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BOOSTER PACKET

LIQUIDS PROPULSION DESIGN TEAM

Welcome to the UF Liquid Propulsion Design Team! This packet is designed to help you

understand what our team is all about and get you up to speed on some of the basics of rocket

propulsion science. We meet every Monday at 5:10 PM in LIT 0207, feel free to join in!

OUR GOAL To design, manufacture, and test low-cost liquid-propelled rocket engines. In addition to engine

development, we will look ahead to creating a full-scale rocket, powered by one of our propulsion

systems, that will participate in the Spaceport America Cup.

TEAM OVERVIEW Our team is divided into sub-teams focused on different systems of our rocket engines. These

are: Propellant Delivery, Mechanical Design, Structural Analysis, Thermal Fluid Analysis,

Electronics, Manufacturing, and Systems. Each sub-team calls for unique expertise, and they all

must work together to make a functional engine. Currently we are in development of a mid-

performance bi-propellant rocket engine, nicknamed the Albatross Engine.

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SVE – SOFTWARE VERIF ICATION ENGINE The SVE is the LPDT’s first propulsion system development effort. SVE’s primary objectives were

to validate the software and design methods used in development, serve as a proof of concept

for a low-cost propulsion system, and establish a baseline for hands-on design, manufacturing,

and testing. The SVE was designed with mechanical simplicity and operational safety in mind.

Propellants

• Fuel: 95% Ethanol

• Oxidizer: 50% Hydrogen Peroxide

Features

• Pressure-Fed Cycle

• Automated control and operation

• Static Tests Conducted

• ~150 N thrust

• Steel and Aluminum Construction

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PROPELLANT DELIVERY

The Propellant Delivery System sub-team is dedicated to figuring out how we move the

propellants from the tank into the chamber. There are many ways of pushing the propellants into

the chamber, however we are going to look at the two most common methods: pressurized gas

propellant feed system and a pump propellant feed system.

PRESSURIZED GAS PROPELLANT FEED SYSTEM

A separate gas supply, usually helium,

pressurizes the propellant tanks to force fuel

and oxidizer to the combustion chamber. To

maintain adequate flow, the tank pressures

must exceed the combustion chamber

pressure. Pressure fed engines have simple

plumbing and lack complex and often

unreliable turbopumps.

Pressure-fed engines have practical limits on

propellant pressure, which in turn limits

combustion chamber pressure. High pressure

propellant tanks require thicker walls and

stronger alloys which make the vehicle tanks

heavier, thereby reducing performance and

payload capacity.

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PUMP PROPELLANT FEED SYSTEM

Some of the propellant is burned in a gas

generator and the resulting hot gas is used to

power the engine's pumps. The gas is then

exhausted. The pumps then push the propellant

through the injector and then into the chamber.

The advantages of this feed system allow for

lighter propellant tanks, since they do not need to

be highly pressurized. Further, in some cases a

pressurizing gas is not needed to keep the

propellant tanks pressurized. However, the

turbopump system introduces very complex

systems, such as the turbopump itself, lube oil

system for bearings, and cooling systems for the

turbopumps. Another variation of this feed

system uses an electric motor and battery to

power the pumps.

Most propellant feed systems are simply variations of these two general designs. For example,

there are many types of turbo pump systems, ones that dump the exhausts from the turbo pump

into the outside environment and others directly into the chamber. When designing a liquid

rocket engine, weight, cost, and complexity of the engine must be taken into consideration

before selecting a feed system.

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MECHANICAL DESIGN The Mechanical Design sub-team is responsible for developing the design for the rocket’s

chamber, nozzle, cooling systems, injectors and many other components. This team combines

advanced calculations with engineering creativity to create functional and efficient engine

components. The Mechanical Design sub-team emphaiszes design simplicity, affordability, and

manufacturability.

CHAMBER & NOZZLE The chamber (1) is where combustion

takes place. The reduced section (t) is

called the nozzle throat; here the flow

of hot combustion gases becomes

sonic (M=1). The nozzle exit (2) is

where the hot combustion gases leave

the engine and provide the thrust for

the rocket. The equation below is the

governing equation for the thrust

force of a rocket engine.

