CMG flywheel attitude control

[Wishbone]

What are the maximum torques that can be achieved for given flywheel mass and speed of rotation?

Another silly question: what is the energy consumption of the attitude control system?

 

[martins]

[math]
\vec{T} = m r^2 \vec{\omega}
[/math]
assuming that the flywheel consists of a ring of radius r, containing its entire mass. Otherwise you have to integrate over the mass distribution.

 

[Tommy]

This may be useful:

[ame="http://en.wikipedia.org/wiki/Gyroscope"]Gyroscope - Wikipedia, the free encyclopedia[/ame]

This may help you determine the rotational inertia of a flywheel. I think the actual torque produced will depend on the length of the lever arm in the gimbaling mechanism as well.

Edit: Actually, the more I think about it, the length of the lever arm shouldn't matter - it would only affect the force needed to rotate the gimbal, but not the effect on the vessel itself.

 

[Wishbone]

This is what I have found:
[ame="http://en.wikipedia.org/wiki/Control_moment_gyroscope"]Control moment gyroscope - Wikipedia, the free encyclopedia[/ame]
The links to an MIT paper and the 6154691 us patent look promising. On the todo list - power requirements (I never trust wiki, it promises "a few hundred watts").

EDIT: L3 DGCMG (of the ISS vintage) specs (assume they are state-of-the-art, or 5-10% behind)

design life: 10 yrs, angular momentum 4760 Nms, nominal speed 6600 rpm,

MAX output torque: 258 Nm

MAX gimbal rate: +-3.1 deg/sec

Size: 1.3x1.37x1.25, mass: 272 kg (funny, but the spec sheet says weight)

Alas, no electricity consumption numbers in the datasheet, will attempt scouring through the ISS manuals etc.

---------- Post added at 03:09 AM ---------- Previous post was at 02:26 AM ----------

Here goes Honeywell M50 (the data are of course sanitised so higher perf is clearly possible, plus it's quite light): http://www51.honeywell.com/aero/com...og-documents/M50_Control_Moment_Gyroscope.pdf

Ang.momentum 25-75 Nms
Speed: 4500,5000,5500,6000,6500,XXXX rpm
Gimbal rot range: 360 deg
bandwidth: 10 Hz
gimbal acc: 3 rad/s^2
Output torque: <0.075 to 75 Nm

POWER CONSUMPTION:
Standby 11 W
Run-up 113 W
Peak torquing 95 W
Quiescent 35 W

Mass: 28 kg