic requirements for the location of the pressure ports and pressure transducers will be

given.

Differential pressure: As the name indicates, it is based on the difference between


two separate pressure ports (see Figure 6). These types of sensors


inputs. Differential mode will be implemented on one of both pressu

Figure 6. Principle of differential pressure sensor

XPL02XPL02XPL02XPL02

pressure measurements will be taken at the front TPS of the CubeSat

during Phase 3 of the mission. This payload will be designed in detail throughout this project,


ts will be presented in section 3, but main requirements c

XPL03XPL03XPL03XPL03


the mission. This way, it will be giving attitude information additional to sun sensors



and the other one in differential mode.

The design of the whole measurement chain is contemplated in this thesis and it will be given a




15

Differential pressure: As the name indicates, it is based on the difference between


). These types of sensors


pressure sensors for

pressure measurements will be taken at the front TPS of the CubeSat

esigned in detail throughout this project,


, but main requirements can be seen in


the mission. This way, it will be giving attitude information additional to sun sensors,



ement chain is contemplated in this thesis and it will be given a




16

Finally, during the development of the project it has been possible to order all components in

order to start with the calibration of the measurement chain of the pressure sensor operating

in differential mode. Thus, in section 4.2 it will be explained in detail the procedure followed

for these tests, the facilities and instruments used and finally, results obtained will be

presented in order to validate the configuration designed. The main requirements for this

payload are presented in APPENDIX 1.

2.2.3.2.2.3.2.2.3.2.2.3. XPL04XPL04XPL04XPL04

This payload aims to monitor laminar to turbulence transition on the side panels, preferably by

shear force measurements. This way, skin friction will be measured by means of four Preston

tubes and it is foreseen that in a preliminary design two of them will be connected in common

with pressure sensors from XPL03. However, it will finally depend on the subject trades of this

payload, considering that one of the pressure sensors from XPL03 will be measuring in

differential mode. The design of this payload is out of scope and will not be dealt with in this

report. However, preliminary design is presented in APPENDIX 1.

2.2.4.2.2.4.2.2.4.2.2.4. XPL05XPL05XPL05XPL05

In this case it is foreseen to record off-stagnation temperature evolution for ground testing method validation purposes. The payload will be composed by ten thermocouples located in the side panels of QARMAN. Its design is out of scope, but a preliminary study is presented in APPENDIX 1.

2.2.5.2.2.5.2.2.5.2.2.5. XPL06XPL06XPL06XPL06

This payload aims to study the species presented during re-entry environment. The embedded

emission spectrometer onboard QARMAN intends to provide the first spectrally resolved data

in the flight regime of from 7.7 km/s at 120 km of altitude and 5 km/s at 50 km, which does not

exist [6]. With information acquired, a better knowledge of the radiation environment will

permit a more accurate sizing of TPS for International Space Station return.

17

2.3.2.3.2.3.2.3. BudgetsBudgetsBudgetsBudgets

Considering the previous configuration for QARMAN, it has been developed the preliminary

budgets for mass (Table 3), power (Table 4) and data (Table 5). By comparing values among all

subsystems requirements, the design of the aerothermodynamic payload is delimited.

2.3.1.2.3.1.2.3.1.2.3.1. Mass budgetMass budgetMass budgetMass budget

In this case, note that the maximum mass expected for the payload sensors is 265 grams. This

way, considering that QARMAN will be housing 33 aerothermodynamic sensors, meeting this

requirement is going to be really challenging. For this reason, measurement chains will need to

be connected between them reducing size and mass.

Subsystem Mass (g) Contingency (g) Mass with

contingency (g) Fraction (%)

Volume

[10cm]

Structural 390 78 468 14.7 n/a

ADCS 250 25 275 8.7 0.20

EPS 225 23 248 7.8 0.33

Solar panels 320 16 336 10.6 n/a

OBC / OBDH 55 6 61 1.9 0.16

GPS (including

antenna) 82 9 91 14.7 0.05

TT&C 239 24 263 8.3 0.46

Heat shield 300 60 360 11.3 0.63

Side panel

therm. Prot. 180 37 217 6.8 n/a

Acquisition

PCB 200 40 240 7.6 0.25

Sensors 265 54 319 10.0 0.25

AeroSDS 250 50 300 9.4 0.50

Total 2827 422 3178 111.9 2.83

Target mass 3000 3

Mass margin

-178 (Target mass–

Total mass with contingency)

-5.93%

(Target mass– Total mass with

contingency) / Target

mass

0.056%

Table 3. Mass budget for QARMAN [5]

18

2.3.2.2.3.2.2.3.2.2.3.2. Power budgetPower budgetPower budgetPower budget

Aerothermodynamic payload of QARMAN will be switched on only during Phase 2 and Phase 3.

Considering Table 4 values, a total power consumption of 4.5771 Watts is foreseen for the

entire mission. Note that during mission 3 no power will be generated, thus power all power

required for the different subsystems will be given by the batteries.

Average Duty Cycle by Mode (%)

Load

Power

consumption

(W)

Safe mode (Phase

1)

Recovery mode

(Phase 0)

Payload ULg

Operation mode

(Phase 1)

In orbit measurements

(Phase 2)

Safe mode (LPM, Phase

2)

Payload VKI

Operation mode

(Phase 3)

OBC 0.2937 100 100 100 100 100 100

UHF/VHF 0.510 10 20 20 20 10 0

S-band Tx (Iridium) 1.25 0 0 0 0 0 100

Attitude

determination 0.5 100 100 100 100 100 100

Attitude control 1.3 0 15 20 0 0 0

GPS 1 100 100 100 100 100 0

EPS 0.250 100 100 100 100 100 100

Aerothermodynamic

payload (Payload

VKI, phase 2)

1.2393 0 0 0 100 0 0

Aerothermodynamic

payload (Payload

VKI, phase 3)

3.3378 0 0 0 0 100

Equivalent number of solar cells

exposed to the sun 5 2.5 2.5 5 5 -

Power consumed (W) 2.09 2.34 2.4 3.47 3.3293 5.6315

Power generated (W) 2.6 2.6 2.7 4.5 4.5 0

Table 4. Power budget for QARMAN [5]

2.3.3.2.3.3.2.3.3.2.3.3. Data budgetData budgetData budgetData budget

The data rate of the active sensors for Phase 2 and 3, have been estimated using the

acquisition frequencies, the amount of sensors and the expected data size of each

measurement according to APPENDIX 1. If required, note that acquisition frequencies of the

systems can be changed.

Systems Phase 1 (diff. Drag) Phase 2 (AeroSDS) Phase 3 (Re-entry)

ADCS, AeroSDS

Gyroscope (3x16bit) [kbpd] [Hz] [kbpd] [Hz] [kbpd] [Hz]

415 0.1 415 0.1 480 10

Accelerometer (3x16bit) 415 0.1 415 0.1 480 10

GPS (7x64bit) - - 645 0.0167 - -

House-keeping (30x16bit,

Phase 3: 5x16bit) 691 0.0167 691 0.0167 480 1

Payload sensors /data 150/400 - 495 - 240 -

Total 1671/400 2661 1680

Table 5. Data budget for QARMAN [5]

19

3.3.3.3. XPL02XPL02XPL02XPL02

3.1.3.1.3.1.3.1. Data Acquisition System designData Acquisition System designData Acquisition System designData Acquisition System design

3.1.1.3.1.1.3.1.1.3.1.1. Stating the Problem and Designing the Payload ObjectivesStating the Problem and Designing the Payload ObjectivesStating the Problem and Designing the Payload ObjectivesStating the Problem and Designing the Payload Objectives

Space vehicles re-entering a planetary atmosphere require the use of a thermal protection

system (TPS) in order to protect them from aerodynamic heating, which is the result of

compression, surface friction with the atmospheric gases and exothermic chemical reactions.

This shield is formed by an ablative material designed to melt and erode away from the vehicle

as it heats up.

There is a great interest to study the properties of these materials (i.e. durability, temperature

capability, thermal conductivity) to improve vehicle performances. So far not much data has

been obtained in a real re-entry flight, mainly because of the high cost to design a dedicated

vehicle for this purpose. For this reason, QARMAN gives engineers a very good opportunity to

help increasing the knowledge of the Earth aerothermodynamic re-entry phenomenon. Hence,

it has been decided to suit a payload formed by two absolute pressure sensors installed into

the TPS (apart from the other two thermocouples). In the following sections there will be

carefully defined the design of this payload and its measurement chain. In the end, a final data

acquisition system will be implemented for testing in VKI facilities.

Taking into account the main requirements for XPL02, which can be consulted in APPENDIX 1,

a list of scientific objectives is developed:

1. Total pressure measurements in the stagnation region.

2. Pressure measurements near the corners.

3. Pressure distribution on the TPS.

4. Dynamic pressure computation.

3.1.2.3.1.2.3.1.2.3.1.2. SubjecSubjecSubjecSubject tradest tradest tradest trades

The subjects participating here are the pressure and the ablation of the TPS. QARMAN will not

have recession sensors in order to keep a simple vehicle design. However, the ablation of the

TPS will determine pressure data obtained with both pressure transducers. This way, pressure

is chosen as the subject under study and, in order to accomplish the scientific objectives

presented above, computation processes for each one need to be defined:

• For scientific objective 1, measurements of the total pressure at a high Mach regime

will be acquired near the stagnation point. That is to say, it is directly the pressure

values obtained from pressure sensors without any change or computation.

20

• The mission objective 2 is simply the data acquired with the pressure sensor located

near the region with lowest pressure which, as given in section 3.2.2, corresponds to

the corner.

• Scientific objective 3 is related to compare the pressure data obtained by both

pressure sensors. These results would allow the reconstruction of the pressure

distribution around the TPS. Even though TPS will include only two pressure sensors,

considering the size of QARMAN it should be enough to at least validate in-flight data

by comparing it with CFD and experiments done in VKI facilities.

• The scientific objective 4 will be calculated taking into account the measurements of

total pressure (P0) obtained near the stagnation point, and static pressure (ps)

measurements obtained from XPL03. For this purpose, the following relation will be

used:

� = �� − ��

3.1.3.3.1.3.3.1.3.3.1.3. Pressure ports and pressure sensors housingPressure ports and pressure sensors housingPressure ports and pressure sensors housingPressure ports and pressure sensors housing

The location of the pressure ports depends on the geometry of the CubeSat TPS. The

configuration proposed for QARMAN will be a ballistic entry in which the angle of attack is

intended to be around zero degrees. Due to the symmetry of the probe there will be four

points with the same aerodynamics characteristics, what means the design of these taps can

be done by multiple ways obtaining the same data. This is an important point to take into

account, because there will be other sensors installed in the TPS. This way, the design

procedure followed is going to be:

• Get pressure data from CFD at different flight altitudes.

• Identify the minima and maxima of the pressure values and where they are.

• Get curves with pressure distribution around the TPS.

• Identify which curve changes the fastest.

• Decide pressure ports location depending on this curve.

On the other hand, in order to properly connect pressure ports with pressure transducers, it

will be designed a spool. This element will be suited in the TPS bounding structure and will

permit a proper connection to the pressure transducers. This way, the sensors will be housed

as close as possible to the TPS, trying to avoid possible pressure losses. In section 3.2 there will

be seen the design of the spool and the housing of the whole configuration in detail.

21

3.1.4.3.1.4.3.1.4.3.1.4. Performance thresholdsPerformance thresholdsPerformance thresholdsPerformance thresholds

According to QARMAN payload requirements [7], the final expected performance for XPL02 is

summarized in Table 6. As you can see, XPL02 will be measuring absolute pressure at two

different points of the TPS. The weight of the whole configuration should not exceed 60 grams,

which means that the measurement chain needs to be really optimized. This payload will be

switched on during phase 3 of the mission, what corresponds to altitudes from 120 km to 50

km (defined in section 1.1). The acquisition frequency is established to 1 Hz, but it is a

parameter that might change depending on the amount of data acquired.

Investigated challenge TPS & environment

Parameter to measure Absolute pressure

Sensor 2 x Pressure sensor

Total mass [kg] (sensor + wiring +

housing) 0.060

Energy consumption/ Piece [mW·h] 4.166666667

Data size/ measurement [bit] 10

Phase 3

Total data size [kB/ phase] 1.5

Acquisition frequency [Hz] 1

Number of measurements 600

Total acquisition duration [h] 0.166667

Response time [ms] 0.1

Power [W/piece] 0.250 Table 6. Performance thresholds for XPL02

3.1.5.3.1.5.3.1.5.3.1.5. Preliminary ConfigurationPreliminary ConfigurationPreliminary ConfigurationPreliminary Configuration

3.1.5.1.3.1.5.1.3.1.5.1.3.1.5.1. Measurement ChainMeasurement ChainMeasurement ChainMeasurement Chain

There exist several signal conditioning considerations in order to accurately measure pressure.

It is necessary to justify each one to take into account all possible aspects before building its

measurement chain. Thus, pressure sensors deal with the concepts specified as following.

• Linearization

Pressure sensors generally produce a linear response across their range of operation, so

linearization is considered unnecessary in this case. Nevertheless, some deviations from the

nominal value can occur, that is why the accuracy of the instruments will be of importance for

the market survey.

22

• Remote sensing

It is related with the distance between the sensor and the signal conditioner. Taking into

account that in the worst case this distance would be the maximum length of the CubeSat (30

cm), the losses due to resistance in the wires can be dismissed.

• Amplification

The output of pressure sensors is relatively small. In order to use all range available in the ADC,

an amplifier is needed. It allows having a better measurement resolution and also improving

the signal-to-noise ratio.

• Filtering

Another important point is to protect the acquisition system from the electrically noisy

environment. QARMAN will be flying at an altitude where plasma has a high density. It means

that the surface of the spacecraft could be electrically charged causing current losses, ion

sputtering and other effects. In order to avoid these errors in the samples, a filter should be

introduced in the measurement chain.

• Offset

When no pressure is applied to the sensor, it is very unlikely that the output is exactly zero.

The offset error can be corrected by two different ways: software compensation or introducing

an offset-nulling circuit. It is well known that the data acquisition system for all sensors will be

implemented on the same card, which means that mass and volume constraints are very

important. For this reason, offset will be corrected by software being this simple, fast and

cheap. In addition it can be done in the VKI facilities.

• Multiplexing

QARMAN will fit 4 pressure sensors. In order to reduce weight and space, it will be introduced

a multiplexor before the analog-to-digital data conversion.

• A/D Converter

QARMAN will be storing digital data due to the simplicity, efficiency and resistance to

corruption among other advantages. Hence, it is necessary an A/D converter because most of

the pressure sensors output only analog data.

Once the different components forming the measurement chain have been defined, the whole

configuration can be seen in Figure 7. Please, note that this is a very preliminary configuration

and the final chain will be designed according to the market survey done in the following

section. This aims to be the base before start working with electronic engineers.

23

Figure 7. Measurement Chain

3.1.5.2.3.1.5.2.3.1.5.2.3.1.5.2. Market surveyMarket surveyMarket surveyMarket survey

a)a)a)a) Pressure sensorPressure sensorPressure sensorPressure sensor

The market survey for the pressure sensor is conducted according to the requirements defined

in section 3.1.4. All components and their properties are listed in Table 9. There should be

noticed that most of them have a response time higher than 0.1 ms. This change is justified

because the ones with a better response time were operating in different pressure ranges (>35

kPa), so they have been dismissed.

Due to the lag of information on datasheets, there might be some mistakes on the accuracy

column. Even though some of them offered a detailed justification for this property, some

other datasheets were including only non-linearity effects. This way, if results obtained on the

VKI facilities are not satisfactory, further information can be required to the suppliers. In

addition, properties such as operating temperature or response time are pretty similar

between them, but important differences can be seen on the supply voltage and weight.

Besides, cost differences are not relevant enough to take a decision based on this.

Finally, it is important to say that some of the pressure sensors found are already amplified,

but their accuracy is also worsened. Pressure ranges is going to be a determinant factor,

because pressure sensors need to operate in a range from near 0 kPa to 20 kPa. In the end, the

transducer chosen is going to be the NPC-1220. The choice justification can be consulted in

section 3.1.5.3.

b)b)b)b) AmplifierAmplifierAmplifierAmplifier

Table 7 summarizes the market survey done for the amplifiers. The performances of these

components are very similar to each other, so the market survey and the final choice will be

done accordingly to their price, size, and power consumption. Note that some of the amplifiers

chosen have a maximum output signal from 10 to 12 Volts, which allows to highly increasing

the measurements resolution. These outputs have been obtained by using the maximum gain

defined in datasheets with the relation:

�� = � �� · ��

24

If necessary, the gain could be adjusted using a resistor in order to decrease or increase the

output signal. Furthermore, operating temperatures and weights are pretty similar between

them, so the main important property here is going to be the voltage supply, because the

satellite will be giving a maximum of 5 Volts to this circuitry.

