16.684 experimental cdio capstone course 1 s t u f f a t e l l i t e e s t b e d n t e t h e r e d o...

16.684 Experimental CDIO Capstone Course 1

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The STUFF16.684 Experimental CDIO Capstone Course

February 25, 1999

16.684 Experimental CDIO Capstone Course GPB, AC, JAW 3

Presentation OutlinePresentation Outline

Program Objective and Motivations Subsystems

– Propulsion– Power and Avionics– Metrology– Communications and Software– Structures

Design Concept Presentation Conclusions


Program ObjectiveProgram Objective

To develop a testbed that demonstrates formation flying algorithms between multiple autonomous satellites with six degrees of freedom, in a microgravity environment


MotivationMotivation

Demand for spacecraft to perform autonomous formation flying missions is increasing– Smaller – Simpler– Cheaper

Current testbeds do not allow full modeling of dynamics related to formation flying


Justification for FlightJustification for FlightTest

EnviromentSimulation

ofDynamics

DOF ExperimentDuration

Cost Comments

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16.684 Experimental CDIO Capstone Course GPB, AC, DRF 7

Specific Science ObjectivesSpecific Science Objectives

1. Develop a set of multiple distinct satellites that interact to maintain commanded position, orientation, and direction

2. Allow for the interchange of control algorithms, data acquisition and analysis, and a truth measure

3. Demonstrate key formation flying maneuvers

4. Demonstrate autonomy and status reporting

5. Ensure the implementation of control algorithms is adaptable to future formation flying missions

6. Allow for testbed operation on KC-135, Shuttle middeck, and ISS

14

PropulsionPropulsion

Dan Feller

Presenter

16.684 Experimental CDIO Capstone Course GPB, DRF, BMP 15

Propulsion RequirementsPropulsion Requirements

Safety– Non-toxic byproducts– Temperatures not to exceed

range (TBD)– Non-touch hazard

Propellant– Propellant supply sufficient to

last at least 20 seconds.

Control – System must provide for 6 DOF– System must provide constant

performance throughout flight duration.

Thrust– Large ISP (TBD)


Propulsion OptionsPropulsion Options Station Keeping / Attitude

– Compressed Gas• Highly Traceable, Cost Effective, Off-the-Shelf Components

– Fans/Propellers• Simple, Cost Effective but ...

– Micro Engines and Rockets• Technology not yet operational

Attitude Control– Reaction Wheels

• large, heavy, large size– Control Moment Gyros (CMGs)

• large size– Magnetic Torquers

• large size, long time to develop, large power demand


Propulsion MetricsPropulsion Metrics

Safety:– Toxicity

– Thermal Hazard

– Touch Hazard

– Fracture Hazard

Impulse Bit(Smallest quanta of thrust)

Traceability

Cost Efficiency

– ISP, Mass ratio

– ISP, Volume ratio

Power Consumption Ease of Replacement Time to Develop


Propulsion DownselectPropulsion Downselect

Prop SystemS

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TOTALWeighting 22% 13% 8% 3% 7% 22% 4% 20% 100%

CompressedGas

4 5 5 5 5 4 5 4 4.3

Fans / Propellers 4 2 1 5 2 2 4 5 3.1

Reaction Wheels 5 3 5 1 3 2 1 2 3.0

KEY: Desirability of option due to applicable Metric is:Very High- 5 High- 4 Medium- 3 Low- 2 Very Low- 1


Compressed Gas OptionsCompressed Gas Options

CO2 (Liquid or Gas)

– Readily Available, Easy Containment, Adequate Thrust, Toxic

N2 / Air (Liquid or Gas)

– High Thrust, Non-Toxic, Difficult Containment

Onboard Compressor– Heavy, High Power Consumption, Low Thrust


Compressed Gas DownselectCompressed Gas Downselect

Prop System

Saf

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TOTAL

Weighting 25% 17% 3% 15% 22% 18% 100%

CO2 (gas) 3 5 5 5 2 5 3.8

CO2 (liquid) 3 5 5 5 4 5 4.3

Air / N2 (gas) 5 5 3 5 2 5 4.3

Air / N2 (liquid) 4 5 2 4 5 4 4.3

OnboardCompressor

5 1 4 2 1 5 3.0


Propulsion BudgetPropulsion Budget

Sub-system demands:– Power: 2W– Volume: 1.5 liter– Mass: 3 kg– Cost: $3000

Sub-system provides:– Thrust: TBD

22

StructuresStructures

Dan Feller

Presenter

16.684 Experimental CDIO Capstone Course DAC, AC, DRF, JES 23

Structures RequirementsStructures Requirements Structural integrity

– Must survive Shuttle launch and landing loads

– Must survive a drop of 4 feet in 2-g

Satisfaction of mass and volume constraints– Container requirement

• Mass: 60lbs = 27kg• Dimensions: Max. 9 in. = 22 cm diameter (middeck locker)

