Encyclopedia Astronautica
DAC Helios ISI-1


Lox/LH2 propellant rocket stage. Loaded/empty mass 1,333,000/120,000 kg. Thrust 49,807.00 kN. Vacuum specific impulse 455 seconds.

Cost $ : 38.700 million. No Engines: 4.

Status: Study 1963.
Gross mass: 1,333,000 kg (2,938,000 lb).
Unfuelled mass: 120,000 kg (260,000 lb).
Height: 22.90 m (75.10 ft).
Diameter: 24.40 m (80.00 ft).
Span: 29.00 m (95.00 ft).
Thrust: 49,807.00 kN (11,197,059 lbf).
Specific impulse: 455 s.
Specific impulse sea level: 365 s.
Burn time: 107 s.

More... - Chronology...


Associated Countries
Associated Engines
  • Chamber/single nozzle Notional lox/lh2 rocket engine. 13,231 kN. Study 1963. Isp=455s. Before moving to favored plug nozzle designs, Bono at Douglas considered having multiple combustion chambers exhaust into a single large nozzle to obtained Improved Specific Impulse. More...

Associated Launch Vehicles
  • DAC Helios ISI American nuclear-powered orbital launch vehicle. As the basic design, but featuring an Improved Specific Impulse chemical stage that used many engines feeding into single large nozzle. More...

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...

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