AD711K AD549S AD745K AD847 AD8671

Voltage supply [V] 4.5 to 18 5 to 18 4.8 to 18 4.5 to 18 4 to 18

Dimensions [mm] 9.5x7.5x3.8 ᴓ9.4x12.7 10.5x7.6x2.65 5.01x3.99x2.59 8.75x4x1.75

Open-Loop Gain

[dB] 112 120 132 74.8 135.6

Output voltage [V] ±13 ±10 ±13 ±3.3 ±3.39

Operating

temperature range

[ºC]

–55 to +125

–55 to +125

-65 to +125 -65 to +125 -40 to +125

Weight [grams] ≈1 ≈1 ≈1 ≈1 ≈1

Settling time to

0.01% [µs] 1 4.5 5 0.065 1.4

Table 7. Set of available amplifiers for the pressure sensor

c)c)c)c) FiltersFiltersFiltersFilters

According to datasheet for pressure sensor NPC-1220, the noise affecting the pressure sensor

occurs in a range of frequencies from 10 Hz to 1 kHz. It means that is required a low pass filter

with a cutoff frequency of 10 Hz. With this input the market survey gets highly restricted and

the filter chosen is defined in Table 8. Note that this kind of filter can be easily developed in

the VKI facilities using a set of resistors and capacitors. The table aims to show and define what

is in the market. Again, the voltage supply is going to be the determinant factor, because it

must be able to operate with 5 Volts or less. For this component, size and mass are not

relevant, but temperature of operation fits to the ones specified for the other components.

Feature MAX7400ESA

Type Low pass filter

Voltage supply [V] 5

Frequency-cutoff [Hz] 10

Filter order 8th

Temperature of operation [ºC] -40 to 85

Offset [mV] ±5mV

Mass [g] 0.1

Volume [mm] 5x4x1.75 Table 8. Filter for pressure sensors

25

Table 9. Set of available pressure sensors for QARMAN

Part number Pressure

range [kPa]

Full scale

span [mV]

Accuracy

[%VFSS]

Response

time [ms]

Mass

[g]

Volume

[mm3]

Operating

temperature [ºC]

Supply

Voltage

[Vdc]

Cost

[dollars]

SX SMT

Series 0 to 34 0 to 75 ±0.5 0.1 10 213 -40 to +125 5 31.92

101B-a19L 0 to 34 0 to 30 ±0.5 ≥1 16 2837 -30 to +100 5 Out of stock

NPC-1220 0 to 34 0 to 50 ±1.3 1 2.5 975 -40 to 125 1.235 28

19 mm

Series 0 to 34 0 to 100 ±1.55 0.1 8 451 -40 to +125 10 138

MS1451 0 to 100 0 to 60 ±1.05 1 0.3 186 -40 to +125 3 Out of stock

HSC Series 0 to 100 0.1 to 3.2 V (amplified)

±1 1 2 726 -40 to +85 3.3 40

40PC150G1A 0 to 100 0 to 4 Volts (amplified)

±4 1 10 1315 -45 to +125 5 35.88

40PC015V2A 0 to 100 0 to 4 Volts (amplified)

±4 1 8 1315 -45 to +125 5 33.81

SSC Series 0 to 100 0.1 to 3.2

Volts (amplified)

±2 1 2 726 -40 to +85 3.3 44

26

d)d)d)d) A/D convertersA/D convertersA/D convertersA/D converters

The main requirement for pressure sensors referring to the output data is that each sample

shall have a size equal or lower to 10 bits. It is also known that there are 4 pressure sensors

following the same measurement chain (2 from XPL02 and 2 from XPL03). Thus, all the A/D

converters should integrate four or more multiplexed input channels. The options available are

specified in detail in Table 10.

Note that all of them are able to operate with a supply voltage lower than 5 Volts. It means all

could properly operate in QARMAN. For some of the converters, the number of channels

available is 8. This might help to reduce weight and volume using some channels for a different

payload, such as the thermocouples, that also require conversion to digital signal. Additionally,

operating temperatures suits perfectly to the one from other components of this chain.

According to the payload requirements of XPL02 the sampling frequency is expected to be 1Hz.

AD7292 AD7298-1 AD7939 MCP3004/3008

Supply

voltage [V] 1.8 to 5.25 2.8 to 3.6 2.7 to 5.25 2.7 5

Resolution

[bits] 10 10 10 10

Channels 8 8 4 8

Operating

temperature

range [ºC]

-40 to +125 -40 to +125 -40 to +85 -40 to +85

Mass [g] - - - -

Volume

[mm] 6x6x0.75 4x4x0.75 5x5x0.85 9.9x6x1.75

Mega-

samples per

second

[MSPS]

0.625 1 1.5 0.075 0.2

Table 10. Available A/D converters for pressure sensors

3.1.5.3.3.1.5.3.3.1.5.3.3.1.5.3. Preliminary measurement chain designPreliminary measurement chain designPreliminary measurement chain designPreliminary measurement chain design

Considering the previous market survey it can be defined the preliminary configuration for the

measurement chain of XPL02. As it’s been explained, QARMAN will be experimenting pressure

values somewhere between 0 and 20 kPa. This way, it is obviously needed to cover this range

also taking into account the main characteristics of the sensors summarized in Table 9.

Knowing that pressure measurements can be obtained in absolute, gauge and differential (as

seen in section 2.2.2), it has been finally decided to test this payload based on absolute

pressure. The main reason is that its value is not influenced by changes in atmospheric

pressure. In addition, it is zero-referenced against the perfect vacuum, so this kind of sensor

27

will only need one pressure intake in the TPS. With this property defined, the market survey

has been carried out and comparisons between all sensors can be done in order to find the

pressure sensor that fits better to QARMAN.

Regarding the properties defined in Table 9, there can be seen that most of them have the

same response time, operating temperature and cost. This way, the final decision prioritizes

the supply voltage, the operating pressure range and the accuracy. Additionally, amplified

sensors have been dismissed due to they are operating in a range from 0 to 100 kPa (larger

than the required one) with a worst accuracy than the unamplified ones. Furthermore, it is

known that a maximum of 5 Volts will be provided to QARMAN’s platform. It means there

must be ensured that XPL02 can work properly with this voltage supply. For all these reasons,

the pressure sensor proposed for XPL02 is the NPC-1220, which is the one that requires less

voltage supply and it is also operating into an adequate pressure range with a very good

accuracy. See Table 11 for detailed information. Moreover, this sensor is one of the lightest

one, which is also a benefit for the whole CubeSat design. There should be also noticed that

the 101B-a19L pressure sensor has been also considered due to its high accuracy and general

performances, but it has been finally dismissed due to its design. Both pressure sensors are

shown in Figure 8 for a better comparison.

Figure 8. On the left, pressure sensor 101B-a19L; on the right, pressure sensor NPC-1220

Another important part of the chain is the filtering process. According to the datasheet,

pressure sensor chosen will be outputting noise from 10 Hz to 1 kHz, which means that a low

pass filter can be required. This kind of filter is a simple electrical circuit which consists of a

resistor in series with a load, and a capacitor in parallel with the load. If a filter is finally

necessary, the idea is to design this component in the electronics laboratory of VKI. In that

case, the filter would not require energy supply, which agrees with the idea of keeping a

simple vehicle design. Just in case, the market survey is already done to have another

possibility. Following the filter, the measurement chain will include an amplifier. Taking into

account the market survey developed for this component, the most suitable amplifier is the

AD8671 because of its low voltage supply and its high gain, which gives better output signal of

10 Volts. Finally, there is the analog-to-digital conversion. For initial tests of XPL02 in the VKI

facilities, it has been chosen the ADS7828E, which is also the same as the one used in XPL01

[2]. Depending on its performance the A/D converters from Table 10 may or not be in

consideration.

28

With all components for the preliminary DAQS for XPL02 decided, the important

characteristics at each point of the circuit are defined. They are summarized in detail in Table

11. Firstly, the pressure sensor datasheet advises to use a supply voltage of 1.235 V, obviously

lower than the 5 Volts available for the platform. Its range fulfills the required one, and taking

into account the accuracy of the sensor, a pressure error of 0.442 kPa is found. Note that this

should be the maximum pressure error obtained at any pressure value, but its validation needs

to be performed in laboratory. Output voltage range and error for the pressure sensor are also

given in the same table. Another important characteristic is the zero output Voltage, because it

defines the lowest pressure the sensor is able to measure. However, by calibration in

laboratory the pressure range can be adjusted, for example by modifying the gain of the

amplifier.

For the preliminary design, the amplifier chosen is the AD8671. As you can see, the voltage

supply meets the one required (less than 5V). Note that the gain presented in the table is the

maximum one, but it can be modified using a simple potentiometer in order to have the

desired output. Finally, there is the analog-to-digital converter ADS7828E. For this component,

the voltage supply required is also in the limits. It has a very good resolution of only 8.33 Pa,

value that corresponds to an absolute error of 0.0245%. In addition, thanks to the high number

of channels the possibility of connecting other payloads to this converter can be considered.

On the other hand, the sampling frequency exceeds by far the 1Hz frequency required.

NPC-1220-005A-3-S

PRESSURE SENSOR

Measurement type Absolute pressure

Supply Voltage [V] 1.235

Pressure Range [kPa] 0 to 34

Pressure Error [kPa] 0.442

Output Voltage Range [mV] 0 to 50

Output Voltage Error [mV] 0.65

Zero Pressure Output [mV] 2

AD8671

Supply Voltage [V] 4 to 18

Gain [dB] 135.6

Output Voltage [V] ±3.39

Offset Voltage [µV] 125

Output Voltage error [mV] 88.14

ADS7828E

Supply Voltage [V] 2.7 to 5

Voltage resolution [mV] 1.66

Pressure resolution [Pa] 8.33

Resolution [bit] 12

Channels 8

Sampling Rate [kHz] 50

Max. Error in Pressure [kPa] 0.442

Table 11. Preliminary measurement chain for XPL02

29

3.1.6.3.1.6.3.1.6.3.1.6. Final configurFinal configurFinal configurFinal configurationationationation

The preliminary design presented in the previous section has been shared with QARMAN

team. The electronic technicians have carefully read and interpreted the datasheets of each

component forming the measurement chain. This way, taking into account their experience,

compatibility between components is checked in order to define a possible configuration.

Therefore, the preliminary configuration defined in previous section is slightly modified. On

one hand, filters are dismissed because technicians think the noise is going to be pretty low.

However, oscilloscope will be used during tests in order to check it. On the other hand,

pressure sensor and the amplifier already chosen will be finally implemented. Finally, instead

of the analog-to digital converter, technicians decided to use the microcontroller MSP430. This

component has an internal 12-bit ADC module which has a maximum conversion rate of 200

kilo-samples per second and an internal reference voltage generator. There are 16 channels in

total, much more than the 8 channels from the ADC selected for the preliminary design.

However, 4 of these channels are internally connected and they cannot be used to take

external measurements; otherwise, the other 12 channels are accessible via the MSP430’s

pins. These and other characteristics are listed in Table 12.

Component MSP430

Supply Voltage [V] 5

ADC integrated Yes

Kilo-samples per second 200

Channels available 12

Resolution [bit] 12

Memory type Flash

Temperature range [ºC] -40 to 85

Maximum input voltage [V] 3.3

Table 12. MSP430 main characterstics

For this reason, two possible configurations are proposed for testing: Version A and Version B.

Each one of them gives different characteristics to the circuitry and it is intended to test both

of them in VKI facilities.

Even though a final configuration is presented here, due to ordering problems the pressure

sensor measuring absolute pressure was not in stock. It means that this project will not cover

the tests for XPL02, but only the configuration and housing design. Luckily, the same pressure

sensor measuring differential pressure has been acquired, so XPL03 tests have been carried

out during the development of this project and they are described in see section 4.2.

30

3.1.6.1.3.1.6.1.3.1.6.1.3.1.6.1. Version AVersion AVersion AVersion A

NPC 1220 pressure sensor will be used in the design. Since the output of the sensor is quite

low, an amplifier circuitry must be connected to the output of the sensor. AD8671 amplifier

has been chosen for this purpose. Application schematic of the pressure sensor can be seen in

Figure 9.

Figure 9. Pressure sensor circuitry and components

The CSR (current set resistor, see the scheme) is placed between negative input of the OP-AMP

and the ground. Since this amplifier operates with negative feedback, negative input voltage

will be equal to the Vref. It means that current value passing through the pressure sensor bridge

circuit is determined as:

� =��

On the other hand, the gain of the buffer amplifier (see red box) can be calculated by means of

the resistors there defined:

� =2 · 100�Ω + 3.3�Ω

3.3�= 61.606

In addition, typical sensor output should be 50 mV, so the output voltage of this configuration

can be easily calculated as follows:

�� = 50$� · 61.606 = 3.08�

Note that 3.08 V is the maximum output differential voltage. The sensor should be driven by

certain amount of current and this is achieved using the current set resistor and the current

source structure also defined in Figure 9. At this point, the configuration and pins connection is

defined as it is shown in Figure 10. Three operational amplifiers will be used: the one in the

31

green are used for the current supply; the ones in the red box are amplifying the pressure

sensor output, also illustrated.

Figure 10. Version A configuration and pin connection

3.1.6.2.3.1.6.2.3.1.6.2.3.1.6.2. VerVerVerVersion Bsion Bsion Bsion B

Pressure sensor output voltage is proportional to the bridge resistor values inside the sensor.

According to the datasheet of the sensor, maximum resistor value is 6k Ω. Considering this

configuration, output voltages from negative and positive leads of the sensor (pins 1 and three

of the NPC-1220 shown in Figure 10) exceed 5 Volts, while the differential voltage between

them is still 50 mV at maximum. This way, once these values are amplified by the circuit inside

the red box, the final output will be around 7 V. At that point, maximum differential output will

be around 3.08 Volts, but the microcontroller chosen cannot measure voltages above 3.3 V.

In order to solve this problem, a differential amplifier with gain 1 could be used in order to get

one single output into the required voltage range. However, it means having three OP-AMP to

only measure the output of one single sensor and also more resistors to complete the circuit.

In the end, it leads to a more complex design and also to error amplification. For this reason,

an instrumental amplifier will be used. These devices are widely used for signal conditioning

circuitry for bridge type sensor. It has two inputs and single-ended output. First stage (two OP-

AMPs on the left on Figure 11) is the buffer stage. It isolates the input and the output.

Furthermore it amplifies the incoming signal depending on the Rgain. The most important

characteristic of this stage is that it has very high input impedance. Thanks to this feature, no

current flow through the input which means no current drawn from the sensor. If some

current draws from the bridge circuitry of the sensor, this would distort the balance of the

bridge giving wrong measurements.

Second stage is a differential amplifier. Usually gain of this stage is set to 1. The main purpose

of this stage is to subtract input signals between them giving single-ended output and being

possible to connect this output directly to the microcontroller.

Instrumental amplifiers input signal has two components: the common mode signal (the

average of both input signals) and the differential signal (difference of both sig

important thing here is that only the differential signal has importance for data acquisition.

Common mode signal must be suppressed, so only the differential signal can reach to the

output. IN-AMPs have very good common mode rejection ratio (CM

variations in the common mode signal cannot affect the output signal.

All this characteristics make IN

resistor values inside the IN

produced with very high precision so, if possible, it is advised to use these chips instead of

building a circuit by using 7 resistors and 3 OP

Thanks to the experience of the electronic technicians, the instrumental amplifi

chosen by them. This way, the IN

characteristics listed in Table

AMP that includes two ident

used for supplying constant current to the sensor and the other one has been used for

reference voltage generation for the IN

OP-AMPs are only for current and voltage supply to the circuit, so once verified these values

remain constant their effects to the pressure sensor outputs can be dismissed. As you can see

in Figure 12, the gain of the IN

gain set resistor. To control it, the following equation presented in the instrumental amplifier

datasheet is used:

Figure 11. Typical instrumental amplifier


average of both input signals) and the differential signal (difference of both sig



AMPs have very good common mode rejection ratio (CMRR), what means that

variations in the common mode signal cannot affect the output signal.

