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I had a hunch that was the case, but this quote from Wikipedia suggests otherwise > Since the reaction wheel is a small fraction of the spacecraft's total mass

I had a hunch that was the case, but this quote from Wikipedia suggests otherwise > Since the reaction wheel is a small fraction of the spacecraft's total mass... The gist from the Wikipedia article suggests momentum wheels (used in Hubble) are very heavy, but reaction wheels, not so much, due to their use for precision movement. Obviously I defer to someone that has more than a cursory Wikipedia articles breadth of knowledge on the subject. Am I misinterpreting Wikipedia, or are the reaction wheels on Keppler more than a "small fraction of the mass"?

sbierwagen 13y ago
Momentum wheels are reaction wheels. I'm not sure why the wikipedia article on them thinks differently-- Hubble wasn't gyrostablized at all, it's a telescope, it can't be allowed to spin. Hubble also masses eleven times that of Kepler. (11,000kg vs 1,000kg) I don't know the actual numbers, but attitude control systems possibly take up a larger percentage of spacecraft mass on Kepler than it does on Hubble.