Re: The Olympics

[Herb Schulz <herbs@INTERACCESS.COM>]

> >  1: What keeps the "gyros" pointing in the same direction?
>
> The conservation of angular momentum.

Howdy,

If the angular momentum of the gyros is conserved that implies that
no external torque is being applies to them.

>  > The fact is that they are "disconnected" from the satellite itself so that
> not external         > torques can be applied to them and are used only to
> measure a RELATIVE angular     > position.
>
> The fact is that your sentence is wrong in both syntax and physics. The
> three gyros are each mounted in gimbal rings having three degrees of
> freedom. When a torquing motor tries to rotate a gyro axis with respect to
> the satellite frame, the result is that the satellite frame rotates with
> respect to the gyro axis which continues to point to its reference star.

The gimbal rings are there to isolate the gyros from external
torques; THAT is why they point in a fixed direction, i.e., their
angular momentum is conserved.


>  >
> >  Aren't the "torquing motors" internal "objects" that are rotating against
> the rest of the     > satellite?
>
> No. The motor frames are fixed with respect to the satellite frame. The
> motor axes are fixed to the gimbal rings.


Sorry, the motors start to rotate because an external (to the rotors
in the motor) torques is applied to them.  The, in turn, apply an
external torque on the surroundings (which are "rigidly" attached to
the satellite) causing the satellite to rotate.

Good Luck,
--
Herb Schulz
(herbs@interaccess.com)