All this characteristics make IN-AMPs proper for bridge type sensors. It is very important that

-AMP are precise. Single commercial integrated circuits (IC) are


building a circuit by using 7 resistors and 3 OP-AMPs.

Thanks to the experience of the electronic technicians, the instrumental amplifi

chosen by them. This way, the IN-AMP AD8226 is decided to suit Version B with main

Table 13. On the other hand, LMP7718 (inside green box) is a dual OP

AMP that includes two identical and separated operational amplifiers. One of them has been


reference voltage generation for the IN-AMP (inside red box). However, note that these two

y for current and voltage supply to the circuit, so once verified these values


, the gain of the IN-AMP represented inside red box can be adjusted thanks to the

. To control it, the following equation presented in the instrumental amplifier

�' =49.4�Ω� � 1

32


average of both input signals) and the differential signal (difference of both signals). The



RR), what means that

AMPs proper for bridge type sensors. It is very important that

egrated circuits (IC) are


Thanks to the experience of the electronic technicians, the instrumental amplifier has been

AMP AD8226 is decided to suit Version B with main

. On the other hand, LMP7718 (inside green box) is a dual OP-

ical and separated operational amplifiers. One of them has been


AMP (inside red box). However, note that these two

y for current and voltage supply to the circuit, so once verified these values


djusted thanks to the

. To control it, the following equation presented in the instrumental amplifier

33

Figure 12. Version B configuration and pin connection

In summary, the advantages respect to Version A can be listed as follows:

• A single IN-AMP is used instead of two OP-AMP.

• Efficiency and noise immunity of the IN-AMP is better.

• Only one external resistor is needed.

• Output is single ended (not differential as Version A), so it is easier to read voltages by

the ADC channel of the microntroller.

For all this reasons, it has been decided that Version B is by far the best configuration. This

way, preliminary tests at VKI facilities will be based on this last version of the measurement

chain. However, as it has been explained, it will be only possible to test the differential

pressure sensor from XPL03 during the development of this thesis, due to absolute pressure

sensors were out of stock when the components were ordered.

Component AD8226


Gain [dB] 60 (adjustable)

Output Voltage [V] 3

Settling time to 0.01% [µs] 350

Operating temperature [ºC] -40 to 125

Volume [mm3] 17.24 Table 13. AD8226 main characteristics

3.2.3.2.3.2.3.2. Pressure ports design and sensor housingPressure ports design and sensor housingPressure ports design and sensor housingPressure ports design and sensor housing

3.2.1.3.2.1.3.2.1.3.2.1. Objectives and main considerationsObjectives and main considerationsObjectives and main considerationsObjectives and main considerations

The Thermal Protection System will fit both pressure taps for pressu

this reason, two holes will be drilled through the shield with the objective of connecting the

atmosphere with the pressure sensor transducers. Their design will be mainly driven by two

important properties:

- The diameter of the ho

- The location of pressure taps in the TPS.

On one hand, it must be verified the holes are wide enough to ensure the air flows properly

through them. This way, it is required to know if the size of the particles coming from the

ablation of the TPS can obstruct the pressure taps. The rate of recession must be known in

order to control and optimize the diameter.

On the other hand, the location of the pressure taps in the TPS will also be guided by testing

this shield in Plasmatron. Knowing its ablation evo

will be acquired. So far, some CFD’s have been done, which tell us that with an ideal attitude of

the satellite (perfectly aligned with the velocity vector) the regions near the stagnation point

and the corners of the TPS are the ones which ablate the fastest. The highest temperatures

and pressures are obtained there, as shown in

will change and the CubeSat will be turning

attack different to zero. It will obviously cause differences from the ideal ablation just

mentioned.

It means the design of the holes placed near the borders of the TPS will be a trade

the structure integrity and the pressure distribution of this region. For example, holes drilled

very close to the corners could cause the fracture of this region and, as a result, the loss of the

symmetry and attitude problems.

Figure 13. TPS at 66 km of altitude. a) Pressure distribution; b) Temperature distribution

Pressure ports design and sensor housingPressure ports design and sensor housingPressure ports design and sensor housingPressure ports design and sensor housing

Objectives and main considerationsObjectives and main considerationsObjectives and main considerationsObjectives and main considerations

The Thermal Protection System will fit both pressure taps for pressure data acquisition. For



The diameter of the holes.

The location of pressure taps in the TPS.



bstruct the pressure taps. The rate of recession must be known in

order to control and optimize the diameter.


this shield in Plasmatron. Knowing its ablation evolution, precious information for its location



of the TPS are the ones which ablate the fastest. The highest temperatures

and pressures are obtained there, as shown in Figure 13. However, in-flight conditions things

will change and the CubeSat will be turning a bit around its velocity vector, having an angle of


It means the design of the holes placed near the borders of the TPS will be a trade

structure integrity and the pressure distribution of this region. For example, holes drilled


symmetry and attitude problems.

TPS at 66 km of altitude. a) Pressure distribution; b) Temperature distribution

34

re data acquisition. For





bstruct the pressure taps. The rate of recession must be known in


lution, precious information for its location



of the TPS are the ones which ablate the fastest. The highest temperatures

flight conditions things

a bit around its velocity vector, having an angle of


It means the design of the holes placed near the borders of the TPS will be a trade-off between

structure integrity and the pressure distribution of this region. For example, holes drilled


TPS at 66 km of altitude. a) Pressure distribution; b) Temperature distribution

Considering the points already presented for QARMAN, the design of the measurement chain

of XPL02 will be similar to the one implemented for the Mars Entry Atmospheri

Development (MEADS) of the Mars Science Laboratory. It is a series of seven pressure ports, in

the thermal protection system that connect

Its general configuration is presented in

a diameter of 2.54 mm, connecting the atmosphere to the heat shield, which is housing a

spool. In the end, this last element allows a proper connection with the sta

which guides the atmosphere pressure to the pressure transducer. For all this, the TPS bonding

structure of QARMAN will be housing a specific spool. The following sections will be focused

on its design.

Figure

3.2.2.3.2.2.3.2.2.3.2.2. Pressure ports design Pressure ports design Pressure ports design Pressure ports design

Unlike MEADS design, QARMAN TPS will be housing only two pressure ports. However, before

taking a decision about where to place them, let’s consider the

see if it is compatible for a CubeSat. As may be seen in

implemented for Mars Science Laboratory mission. Points P1 and P2 are located in the

stagnation point to provide a nearly direct measurement of the total pressure in the high Mach

regime. Ports P3, P4 and P5 lie on the spherical nose cap and are placed in order to take

advantage of the simple geometry for angle

at the geometric center, provides a nearly direct total pressure measurement at the low Mach

regime prior to parachute deployment. The final two ports are located in the horizontal plane

of symmetry, approximately 1 meter from the centerline.

axis measurements needed to estimate the angle of sideslip. The pressure ports are connected

to pressure transducers via the stainless steel tube system


of XPL02 will be similar to the one implemented for the Mars Entry Atmospheri


the thermal protection system that connects via stainless steel tubing to pressure transducers.

Its general configuration is presented in Figure 14. In this case, the holes drilled in the TPS have


spool. In the end, this last element allows a proper connection with the sta



Figure 14. MEADS transducer and tube configuration [8]

Pressure ports design Pressure ports design Pressure ports design Pressure ports design


taking a decision about where to place them, let’s consider the option taken by MEADS and

see if it is compatible for a CubeSat. As may be seen in Figure 15, seven pressure ports are


n point to provide a nearly direct measurement of the total pressure in the high Mach


advantage of the simple geometry for angle-of-attack measurements. Additionally,



of symmetry, approximately 1 meter from the centerline. The ports P6 and P7 provide the off


to pressure transducers via the stainless steel tube system already illustrated in

35


of XPL02 will be similar to the one implemented for the Mars Entry Atmospheric Data System


via stainless steel tubing to pressure transducers.

. In this case, the holes drilled in the TPS have


spool. In the end, this last element allows a proper connection with the stainless steel tube,




option taken by MEADS and

, seven pressure ports are


n point to provide a nearly direct measurement of the total pressure in the high Mach


attack measurements. Additionally, P4, located



The ports P6 and P7 provide the off-


illustrated in Figure 14.

Figure

QARMAN TPS is going to house two thermal plugs and a spectrometer, apart from the two pressure ports of XPL02. On one hand, the spectrometer will be located exactly at thestagnation point of the TPS. On the other hand, both thermocouples will be placed diagonal direction between the stagnation point and the corner.

In addition, the CFD’s done at the altitudes of 66 km, 60 km, 53 km and 50 km show the

pressure distribution around the TPS during re

be observed that regions near the stagnation point have higher pressures than regions near

the corners. For a more detailed press

At this point, taking into account all this information one first decision can be made: the two

pressure ports shall be located at the points of maximum and minimum pressure. This can be

translated into placing them somewhere near the stagnation point and near the corner. It

would allow QARMAN to get data required to accomplish the payload objectives and it would

also give interesting information for further TPS designs by comparing these two points.

Another obvious but important thing is that both pressure ports must be housed diagonally

opposed from the thermocouples, avoiding crowded regions and cabling related problems.

Figure 15. MEADS pressure ports configuration

QARMAN TPS is going to house two thermal plugs and a spectrometer, apart from the two pressure ports of XPL02. On one hand, the spectrometer will be located exactly at thestagnation point of the TPS. On the other hand, both thermocouples will be placed diagonal direction between the stagnation point and the corner.


ibution around the TPS during re-entry. This can be seen in Figure


the corners. For a more detailed pressure distribution at each altitude, consult



o placing them somewhere near the stagnation point and near the corner. It



other obvious but important thing is that both pressure ports must be housed diagonally


36

QARMAN TPS is going to house two thermal plugs and a spectrometer, apart from the two pressure ports of XPL02. On one hand, the spectrometer will be located exactly at the stagnation point of the TPS. On the other hand, both thermocouples will be placed in the


Figure 16. It can easily


ure distribution at each altitude, consult APPENDIX 2.



o placing them somewhere near the stagnation point and near the corner. It



other obvious but important thing is that both pressure ports must be housed diagonally


37

Figure 16. TPS pressure distribution at a) 66 km; b) 60 km; c) 53 km; d) 50 km of altitude

Once the region is decided, it is time to know exactly where to place the pressure ports and

which diameter will they have. From CFD’s at the different four altitudes, the TPS pressure

distribution from the stagnation point to the corner is obtained as a function of axis Z (see axis

in Figure 17). Thus, it can be noticed that at Z=0 m maximum pressure is obtained and near

Z=0.05 m it is reached the minimum one as expected. In addition, it can be seen that as

altitude increases, pressure changes become smoother around the stagnation point. The same

happens near the corner.

For this reason, the first pressure port P1 will be located where pressure starts dropping more

rapidly for the most critical altitude, which is 50 km. This point corresponds to Z=0.015 m.

Represented with the grey vertical line in Figure 17. On the other hand, pressure port P2 is

going to be placed at Z=0.04 m, represented too, which corresponds to a point where pressure

has decreased an important amount at all altitudes and it is far enough from the corner

avoiding structural problems. However, this configuration must be tested in Plasmatron

(facility described in section 4.2.2) to validate the design.

Finally, there is only one thing left: the size of the pressure ports. Taking into account the

diameter of the holes made for MEADS is 2.54 mm, it has been decided to make a preliminary

design with holes 20 % smaller than the previous ones, which corresponds to 2 mm diameter.

38

Figure 17. TPS pressure distribution as a function of altitude

3.2.3.3.2.3.3.2.3.3.2.3. Spool options consideredSpool options consideredSpool options consideredSpool options considered

In order to properly connect the pressure ports from the TPS with the pressure transducers, it

will be designed a specific spool for QARMAN. This element will be similar to the one used in

MEADS (see Figure 14), but different options has been considered for its design. In the end,

taking into account the advantages and disadvantages of each one, a final design will be

proposed for further tests in Plasmatron.

As it has been explained in the previous section, both holes drilled in the TPS for the pressure

ports have a diameter of 2 mm. This way, in-flight air will get in the holes and it will also pass

through the 50 mm of TPS. The thermal shield will be attached to a boundary metallic

structure, which is going to house the spool. So far, neither the material nor the shape of the

metallic structure is defined, just some preliminary and incomplete CATIA designs have been

developed. Hence, it has been decided that the design of the spool will guide the final design

of the TPS boundary structure. Taking this into account, it is intended to create a spool

minimizing the thickness of this structure and therefore the weight of the satellite.

The main objective of the spool is to enable the connection between the pressure ports and

the plastic tube which will end up at the pressure transducer. Thus, the basic requirement is

that the spool shall have an outer section so the tube can be connected, but the global design

can differ in many ways. That is why three different options have been presented in order to

choose the best one.

39

3.2.3.1.3.2.3.1.3.2.3.1.3.2.3.1. Option 1Option 1Option 1Option 1

First design, presented in Figure 18, is very similar to the one for MEADS. In that case the spool

was housed in a heat shield, but the basics are the same: one unique body inserted in the TPS

boundary structure. This one seems to be the simplest one for the manufacturing of the spool

and reliability. Note that its hole has two times the diameter of the pressure ports; this is done

to avoid obstruction problems during TPS ablation. It is also perfectly suited to the bonding

structure, so it is really optimized in size. However, it has the inconvenient that it needs to be

manufactured together with the boundary structure, due to its geometry. In APPENDIX 3 there

can be seen the drawings of this design.

Figure 18. Option 1 for the spool (in green)

40


Thinking on a different design to solve the manufacturing problems from the previous one, it

has been presented the one shown in Figure 19. In this case, the spool manufacture is a little

more complex, especially because of its shape. As one can see, the conical head of the bolt is

the only element housed in the boundary structure and it avoids the bolt to get away

downwards. To hold the spool on the other direction, a nut is placed right after the boundary

structure. For this reason, a thread is created the way you can see in Figure 19. If necessary,

the nut could be soldered to the boundary structure for a permanent union. Similarly to the

previous design, the hole of the spool has a diameter 2 mm larger than the pressure ports one

for the same reason. APPENDIX 3 shows the geometric characteristics for this design.

Figure 19. Option 2

41


The last of the three preliminary designs, shown in Figure 20, is a mix between the previous

ones. On one hand, it is really optimized in size, due to almost the entire spool remains inside

the boundary structure and the manufacture seems to be the simplest one. On the other hand,

the idea of a thread has been also implemented in this case, but now it connects the metallic

structure with the spool. Again, in order to avoid possible obstructions, the diameter of the

hole is two times the one drilled for the pressure taps. In addition, a new section is added to

the head of the spool, which is housed inside the TPS. This will ensure a perfect connection of

the spool with the pressure ports from the TPS and it will help avoiding relative displacements

between the boundary structure and the thermal shield. The only problem for this design

could be to perfectly suit the spool inside the bonding structure. There is not a solid position

for this element, so the engineers must be really carefully during the assembly. For this reason,

solder could be required. Consult APPENDIX 3 for detailed drawings of this design.

Figure 20. Option 3

42

3.2.4.3.2.4.3.2.4.3.2.4. SpoolSpoolSpoolSpool final design final design final design final design

The design chosen for the preliminary tests in Plasmatron is shown in Figure 21. It can be seen

as the fusion of all three preliminary designs. Firstly, it has been chosen the design from option

one for the body of the spool, which means this element has only one position once suited to

the TPS boundary structure. It helps avoiding problems during assembly. Secondly, it has been

decided to use almost the same kind of thread as the one from option 2. The only difference is

that it has been introduced an improvement due to the new design: the spool will be threaded

with the TPS boundary structure, giving more solidity to the system. Additionally, it will be

included a nut to the design giving two main advantages:

- The configuration allows the assembly and disassembly of the spool if required.

- It is a flexible design considering that the thickness of the TPS boundary structure

could change due to weight or size constraints.

In addition, the nut can be soldered either to the boundary structure or to the thread in order

to ensure both bodies will not separate from each other because of vibrations or other in-flight

forces. For the design of the spool, the VKI engineers will take advantage from the facilities

available there, which allow them to manufacture any kind of shape, regardless of whether or

not it is a commercialized and normalized design. Due to the size of this component, that’s to

say low weight, it has been decided to use stainless steel as a material because of its

mechanical properties such as its high corrosion resistance or its high ultimate tensile strength

(860 MPa versus 400 Mpa for structural steel). Furthermore, see in Figure 21 that the threaded

section of the spool is long enough to allow a proper plastic tube connection to the pressure

transducer. Note that this length can be changed whenever necessary, depending on how

deep the plastic tube needs to be connected.

