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Copy of Spacecraft Subsystem Design
Transcript of Copy of Spacecraft Subsystem Design
Assuming Ideal Gas Law, PV=nRT, at EOL
Initial gas volume (ullage) pressurized to beginning-of-life pressure.-->
Allow to expand and decrease in pressure
Save cost, complexity of the system
Thrust, pressure, propellant flow rate decrease, inertial changes
Spacecraft Subsystem Design
To use this system
Mission must allow the large tank volume
Accommodate decrease thrust level
More common to monopropellant and cold gas
Wide range of thruster inlet operating pressure Bipropellant
Limited due to the need of fuel-oxidizer mixture ratio
Mass of pressurant gas
Size & mass of high pressure tank
Pressurant Mass Determination
WHAT YOU NEED TO BEGIN???
Max BOL operating pressure & temperature of high pressure tank
Determine density at this state
AGAIN, WE ASSUME............
All pressurant gas is held within the high-pressure tank at BOL.
Chan Man Ze
Looi Seng Tzer
Lai Mei Ling
P : EOL tank pressure
M_gas : Pressurant gas mass (unknown)
R_gas : Specific gas constant
T : EOL gas temperature
V_p : Propellant tank volume
V_pres : Pressurant tank volume (unknown)
Substitue Eq.1 & 2 into Eq.3, finally get
Remember to calculate the pressurant tank volume!!!
YOU ARE SOOOOO CLOSE TO IT!!!!!
Pressure times Volume, PV =
Estimated max operating pressure, P_BOL
Pressurant tank volume
Allow gas to flow in one direction
Prevent fuel and oxidizer vapour from migrating/ mixing with each other in a shared pressurized system
Maximize Propellant in given volume
Consistent Thrust and impulse
Consistent mixture ratio (bipropellant)