– Single satellite should be less than 7 kg

– Structure should be ~10% of total satellite mass (0.7 kg)

– Structure should provide easy accessibility to internal components

Must be manufacturable and safe under crew handling

16.684 Experimental CDIO Capstone Course DAC, DRF, JES 24

Structures OptionsStructures Options Shape

– Cube – Sphere– Polyhedron

Assembly– Truss– Shell (no internal

truss)– Hybrid (a truss

structure with paneling)

Materials– Alloys and metals– Composites– Plastics and

polycarbonates


Structures CriteriaStructures Criteria Integrity

– Internal and external load carriage

Safety– Fracture toughness (structure cannot shatter)– Sharp edges & corners

Feasibility– Manufacturing – Internal accessibility– Cost


Shape DownselectShape Downselect

Integrity Safety Feasibility TOTAL30% 30% 40% 100%

Cube 4 2 5 3.8

Sphere 5 5 1 3.4

Polyhedron 4 4 4 4


Assembly DownselectAssembly Downselect

Integrity Safety Feasibility TOTAL

30% 30% 40% 100%

Truss 3 4 5 4.1

Shell 3 4 3 3.3

Hybrid 4 4 4 4


Materials DownselectMaterials Downselect

Integrity Safety Feasibility TOTAL

30% 30% 40% 100%

Metals &Alloys 4 3 5 4.1Composites 5 3 3 3.6Plastics 3 4 4 3.7


Structures BudgetStructures Budget

Mass– TBD, pending estimates of other sub-systems

Volume– TBD, but must fit within a STS mid-deck

locker, i.e. greatest dimension < 9 in.

Cost– TBD, pending allowance notification

30

Power and AvionicsPower and Avionics

Chad Brodel

Presenter

16.684 Experimental CDIO Capstone Course JAW, SEC 31

Power and Avionics RequirementsPower and Avionics Requirements

Total power should be approximately 18 W– Total Volts and Amps TBD

All hardware must be contained in individual satellite

Data storage must be adequate Components must be compatible with KC-

135, Shuttle, and ISS environments System should be traceable to existing

satellites


Power DistributionPower Distribution


Power OptionsPower Options

Battery Power– Non-rechargeable batteries

• Alkaline• Carbon Zinc• Lithium• Silver Oxide• Zinc Air• Silver Zinc

– Rechargeable• Nickel Cadmium• Nickel Metal Hydride

Solar Cells


Power CriteriaPower Criteria Energy Density

– By mass– By volume

Size– Weight– Volume

Cost Safety

Number of Batteries for 12V

Operating Temperature Range

Capacity Approximate Lifetime


Power DownselectPower DownselectB

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Non-rechargeable 10% 10% 10% 8% 5% 10% 10% 12.5% 2.5% 10% 12% 100%Alkaline 3 3 3 4 3 5 4 4 4 3 3 3.03

Carbon Zinc 3 3 4 5 2 5 4 4 3 3 3 3.135Lithium 3 4 4 4 4 4 3 4 5 5 5 3.645

Silver Oxide 4 4 5 5 4 2 4 2 3 2 1 2.945Zinc Air 5 5 4 4 4 5 1 4 3 5 5 3.695

Silver Zinc ? ? ? ? ? ? ? ? ? ? ?

RechargeableNiCad 2 3 2 2 4 2 3 2 4 3 3 2.37NiMH 2 4 2 2 4 2 4 2 3 5 4 2.865


Power RecommendationsPower Recommendations

Batteries– Non-rechargeable: Lithium

• Lifetime approximately 40 minutes

– Rechargeable: NiMH• Lifetime approximately 30 minutes

Solar cells should be considered


Power BudgetPower Budget

Sub-system demands:– Weight : 300 g– Volume : 250 cm

3

– Cost : TBDSub-system provides:

– 18 W– Voltage and Amps TBD


Specific Avionics RequirementsSpecific Avionics Requirements

Sufficient data storage capacityVolume and weight TBDSystem must be compatible with

communications, propulsion, and metrology

Low power drain


Avionics OptionsAvionics Options

Build Custom ProcessorsPurchase Processors

– Commercial Processor Options• Tattletale TFX - 11• Tattletale 5F/5F - LCD• Spectrum INDY• Crickets

40

Communication and SoftwareCommunication and Software

Chad Brodel

Presenter

16.684 Experimental CDIO Capstone Course GPB, CSB, SLC 41

Communication & Software Communication & Software

Satellite to Satellite (STS) – Real time– Send, receive, and temporarily store data– Compatible with KC-135 / Shuttle systems– Must be traceable to existing satellite

technology Satellite to Ground (STG)

– Does not have to be real time– Data must be recorded for post-flight

analysis– Must be compatible with KC-135 /

Shuttle systems

• Communication Requirements:


