S-V

Centaur

Centaur-2A upper stage of an Atlas IIA
Manufacturer	General Dynamics Martin Marietta Lockheed Martin United Launch Alliance
Country of origin	United States
Used on	Atlas-Centaur Atlas G Atlas I Atlas II Atlas III Atlas V Titan IIIE Titan IV(401)A/B Saturn I (unflown) Space Shuttle (unflown)
General characteristics
Height	12.68 m (499 in)
Diameter	3.05 m (120 in)
Gross mass	2,247 kg (4,954 lb) (single engine) 2,462 kg (5,428 lb) (dual engine)
Propellant mass	20,830 kg (45,920 lb)
Associated stages
Derivatives	ACES
Launch history
Status	Active
Total launches	223 as of February 2015[update]
First flight	9 May 1962
Engine details
Engines	1 or 2 RL10
Thrust	99.2 kN (22,300 lbf) (single engine) 198.4 kN (44,600 lbf) (dual engine)
Specific impulse	450.5 s
Burn time	Variable
Fuel	LOX/LH2

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 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 was the brainchild of Karel J. "Charlie" Bossart (the man behind the Atlas ICBM) and Dr. Krafft A. Ehricke, both Convair employees. Their design was essentially a smaller version of the Atlas, with its concept of using lightweight "stainless steel balloon" tanks whose structural rigidity was provided solely by the pressure of the propellants within. To keep the tanks from collapsing prior to propellant loading, they were either kept in "stretch" or pressurized with nitrogen gas.

Centaur is powered by one or two RL10 rocket engines (SEC and DEC variants respectively).

In 1956 Krafft Ehricke of Convair began to study a liquid hydrogen upper stage rocket. In 1958 the project started through a joint between Convair, Advanced Research Projects Agency (ARPA) and U.S. Air Force. In 1959 NASA assumed ARPA's role. Development started at NASA's Marshall Space Flight Center and then at Lewis Research Center, now the Glenn Research Center, but proceeded slowly, with the first (unsuccessful) test flight in May 1962. In the late 1950s and early 1960s Centaur was proposed as a high energy upper stage for the Saturn I, Saturn IB and Saturn V rockets, under the designation S-V (pronounced "ess five") in accordance with the numbering of other stages of Saturn rockets. However, Centaur never flew on any Saturn vehicle, though the Saturn I used a cluster of six RL10 engines on its second stage.