Slide 42 of 125
The mid/late 1970s future space transportation studies were dominated by solar power satellite
(SPS) launch requirements. Proposed by Peter Glaser in the late 1960s, the SPS program called
for the construction of giant solar collector satellites in space that would beam down energy
in the form of microwave radiation to receivers on the ground. The initial studies indicated
SPS could provide cheaper electrical power than other options. But the satellites
would have to be enormous, spanning several kilometers and weighing tens of thousands of tons. They would be assembled in space from components launched by low-cost heavy-lift rockets.
The initial NASA/Johnson Space Center launch studies from 1976 assumed a very large reusable VTVL TSTO vehicle (right) would be used for launching 700-tonne SPS subassemblies into a 500km low Earth orbit. The expected recurring launch cost was approximately $23 million  or $33 per kilogram. All launch vehicle components except the large payload fairing would be reusable and the 1st & 2nd stages would land at sea.
Liftoff thrust: Total Mass: 14,203t. Length: 101.8m.
Payload capability: 700t to a 90km x 500km transfer orbit; Payload bay: 24.4m diameter.
Stage 1 : 24 x LOX/propane rocket engines. Liftoff thrust: . Isp: Gross Mass: 9,042t. Empty Mass: 865t. Length: . Diameter: 24.4m. Propellants: LOX/propane.
Stage 2 : 12 x LOX/LH2 rocket engines. Liftoff thrust: . Isp: Gross Mass: 4,953t including 700t payload and 3,832t propellants. Empty Mass: 421t. Length: . Diameter: 24.4m. Propellants: LOX/LH2.
In early 1977, NASA/JSC decided to replace the VTVL recovery scheme to reduce the risk of vehicle loss that might be consequent to the sea recovery of the ballistic launch vehicles. The new VTHL TSTO baseline design was heavier for the same payload, and the development cost was expected to be higher. However, the vehicle would have better maneuvrability and landing safety. Its crossrange capability was good enough to allow several landing opportunities per day, so the vehicle would not have to fly single orbit-once-around missions like the VTVL TSTO. The expected launch cost was $13.5 million or $30 per kilogram. The payload compartment was reusable since NASA believed the solar power satellite payloads could be redesigned to fit within a smaller 15.2-meter diameter envelope. The payload capability was also slightly reduced, to 454 metric tons.
Liftoff thrust: Total Mass: 9,526t. Length: 110m.
Payload capability: 454t to a 500km low Earth orbit; Payload bay: 15.2m diameter.
Stage 1 : 16 x LOX/propane rocket engines. Liftoff thrust: . Isp: Gross Mass: 6,500t. Empty Mass: 635t. Length:82.3m . Diameter: 15.2m. Propellants: LOX/propane.
Stage 2 : 14 x LOX/LH2 rocket engines. Liftoff thrust: . Isp: Gross Mass: 3,000t including 454t payload. Empty Mass: 363t. Length: 76.2m. Diameter: 15.2m. Propellants: LOX/LH2.
”Space Solar Power - The Transportation Challenge” -- Davis, Space Manufacturing Facilities II (Proceedings of the Third Princeton/AIAA Conference, May 9-12 1977) p.35