> It's the spin up and spin down that actually make the orientation changes, though. You can't spin up infinitely, so once a reaction wheel is spinning as fast

> It's the spin up and spin down that actually make the orientation changes, though. You can't spin up infinitely, so once a reaction wheel is spinning as fast as it can, you can't accelerate it further, and you can't rotate the spacecraft in the opposite direction on that axis any longer. precisely. angular momentum. > I don't think reaction wheels are capable of gross orientation changes at all -- only very minor alignment corrections. nah. as an example, SORCE has nothing but wheels and a torquer bar (or two?), and aims all over the sky.