BOEING

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Boeing also investigated large two-stage vertical takeoff, horizontal landing (VTHL TSTO) heavy-lift reusable launch vehicles for 380-420t payloads. The company's "reference vehicle" from 1976 was used as a baseline for NASA's early SPS technology assessments. Its gross liftoff mass was 11,000t and the payload capability was 420t. The specific transportation cost was $44/kg [1978 economic conditions].

Later trade studies by Boeing & Rockwell from 1980 indicated a smaller 4,000t GLOW version capable of launching 120-tonne payloads actually would be more economical although the marginal launch cost per kilogram of payload would be slightly higher.

This alternative Boeing design from 1977-78 had a core diameter of 15.24m. The total length was 140.7 meters and the kerosene/LOX booster's wingspan was 60.5m. The 76.3-meter long orbiter used hydrogen+oxygen fuel. The liftoff weight was about 9500t and the payload capability was 381t. This vehicle would have been much bigger than the Space Shuttle (right, to scale).

Alternative Boeing TSTO concept from 1979.

”Transportation for Solar Power Satellites” – Shelton, SPACEFLIGHT 1982/January/p.2

"Space Industrialization Volume II" -- (Ed.) Brian O'Leary, 31272 Flying Cloud Drive, Laguna Niguel, CA.