INJECTOR The injector is located at the forward end of the

combustion chamber. It is typically bolted onto

the chamber via flanges located on the exterior of

the chamber. The injector’s main objective is to

atomize the fuel and oxidizer into the combustion

chamber while also ensuring proper mixing. A

homogenous atomized fuel and oxidizer mixture is

crucial to the performance of the engine, and

helps mitigate problems that can arise during the

combustion process, such as wall streaking or

excessive thermal flux on wall chambers.

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ANALYSIS

The Structural Analysis sub-team works with computer programs such

as RPA and ANSYS to run simulations on various components of the

engine. Analysis is crucial for the safety and success of the project. This

sub-team targets possible structural and thermal anomalies before

the testing phase which consequently saves us time and money down

the line along with ensuring the highest standard of safety.

STRUCTURAL Structural analysis is the study of how a design will react when placed

under loads that you expect the structure to be under. By studying

the response of the structure under stress, you can learn useful

properties of the design such as max stress, failure points, and how

the design will react. A common procedure is a stress/strain analysis.

This will tell you where the max stress is expected to occur in your

design. Failure analysis is also common. Analyzing the types of failure

as well as where the failure will most likely happen is useful when

evaluating your design. Using this, you can design and plan to mitigate

the risk as well as strengthen weak points in your design.

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THERMAL FLUIDS Uses CFD software, ANSYS Fluent, to simulate

fluid flow through components of a rocket

engine to verify performance before actual

testing.

OUR MISSION To make sure our rocket engine is producing the most optimized thrust (force that moves the

rocket) to propel the rocket as precisely as possible while keeping the flow safe and under

control. We realize this and gage our designs through CFD simulations.

WHAT IS CFD? Computational Fluid Dynamics is the process of numerically solving a set of equations that govern

fluid motion. CFD is a three-step process:

1) Pre-Processing

a) Geometry

b) Computation grid generation

2) Solver

a) Solution of the discretized Equations of Motion

b) Convergence and Stability

3) Post-Processing

a) Inspection of solution

b) Graphing and representation of results

PRE-PROCSSING During pre-processing, we will import the geometry of

the rocket component such as the injector, propellant

pipes, combustion chamber or nozzle. We want to

simulate the mass flow rates and pressure drops

through these components to verify that we’re getting

the right number for optimal thrust.

We generate a computational grid overlaid onto each

component where the equations of motion are solved

locally - we’re basically generating a mesh where these

equations are solved in small regions that make up the

bigger picture.

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SOLVER After setting boundary conditions and

specifying fluid and component materials in

pre-processing, the built-in code of the ANSYS

software does the rest of the work. Here,

Navier-Stokes equations or turbulent models

are used to converge to a solution as the fluid

flows through our components.

POST-PROCSSING Once a solution converges, we analyze the

results. Graphical representations of the

solutions and flow visualizations are used to

compare the results we get from the simulation

to the results we want for our rocket

performance.

SKEPTICISM

Skepticism is one of the most important pillars of

CFD. We always question our results and double-

check if they make sense. CFD is a very powerful

tool but if not used correctly it could be

misleading. We stress the importance of

checking each other’s work and making sure we

are using the correct methods to get the correct

result.

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ELECTRONICS The Electronics sub-team works to design and build all electrical components of the engine and

testing instruments. The primary focus of testing electronics is developing an Engine Health

Control system to monitor the status of the engine during testing. This system can be broken

down into data acquisition, wiring, and testing and data analysis. After extensive testing the

design of the rocket will progress towards flight, which mandates flight controller electronics

housed in an avionics subsystem.

DATA ACQUISITON Data acquisition is currently conducted with LabVIEW and an Arduino board as a microcontroller

and various necessary sensors such as thermocouples, pressure transducers, strain gages, and

load cells. The sensor data is collected as voltage values, converted into appropriate units, and

checked against set engine parameters. If a sensor value reaches dangerous values, then the

engine automatically runs a shutdown sequence. (Ex. If exterior chamber Temperature reaches

above 800 K, then run engine shutdown.) This ensures expected performance of the engine is

maintained and safety of the system is enforced.

Engine Health Control System in LabVIEW

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SENSOR TERMINOLOGY Excitation voltage: the power required to run a sensor

Signal: the information that a sensor outputs

DAQ: a device that turns raw signals into something a computer understands.

