Encyclopedia Astronautica

Credit: Boeing / Rocketdyne
Rocketdyne lox/lh2 rocket engine. 1192 kN. Development ended 1999. Isp=439s. Linear aerospike engine for X-33 SSTO technology demonstrator. Based on J-2S engine developed for improved Saturn launch vehicles in the 1960's.

Gas generator cycle; throttling 40% to 119% of nominal thrust; differential thrust between two engines plus-minus 15%. X-33 Advanced Technology Demonstrator Development. Designed for booster applications. Gas generator, pump-fed.

Chamber Pressure: 58.00 bar. Area Ratio: 58. Oxidizer to Fuel Ratio: 5.5.

AKA: J-2S Linear Aerospike; RS-69.
Status: Development ended 1999.
Height: 2.01 m (6.59 ft).
Diameter: 3.38 m (11.08 ft).
Thrust: 1,192.00 kN (267,972 lbf).
Specific impulse: 439 s.
Specific impulse sea level: 339 s.
First Launch: 1998.

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Associated Countries
See also
Associated Launch Vehicles
  • X-33 American winged rocketplane. NASA-sponsored suborbital unmanned prototype for a single-stage-to-orbit rocketplane. The Lockheed Martin vehicle would have used a linear aerospike engine, metallic insulation, and other features similar to their Starclipper shuttle proposal of 1971. In 1999 catastrophic failure of the composite fuel tank during static test brought into question the technical feasiblity of the design. The program was cancelled in 2001 before any flight articles were completed and after over $1.2 billion had been expended. 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
  • X-33 Lox/LH2 propellant rocket stage. Loaded/empty mass 123,800/28,600 kg. Thrust 2,284.00 kN. Vacuum specific impulse 439 seconds. More...

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