re: Mir orbital control

Leigh Palmer (palmer@sfu.ca)
Thu, 21 Aug 1997 08:20:37 -0700

I could understand how loss of power could lead to a rotationally
stabilized spacecraft "spinning out of control" *if* the inertial
reservoir (the reaction wheels) were spinning at appreciable speeds
at the time of power loss. Frictional coupling of the wheels to the
spacecraft would slowly transfer the angular momentum of the wheels
to the spacecraft as a whole when power failed.

What I don't understand (and perhaps someone here can help me with)
is why the wheels would possess any appreciable angular momentum.
It seems to me they should be maintained with angular speeds with
respect to the rest of the craft which are as small as possible.
This can be done by electromagnetically torquing* the spacecraft in
Earth's magnetic field. Is my picture missing something important?

I realize that the solar panels on Mir might be articulated in some
complicated manner that would render them less effective, but
partial electrical power should be maintainable with some static
configuration or other.

Leigh

*ugly word - means "applying a torque"