Encyclopedia Astronautica
Nerva 2/NTR


American space tug. Study 2005. Upper stage / space tug - study completed 1991. Late 1980's update of 1960's Nerva design.

Late 1980's update of 1960's Nerva design.

Unit Cost $: 200.000 million.

Gross mass: 158,400 kg (349,200 lb).
Unfuelled mass: 27,000 kg (59,000 lb).
Height: 47.60 m (156.10 ft).
Diameter: 10.00 m (32.00 ft).
Span: 10.00 m (32.00 ft).
Thrust: 333.00 kN (74,861 lbf).
Specific impulse: 925 s.

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Associated Countries
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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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