Turning with a reaction wheel.
How can a spacecraft turn without pushing space?
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How can a spacecraft turn without pushing space?
Fit the wheel and controller before commanding a rotation.
A motor accelerates an internal wheel and applies an opposite torque to the spacecraft. With no external torque, the total angular momentum stays unchanged. The body rate depends on both inertias because the wheel command is measured relative to the rotating spacecraft. A finite wheel speed limits how much momentum can be stored.
Single isolated axis initially at rest, Ibody 80 kg·m² and Iwheel 0.2 kg·m². Wheel command is speed relative to the body. No external torque or momentum unloading. Display motion is slowed by a common factor 0.2; numerical rates retain physical units.
Turn the spacecraft at 5–7°/s without saturating the wheel.
Turn the spacecraft by changing relative wheel speed.