Encyclopedia Astronautica

Credit: Lockheed Martin
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.

For Centaur IIIA, one of Centaur IIAS's two RL10A-4 engines is removed. The remaining engine is 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 are 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 is jettisoned. The second Centaur ignition occurs about 23 minutes into the flight, continues for about three minutes, and is followed several minutes later by the separation of the spacecraft from Centaur.

Engine: 167 kg (368 lb). Chamber Pressure: 39.00 bar. Area Ratio: 84. Thrust to Weight Ratio: 60.53.

Status: Out of production.
Unfuelled mass: 167 kg (368 lb).
Diameter: 1.53 m (5.00 ft).
Thrust: 99.10 kN (22,279 lbf).
Specific impulse: 451 s.
Burn time: 740 s.
Number: 2 .

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

See also
Associated Launch Vehicles
  • Atlas IIIA American orbital launch vehicle. The Atlas IIIA was a development of the Atlas using Russian engines in place of the Rocketdyne MA-5 booster/sustainer group used on all previous models. It was the centerpiece of Lockheed Martin's strategy to remain a leader in the commercial launch services industry. However customers never materialized, and it was used for only two launches in 2002-2004 before being replaced by the Atlas V. More...

Associated Manufacturers and Agencies
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...

Associated Stages
  • Centaur IIIA Lox/LH2 propellant rocket stage. Loaded/empty mass 18,710/1,905 kg. Thrust 99.16 kN. Vacuum specific impulse 451 seconds. Single-engine Centaur for Atlas IIIA. More...

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