Encyclopedia Astronautica
Nerva Gamma

Nuclear/LH2 propellant rocket stage. Loaded/empty mass 18,643/5,829 kg. Thrust 81.00 kN. Vacuum specific impulse 975 seconds. Improved version of the Alpha nuclear stage designed to fit into the space shuttle payload bay. Additional propellant modules could be added in orbit. Such propellant modules would have a mass of 23,181 kg, including 21,265 kg of usable propellant. Given an Alpha engine development program, it would have been flight tested by 1984. In addition to propulsion, it would provide 10 to 25 MWe power for missions of two to five years duration.

Propellant Formulation: Nuclear/Slush Hydrogen.

Status: Development 1972.
Gross mass: 18,643 kg (41,100 lb).
Unfuelled mass: 5,829 kg (12,850 lb).
Height: 18.29 m (60.00 ft).
Diameter: 4.50 m (14.70 ft).
Span: 4.50 m (14.70 ft).
Thrust: 81.00 kN (18,209 lbf).
Specific impulse: 975 s.
Burn time: 1,500 s.

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Associated Countries
Associated Engines
  • Nerva Gamma DoE nuclear/lh2 rocket engine. 81 kN. Study 1972. Isp=975s. The final Nerva Gamma flight engine was an improved version of the Alpha, a small engine that could be launched together with its stage and a payload in a single space shuttle launch. More...

Associated Propellants
  • Nuclear/LH2 Nuclear thermal engines use the heat of a nuclear reactor to heat a propellant. Although early Russian designs used ammonia or alcohol as propellant, the ideal working fluid for space applications is the liquid form of the lightest element, hydrogen. Nuclear engines would have twice the performance of conventional chemical rocket engines. Although successfully ground-tested in both Russia and America, they have never been flown due primarily to environmental and safety concerns. 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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