Software RequirementsSoftware Requirements

Software is the interface between input (metrology) and output (propulsion)

Requirements:– Must have common programming language– Must be flexible to allow execution of complex

maneuvers– Must develop efficient code compiling techniques


Communication Methodology OptionsCommunication Methodology Options

All equal authority– Satellites interact to decide how to execute array

maneuver

Master / Slave– One satellite gives commands to all others

Hierarchy / Command Chain– Satellites ranked in authority– Easy command transition in case of failure


Communication Methodology SelectionCommunication Methodology Selection Hierarchy / Command chain ensures no confusion

– Satellites numbered 1-3: one control stream– No. 1 Satellite

• Receives control algorithm from ground

• Determines each satellite’s position in array

• Sends commands to other satellites

• Sends own health status info to ground

– Other Satellites• Communicate position, velocity and acceleration data to No. 1

• Sends own health status data to ground

• If No. 1 fails, each satellite will shift up in hierarchy


Data Transfer OptionsData Transfer OptionsDownload Data:

– Continuously• Larger power requirement• Uses up bandwidth

– Post Flight• Possibility of losing on-board data • Long download time• Larger on-board memory cache required

– At regular intervals• Efficient combination of options• Our recommendation


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Notes

Weighting 15% 15% 20% 20% 10% 10% 10% 100%

RF(radio ethernet)

2 5 2 5 5 5 2 3.65 A,F

IR 3 2 3 4 4 2 3 2.60 C

Ultrasonic 4 4 2 3 3 3 3 2.80 B,D,E

A – may interfere with KC-135 or shuttle systemsB – may interfere with metrologyC – only works with sensors in direct line of sightD – not traceable for use in spaceE – possibly damaging to other onboard experimentsF – relatively slow rate of transfer

Communication DownselectCommunication Downselect


Communication Hardware SelectionCommunication Hardware Selection

Best Option (STS, STG): RF – Excellent range– Low power requirement– Reasonable bandwidth and accuracy– Single sensor– Cost effective– Possibility of interference on KC-135, Shuttle

middeck


Budgets ConstraintsBudgets Constraints

Power – Communications sensors and receivers ~ 2 Watts each

(1 RF STG and 1 RF STS per satellite)

Mass – Communication sensors and receivers ~ 8 grams per satellite

Volume– Sensors relatively flat / surface mounted (small)

49

MetrologyMetrology

Fernando Perez

Presenter

16.684 Experimental CDIO Capstone Course AC, SYC, SLJ, FP 50

Metrology OverviewMetrology Overview

Two subsystems– Navigation metrology

• Real-time position and attitude determination• On-board navigation system• Accurate

– Truth measure• Verification of position and attitude• Probably some sort of off-board camera or

ranging system


Navigation Metrology RequirementsNavigation Metrology Requirements

Real time--10 Hz Accuracy

– Position to 1 cm (TBR)– Attitude to 1º (TBR)

Must meet space shuttle and KC-135 interface, interference, & safety requirements

Setup in 20 minutes (TBR)

Interface with other subsystems– Communications– Avionics– Power

• Onboard = 2 W (TBR)

• Off-board = 10 W (TBR)

– Structures• Mass = 0.3 kg (TBR)

• Volume = 20 mL (TBR)


Navigation Metrology OptionsNavigation Metrology Options

Position– IR/Ultrasound– Ultrasonic Ranging– Gyros/

Accelerometers– Synchronized

clock/RF/IR

Attitude– Gyros/

Accelerometers– IR/Ultrasound– Pure IR


Navigation Metrology CriteriaNavigation Metrology Criteria

Metrics– Complexity– Cost– Accuracy

Constraints– Onboard Power– Volume– Real time– Mass– Safety– Interference


POSITION

Complexity Cost Accuracy TOTAL Constraints30% 30% 40% 100%

IR/Ultrasound 3 3 4 3.4 Line of sightUltrasonic Ranging 2 4 1 2.2 Line of sight, accuracyGyros/Accelerometers 2 2 1 1.6 Cost, power, volume, computational power, may

affect satellite dynamicsSynch Clock/RF/IR signal 1 1 5 2.6 Cost

ATTITUDE


Gyros/Accelerometers 3 2 4 3.1 Cost, power, volume, may affect satellite dynamicsIR/Ultrasound 2 3 4 3.1 Distance between sensors (size of flyer)Pure IR 1 1 5 2.6 Distance between sensors (size of flyer)

Navigation Metrology DownselectNavigation Metrology Downselect

Note: Power, Volume, Safety, and Interference were considered on a binary scale and are listed as constraints where the subsystem requirements were not met


Truth Measure Metrology RequirementsTruth Measure Metrology Requirements

Accuracy– Position to 1 cm (TBR)– Attitude to 1º (TBR)

