fisher@dvinci.DEC (Burns Fisher, MRO3-1/E13, 231-4108) (04/09/84)
> Something I've been wondering about for a long time is why the >technology of Oberth wheels has not been much used for attitude/spin >control in space. The idea goes like this: > Inside your ship, you have a flywheel spun by a small motor. >If you start with both ship and wheel not spinning, then you can spin the >ship by turning the wheel the other way... Gyroscopes are actually used in a similar manner in (some) current spacecraft. I believe the difference is that the gyros are spun up ahead of time, either on the ground or using attitude control engines to keep the craft stable while they are spun up. Then the gyros are used as a solid something to push against to stabilize or turn the spacecraft. I don't know what the advantage of using this method is over pure attitude jets. Just less fuel? Finer control? Note that this method does not mean that no attitude engines are needed. The gyros can only absorb a certain amount of delta- (aaaaagh what is the symbol for angular momentum? p?) before they saturate and have to be "unwound" using the engines. Note: The above is only second-hand knowledge gleaned from Aviation Week etc., mainly during the Skylab reactivation and stabilization effort. If anyone has corrections or more details, feel free. Burns UUCP: ... {decvax|allegra|ucbvax}!decwrl!rhea!dvinci!fisher ARPA: decwrl!rhea!dvinci!fisher@{Berkeley | SU-Shasta}