Space Propulsion - IAP/TU Wien
Space Propulsion - IAP/TU Wien
Space Propulsion - IAP/TU Wien
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eaction wheel, cont’d<br />
<strong>Space</strong> <strong>Propulsion</strong><br />
Example 9: Reaction Wheel Unloading<br />
How much propellant does it take to unload one of the Magellan wheels, and<br />
how long does it take? (JPL Venus Mission, 1994)<br />
The Magellan wheel characteristics are:<br />
maximum momentum = 27 N-m-s<br />
maximum wheel speed = 4000 rpm = 418.879 rad/s<br />
The thruster pair to be used has the following characteristics:<br />
thrust = 1 N; moment arm = 2m<br />
pulsing specific impulse 1500 m/s.<br />
the propellant mass required to unload it is<br />
m<br />
H<br />
LI<br />
27<br />
=<br />
2*1500<br />
p =<br />
=<br />
sp<br />
0.009<br />
[ kg]<br />
engine burn time required to unload is<br />
H 27<br />
t = = = 6.75<br />
nFL 2*1*2<br />
[ s]