Encyclopedia Astronautica
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.

LEO Payload: 454,500 kg (1,002,000 lb) to a 325 km orbit in 1985 dollars. Flyaway Unit Cost $: 105.700 million.

Stage Data - DAC Helios ISI

  • Stage 1. 1 x DAC Helios ISI-1. Gross Mass: 1,333,000 kg (2,938,000 lb). Empty Mass: 120,000 kg (260,000 lb). Thrust (vac): 49,807.000 kN (11,197,059 lbf). Isp: 455 sec. Burn time: 107 sec. Isp(sl): 365 sec. Diameter: 24.40 m (80.00 ft). Span: 29.00 m (95.00 ft). Length: 22.90 m (75.10 ft). Propellants: Lox/LH2. No Engines: 4. Engine: Chamber/single nozzle. Status: Study 1963.
  • Stage 2. 1 x DAC Helios ISI-2. Gross Mass: 1,070,000 kg (2,350,000 lb). Empty Mass: 214,000 kg (471,000 lb). Thrust (vac): 17,926.000 kN (4,029,925 lbf). Isp: 850 sec. Burn time: 392 sec. Diameter: 21.30 m (69.80 ft). Span: 38.10 m (124.90 ft). Length: 27.40 m (89.80 ft). Propellants: Nuclear/LH2. No Engines: 4. Engine: NERVA 1mlbf. Status: Study 1963.

Status: Study 1963.
Gross mass: 2,948,400 kg (6,500,100 lb).
Payload: 454,500 kg (1,002,000 lb).
Height: 60.00 m (196.00 ft).
Diameter: 24.40 m (80.00 ft).
Thrust: 39,955.80 kN (8,982,421 lbf).
Apogee: 325 km (201 mi).

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...
  • NERVA 1mlbf Notional nuclear/lh2 rocket engine. 8963 kN. DAC Helios, DAC Helios ISI studies 1963. Isp=850s. More...

See also
  • DAC Helios Douglas/Bono 1963 concept for a chemical-boosted / nuclear upper stage launch vehicle, designed as alternatives to the Convair/Ehricke Helios. The baseline version used a nuclear, recoverable upper stage boosted above the atmosphere by a minimum chemical stage. More...

Associated Manufacturers and Agencies
  • Douglas American manufacturer of rockets, spacecraft, and rocket engines. Boeing Huntington Beach, Huntington Beach, CA, USA. More...

Associated Stages
  • 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. More...
  • DAC Helios ISI-2 Nuclear/LH2 propellant rocket stage. Loaded/empty mass 1,070,000/214,000 kg. Thrust 17,926.00 kN. Vacuum specific impulse 850 seconds. More...

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