Newton's Third Law States that Every Action Has an Equal and Opposite Reaction

To stop or slow down a spacecraft, a force must be applied in the direction opposite to its motion. Exerting a force results in an equal force in the opposite direction (like the recoil a person feels when firing a gun). When a spacecraft fires a thruster rocket, the exhaust gas pushes against the thruster and the thruster pushes against the exhaust gas. The gas and rocket move in opposite directions.

(Rev. 09/19/96)