Reply to post: Reaction wheels

Voyager 1 fires thrusters last used in 1980 – and they worked!

Robert Sneddon

Reaction wheels

Reaction wheels and gyros only work to alter the orientation of a spacecraft while they are spinning. Slow them down to a stop to save electricity and wear and tear on the bearing etc. and the spacecraft settles back into its original orientation. They don't last forever -- the Hubble space telescope has/had multiple redundant sets of reaction wheels used for tracking during observations and most of them have stopped working IIRC.

Expend some mass through a thruster, the spacecraft will rotate. Fire off some more mass in the opposite direction, it will stop rotating and stay in its new orientation.

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