Figure 21. Spool final design

43

Finally, it has been implemented the idea of including a new upper section to the spool to

connect with the TPS. As commented in 3.2.3.3, it allows an improved assembly between the

TPS and its boundary structure, ensuring a proper air flow throughout the pressure ports.

However, this is a preliminary design for the tests of XPL02, so in the end size can suffer some

changes, even though based on the same idea.

For a better understanding of the whole configuration and the final spool design, the assembly

and final drawings are included in Figure 22 and Figure 23, respectively. Note that for an ISO

metric 6 thread (M6), the pitch must be 1 mm and that the nut designed has a thickness of 3

mm. Taking into account this component will not be subjected to high stresses, these sizes

should be enough. However, remember soldering can be applied to the nut if necessary.

Figure 22. Final assembly between the spool (green) and the nut (purple)

Figure 23. On the left, front and top drawings of the nut; on the right, front and top drawings of the bolt

44

4.4.4.4. XPL03XPL03XPL03XPL03

4.1.4.1.4.1.4.1. Data acquData acquData acquData acquisition system designisition system designisition system designisition system design

4.1.1.4.1.1.4.1.1.4.1.1. Stating the problem and designing the payload objectivesStating the problem and designing the payload objectivesStating the problem and designing the payload objectivesStating the problem and designing the payload objectives

In-flight, QARMAN will be experiencing forces such as gravity, drag or lift that might disturb the

CubeSat from its normal flight path. These attitude changes must be controlled near real time,

checking the orbit is the expected one. For this purpose, components such as sun sensors,

accelerometers and gyroscopes are suited to the CubeSat (see section 2.1 for further

information). This instrumentation will provide basic stability and control instrumentation such

as angular rates, normal and lateral accelerations and pitch and roll attitudes. Additionally, the

set of aerothermodynamic payload for QARMAN will include the XPL03. This one will be

formed by two pressure sensors, aiming to determine the stability of QARMAN during Phase 2

and Phase 3 of the mission. Such as it has been explained in section 1.1, these phases

correspond to a range of altitude from 330 km to about 50 km.

Unlike XPL02, it has been decided that one of the pressure sensors from XPL03 will be working

in differential mode, and the other one in absolute mode. It means that there is going to be

three pressure ports located somewhere in the side panels of QARMAN, at or near the nose of

the vehicle. Differential pressure will be measured in the horizontal or vertical axes, relative to

the CubeSat. The pressure differential is used together with the dynamic pressure to

determine the angle of attack and/or sideslip of the aircraft. For this reason, it is going to be

really important to share data obtained with this payload to total pressure values obtained

from XPL02, which is formed by two absolute pressure sensors. On the other hand, the sensor

measuring absolute pressure will give static pressure measurements to QARMAN, generating

important data to meet more scientific objectives.

Now, taking into account the main requirements for XPL03, which can be consulted in

APPENDIX 1, the list of scientific objectives is developed for this payload:

1. Differential pressure measurements

2. Static pressure measurements

3. Number of Mach

4. Angle of attack or angle of sideslip of QARMAN

5. Local air flow density

6. CubeSat velocity

45

4.1.2.4.1.2.4.1.2.4.1.2. Subject tradesSubject tradesSubject tradesSubject trades

For XPL03 the subject under study is going to be the pressure. Even though this payload is

going to be virtually connected to other payload to meet new scientific objectives, the aim for

these 2 pressure sensors is clear and simple: measure in-flight differential and absolute

pressure. In order to fulfill the scientific objectives already chosen, the rebuilding of each one

of them is as follows:

• For the scientific objective 1, the differential pressure is directly the data acquired with

the sensor measuring in differential mode.

• The scientific objective 2 will work the same way than the pressure sensors from

XPL02, but due to the location of this payload, measurements will be giving static

pressure data.

• To meet scientific objective 3, it will be required to share static pressure values from

this payload with the total pressure values from XPL02. This way, dynamic pressure

will be obtained allowing the calculation of the Mach number by means of the

following relation:

� =*2· �� · +,

Where for early tests the specific heat (γ) value will be 1.4; ps, is going to be the static

pressure; q, the dynamic pressure and, M, the Mach number.

• Scientific objective number 4 can be either the computation of the angle of attack

(AoA) or the sideslip angle (β) by means of data acquired with pressure sensor

measuring in differential mode. This objective will be finally defined in further

documents, but it will basically depend on the location of the pressure ports taking

into account the regions where QARMAN is less crowded. For this reason, according to

this location, data acquired will allow to compute the angle of attack, if pressure ports

are in the top and bottom panels, or the sideslip angle, if pressure ports are located in

the side panels of the CubeSat. In any case, the relation for the computation of this

parameter will be the same:

-.- = / =∆��

Where ∆Ps is the differential pressure and, q, is the dynamic pressure.

• To fulfill scientific objective 5, the ideal gas law will be used, assuming the air flow as

an ideal gas. This way, with values of static pressure (ps) from XPL03 and its local

absolute temperature (T) of thermocouples from XPL05, the air flow density can be

calculated:

�� = 1 · � · 2

46

Where R is called the gas constant and it is equal to 8.314. J·mol-1·K-1.

• For scientific objective 6, the Mach number calculated is required. Then, taking the

absolute temperature (T) data from thermocouples of XPL05, the speed of sound (a)

can be calculated, allowing to obtain the velocity (V) of the CubeSat. The expression

used is shown as follows:

+ =�

3* · � · 2

Where R is called the gas constant and it is equal to 8.314. J·mol-1·K-1; and γ, is the

specific heat ratio and it will be equal to 1.4.

4.1.3.4.1.3.4.1.3.4.1.3. Pressure ports and pressure sensors housingPressure ports and pressure sensors housingPressure ports and pressure sensors housingPressure ports and pressure sensors housing

On one hand, the differential pressure sensor measuring either the angle of attack or the

sideslip angle is normally located with pressure ports diametrically opposite from each other.

For this purpose, they need to be connected to the pressure transducer housed in the

CubeSat. In order to equalize pressure losses, the sensor should be located at the same

distance from both side panels, that’s to say, somewhere in the symmetry axis of QARMAN. In

addition, both pressure ports need to be at the same distance from the CubeSat forward tip, in

order to ensure zero pressure difference at zero flow angle for an ideal case. In further studies,

once their location is more restricted, pressure losses depending on the pipe bendings, lengths

and widths can be calculated in the laboratories. As the flow angle increases or decreases from

zero, the differential pressures sensed between these ports will change and this measured

difference is going to be used to determine the required angle.

On the other hand, pressure port for the measurement of the absolute pressure needs to be

drilled exactly perpendicular to the airflow stream to properly measure the static pressure

required. Due to the square cross-section of QARMAN, the pressure port for this payload can

be located anywhere in the side panels. Ideally, QARMAN should have an attitude of 0º of

angle of attack, but it will not be possible in real flight, so the quality of the static pressure

measurements will be subjected to the attitude control subsystem.

At this point of the XPL03 design, the preliminary design for the location of the pressure ports

and the housing of the pressure sensors cannot be done yet. Therefore, it is required to

perform the same CFD’s as the ones obtained for XPL02, but also considering the side panels of

QARMAN. For this reason, this project will not cover the housing configuration for XPL03.

However, in Figure 24 there can be seen the base for the sensor housing and pressure ports

configuration of this payload.

47

Figure 24. General housing configuration for XPL03

4.1.4.4.1.4.4.1.4.4.1.4. Performance thresholdsPerformance thresholdsPerformance thresholdsPerformance thresholds

Similar to XPL02, this payload will be formed by two pressure sensors, but in this case one will

be measuring in absolute pressure and the other one in differential pressure. In Table 14 it is

shown the requirements established for this payload. As you can see, it is foreseen to have a

total mass of 0.06 kg, which is the same than the one for XPL02. The energy consumption for

XPL03 shall be 840 mW·h/sensor at maximum, a value much greater than the 4.16

mW·h/sensor for XPL02, and being the second payload in consumption after the spectrometer.

However, as seen in Table 14, the total acquisition duration of 336 hours is also higher than

the 0.16 hours of XPL02 (even though during Phase 2 power supply will be covered by solar

panels), due to the fact it will be switched on during Phase 2. Remember that Phase 2 goes

from an altitude of 330 km to 120 km, significantly increasing the acquisition time available

respect to Phase 3. For this reason, acquisition frequency can be set to 0.1 Hz, ten times lower

than the 1 Hz defined for XPL02.

Investigated challenge TPS & environment

Parameter to measure Absolute and differential

pressure

Sensor 2 x Pressure sensor

Total mass [kg] (sensor + wiring +

housing) 0.060

Energy consumption/ Piece [mW·h] 840

Data size/ measurement [bit] 10

Phase 2

Total data size [kB/ phase] 302.4

Acquisition frequency [Hz] 0.1

Number of measurements 120960

Total acquisition duration [h] 336

Response time [ms] 0.1

Power [W/piece] 0.250 Table 14. Performance thresholds for XPL03

48

4.1.5.4.1.5.4.1.5.4.1.5. Measurement chain and final configurationMeasurement chain and final configurationMeasurement chain and final configurationMeasurement chain and final configuration

As it has been explained throughout this section, XPL03 will be formed by two pressure

sensors. One of them will be measuring in absolute pressure, thus it will have exactly the same

measurement chain as the one defined for XPL02. The other sensor will work in differential

mode, comparing pressure between two different pressure ports drilled in the side panels.

However, this is going to be the only difference respect to previous payload, so the signal

conditioning will have the same requirements:

• Sensor output voltage amplification.

• It shall include a low pass filter.

• Offset correction.

• Multiplexing the output with other payload output signals to reduce weight and size.

• Analog-to-digital data conversion.

This way, taking previous payload design experience, the final measurement chain

configuration for testing this payload will be exactly the same as Version B from XPL02. In

Table 15 there are listed the most important characteristics of the system. It should be noted

that the theoretical maximum pressure error should be less than 442 Pa and that after testing

the circuit on a breadboard with an oscilloscope, the introduction of a filter into the circuit has

been dismissed due to the low outputting noise. In addition, the microcontroller incorporates

an analog-to-digital converter, so this component is going to be in charge of the data

conversion and it will also incorporate the software to command this payload. It is also

important to notice that maximum input voltage for the microcontroller is 3.3 V, this needs to

be taken into account especially during the testing of XPL03, which are widely described in the

following section.

The detailed configuration and pin connection can be seen in Figure 25. All components

forming the measurement chain are there defined. Current supply for the pressure sensor will

be controlled with the amplifier inside the blue box, which is going to be connected to the

pressure sensor, inside the green box. Finally, the output signal from the sensor is sent the

instrumental amplifier, whose output is the input of the ADC housed in the microcontroller.

Figure 25. XPL03 configuration and pin connection

49

NPC-1220-005A-3-S

PRESSURE SENSOR

Measurement type Absolute pressure


Pressure Range [kPa] 0 to 34

Pressure Error [kPa] 0.442

Output Voltage Range [mV] 0 to 50

Output Voltage Error [mV] 0.65

Zero Pressure Output [mV] 2

AD8226


Gain [dB] 60 (adjustable)

Output Voltage [V] 3

Output Voltage error [mV] 39

Operating temperature [ºC] -40 to 125

MSP430F5438A

(microcontroller)

Component series MSP430

Supply Voltage [V] 5

ADC integrated Yes

Kilo-samples per second 200

Channels available 12

Resolution [bit] 12

Memory type Flash

Temperature operating range [ºC] -40 to 85

Maximum input voltage [V] 3.3

Voltage resolution [mV] 0.73

Pressure resolution [Pa] 8.3

Max. Error in pressure [kPa] 0.442

Table 15. Final measurement chain for XPL03

50

4.2.4.2.4.2.4.2. Ground Testing methodology anGround Testing methodology anGround Testing methodology anGround Testing methodology and Extrapolation to Flightd Extrapolation to Flightd Extrapolation to Flightd Extrapolation to Flight

4.2.1.4.2.1.4.2.1.4.2.1. Motivation and requirementsMotivation and requirementsMotivation and requirementsMotivation and requirements

The goal of the pressure sensors located in the side panels is to measure the static and

differential pressure during atmospheric re-entry. As seen in section 3.1.6, it has been

proposed two different configurations for the data acquisition system of XPL02. However, it

has been decided to implement only Version B for the preliminary design of both

measurement chains. In this section there is going to be tested the differential pressure sensor

from XPL03, which was the only pressure sensor available when ordering. The system will be

tested at the VKI facilities and thus, it will be possible to make some corrections on their

calibration, if required. By the end of these tests, the whole measurement chain for the

differential pressure sensor from XPL03 will be validated, making the necessary changes and

adjustments to fulfill the requirements.

In order to reproduce near vacuum pressure conditions it is foreseen to use the Induction-

Coupled Plasma Minitorch. The facility operates in a range of pressure from 3 kPa to 100 kPa,

which is enough for the pressure sensors that are able to work from 0 to 34 kPa. This way,

note that tests will be covering the 91.2% of the sensors operating range. All differential

pressures will be sampled at a rate of 1 Hz as specified in the requirements. During tests, a

mercury manometer will be used to check pressure differentials inside the vacuum chamber,

taking those values as reference, in order to compare them against the acquired ones with the

DAQS of XPL03. With these results, a calibration of the system will be performed by modifying

either the circuitry or the software. In addition, it must be ensured the electromagnetic field

generated by the facility does not affect the data acquisition. For this reason, it will be

required some kind of protection for testing, which is going to be an aluminum foil.

These tests also aims to generate valuable data for the absolute pressure sensors calibration

included in XPL02 and XPL03. By the end of this section, it will be possible to check the real

specifications of the entire system, comparing them to the expected ones. Even though it is

out of scope, it is expected to test this payload in Plasmatron, a facility able to simulate near

real re-entry conditions. Some of the characteristics of the facilities used for the testing of

XPL03 are defined in the following section.

4.2.2.4.2.2.4.2.2.4.2.2. Facilities and main testing componentsFacilities and main testing componentsFacilities and main testing componentsFacilities and main testing components

• INDUCTION-COUPLED PLASMA MINITORCH

It is a high enthalpy facility able to generate a vertical jet of plasma in a tube shaped chamber

of 0.3 m of diameter and 1.2 m long. The facility, shown in Figure 26, is able to work in a range

of pressure from 30 mbar to atmospheric. The plasma is generated by electrical induction

inside a 3 cm diameter not refrigerated quartz tube, with a power consumption of 15 kW. In

addition, a recirculating water system is used to protect the test chamber from plasma

51

heating, as well as to cool the gas extracted from the test chamber by a 190 m3/h vacuum

pump. The system operates normally in the subsonic regime, but by addition of a cooled Laval

nozzle a supersonic plasma jet at Mach 2.2 can be obtained. Argon, nitrogen, carbon dioxide,

air or other gas mixtures can be used to

generate the plasma.

The instrumentation includes cooled

pressure and heat flux probes, Langmuir

probes, and a laser Doppler velocimeter.

One important advantage is that Minitorch

can use some of the Plasmatron

instrumentation, such as the emission

spectrometer and the two-color pyrometer.

Even though for the current test the facility

is going to be used as a vacuum chamber, it

can also be used for inductively coupled

plasma torch optimization studies or for

comparisons with numerical simulations of

inductively coupled plasma flows.

• PLASMATRON

The Plasmatron, shown in Figure 27, is a high enthalpy facility in which a jet of plasma is

generated in a test chamber kept at sub-atmospheric pressure (between 5 and 200 mbar). The

plasma is generated by heating a gas (argon, N2 , CO2, air or any other gas mixture) to

temperatures up to about 10000 K, using electrical current loops induced inside a plasma

torch. Its Plasma generator offers much better plasma purity compared to classical arcjets, as

there is no pollution from any

vaporized electrode material.

The facility, which is the most

powerful induction-coupled plasma

wind tunnel in the world, has a

power consumption of 1.2 MW. The

plasma generator feeds the single-

turn inductor of an 80 mm or 160

mm diameter plasma torch, which is

mounted on a 1.4 m diameter, 2.5 m

long, water-cooled test chamber.

