Centaur is a rocket stage designed for use as the upper stage of space launch vehicles and is currently used on the Atlas V. Centaur boosts its satellite payload to geosynchronous orbit or, in the case of an interplanetary space probe, to or near to escape velocity. Centaur was the world's first high-energy upper stage, burning liquid hydrogen (LH2) and liquid oxygen (LOX), and has enabled the launch of some of NASA's most important scientific missions over its 50-year history. Centaur is powered by one or two RL10 rocket engines (SEC and DEC variants respectively).