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Copy of Spacecraft Subsystem Design

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by

Caesar Looi

on 1 June 2014

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Transcript of Copy of Spacecraft Subsystem Design

WHAT FORMULAS ARE INVOLVED?????
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
Ads
Simple
Save cost, complexity of the system
Disad
Thrust, pressure, propellant flow rate decrease, inertial changes
Large tank
Blow-Down System
Spacecraft Subsystem Design
Facts.......
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
Transition*
AND Facts.....
Mass of pressurant gas
Size & mass of high pressure tank
Pressurant Mass Determination
WHAT YOU NEED TO BEGIN???
Estimate:
Max BOL operating pressure & temperature of high pressure tank
Determine density at this state
STEP ONE
STEP TWO
AGAIN, WE ASSUME............
All pressurant gas is held within the high-pressure tank at BOL.
STEP THREE
Group 6
Lovely Members
Chan Man Ze
Looi Seng Tzer
Lai Mei Ling
Hippy
Aspects of
Pressurization Systems
Blow-Down Systems
Regulated Systems
Pressurant Mass
Determination
Regulators &
Check Valves
??HOW??
!*HOW??
WHyY?
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)
Eq.1
Eq.2
Eq.3
Substitue Eq.1 & 2 into Eq.3, finally get
Eq.4
Remember to calculate the pressurant tank volume!!!
YOU ARE SOOOOO CLOSE TO IT!!!!!
LAST STEP
Pressure times Volume, PV =
Estimated max operating pressure, P_BOL
*
Pressurant tank volume


WHITEBOARD PLEASEEee~


Check Valves
Function
Allow gas to flow in one direction
Prevent
Prevent fuel and oxidizer vapour from migrating/ mixing with each other in a shared pressurized system
Bipropellant
If mixed………
Maximize Propellant in given volume
Consistent Thrust and impulse
Consistent mixture ratio (bipropellant)


Advantages
Full transcript