Hot gas from the test chamber exits

through a group of three rotary-vane

Figure 26. Induction-Coupled Plasma Minitorch

Figure 27. Plasmatron from Von Karman Institute

52

vacuum pumps and a Roots pump, which are capable of extracting 3900 m3/h, with a terminal

vacuum capability of 0.04 mbar.

A 1050 kW cooling system using a closed loop deionized water circuit (2090 litres/min) and

fan-driven air coolers provide cooling to all facility components. Plasmatron is controlled using

two PC's for controlling and monitoring operations. Available instrumentation includes

intrusive cooled pressure and heat flux probes, a one-meter emission spectrometer with CCD

camera and a two-color pyrometer.

• MERCURY MANOMETER

This device uses liquid mercury to

measure the differential pressure

between two points. Particularly, the

manometer from Von Karman Institute

illustrated in Figure 28 has a

measurable span of 700 mmHg and a

pressure resolution of ±0.1 mmHg.

During the testing one pressure tap will

be directly connected to the vacuum

chamber and the other one will be let

free measuring the atmospheric

pressure.

• ELECTROMAGNETIC FIELD PROTECTION

As it has been commented before, the

data acquisition system of XPL03 is going

to be installed near the vacuum chamber

during the testing. For this reason, it has

been decided to place an aluminum foil

between the facility and the circuitry in

order to avoid electromagnetic related

problems as shown in Figure 29.

Figure 28. Mercury manometer

Figure 29. Electromagnetic field protection

53

• DIGITAL ATMOSPHERIC PRESSURE SENSOR

Before starting the tests and right after they have finished, atmospheric pressure has been

noted in order to identify possible variations. The device has a resolution of ±0.1 Pascal and is

illustrated in Figure 30.

Figure 30. Digital atmospheric pressure sensor

• MERCURY THERMOMETER

The same way as atmospheric pressure, atmospheric temperature has been noted before

starting the tests and once they have been finished. It has been used a mercury thermometer

with a resolution of ±0.1ºC and it has been placed next to the measurement chain of XPL03.

• DATA ACQUISITION SYSTEM

The measurement chain for the differential pressure sensor of XPL03 has been implemented

on a breadboard, as you can see in Figure 31. All components are properly connected between

them to meet the configuration of Version B. As you can see, one of the pressure ports was let

free to the atmospheric pressure and the other one, with the transparent silicon tube, has

been directly connected to the vacuum chamber. All data generated by this circuit has been

sent to a laptop incorporating the required software.

Figure 31. DAQS of the differential pressure sensor of XPL03

54

• MULTIMETER

This device is going to be used to get voltage data connecting it to different points of the

circuit in order to check everything is going well during tests. In addition, it will be collected

the voltage outputs from the instrumental amplifier to compare them to the values gathered

with the laptop and identify possible errors in the system.

4.2.3.4.2.3.4.2.3.4.2.3. TesTesTesTest matrixt matrixt matrixt matrix

It has been intended to perform as many tests as possible to include them in this thesis. At

each one of them, differential pressures have been introduced to the measurement chain

expecting to get realistic values for parameters like accuracy, linearity, hysteresis or

repeatability. For this reason, pressure inside the vacuum chamber has been increased and

decreased at least two times in each test. Note from that for each differential pressure, the

measurement chain is going to collect 50 times the same value (ideally) in one second during 9

seconds. It means that for each pressure generated there is going to be 450 values, hence a

data acquisition frequency of 50 Hz. Electronic technicians have decided to proceed this way in

order to get a more reliable output value from the measurement chain. Vacuum chamber

pressure is going to be calculated with the difference between measured atmospheric

pressure and the differential pressure generated (Patm - ∆P). Main elements for the testing

matrix are shown in Table 16, but specific test matrixes obtained for each test are defined in

APPENDIX 4: Detailed test matrixes.

On the other hand, multimeter is going to be used to measure the following voltage values:

• Supplied voltages to the OP-AMP and the IN-AMP.

• Pressure sensor Pin-2 voltage

• Pressure sensor Pin-4 voltage

• Pressure sensor output voltage

• IN-AMP output voltage

Table 16. Test matrix

Test

Name

Differential

pressure [mmHg]

Number of

measurements

Data Acquisition

Frequency [Hz]

Vacuum chamber

pressure [kPa]

0 0 9x50 50 Patm - ∆P

1 . 9x50 50 Patm - ∆P

. . 9x50 50 Patm - ∆P

. n-1 9x50 50 Patm - ∆P

. n 9x50 50 Patm - ∆P

. n-1 9x50 50 Patm - ∆P

. . 9x50 50 Patm - ∆P

N 0 9x50 50 Patm - ∆P

55

4.2.4.4.2.4.4.2.4.4.2.4. Test procedureTest procedureTest procedureTest procedure

Step Description

1 Note the atmospheric pressure of the laboratory using the digital manometer.

2 Note the room temperature before starting the test with the mercury thermometer

available in the laboratory.

3

Set the mercury manometer to zero before connecting it to the vacuum chamber,

taking into account that atmospheric pressure changes from one day to the other

and it can cause some deviations to the device.

4 Connect the mercury manometer to the pressure port number 2 located on the

bottom of the vacuum chamber (see Figure 32).

5

Connect QARMAN’s pressure measurement chain to pressure port number 1 located

on the bottom of the vacuum chamber (see Figure 32). Also connect the chain to the

laptop with the data acquisition software.

6

Switch on the buttons V1, V2, C1 and PV (regardless of the sequence followed)

located in the control panel of the laboratory (Figure 32). Wait around 20 minutes

until the system warms up and stabilizes.

7 Ensure that valves A, B and E are opened and C and D are closed in order to create

vacuum into the vacuum chamber (see Figure 33 and Figure 34).

8 Check for any pressure loss in the vacuum chamber pressure ports and correct them.

9 Open valve D and valve C to create a zero pressure difference with the atmosphere

(first test matrix value) and acquire values with the laptop and the voltimeter.

10 Use the mercury manometer to verify the measured differential pressure never

exceeds 34 kPa (or 255 mmHg).

11

Regulate valve C in order to reach the differential pressure corresponding to the

second point of the test matrix. This valve will be controlled and held manually, it

means this is going to be the main oscillations source.

12 Wait around 5 seconds to stabilize the pressure inside the vacuum chamber.

13 Start data acquisition at 50 Hz with the pressure measurement chain connected to

the laptop and save the values.

14 Once step 13 is completed, use the multimeter to check the 5V voltage supply of the

Operational amplifier and the IN-AMP.

15 Use the multimeter to measure the pressure sensor voltage of Pin-2 (see Table 18)

16 Use the multimeter to measure the input voltage of the pressure sensor, which

corresponds to Pin-4 (see Table 18).

17 Use the multimeter to measure the output voltage of the pressure sensor, which

corresponds to the voltage difference between Pin-1 and Pin-3 (see Table 188).

18 Use the multimeter to measure the output voltage of the IN-AMP.

19 Repeat steps from 11 to 18 in order to measure all differential pressure data defined

in the test matrix.

Table 17. Test procedure

56

For a better understanding of the testing procedure in the laboratory, pictures shown in Figure

32, Figure 33 and Figure 34 have been taken describing the different elements participating

during the process. See Table 17 for a detailed description of the role of them.

Figure 32. On the left, vacuum chamber pressure ports; on the right, vacuum chamber control panel

Figure 33. Valve A and B of the vacuum chamber

Figure 34. Valves C, D and E of the vacuum chamber

57

4.2.5.4.2.5.4.2.5.4.2.5. The testingThe testingThe testingThe testing circuit circuit circuit circuit aaaand pin connectionnd pin connectionnd pin connectionnd pin connection

NPC 1220 pressure sensor will be used in the design. Since the output of the sensor is quite

low, an amplifier circuitry must be connected to the output of the sensor. AD8226

instrumental amplifier has been chosen for this purpose. The scheme of the application for the

pressure sensor is shown in Figure 35.

Figure 35. Pressure sensor basic circuit scheme [9]

The region in dotted line is the internal equivalent circuit of the pressure sensor advised in the

datasheet. The component marked A1 (in the green box) is an Operational Amplifier (OP-AMP)

which is used as a current source. On the other hand, LMP7718 has two OP-AMPs inside each

one of them used as current source and reference voltage generator, explained later. The red

box is a buffer stage. Although the OP-AMP (in the green box) has been used for the testing

circuitry, this buffer stage was dismissed for Version B and replaced by the instrumental

amplifier AD8226. Since test circuit topology is different than the suggested topology, gain

calculations will be made differently (explained in Test 1 from section 4.2.6.1).

AD8226 is suitable for bridge type sensor signal conditioning. LMP7718 is a dual OP-AMP

which includes two identical and separated operational amplifiers. One of them has been used

for supplying constant current to the sensor and the other one for the reference voltage

generation for the IN-AMP.

At this point, pin connections for all three components forming the circuit are presented in

detail in Table 188, Table 19 and Table 20.

58

DESCRIPTION CONNECTION

PIN-1 NEGATIVE OUTPUT OF THE SENSOR

(OUTPUT -) TO + OR - INPUT OF THE IN-AMP

PIN-2 NEGATIVE SUPPLY PIN OF THE SENSOR

(SUPPLY-) TO THE PIN-6 (SENSOR) AND PIN-

2(OPAMP)

PIN-3 POSITIVE OUTPUT OF THE SENSOR

(OUTPUT +) TO + OR - INPUT OF THE IN-AMP

PIN-4 POSITIVE SUPPLY PIN OF THE SENSOR

(SUPPLY +) TO THE CURRENT SOURCE OPAMP

OUTPUT

PIN-5 INTERNAL CURRENT SET RESISTOR TO THE GROUND

PIN-6 INTERNAL CURRENT SET RESISTOR TO THE PIN-2

PIN-7 NOT CONNECTED FACTORY TEST POINTS

PIN-8 NOT CONNECTED FACTORY TEST POINTS Table 18. Pin description and connection for pressure sensor


PIN-1 NEGATIVE INPUT OF THE IN-AMP TO + OR - OUTPUT OF THE PRESSURE SENSOR

PIN-2 CONNECTION FOR GAIN SET RESISTOR TO Rg

PIN-3 CONNECTION FOR GAIN SET RESISTOR TO Rg

PIN-4 POSITIVE INPUT OF THE IN-AMP TO + OR - OUTPUT OF THE PRESSURE SENSOR

PIN-5 NEGATIVE SUPPLY PIN TO THE GROUND

PIN-6 REFERENCE PIN TO REFERENCE VOLTAGE SUPPLY

PIN-7 OUTPUT OF THE IN-AMP TO THE MICROCONTROLLER

PIN-8 POSITIVE SUPPLY PIN TO THE Vcc(5V) Table 19. Pin description and connection for AD8226


PIN-1 OUTPUT OF THE OPAMP-1 POSITIVE SUPPLY PIN OF THE SENSOR (SUPPLY +)

PIN-2 NEGATIVE INPUT OF THE OPAMP-1 NEGATIVE SUPPLY PIN OF THE SENSOR (SUPPLY-)

PIN-3 POSITIVE INPUT OF THE OPAMP-1 TO 1.2V REFERENCE VOLTAGE

PIN-4 NEGATIVE SUPPLY PIN TO THE GROUND

PIN-5 POSITIVE INPUT OF THE OPAMP-2 TO IN-AMP REFERENCE VOLTAGE (1.65V)

PIN-6 NEGATIVE INPUT OF THE OPAMP-2 TO THE OUTPUT OF THE OPAMP-2

PIN-7 OUTPUT OF THE OPAMP-2 TO THE REFERENCE PIN OF THE IN-AMP(PIN-6)

PIN-8 POSITIVE SUPPLY PIN TO THE Vcc(5V) Table 20. Pin description and connection for LMP7718

• CURRENT SOURCE CIRCUITRY

NCP1220 pressure sensor requires constant current to operate. For this reason, it has an

internally current set resistor to create constant current (see

current to the sensor, a current source circuit must be built. This can be done by using one OP

AMP and a reference voltage source. The current set resistor is placed between negative input

of the OP-AMP and the ground. Since OP

input voltage is equal to the V

bridge circuit is determined as V

source.

The current set resistor value has

that sensor needs 1,2V/1436 = 0,83µA to operate. Datasheet suggest using 1.235V for the

current source OP-AMP. There is no proper power source in the lab for this purpose, so the

voltage output of the microcontroller (4,876V) and a voltage divider topology have been used

to obtain 1.2V. Configuration is shown in

has been set to 1.2V and the supply voltage at the s

this value would have exceeded 5V, the OP

with more than 5V to work properly. Since satellite platform is able to supply a maximum of

5V, it would have been a problem a

sensor voltage demand is below the supply voltage, so there is no problem to make it work.

Figure

CURRENT SOURCE CIRCUITRY


internally current set resistor to create constant current (see Figure 36). To supply constant

ent to the sensor, a current source circuit must be built. This can be done by using one OP


AMP and the ground. Since OP-AMP operates with negative feedback, the negative

input voltage is equal to the Vref. This means that current value which is passing through the

bridge circuit is determined as Vref/CSR (Current Set Resistor). This structure works as a current

The current set resistor value has been measured as 1,436KΩ by using multimeter. It means


AMP. There is no proper power source in the lab for this purpose, so the

microcontroller (4,876V) and a voltage divider topology have been used

to obtain 1.2V. Configuration is shown in Figure 36. This way, the voltage at the sensor PIN

has been set to 1.2V and the supply voltage at the sensor PIN-4 has been observed as 4.44V. If

this value would have exceeded 5V, the OP-AMP should have been required to be supplied


5V, it would have been a problem and a new voltage supply would have been needed. But


Figure 36. Current source circuit for pressure sensor

59


). To supply constant

ent to the sensor, a current source circuit must be built. This can be done by using one OP-


back, the negative

. This means that current value which is passing through the

/CSR (Current Set Resistor). This structure works as a current

been measured as 1,436KΩ by using multimeter. It means


AMP. There is no proper power source in the lab for this purpose, so the

microcontroller (4,876V) and a voltage divider topology have been used

. This way, the voltage at the sensor PIN-2

4 has been observed as 4.44V. If

AMP should have been required to be supplied


nd a new voltage supply would have been needed. But


4.2.6.4.2.6.4.2.6.4.2.6. Testing resultsTesting resultsTesting resultsTesting results

4.2.6.1.4.2.6.1.4.2.6.1.4.2.6.1. Test 1Test 1Test 1Test 1

The output pins of the sensor (PIN

AMP (PIN-1 and PIN-4). A variable resistor has been used as a gain set resistor. The value of the

resistor was not precisely constant when measuring with the multimeter;

1,436kΩ. Therefore, the gain of the amplifier can be calculated using the relation from the

datasheet, so in this case it has a value of (49400/1436)+1 =35.4. Test circuitry can be seen in

Figure 37.

Using the multimeter it has been checked that around 16mV is the natural output offset of the

IN-AMP when no voltage difference is applied at the input. Since 50mV sensor output

corresponds to 34kPa, 10kPa corresponds to around 16

possible to observe voltage differences under 10kPa of differential pressure. This will be taken

into account to be corrected for Test 2.

The most important result obtained duri

sensor output over 10kPa. See

used to measure the pin voltages specified in section

especially to know the sensor output voltages in order to be able to calculate the gain of the

IN-AMP. Within a 2σ confidence interval the maximum standard deviation is ±0.01760213.

Error bars are represented in the same figure.

output pins of the sensor (PIN-1 and PIN-3) have been connected to the input of the IN

4). A variable resistor has been used as a gain set resistor. The value of the

resistor was not precisely constant when measuring with the multimeter;



Figure 37. Circuit configuration for Test 1


AMP when no voltage difference is applied at the input. Since 50mV sensor output

nds to 34kPa, 10kPa corresponds to around 16-17mV, which means that it is not


into account to be corrected for Test 2.

The most important result obtained during this test is the linear behavior of the pressure

sensor output over 10kPa. See Figure 38. Note that in this test the multimeter has not been

used to measure the pin voltages specified in section 4.2.4. It is of importance to check it,


Within a 2σ confidence interval the maximum standard deviation is ±0.01760213.

Error bars are represented in the same figure.

60

3) have been connected to the input of the IN-

4). A variable resistor has been used as a gain set resistor. The value of the

resistor was not precisely constant when measuring with the multimeter; it was around




AMP when no voltage difference is applied at the input. Since 50mV sensor output

17mV, which means that it is not


ng this test is the linear behavior of the pressure

. Note that in this test the multimeter has not been

. It is of importance to check it,


Within a 2σ confidence interval the maximum standard deviation is ±0.01760213.

