DAC Helios

American nuclear-powered orbital launch vehicle. 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.

LEO Payload: 454,500 kg (1,002,000 lb) to a 325 km orbit.

Stage Data - DAC Helios

• Stage 1. 1 x DAC Helios-1. Gross Mass: 1,660,000 kg (3,650,000 lb). Empty Mass: 149,000 kg (328,000 lb). Thrust (vac): 52,926.000 kN (11,898,238 lbf). Isp: 410 sec. Burn time: 113 sec. Isp(sl): 345 sec. Diameter: 24.40 m (80.00 ft). Span: 29.00 m (95.00 ft). Length: 16.20 m (53.10 ft). Propellants: Lox/LH2. No Engines: 4. Engine: Chamber/single nozzle. Status: Study 1963.

• Stage 2. 1 x DAC Helios-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: 2. Engine: NERVA 1mlbf. Status: Study 1963.