3) The illustrated spacecraft (right) contains a 4-for-3
array of reaction wheels.
a) What are the maximum spacecraft rates
(x, wy and wz ) if all wheels are operating and the
spacecraft's net momentum is zero? Express your
answers in degrees /second.
b) What is the spacecraft's maximum Z-axis
angular rate, if the -Y wheel has failed? Assume that
the spacecraft's net momentum is zero. Express your
answer in degrees/second.
c) If the spacecraft's initial conditions are ®x
B (4 places)
= wy = QZ = 0 and wheel momentum is as illustrated
below, what is the maximum possible spacecraft rate
about the Z axis?
Each one of four identical reaction wheels has
the following capabilities:
H = + 60 ft-lb-sec
T = I 42 oz-in
The reaction wheels are arranged in a pyramid
configuration as shown above, with ß =30 deg.
Spacecraft moments of inertia are:
Ixx = 500 sl-ft2
Iyy = 500 sl-ft²
Izz = 700 sl-ft²
Products of inertia = 0
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