61

Figure 38. Differential pressure vs. IN-AMP Output for Test 1

4.2.6.2.4.2.6.2.4.2.6.2.4.2.6.2. Test 2 Test 2 Test 2 Test 2

In this case, the gain set resistor of the IN-AMP has been adjusted to around 1,266kΩ, what

leads to a gain of around 40. It has been done to gather higher voltage values at the output of

the chain. Note that the gain has been specified such a way that the output cannot exceed

3.3V (remember that this is the maximum microcontroller input voltage). Furthermore, in this

test the multimeter has been used to measure the output of the sensor for all differential

pressure values. Test results can be seen in Figure 39 and Figure 40.


0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 10 20 30 40

Ou

tpu

t v

olt

ag

e [

[V]

Differential pressure [kPa]

Increasing 1

Decreasing

Increasing 2

0

0.5

1

1.5

2

2.5

0 5 10 15 20 25 30 35

Ou

tpu

t v

olt

ag

e [

[V]


Increasing 1

Decreasing

Increasing 2

62

Note that the output of the IN-AMP has been increased. From this result, it can be concluded

that there is no problem with the gain (except for precisely adjusting it). However, after data

treatment it has been found that the standard deviation for a 2σ confidence interval is found

to be ±0.04190201 kPa, which is inside the expected margins.

Even though the output of the measurement chain represented over the differential pressure

seems to be linear, the resulting gain evolution during test is observed to be pretty random.

For this reason, there might be some measurement mistakes for this test, because it is not

normal to observe a variable gain while observing a linear behavior of the system output. In

addition, it needs to be commented that during this test it has been observed that output of

the IN-AMP changes when the multimeter probes are connected to the sensor output.

Figure 40. IN-AMP gain for Test 2

0

5

10

15

20

25

30

35

40

45

50

0 5 10 15 20 25 30 35

Ga

in

Differential Pressure [kPa]

Increasing 1

Decreasing

Increasing 2

63


This test has been the most problematic one. Once it started, it has been noticed that acquired

data was wrong, because no output voltage was acquired with the laptop. Thus, test has been

stopped. After thinking about it, it has been finally found that the reason of the problem was

that the silicon tube was connected to a different pressure port of the pressure sensor. For this

reason, it has been noticed that sensor can output positive and negative values. Therefore,

when differential pressure increased, pressure difference was outputted as a negative value.

Since the lowest output value of the IN-AMP is around 0V, all negative voltage inputs to this

component are taken as 0V at the output.

Additionally, when the voltimeter probes have been connected between the positive output of

the sensor and the ground, it has been noticed that the output of the amplifier acquired with

the laptop changed to 3.3V, corresponding to the maximum output value. Therefore, when

voltimeter probes have been connected between the negative output of the sensor and the

ground, output obtained with the laptop has been observed to be around 0V. It could be

caused due to the internal high resistance of the voltmeter changes the input impedance of

the amplifier while sensor is connected. Nevertheless, this effect only occurs when connecting

the voltimeter to the measurement chain, so as long as data acquisition is performed either

before or after the voltimeter data acquisition, no problems on the outputted voltages should

be expected.

Note that for all 6 tests performed throughout this thesis, the problem has not been solved.

However, it is presented a possible solution for further tests: it consists in connecting a

differential capacitor between both IN-AMP inputs. This capacitor would behave like a low

pass filter. Therefore, radio frequency interference (RFI) filter should be considered too, even

though this new implementation is considered out of scope.

This way, it was the most problematic test of all of them, but it was also the most helpful one.

It allowed a better understanding of the behavior of the sensor and the whole measurement

chain. Thus, once corrections according to the information obtained have been made,

successful results can be expected for the rest of tests.


This test was focused to see differential pressure values less than 10 kPa taking into account

the uncovered features of the pressure sensor during Test 3.

measure as close as possible to 0 kPa of difference. The problem in previous tests could be

that the IN-AMP was outputting 0V under 10 kPa because it was not able to detect the really

small voltage outputs from the pressure sen

a reference voltage of 1V to the IN

with the laptop should be ideally 1V.

In order to test this new configuration, silicon tube has been connected

the pressure sensor, so the outputs of the IN

3.3V at maximum.

To apply a reference voltage to the V

topology has been used the same way it has been implemented for the voltage supply of the

pressure sensor.

Even though it is not recommended by the IN

42Figure 39, the output of the amplifier has been observed linear all over the range (0

However, in further tests an OP

that in this case the standard deviation for a 2σ confidence interval has a value of

±0.12492795, much higher than the one from Test 2.


the uncovered features of the pressure sensor during Test 3. Note that it is required to


AMP was outputting 0V under 10 kPa because it was not able to detect the really

small voltage outputs from the pressure sensor. For this reason, it has been decided to supply

a reference voltage of 1V to the IN-AMP, meaning that for 0 sensor output the acquired value

with the laptop should be ideally 1V.

In order to test this new configuration, silicon tube has been connected to the positive input of

the pressure sensor, so the outputs of the IN-AMP should remain somewhere between 1V and

To apply a reference voltage to the Vref pin of the IN-AMP (see Figure 41


Figure 41. Circuit configuration for Test 4

Even though it is not recommended by the IN-AMP datasheet, as you wi

, the output of the amplifier has been observed linear all over the range (0

However, in further tests an OP-AMP will be used for the reference voltage generation. Note


0.12492795, much higher than the one from Test 2.

64


Note that it is required to


AMP was outputting 0V under 10 kPa because it was not able to detect the really

sor. For this reason, it has been decided to supply

AMP, meaning that for 0 sensor output the acquired value

to the positive input of

AMP should remain somewhere between 1V and

41), voltage divider


AMP datasheet, as you will see in Figure

, the output of the amplifier has been observed linear all over the range (0-34kPa).

voltage generation. Note


65


On the other hand, in order to remain under the 3.3V at the microcontroller input, the gain of

the IN-AMP has been reduced compensating the reference voltage just included. Thus, by

modifying the gain set resistor of the IN-AMP the expected gain should be around 27. Note in

Figure 43 that with this new configuration the gain remains almost constant during the test

with all values around the expected gain.


1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

0 10 20 30 40

Ou

tpu

t v

olt

ag

e [

[V]


Increasing

Decreasing

20

22

24

26

28

30

32

34

0 10 20 30 40

Ga

in


Increasing

Decreasing

4.2.6.5.4.2.6.5.4.2.6.5.4.2.6.5. Test Test Test Test 5555

As commented in Test 3, the sensor is sensitive to positive and negative pressure sensors. That

is to say, if pressure from the sensor is changed as +ΔP, output voltage difference would

change +ΔV and, if pressure is changed as

So a reference voltage must be included to the IN

differential pressure range of the sensor. Analog

microcontroller can measure the voltage values up to 3.3V,

the IN-AMP must be kept below this point. For this reason, the circuit has been built such a

way that for a sensor output of

pressure difference will be corresponding

AMP will be outputting +3.3V (see

DESCRIPTION

NEGATIVE MAXIMUM

PRESSURE

DIFFERENCE OUTPUT

PRESSURE

SENSOR

IN-AMP ~0.017VTable 21

In order to obtain this configuration, reference voltage PIN of the IN

the second OP-AMP inside the LMP7718 IC of the testing configuration. Topology can be seen

on Figure 44. The reason of using this configuration is that voltage reference node of the IN

AMP must be driven with very low impe

would be amplified more than the negative input resulting in a bad CMRR (common

rejection ratio) performance. In this case, the output of the OP

impedance.

Figure

5 Note: ~0.017V is the natural zero output of the amplifier (



change +ΔV and, if pressure is changed as –ΔP, output voltage difference would change

So a reference voltage must be included to the IN-AMP in order to measure the entire

differential pressure range of the sensor. Analog-to- digital converter inside the MSP430

microcontroller can measure the voltage values up to 3.3V, so the maximum output voltage of

AMP must be kept below this point. For this reason, the circuit has been built such a

way that for a sensor output of -50mV the output of the IN-AMP is 0V. Furthermore, zero

pressure difference will be corresponding to 1.65V and for a sensor output of +50mV the IN

AMP will be outputting +3.3V (see Table 21).

NEGATIVE MAXIMUM

PRESSURE

DIFFERENCE OUTPUT

ZERO PRESSURE

DIFFERENCE

OUTPUT

POSITIVE MAXIMUM

PRESSURE

DIF

-50mV 0V

~0.017V5 1.65V 21. Pressure sensor and IN-AMP outputs for Test 5

In order to obtain this configuration, reference voltage PIN of the IN-AMP has been driven by

AMP inside the LMP7718 IC of the testing configuration. Topology can be seen

. The reason of using this configuration is that voltage reference node of the IN

AMP must be driven with very low impedance. Otherwise, positive input signal of the IN

would be amplified more than the negative input resulting in a bad CMRR (common

rejection ratio) performance. In this case, the output of the OP-AMP used has very low

Figure 44. Reference voltage generation for Test 5

Note: ~0.017V is the natural zero output of the amplifier (the output offset)

66



ence would change –ΔV.

AMP in order to measure the entire

digital converter inside the MSP430

so the maximum output voltage of

AMP must be kept below this point. For this reason, the circuit has been built such a

AMP is 0V. Furthermore, zero

to 1.65V and for a sensor output of +50mV the IN-

POSITIVE MAXIMUM

PRESSURE

DIFFERENCE

OUTPUT

+50mV

+3.3V

AMP has been driven by

AMP inside the LMP7718 IC of the testing configuration. Topology can be seen

. The reason of using this configuration is that voltage reference node of the IN-

dance. Otherwise, positive input signal of the IN-AMP

would be amplified more than the negative input resulting in a bad CMRR (common-mode

AMP used has very low

For this test, the reference voltage of the instrumental amplifier has been increased to 1.65V.

On the other hand, the gain of the IN

increased respect to Test 4, the input voltage of the microcontroller is still under 3.3V. Note

that in previous tests the acquired voltage with the laptop was below 3V.

During this test, the silicon tube has been connected to both pressure ports of the sensor,

order to obtain values for its entire range. Firstly, the silicon tube has been connected to the

positive port and then to the negative one. Remember that in QARMAN this payload is going

to be working as a differential pressure sensor, hence positive a

acquired depending on the CubeSat attitude. The testing configuration for Test 5 can be seen

in Figure 45.

Results obtained with this configuration are really satisfactory. Linear behavior is observed for

the entire differential pressure range (see

expected behavior. This is because du

were missed. In this test the standard deviation for a 2σ confidence interval has a value of

±0.109628386, lower than the previous values, what means that calibration of the

measurement chain is improv


On the other hand, the gain of the IN-AMP has been set to 32.6. Even though both values have

sed respect to Test 4, the input voltage of the microcontroller is still under 3.3V. Note

that in previous tests the acquired voltage with the laptop was below 3V.

During this test, the silicon tube has been connected to both pressure ports of the sensor,



to be working as a differential pressure sensor, hence positive and negative outputs can be


Figure 45. Test configuration for Test 5

ed with this configuration are really satisfactory. Linear behavior is observed for

the entire differential pressure range (see Figure 46). However, there are few values out of the

expected behavior. This is because during data acquisition with the laptop two measurements


0.109628386, lower than the previous values, what means that calibration of the

measurement chain is improving.

67


AMP has been set to 32.6. Even though both values have

sed respect to Test 4, the input voltage of the microcontroller is still under 3.3V. Note

During this test, the silicon tube has been connected to both pressure ports of the sensor, in



nd negative outputs can be


ed with this configuration are really satisfactory. Linear behavior is observed for

). However, there are few values out of the

ring data acquisition with the laptop two measurements


0.109628386, lower than the previous values, what means that calibration of the

68


Finally, as you can see in Figure 47, the gain obtained is also constant. There are some points

which do not fit perfectly to the line, but this is because differential pressure inside the

vacuum chamber was controlled manually and near zero values it is hard to remain it constant.

To improve the test, more measurements should be taken at low pressure values. However,

note that the gain stays around the expected 32.6.


0

0.5

1

1.5

2

2.5

3

3.5

-40 -30 -20 -10 0 10 20 30 40

Ou

tpu

t v

olt

ag

e [

[V]


Increasing +

Decreasing +

Increasing -

Decreasing -

25

27

29

31

33

35

37

39

-40 -20 0 20 40

Ga

in


Increasing positive

Decreasing positive

Decreasing negative

Increasing negative

69


Unlike Test 5, for this test the silicon tube has been connected firstly to the negative pressure

port of the pressure sensor. For this reason, data represented in Figure 48 is symmetrically

opposite to the one represented in Figure 46 from previous test.

In this case, the gain has been set to 30.2 in order to see if the pressure sensor is able to work

properly over 35 kPa, maintaining the linear behavior. For this reason, constant resistors have

been used to fix the gain set resistor to 1690 Ω. Ideally, it would be good to have one constant

resistor, but due to the value required, it is necessary to use a combination of commercialized

ones.

As shown in Figure 48, linear behavior is observed for the output of the measurement chain,

even applying near 40 kPa of differential pressure. However, note that Increasing- values from

the figure do not fit perfectly to the line. This is because during data acquisition of this range a

couple of measurements have been missed, producing a wrong combination between the

output voltage acquired and the differential pressure. In addition, note that the standard

deviation for a 2σ confidence interval has a value of ±0.02069516 kPa for this test, which

corresponds to the lowest standard deviation acquired so far.


0

0.5

1

1.5

2

2.5

3

3.5

-40 -20 0 20 40 60

Ou

tpu

t v

olt

ag

e [

[V]


Increasing -

Decreasing -

Increasing +

Decreasing +

70

Finally, Figure 49 shows the evolution of the gain obtained for Test 6. Notice that it remains

almost constant for all range. Again, differential pressure values in the vacuum chamber

around 0 kPa are hard to remain constant, that’s why in this region gain values are out of the

constant line. However, it can be stated that the pressure sensor is able to measure differential

pressures from 0 kPa to at least 40 kPa, preserving its good performances.


27

28

29

30

31

32

33

34

35

-50 -30 -10 10 30 50

Ga

in


Increasing positive

Decreasing positive

Decreasing negative

Increasing negative

71

5.5.5.5. ConclusionsConclusionsConclusionsConclusions

This thesis started with the main purpose to give a preliminary design for the data acquisition

system of XPL02 and XPL03 fitted in QARMAN. It has been described the present situation of

the CubeSat, explaining decisions already made on the different subsystems as well as giving

its preliminary configuration with updated budgets of mass, power and data. Considering

these aspects, it has been possible to develop a proper design for both payloads.

On the one hand, XPL02 design can be seen as the starting point for all pressure related

payload of the spacecraft. This way, with the market survey performed it has been proposed a

preliminary configuration taking into account the main theoretical requirements for this kind

of payload. However, sharing this information with electronic professional staff from VKI some

changes have been carried out on the measurement chain, applying the previous information

in a more practical way that is beyond the scope of a student. Hence, it can be stated that

work in group has been crucial for the success of this work. Therefore, all ideas together have

ended up in one final version for the testing of this payload in further studies, so fulfilling the

objectives presented in the beginning.

In addition, the housing configuration for XPL02 has been developed considering all the way

from the pressure ports located in the TPS until the pressure transducers located in the DAQS

card. For this reason, the position of both pressure taps have been carefully defined and sized,

according to the valuable data acquired from the CFDs developed at the critical altitudes of the

mission. Moreover, throughout this work it has been designed a spool, which is the

component that will ensure a proper connection between the incoming atmospheric flow from

the TPS ports and the tube that will send it to the pressure transducer. Again, after sharing

different options with QARMAN team, a final design for this component has been decided.

On the other hand, the data acquisition system for XPL03 has been considered to be the same

as the one for XPL02 since both are the pressure related sensors. Due to the low operating

pressure range of these payloads (between vacuum and 20kPa), it is very important the

calibration tasks performed in ground facilities. Actually, the scheduled time for the

development of this thesis has been prolonged in order to include some of the testing results.

This way, the calibration process for the measurement chain of the differential pressure sensor

for XPL03 has been presented throughout this thesis. Therefore, it has been a rewarding

opportunity to see how real life is when applying theory at the laboratory. Problems always

pass through this kind of work modifying not only the expected timetable, but also the

procedure. However, it can be conclude there has been an evolution from one test to the

other, even though all of them were performed in less than one week.

