Space Propulsion - IAP/TU Wien

eaction wheel, cont’d
Space Propulsion
A S/C can be rotated by an angle Θ by application
of a torque T for time interval t
Θ =
Tt
2
2
I v
this torque can be supplied by an accelerating flywheel;
angular acceleration α W
is supplied by a motor
T α w I w
=
v
The resulting S/C rotation angle is
and the increase in wheel speed:
αW
I
Θ =
2I
W
t
2
Δω
w
= α w
t
The S/C can be returned to its original position by applying the opposite torque to the flywheel;
the net increase in flywheel rotational speed then is 0 (neglecting friction). Due to unbalanced torques
however, the flywheel eventually will reach its upper angular speed limit and then is not fully
available for maneuvering any more. To become maneuverable again it must be „unloaded“, i.e.
its angular speed must be brought to 0 again.
cont’d