How do you Control Altitude in Space?
Because the control surfaces that an airplane uses cannot work in airless space, a spacecraft relies on a different form of altitude control. To change orientation, a spacecraft applies torque (a twisting force) by firing small rockets or by spinning internal wheels.
To rotate a spacecraft, a pair of thruster rockets on opposite sides of the vehicle are fired in opposite directions. To stop the rotation, a second pair is fired to produce an opposing force. The Space Shuttle’s Reaction Control System provides the thrust for attitude maneuvers (roll, pitch, and yaw), and for small velocity changes along the Shuttle’s longitudinal axis (front to back). See the Space Shuttle Discovery at the National Air and Space Museum's Steven F. Udvar-Hazy Center.
Some satellites use a system of reaction wheels—basically gyroscopes—to change their altitude in space. The rapidly spinning wheels carry a lot of rotational momentum that the spacecraft can tap to change its own orientation. To do this in all three dimensions of space, the spacecraft must use three rotating wheels oriented at right angles to one another.
How Can Thrust Help Change Altitude?
Most spacecraft use small thruster rockets to control their altitude. To rotate a spacecraft, a pair of thruster rockets on opposite sides of the vehicle are fired in opposite directions. To stop the rotation, a second pair is fired to produce an opposing force.