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. Flyaway Unit Cost 1985$: 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.