Rocket engine
This article is about a type of reaction engine. For rocket-propelled vehicles, see Rocket. For reaction engines not possessing a de Laval nozzle, see Reaction engine. RS-68 being tested at NASA's Stennis Space Center. The nearly transparent exhaust is due to this engine's exhaust being mostly superheated steam (water vapour from its propellants, hydrogen and oxygen) Viking 5C rocket engine A rocket engine uses stored rocket propellant mass for forming its high-speed propulsive jet. Rocket engines are reaction engines, obtaining thrust in accordance with Newton's third law. Most rocket engines use combustion, although non-combusting forms (such as cold gas thrusters) also exist. Vehicles propelled by rocket engines are commonly called rockets. Since they need no external material to form their jet, rocket engines can perform in a vacuum and thus can be used to propel spacecraft and ballistic missiles. Compared to other types of jet engines, rocket engines are by far the l