Must meet space shuttle and KC-135 interface, interference, & safety requirements

Interface with other subsystems (not an onboard system)

Off-board requirements– Power = 2 W (TBR)– Structures

• Mass = 20 kg (TBR)• Volume = 5000 mL

(TBR)


Truth Measure Metrology OptionsTruth Measure Metrology Options

Position– External fixed cameras– Onboard cameras– External tracking

cameras– Informed tracking

cameras with rangefinders

– Radar ranging– Reverse IR/Ultrasound

Attitude– External fixed cameras– Onboard cameras– Reverse IR/Ultrasound


Truth Measure Metrology CriteriaTruth Measure Metrology Criteria

Metrics– Complexity– Cost– Accuracy

Constraints– Onboard power– Off-board power– Onboard volume– Off-board volume– Mass– Safety– Interference


Truth Measure Metrology DownselectTruth Measure Metrology DownselectPOSITION


External fixed cameras (3) 4 4 2 3.4 Size of test area, may not be real timeOnboard cameras 2 2 2 2.0 Volume, weight, power, not real timeExternal tracking cameras (9) 2 2 3 2.3 Size of test area, tracking systemInformed tracking cameras/Rangefinders 3 3 4 3.3 Size of test area, camera control systemRadar ranging 3 3 4 3.3 Safety, test area, interferenceReverse IR/Ultrasound 2 3 5 3.2 Experimental bias

ATTITUDE


External cameras 4 4 2 3.4 Size of test areaOnboard cameras 2 2 3 3.3 Volume, mass, not real timeReverse IR/Ultrasound 2 3 5 3.2 Distance between sensors, experimental bias

Note: Power, Volume, Safety, and Interference were considered on a binary scale and are listed as constraints where the subsystem requirements were not met


Metrology SelectionsMetrology Selections

Navigation Metrology– IR/Ultrasound for

both position and attitude

• Accurate• Inexpensive• Meets power, mass,

and volume requirements

Truth Measure Metrology– External fixed

cameras for both position and attitude

• Could be made real-time

• Off-board system does not require onboard power, mass, or volume


Metrology BudgetsMetrology Budgets

Note: Although separate downselects were performed for attitude and position determination, the same solution emerged for both parts of each metrology subsystem

Power Mass Volume

Onboard Offboard Onboard Off-board Onboard Off-board

NavigationMetrology –IR/Ultrasound

1800mW

6175 mW 24 g 16 g 8 mL 6 mL

Truth MeasureMetrology –ExternalCameras

N/A 7800 mW N/A 30 g N/A 29 mL

TotalOnboardPower

Total Off-boardPower

TotalOnboard

Mass

Total Off-boardMass

TotalOnboardVolume

Total Off-board Volume

1800mW

13,975mW

24 g 46 g 8 mL 35 mL

61

Design Concept PresentationDesign Concept Presentation& Conclusion& Conclusion

Stephanie Chen

Presenter

16.684 Experimental CDIO Capstone Course SLC, SEC 62

Summary of ConceptSummary of Concept

Propulsion– Compressed Gas

• Liquid CO2 or N2/Air

Structure– Polyhedral truss and shell assembly– Metals and alloys


Summary of Concept (cont.)Summary of Concept (cont.)

Power– Battery Power

• Lithium, NiMH

Avionics– TATTLETALE processor


Summary of Concept (cont.)Summary of Concept (cont.)

Communication and Software– RF (Radio Ethernet)– Hierarchy of satellites

Metrology– Navigation

• IR/ultrasound -- measures position and attitude

– Truth Measure• External fixed cameras


Budget per SatelliteBudget per SatelliteDistributedMass (kg)

NeededMass (kg)

DistributedPower (W)

NeededPower (W)

Propulsion 2 3 10 2

Structure 0.7 TBD 0 0

Power/Avionics 2 0.27 4 4

Comm/Software 0.3 0.008 2 4

Metrology 0.3 0.024 2 1.8

Total 5.3 3.3 18 11.8

Margin 76% 47% 43% 37%


Preparation for PDRPreparation for PDR

Finalize Design– Set subsystem architecture– Research hardware components– Analyze subsystem integration– Identify and consult experts

Prepare Documentation– Compile hardware specs– Validate design


ConclusionsConclusions

Subsystems– Preliminary designs investigated– Component research underway

Satellite Testbed– Designed to be flown on KC-135 and

shuttle middeck– Technology traceable to future satellite

missions

16.684 Experimental CDIO Capstone Course 68

THE END!THE END!

16.684 experimental cdio capstone course 1 s t u f f a t e l l i t e e s t b e d n t e t h e r e d o...

Documents

direction satellites

set of satellites

initialization satellites

multiple autonomous

truth measure satellites

flight slide

iss slide

downloaded data slide