Thermocouples: these sensors utilize a changing resistance to measure temperature. This

means they require no excitation voltage. Different thermocouples can tolerate and measure

different temperatures.

Pressure transducer: measures pressure and usually requires excitation. Must be sealed to

provide accurate readings.

Load Cell: measures amount of load applied to the sensor; used for measuring engine thrust.

Strain Gage: measures strain in an axial direction of the sensor, which can be used to solve for

stress and pressure values inside of pressure vessels or the combustion chamber.

RF: Radio frequency modules are used for data transfer over a long distance. This is useful

during flight as well as during testing to maintain a proper safety distance from the test engine.

Altimeter: measures altitude of the rocket during flight using ambient pressure values.

WIRING The wiring process begins after creating the data acquisition system. Once all sensors are planned

and the software is written sensors can be purchased and tested to learn their capabilities,

limitations and how to wire them. This information is then recorded and made into a wiring

diagram for the full system. The wiring diagram can then be utilized to create the data acquisition

system. Wiring includes cutting, stripping, twisting, soldering and heat shrinking wires.

AVIONICS SUB-SYSTEM The avionics subsystem is an area of the

rocket where electronics are housed to be

able to withstand the forces of flight and

operate all electronic processes on the

rocket. Common flight controllers are

altimeters, radio frequency modules to

transfer data, GPS, and a system used to

automate the operation of the engine.

Example of an avionics bay

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MANUFACTURING The Manufacturing sub-team cooperates with the all other teams to efficiently create parts from

various materials. This sub-team includes researching manufacturing techniques, solid model and

drawing generation, and experience with manual and CNC machining.

MILLING

Using a rotating tool to remove material from a

clamped workpiece by moving the workpiece on 3

axes (x, y, z). Performs high precision and accuracy

cuts and allows for smooth surface finishes.

Generally used with rectangular workpieces or cuts.

LATHING

Using a stationary tool to remove material from a

rotating workpiece by moving the tool on 2 axes (x,

z). Same basic benefits of Milling, but generally used

on cylindrical workpieces.

CNC

Computer numeric controlled manufacturing

involves using a computer to perform the previously

mentioned machining techniques, allowing for the

accurate and precise movement of 2 or more axes

simultaneously. This allows for easily and relatively

quickly created curves/fillets, and many other

complex designs that are hard or impossible to

create by hand.

GENERAL WORK

Operating chop saw, welding, soldering, angle

grinding, and any other function of creation and

assembling (and sometimes destruction) required.

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SYSTEMS The purpose of Systems is to function as a bridge between all other sub-teams, coordinating the work done to

ensure the entire propulsion system preforms properly. Systems lays out the design requirements for each

engine sub-system placing an emphasis on safety, cost, and complexity. The team will then serve to advise the

Mechanical Design, Propellant Delivery, and Electronics sub-teams on the design of their components. The

Systems sub-team will also plan and help conduct tests to characterize the function of the engine and its

different subsystems as well as provide information to aid in component design. A good understanding of all

the engine subsystems is needed to perform these tasks

DESIGN CONSTRAINTS Design constraints are limitations placed on the design of a component. They can affect things like the

dimensions of a component, types of sensors purchased, or the materials used in construction. These can come

from several sources like other components of the engine, the testing cell or stand, the flight vehicle, or even

competition requirements. When only a few components interact with each other these can be simple to

manage, but in a more complicated engine they are much harder to handle. Temperature, pressure, mass,

dimensions of other components, and chemical properties are just a few of the examples of constraints placed

on engine design.

TESTING A test of the engine and its subsystem is a complicated undertaking. It requires a lot of events to be executed

perfectly in short succession on order for it to be successful. Putting together a procedure is essential to the

success of a test. It helps keep everyone helping with the test on track and focused. It also shows officials with

the University and emergency services our plans and how best to help us.

Another part of planning for testing is characterizing the way the engine will fail. One way to do this is a Failure

Mode Effects and Criticality analysis (FMECA). These consider all the ways the engine could fail and ranks the

likelihood of the failures occurring against how bad a failure would be. For example, a sensor failing would be

more likely to occur than an oxidizer leak but the latter would be more severe. A way of finding the probability

of failure caused by a specific component is a fault tree analysis. This forms a mathematical model of the engine

by tracing all the parts that interact with each other during operation.