Encyclopedia Astronautica
Centaur IIIA


American space tug. One launch, , 2000. Upper stage / space tug - out of production. Single-engine Centaur for Atlas IIIA.

The Lockheed Martin manufactured Centaur IIIA upper stage was powered by one Pratt & Whitney RL10A-4-1 turbopump-fed engine burning liquid oxygen and liquid hydrogen. Using the proven flight design of the Centaur IIAS stage, the only changes to Centaur for IIIA were in the aft region of the stage. For Centaur IIIA, one of Centaur IIAS's two RL10 engines was removed. The remaining engine was re-positioned to a center-mount, and electro-mechanical thrust vector control actuators replace the hydraulically actuated system previously in use. Guidance, tank pressurization, and propellant usage controls for both Atlas and Centaur phases were provided by the inertial navigation unit (INU) located on the forward equipment module. The first Centaur burn lasts about nine minutes after which the Centaur and its payload coast in a parking orbit. During the first burn, approximately ten seconds after ignition, the payload fairing was jettisoned. The second Centaur ignition occurs about 23 minutes into the flight, continues for about three minutes, and was followed several minutes later by the separation of the spacecraft from Centaur.

For Centaur IIIA, one of Centaur IIAS's two RL10A-4 engines was removed. The remaining engine was re-positioned to a center-mount, and electro-mechanical thrust vector control actuators replace the hydraulically actuated system previously in use. Guidance, tank pressurization, and propellant usage controls for both Atlas and Centaur phases were provided by the inertial navigation unit (INU) located on the forward equipment module. The first Centaur burn lasts about nine minutes after which the Centaur and its payload coast in a parking orbit. During the first burn, approximately ten seconds after ignition, the payload fairing was jettisoned. The second Centaur ignition occurs about 23 minutes into the flight, continues for about three minutes, and was followed several minutes later by the separation of the spacecraft from Centaur.

Unit Cost $: 25.000 million.

Gross mass: 18,710 kg (41,240 lb).
Unfuelled mass: 1,905 kg (4,199 lb).
Height: 10.00 m (32.00 ft).
Diameter: 3.05 m (10.00 ft).
Span: 3.05 m (10.00 ft).
Thrust: 99.16 kN (22,291 lbf).
Specific impulse: 451 s.
Number: 1 .

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Associated Countries
Associated Engines
  • RL-10A-4-1 Pratt and Whitney lox/lh2 rocket engine. 99.1 kN. Out of production. Isp=451s. Used on Atlas IIIA launch vehicle. First flight 2000. Version with one of engines removed; remaining engine re-positioned to center-mount; new electro-mechanical gimbals. More...

See also
Associated Propellants
  • Lox/LH2 Liquid oxygen was the earliest, cheapest, safest, and eventually the preferred oxidiser for large space launchers. Its main drawback is that it is moderately cryogenic, and therefore not suitable for military uses where storage of the fuelled missile and quick launch are required. Liquid hydrogen was identified by all the leading rocket visionaries as the theoretically ideal rocket fuel. It had big drawbacks, however - it was highly cryogenic, and it had a very low density, making for large tanks. The United States mastered hydrogen technology for the highly classified Lockheed CL-400 Suntan reconnaissance aircraft in the mid-1950's. The technology was transferred to the Centaur rocket stage program, and by the mid-1960's the United States was flying the Centaur and Saturn upper stages using the fuel. It was adopted for the core of the space shuttle, and Centaur stages still fly today. More...

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