How do action and reaction forces work in a rocket launch?

Rocket engines burn fuel to produce high-speed exhaust that is expelled downward. By Newton’s third law, the exhaust pushes back on the rocket with an equal and opposite force, lifting it upward. Rockets work in space as well as in air because they do not need to push against the atmosphere; they only need propellant to throw mass backward. The first liquid-fueled rocket was launched successfully by Robert H. Goddard in 1926. Modern launch vehicles rely on the same action-reaction principle, but with far more powerful engines and staging systems.