Encyclopedia Astronautica
Saturn S-N V-25(S)U

Nuclear/LH2 propellant rocket stage. Loaded/empty mass 245,760/71,190 kg. Thrust 889.33 kN. Vacuum specific impulse 825 seconds. Version of Nerva studied by Boeing for manned Mars expedition.

Status: Study 1968.
Gross mass: 245,760 kg (541,800 lb).
Unfuelled mass: 71,190 kg (156,940 lb).
Height: 48.17 m (158.03 ft).
Diameter: 10.06 m (33.00 ft).
Span: 10.06 m (33.00 ft).
Thrust: 889.33 kN (199,928 lbf).
Specific impulse: 825 s.
Burn time: 1,500 s.

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Associated Countries
Associated Engines
  • Nerva DoE nuclear/lh2 rocket engine. 266 kN. Study 1968. Early version of Nerva engine proposed for use in Saturn and RIFT configurations in 1961. Isp=800s. More...

Associated Launch Vehicles
  • Saturn V-25(S)U American orbital launch vehicle. Boeing study, 1968. 4 156 inch solid propellant boosters; Saturn IC stretched 498 inches with 6.64 million pounds propellant and 5 F-1 engines; S-II standard length with 5 J-2 engines. This vehicle would place Nerva nuclear third stage into low earth orbit, where five such stages would be assembled together with the spacecraft for a manned Mars expedition. 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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