Gross Mass: 2,268,000 kg.
Empty Mass: 143,000 kg. Thrust (vac): 2,721,000 kgf. Isp: 426 sec. Burn time: 327 sec. Propellants: Lox/LH2Diameter: 21.3 m. Span: 21.3 m. Length: 27.4 m. Country: USA. No Engines: 4. M-1Status: Study 1963. Comments: Operational date would have been July 1977. Recoverable stage. .