Thus, regardless of human errors, circuitry related problems have been present in every single

test. Basically, they were based on an uncompleted understanding of some components

performances, such as the pressure sensor. But as you have seen in the report, everything

ended up with a really good calibration of the data acquisition system for this payload. For

example, consider that in the preliminary measurement chain design based on datasheets

information it was expected pressure errors around ±400Pa. In the end, the last test (Test 6)

showed that it has been achieved a standard deviation around ±20Pa from the mean value. For

72

this reason, work developed in the laboratory can be considered a real success, considering

the final configuration chosen as a good one for further tests in Plasmatron.

Finally, taking into account that this thesis is going to be the end of the road after many years

studying, I can say that it has been a very experience. The opportunity I have been given to

work with many different people from all around the world has been outstanding, especially

taking into account that in my home university this kind of thesis are developed almost alone,

between books and computers. With this, I had the opportunity to see how team work is in a

real project, a thing that not all students can say before finishing their studies. This way, I

personally gained an invaluable hands-on experience in satellite design, learning a lot of things

related to the world of CubeSats. I also had the pleasure to attend the 6th QB50 Workshop that

took place in Von Karman Institute, where I was able to note the importance of sharing ideas

and how everybody counts. Future is uncertain, but what I can finally conclude is that I want to

go on the space way.

6.6.6.6. Future workFuture workFuture workFuture work

This thesis needs to be considered as a preliminary work for the design of XPL02 and XPL03

payloads, taking them as a starting point for the forthcoming tests. So far, tests performed in

the vacuum chamber allowed QARMAN team to check the measurement chain is working

properly, as well as to calibrate it.

At this moment, pressure ports location and the entire measurement chain for XPL02 are

ready to be tested in Plasmatron in order to validate the configuration proposed. However, the

next step for this payload should be to start manufacturing the spool that is going to be

assembled at the TPS bonding structure. It is really important to test the whole configuration

design in order to see whether the component can stand entry vibrations with only the thread

or it needs to be soldered. Note that if soldering is finally applied, the design can be simplified

excluding the nut.

Referring to the housing configuration for XPL03, this thesis only covers a very preliminary

design with the main requirements for it. This way, it needs to be updated once the exact

position of the data acquisition system card is defined. In addition, CFDs related to the side

panels will be of importance in order to make a decision on the final location of the pressure

ports, especially the ones for the differential pressure sensor which are going to delimitate the

scientific objectives.

Finally, it is also advised to find a method to test XPL03 in which the vacuum chamber pressure

is not controlled by hand, because it is an important source of errors. However, since it is

foreseen to test this payload in the Plasmatron, this problem can be dismissed. On the other

hand, it is required to test pressure sensors operating in absolute mode for their calibration.

Even though sensor output voltage range should be the same regardless of the mode, some

adjustments on the gain of the instrumental amplifier can be needed.

73

7.7.7.7. ReferencesReferencesReferencesReferences

[1] M. J. Muylaert, «Call for CubeSat proposals for QB50,» Brussels, Belgium, 2013.

[2] I. Sakraker, XPL01 development: QARMAN TPS recession and heating, Belgium, 2013.

[3] R. Munakata, CubeSat design specifications, California, 2009.

[4] I. company, ISIPOD CubeSat deployer, Delft, Netherlands, 2013.

[5] C. Asma, I. Sakraker, T. Scholz, G. Bailet, G. Kerschen y L. Dell'Elce, QB50 PDR Summary

report template, Brussels, Belgium, 2013.

[6] S. Lein, Optical emission spectroscopic experiments for in-flight entry research. 8th

International Planetary Probe Workshop, Portsmouth, Virginia, June 2011.

[7] ARV-Team, In-Flight Verification Package, Brussels, Belgium, 2011.

[8] A. Little, D. Bose, C. Karlgaard, M. Munk, C. Kuhl, M. Schoenenberger, C. Antill, R.

Verhappen, P. Kutty y T. White, MEDLI: Hardare performance and data reconstruction,

Hampton, US, 2013.

[9] S. GE Industrial. [Online]. Available: http://www.ge-mcs.com/download/pressure-

mems/920_276a.pdf. [Accessed 15 08 2013].

[10] C. Kilic, «Deployment Strategy Study of QB50 Network of CubeSats,» Brussels, Belgium,

2013.

[11] A. Devices. [Online]. Available: http://www.analog.com/static/imported-

files/data_sheets/AD8671_8672_8674.pdf. [Accessed 15 08 2013].

[12] J. Karki, "Signal Conditioning Wheatstone Resistive Bridge Sensors," 1999. [Online].

Available: http://www.ti.com/lit/an/sloa034/sloa034.pdf. [Accessed 15 08 2013].

[13] T. Instruments. [Online]. Available: http://www.ti.com/lit/ds/symlink/msp430f5438a.pdf.

[Accessed 15 08 2013].

[14] A. Devices. [Online]. Available: http://www.analog.com/static/imported-

files/data_sheets/AD8226.pdf. [Accessed 15 08 2013].

[15] S. N. I. o. Technology, "Preston Tube Measurement: The Simplest Method," Surabaya,

Indonesia, May, 2003.

[16] I. Sakraker, G. Bailet y T. Scholz, «Preliminary sensors selection,» Brussels, Belgium, 2013.

[17] N. Semiconductor. [Online]. Available: http://www.alldatasheet.com/datasheet-

74

pdf/pdf/207786/NSC/LMP7718.html. [Accessed 15 08 2013].

[18] B. A. Olshausen. [Online]. Available:

http://redwood.berkeley.edu/bruno/npb261/aliasing.pdf. [Accessed 15 08 2013].

[19] G. R. Center. [Online]. Available: http://www.grc.nasa.gov/WWW/k-

12/airplane/isentrop.html. [Accessed 15 08 2013].

[20] S. Watkins, P. Mousley and G. Vino, The Development and Use of Dynamic Pressure

Probes, Sydney, Australia, December 2004.

[21] S. Yahya, Fundamentals of compressible flow, Third edition ed., New Delhi: New Age

International, 2003.

[22] First Sensors; Sensor Technics, [En línea]. Available:

http://www.sensortechnics.com/cms/upload/appnotes/AN_Selection-pressure-

sensor_E_11159.pdf. [Último acceso: 15 08 2013].

[23] T. J. Larson, S. A. Whitmore, L. Ehernberger, J. B. Johnson y P. M. Siemers, «Qualitative

Evaluation of a Flush Air Data System at Transonic Speeds and High Angles of Attack,»

Edwards, California, April 1987.

[24] P. Gallais, Atmospheric Re-entry Vehicle Mechanics, New York: Springer, 2007.

[25] K. M. Tacina, R. Fernandez, J. W. Slater y S. M. Moody, An Analysis of Pitot and Static

Pressure Measurements in an Unsteady Supersonic Flow, Portland, Oregon, 2004.

[26] P. Lau, Calculation of flow rate from differential pressure devices - orifice plates, Sweden,

2008.

[27] F. W. Hagen, Angle of attack sensor using inverted ratio of pressure differentials, United

States, 1991.

75

APPENDIXAPPENDIXAPPENDIXAPPENDIX 1111: Set of sensors: Set of sensors: Set of sensors: Set of sensors

• Set of sensors for the aerothermodynamic payload of QARMAN:

Investigated

challenge

Parameter

to measure Sensor

Total

mass

[kg]

Energy

consumption

[W/h]

Data

size/Meas.

[bit]

Phase

Total data

size

[kB/Phase]

TPS

efficiency

Temperature distribution

12 x TC 0.012 0.003 14 3 12.60

TPS &

environment Pressure

2 x Pressure sensor

0.050 0.083 10 3 0.15

Stability Pressure 2 x Pressure

sensor 0.05 168 10 2 302.4

Rarefied flow

conditions

Low pressure / Vacuum

1 x Vacuum sensor

0.011 75.6 -75.6 10 1-2 151.20 – 151.20

Shear force,

laminar to

turbulence

transition

Skin friction

4 x Preston tube (2

common sensors with

stability payload)

0.05 336 – 0.083 10 2 -3 60.48 – 0.15

Off-

stagnation

temperature

Temperature 10 x TC 0.010 168 – 0.003 14 2 – 3 211.68 –

1.05

ATD

Environment Species

1 x Spectrometer

1 x Photodiode

0.084 –

0.001 0.208 – 0.083 28 – 10 3 – 3 2.50 – 0.15

Total with

safety

margin 1.2

0.319 988.395 (Phase 3:

0.556)

1073.47 (Phase 3:

21.12)

76

APPENDIX 2APPENDIX 2APPENDIX 2APPENDIX 2: TPS pressure distribution: TPS pressure distribution: TPS pressure distribution: TPS pressure distribution

• Detailed pressure distribution on the TPS at an altitude of 50 km:


77



APPENDIXAPPENDIXAPPENDIXAPPENDIX 3333: XPL03 spool design options: XPL03 spool design options: XPL03 spool design options: XPL03 spool design options• Design 1 spool drawing:

• Design 2 of the spool. On the left, drawing of the bolt; on the right, drawing of the nut:

: XPL03 spool design options: XPL03 spool design options: XPL03 spool design options: XPL03 spool design options gn 1 spool drawing:

Design 2 of the spool. On the left, drawing of the bolt; on the right, drawing of the nut:

78

Design 2 of the spool. On the left, drawing of the bolt; on the right, drawing of the nut:

• Drawing for design 3 of the spool:

Drawing for design 3 of the spool:

79

80

APPENDIX 4: APPENDIX 4: APPENDIX 4: APPENDIX 4: Detailed test matrixesDetailed test matrixesDetailed test matrixesDetailed test matrixes

• Test matrix 1Test matrix 1Test matrix 1Test matrix 1 (13:40 h, 10(13:40 h, 10(13:40 h, 10(13:40 h, 10----07070707----2013)2013)2013)2013) Test Name Differential pressure [mmHg] Number of measurements Data Acquisition Frequency [Hz] Vacuum chamber pressure [kPa]

1 0 9x50 50 100.805

2 22 9x50 50 97.8719079

3 38.9 9x50 50 95.61875987

4 98.1 9x50 50 87.72607566

5 129.9 9x50 50 83.48642435

6 146.8 9x50 50 81.23327632

7 165 9x50 50 78.80680922

8 187.8 9x50 50 75.76705922

9 215.15 9x50 50 72.12069245

10 241.2 9x50 50 68.64764475

11 234.7 9x50 50 69.51424014

12 207.5 9x50 50 73.14060856

13 196 9x50 50 74.6738158

14 177.5 9x50 50 77.14027961

15 164.4 9x50 50 78.88680264

16 130.7 9x50 50 83.37976645

17 117.9 9x50 50 85.08629277

18 86.7 9x50 50 89.24595066

19 65.4 9x50 50 92.08571711

20 42.4 9x50 50 95.15213158

21 32.3 9x50 50 96.4986875

22 21 9x50 50 98.00523026

23 150.7 9x50 50 80.71331909

24 199.7 9x50 50 74.18052304

25 228.4 9x50 50 70.35417106

Initial atmospheric pressure = 1008.05 mbar / Final atmospheric pressure = 1008.05 mbar

Initial laboratory temperature = 24.7 ºC / Final laboratory temperature = 24.7 ºC

81

• Test matrix 2Test matrix 2Test matrix 2Test matrix 2 (12:30 h, 11(12:30 h, 11(12:30 h, 11(12:30 h, 11----07070707----2013)2013)2013)2013)

Test

Name

Differential

pressure

[mmHg]

Number of

measurements

Data

Acquisition

Frequency

[Hz]

Vacuum chamber

pressure [kPa]

Supplied Voltage [V] Pressure sensor

Pin-2 voltage

[V]

Pressure sensor

Pin-4 voltage

[V]

Pressure sensor

output voltage [V]

IN-AMP output

voltage [V] OpAMP IN-AMP

1 0 9x50 50 100.95485 4.866 4.866 1.2 4.433 0 0.0157

2 10.7 9x50 50 99.5283007 4.866 4.866 1.2 4.433 0.0018 0.0166

3 27.8 9x50 50 97.2484882 4.866 4.866 1.2 4.433 0.0053 0.0155

4 37.3 9x50 50 95.9819257 4.866 4.866 1.2 4.433 0.007 0.0155

5 45.6 9x50 50 94.87535 4.866 4.866 1.2 4.433 0.0081 0.0154

6 58.4 9x50 50 93.1688237 4.866 4.866 1.2 4.433 0.0111 0.015

7 69.5 9x50 50 91.6889454 4.866 4.866 1.2 4.433 - -

8 80.5 9x50 50 90.2223993 4.866 4.866 1.2 4.433 0.0131 0.0149

9 89.8 9x50 50 88.9825013 4.866 4.866 1.2 4.433 0.0152 0.0652

10 98.9 9x50 50 87.7692678 4.866 4.866 1.2 4.433 0.0169 0.1801

11 115.8 9x50 50 85.5161197 4.866 4.866 1.2 4.433 0.0187 0.295

12 126 9x50 50 84.1562316 4.866 4.866 1.2 4.433 0.0217 0.496

13 132.8 9x50 50 83.2496395 4.866 4.866 1.2 4.433 0.0249 0.722

14 145.3 9x50 50 81.5831099 4.866 4.866 1.2 4.433 0.0273 0.882

15 161.5 9x50 50 79.4232875 4.866 4.866 1.2 4.433 0.0302 1.075

16 172.4 9x50 50 77.9700737 4.866 4.866 1.2 4.433 0.0322 1.22

17 188.1 9x50 50 75.8769125 4.866 4.866 1.2 4.433 0.0351 1.394

18 205.4 9x50 50 73.5704355 4.866 4.866 1.2 4.433 0.0384 1.628

19 217.8 9x50 50 71.9172382 4.866 4.866 1.2 4.433 0.0408 1.798

20 225 9x50 50 70.9573171 4.866 4.866 1.2 4.433 0.0422 1.887

21 235.9 9x50 50 69.5041033 4.866 4.866 1.2 4.433 0.044 2.01

22 244.4 9x50 50 68.3708632 4.866 4.866 1.2 4.433 0.0457 2.126

82

23 250 9x50 50 67.6242579 4.866 4.866 1.2 4.433 0.0466 2.2

24 241.3 9x50 50 68.7841625 4.866 4.866 1.2 4.433 0.045 2.08

25 228.3 9x50 50 70.5173533 4.866 4.866 1.2 4.433 0.0427 1.922

26 203.6 9x50 50 73.8104158 4.866 4.866 1.2 4.433 0.0379 1.6

27 178.6 9x50 50 77.143475 4.866 4.866 1.2 4.433 0.0333 1.283

28 152.5 9x50 50 80.6231888 4.866 4.866 1.2 4.433 0.0285 0.967

29 126.3 9x50 50 84.1162349 4.866 4.866 1.2 4.433 0.0236 0.625

30 123.8 9x50 50 84.4495408 4.866 4.866 1.2 4.433 0.0232 0.569

31 105.7 9x50 50 86.8626757 4.866 4.866 1.2 4.433 0.0197 0.371

32 100.3 9x50 50 87.5826165 4.866 4.866 1.2 4.433 0.0189 0.311

33 87.9 9x50 50 89.2358138 4.866 4.866 1.2 4.433 0.0164 0.156

34 82.3 9x50 50 89.9824191 4.866 4.866 1.2 4.433 0.0155 0.085

35 69.6 9x50 50 91.6756132 4.866 4.866 1.2 4.433 0.0123 0.0148

36 60.5 9x50 50 92.8888467 4.866 4.866 1.2 4.433 0.0114 0.0149

37 56 9x50 50 93.4887974 4.866 4.866 1.2 4.433 0.0106 0.015

38 44.1 9x50 50 95.0753336 4.866 4.866 1.2 4.433 0.0084 0.0152

39 36.7 9x50 50 96.0619191 4.866 4.866 1.2 4.433 0.0071 0.0152

40 34.6 9x50 50 96.3418961 4.866 4.866 1.2 4.433 0.0066 0.0154

41 30 9x50 50 96.9551789 4.866 4.866 1.2 4.433 0.0056 0.0154

42 23.4 9x50 50 97.8351066 4.866 4.866 1.2 4.433 0.0045 0.0155

43 14.3 9x50 50 99.0483401 4.866 4.866 1.2 4.433 0.0027 0.0157

44 9.6 9x50 50 99.6749553 4.866 4.866 1.2 4.433 0.0019 0.0157

45 6.1 9x50 50 100.141584 4.866 4.866 1.2 4.433 0.0012 0.0157

46 1.4 9x50 50 100.768199 4.866 4.866 1.2 4.433 - -

47 186.7 9x50 50 76.0635638 4.866 4.866 1.2 4.433 0.0344 1.36

48 233.1 9x50 50 69.8774059 4.866 4.866 1.2 4.433 0.0418 1.858

83


Initial laboratory temperature = 23 ºC / Final laboratory temperature = 24.4 ºC


Test

Name

Differential

pressure

[mmHg]

Number of

measurements

Data

Acquisition

Frequency

[Hz]

Vacuum chamber

pressure [kPa]

Supplied Voltage

[V] Pressure sensor

Pin-2 voltage [V]

Pressure sensor

Pin-4 voltage [V]

Pressure sensor

output voltage [V]

IN-AMP output


1 0 9x50 50 100.9874 4.866 4.866 1.2 4.33 0 1.058

2 14 9x50 50 99.12088684 4.866 4.866 1.2 4.33 0.0026 1.1078

3 22.9 9x50 50 97.93431776 4.866 4.866 1.2 4.33 0.0043 1.207

4 41.7 9x50 50 95.42785724 4.866 4.866 1.2 4.33 0.008 1.257

5 52.5 9x50 50 93.98797566 4.866 4.866 1.2 4.33 0.01 1.329

6 69.7 9x50 50 91.69483092 4.866 4.866 1.2 4.33 0.0132 1.419

7 83.4 9x50 50 89.86831448 4.866 4.866 1.2 4.33 0.0161 1.491

8 99.8 9x50 50 87.68182764 4.866 4.866 1.2 4.33 0.0191 1.577

9 113.5 9x50 50 85.85531119 4.866 4.866 1.2 4.33 0.0218 1.648

10 129.4 9x50 50 83.73548553 4.866 4.866 1.2 4.33 0.025 1.732

11 153.6 9x50 50 80.50908422 4.866 4.866 1.2 4.33 0.0292 1.8396

12 174.4 9x50 50 77.73597896 4.866 4.866 1.2 4.33 0.033 1.929

13 197.2 9x50 50 74.69622896 4.866 4.866 1.2 4.33 0.0382 2.068

14 214.2 9x50 50 72.4297487 4.866 4.866 1.2 4.33 0.0414 2.172

15 240.5 9x50 50 68.92337041 4.866 4.866 1.2 4.33 0.0463 2.304

16 252.6 9x50 50 67.31016975 4.866 4.866 1.2 4.33 0.0486 2.365

17 264.5 9x50 50 65.72363357 4.866 4.866 1.2 4.33 0.051 2.426

18 280.1 9x50 50 63.64380462 4.866 4.866 1.2 4.33 0.0538 2.352

84

19 269.9 9x50 50 65.00369278 4.866 4.866 1.2 4.33 0.0516 2.446

20 247 9x50 50 68.05677501 4.866 4.866 1.2 4.33 0.0473 2.333

21 222.7 9x50 50 71.29650856 4.866 4.866 1.2 4.33 0.0429 2.352

22 176.7 9x50 50 77.42933751 4.866 4.866 1.2 4.33 0.0339 2.352

23 150.5 9x50 50 80.92238356 4.866 4.866 1.2 4.33 0.0289 1.8412

24 134.6 9x50 50 83.04220922 4.866 4.866 1.2 4.33 0.0258 1.762

25 116.2 9x50 50 85.4953408 4.866 4.866 1.2 4.33 0.0227 1.669

26 107.9 9x50 50 86.60191645 4.866 4.866 1.2 4.33 0.021 1.632

27 97.8 9x50 50 87.94847237 4.866 4.866 1.2 4.33 0.0188 1.5605

28 81 9x50 50 90.18828816 4.866 4.866 1.2 4.33 0.0159 1.479

29 81.2 9x50 50 90.16162369 4.866 4.866 1.2 4.33 0.0156 1.4685

30 71.1 9x50 50 91.50817961 4.866 4.866 1.2 4.33 0.0135 1.4146

31 56.4 9x50 50 93.46801842 4.866 4.866 1.2 4.33 0.0106 1.3375

32 46.4 9x50 50 94.80124211 4.866 4.866 1.2 4.33 0.0088 1.29

33 31.9 9x50 50 96.73441645 4.866 4.866 1.2 4.33 0.0063 1.219

34 25 9x50 50 97.65434079 4.866 4.866 1.2 4.33 0.0047 1.176

35 17.4 9x50 50 98.66759079 4.866 4.866 1.2 4.33 0.0033 1.142

36 12.8 9x50 50 99.28087368 4.866 4.866 1.2 4.33 0.0022 1.112

37 0 9x50 50 100.9874 4.866 4.866 1.2 4.33 0 1.0575



85


Test

Name

Differential

pressure

[mmHg]

Number of

measurements

Data

Acquisition

Frequency [Hz]

Vacuum chamber

pressure [kPa]

Supplied

Voltage [V] Pressure sensor

Pin-2 voltage [V]

Pressure sensor

Pin-4 voltage [V]

Pressure sensor

output voltage [V]

IN-AMP output

voltage [V] OpAM

P

IN-

AMP

1 0 9x50 50 100.9605 4.866 4.866 1.2 4.33 0 1.635

2 18.9 9x50 50 98.44070724 4.866 4.866 1.2 4.33 0.0036 1.75

3 39 9x50 50 95.76092763 4.866 4.866 1.2 4.33 0.0065 1.8575

4 43.1 9x50 50 95.21430592 4.866 4.866 1.2 4.33 0.0081 1.91

5 57.2 9x50 50 93.33446053 4.866 4.866 1.2 4.33 0.0108 1.982

6 71.4 9x50 50 91.4412829 4.866 4.866 1.2 4.33 0.0134 2.08

7 79.6 9x50 50 90.34803948 4.866 4.866 1.2 4.33 0.015 2.134

8 95.7 9x50 50 88.20154935 4.866 4.866 1.2 4.33 0.018 2.232

9 109.3 9x50 50 86.38836514 4.866 4.866 1.2 4.33 0.0206 2.315

10 120 9x50 50 84.9618158 4.866 4.866 1.2 4.33 0.0225 2.38

11 146.4 9x50 50 81.44210527 4.866 4.866 1.2 4.33 0.0277 2.545

12 179.3 9x50 50 77.05579935 4.866 4.866 1.2 4.33 0.0338 2.743

13 200 9x50 50 74.29602633 4.866 4.866 1.2 4.33 0.0378 2.863

14 219.7 9x50 50 71.66957567 4.866 4.866 1.2 4.33 0.0414 2.991

15 258.8 9x50 50 66.45667107 4.866 4.866 1.2 4.33 0.0487 3.235

16 269.3 9x50 50 65.0567862 4.866 4.866 1.2 4.33 0.0509 3.3

17 289.6 9x50 50 62.35034212 4.866 4.866 1.2 4.33 0.0546 3.42

18 271 9x50 50 64.83013817 4.866 4.866 1.2 4.33 0.051 3.289

19 191.4 9x50 50 75.44259869 4.866 4.866 1.2 4.33 0.0358 2.81

20 114.1 9x50 50 85.74841777 4.866 4.866 1.2 4.33 0.0214 2.344

21 77.5 9x50 50 90.62801645 4.866 4.866 1.2 4.33 0.0148 2.127

86

22 52.4 9x50 50 93.9744079 4.866 4.866 1.2 4.33 0.01 1.983

23 0 9x50 50 100.9605 4.866 4.866 1.2 4.33 0 1.648

24 0 9x50 50 100.9605 4.866 4.866 1.2 4.33 0 1.64

25 -23 9x50 50 104.0269145 4.866 4.866 1.2 4.33 0.0042 1.5

26 -34 9x50 50 105.4934605 4.866 4.866 1.2 4.33 0.0063 1.434

27 -45.9 9x50 50 107.0799967 4.866 4.866 1.2 4.33 0.0085 1.362

28 -56.9 9x50 50 108.5465428 4.866 4.866 1.2 4.33 0.0105 1.2975

29 -70.6 9x50 50 110.3730592 4.866 4.866 1.2 4.33 0.0131 1.2129

30 -81.1 9x50 50 111.7729441 4.866 4.866 1.2 4.33 0.0151 1.1509

31 -98.2 9x50 50 114.0527566 4.866 4.866 1.2 4.33 0.0183 1.0471

32 -120.3 9x50 50 116.9991809 4.866 4.866 1.2 4.33 0.0223 0.9134

33 -136.4 9x50 50 119.145671 4.866 4.866 1.2 4.33 0.0253 0.82

34 -162.4 9x50 50 122.6120526 4.866 4.866 1.2 4.33 0.0302 0.6547

35 -186.5 9x50 50 125.8251217 4.866 4.866 1.2 4.33 0.0345 0.519

36 -205.7 9x50 50 128.3849112 4.866 4.866 1.2 4.33 0.0381 0.4

37 -228.7 9x50 50 131.4513256 4.866 4.866 1.2 4.33 0.0426 0.256

38 -267.8 9x51 51 136.6642302 4.866 4.866 1.2 4.33 0.05 0.017

39 -280 9x52 52 138.2907631 4.866 4.866 1.2 4.33 0.0522 0.017

40 -270 9x53 53 136.9575395 4.866 4.866 1.2 4.33 0.0501 0.0169

41 -249.5 9x54 54 134.2244309 4.866 4.866 1.2 4.33 0.0464 0.132

42 -218.7 9x55 55 130.118102 4.866 4.866 1.2 4.33 0.041 0.3069

43 -171 9x56 56 123.758625 4.866 4.866 1.2 4.33 0.0326 0.5773

44 -123 9x57 57 117.3591513 4.866 4.866 1.2 4.33 0.023 0.8895

45 -93.2 9x58 58 113.3861447 4.866 4.866 1.2 4.33 0.018 1.042

46 -63.6 9x59 59 109.4398026 4.866 4.866 1.2 4.33 0.0122 1.194

47 -45 9x60 60 106.9600066 4.866 4.866 1.2 4.33 0.0083 1.3677

87

48 -31 9x61 61 105.0934934 4.866 4.866 1.2 4.33 0.0057 1.4432

49 -0.2 9x62 62 100.9871645 4.866 4.866 1.2 4.33 0 1.64


Initial laboratory temperature = 24.2 ºC / Final laboratory temperature = 25 ºC


Test

Name

Differential

pressure

[mmHg]

Number of

measurements

Data

Acquisition

Frequency [Hz]

Vacuum

chamber

pressure [kPa]

Supplied Voltage

[V] Pressure sensor

Pin-2 voltage [V]

Pressure sensor

Pin-4 voltage [V]

Pressure sensor

output voltage [V]

IN-AMP output


1 0 9x50 50 100.9257 4.866 4.866 1.2 4.33 0 1.6453

2 8.2 9x50 50 99.83245658 4.866 4.866 1.2 4.33 0.0012 1.609

3 17.5 9x50 50 98.59255855 4.866 4.866 1.2 4.33 0.0031 1.5488

4 30.6 9x50 50 96.84603553 4.866 4.866 1.2 4.33 0.0056 1.473

5 37.7 9x50 50 95.89944671 4.866 4.866 1.2 4.33 0.0069 1.4328

6 55.7 9x50 50 93.49964408 4.866 4.866 1.2 4.33 0.0103 1.3286

7 66.8 9x50 50 92.01976579 4.866 4.866 1.2 4.33 0.0123 1.27

8 87.2 9x50 50 89.29998948 4.866 4.866 1.2 4.33 0.0162 1.1534

9 107.2 9x50 50 86.63354211 4.866 4.866 1.2 4.33 0.0199 1.042

10 132.3 9x50 50 83.28715066 4.866 4.866 1.2 4.33 0.0246 0.8984

11 154.4 9x50 50 80.34072632 4.866 4.866 1.2 4.33 0.0285 0.7783

12 181.7 9x50 50 76.70102567 4.866 4.866 1.2 4.33 0.0337 0.6245

13 198.2 9x50 50 74.50120659 4.866 4.866 1.2 4.33 0.0368 0.5332

14 214.2 9x50 50 72.3680487 4.866 4.866 1.2 4.33 0.0396 0.4477

15 236.5 9x50 50 69.39495988 4.866 4.866 1.2 4.33 0.0438 0.318

16 252.8 9x50 50 67.22180528 4.866 4.866 1.2 4.33 0.0466 0.2335

17 269.3 9x50 50 65.0219862 4.866 4.866 1.2 4.33 0.0498 0.135

88

18 283.2 9x50 50 63.16880528 4.866 4.866 1.2 4.33 0.0525 0.059

19 290.5 9x50 50 62.19555199 4.866 4.866 1.2 4.33 0.0536 0.023

20 299 9x50 50 61.06231186 4.866 4.866 1.2 4.33 0.0552 0.017

21 270.7 9x50 50 64.83533488 4.866 4.866 1.2 4.33 0.05 0.1328

22 249.6 9x50 50 67.64843686 4.866 4.866 1.2 4.33 0.0462 0.248

23 178.5 9x50 50 77.12765725 4.866 4.866 1.2 4.33 0.033 0.6447

24 137.2 9x50 50 82.63387106 4.866 4.866 1.2 4.33 0.0252 0.88

25 77.8 9x50 50 90.55321974 4.866 4.866 1.2 4.33 0.0143 1.2115

26 58 9x50 50 93.19300263 4.866 4.866 1.2 4.33 0.0107 1.3213

27 0.2 9x50 50 100.8990355 4.866 4.866 1.2 4.33 0 1.6465

28 0 9x50 50 100.9257 4.866 4.866 1.2 4.33 0 1.6487

29 25.5 9x50 50 97.52597961 4.866 4.866 1.2 4.33 0.0048 1.793

30 43.7 9x50 50 95.0995125 4.866 4.866 1.2 4.33 0.0082 1.8955

31 65 9x50 50 92.25974606 4.866 4.866 1.2 4.33 0.0122 2.015

32 93.7 9x50 50 88.43339408 4.866 4.866 1.2 4.33 0.0177 2.178

33 112.7 9x50 50 85.90026908 4.866 4.866 1.2 4.33 0.0212 2.277

34 135.8 9x50 50 82.82052238 4.866 4.866 1.2 4.33 0.0255 2.42

35 150 9x50 50 80.92734474 4.866 4.866 1.2 4.33 0.0283 2.5

36 165.7 9x50 50 78.83418356 4.866 4.866 1.2 4.33 0.0312 2.589

37 191.6 9x50 50 75.38113422 4.866 4.866 1.2 4.33 0.036 2.733

38 217.3 9x51 51 71.95474935 4.866 4.866 1.2 4.33 0.0409 2.88

39 231.8 9x52 52 70.02157501 4.866 4.866 1.2 4.33 0.0435 2.96

40 245.1 9x53 53 68.24838751 4.866 4.866 1.2 4.33 0.046 3.04

41 256.6 9x54 54 66.71518028 4.866 4.866 1.2 4.33 0.0482 3.102

42 269 9x55 55 65.06198291 4.866 4.866 1.2 4.33 0.0506 3.177

43 282.1 9x56 56 63.31545988 4.866 4.866 1.2 4.33 0.053 3.247

89

44 291.4 9x57 57 62.07556186 4.866 4.866 1.2 4.33 0.0547 3.3

45 295.3 9x58 58 61.55560462 4.866 4.866 1.2 4.33 0.0554 3.322

46 270.8 9x59 59 64.82200265 4.866 4.866 1.2 4.33 0.0507 3.177

47 233.1 9x60 60 69.84825593 4.866 4.866 1.2 4.33 0.0437 2.968

48 190.8 9x61 61 75.48779212 4.866 4.866 1.2 4.33 0.0359 2.737

49 153.9 9x62 62 80.40738751 4.866 4.866 1.2 4.33 0.0288 2.516

50 121.4 9x63 63 84.74036448 4.866 4.866 1.2 4.33 0.0231 2.372

51 92.8 9x64 64 88.55338422 4.866 4.866 1.2 4.33 0.0173 2.168

52 75 9x65 65 90.92652237 4.866 4.866 1.2 4.33 -0.0141 2.08

53 46 9x66 66 94.79287106 4.866 4.866 1.2 4.33 -0.0086 1.9085

54 0.4 9x67 67 100.8723711 4.866 4.866 1.2 4.33 0 1.6507



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