NASA / DoD A.A.C.B. CLASS I & II [1965-66]
Notes:
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Although NASA's Committee on Hypersonic Lifting Vehicles formally endorsed the development of a fully reusable two-stage launch vehicle in June 1964, the military and NASA remained relatively uninterested. Apollo and other projects received most of the attention and resources from space planners. However, NASA and the Department of Defense did a gree to set up joint Aeronautics & Astronautics Coordinating Board (AACB) Subpanel on Reusable Launch Vehicle Technology in August 1965. The AACB subpanel then examined various NASA and USAF candidate concepts over the next twelve months. The emphasis was on manned space station crew transfer/resupply missions with relatively small payloads of 907kg in addition to a crew of 4-6 astronauts.
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The AACB concepts belonged to three different classes. All Class 1 designs used a small 6800-kilogram reusable lifting-body spaceplane to carry the crew and payload. The most advanced Class 1 concept (top) consisted of a horizontal launch & landing (HTHL) winged booster plus expendable upper stage to lift the lifting-body orbiter into orbit. The gross liftoff mass was 544,310kg, the expected development cost was $2.5 billion [1965 dollars] and the cost per launch would have been $15 million. Alternatively, the Class 1 lifting-body orbiter could have been launched on an existing USAF Titan IIIM expendable booster (left). This option would have cost only $700 million to develop, plus $19 million per launch over ten years. If the Saturn IB (center) were used, the development cost would stay the same but the cost per mission would increase to $36 million. Finally, a new expendable low-cost booster (right) could have been developed for $2,000 million; the marginal launch cost would have been only $14 million. The gross liftoff weights were expected to be 825,538kg (Titan IIIM+Class I), 587,855kg (Saturn IB+Class I) and 395,986kg (new expendable LOX/LH2 booster) respectively. The AACB panel preferred the Class I option since it would cost less to develop and the development risk would be lower than for an advanced fully reusable system. A Class I vehicle could become operational as early as 1974 and the comparatively low development cost could be amortized in only a few flights.
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The AACB Class II concepts were fully reusable all-rocket TSTO vehicles. The orbiter retained the lifting-body shape but it was much larger since it had to carry internal tanks for the oxygen+hydrogen rocket propellant. These designs were designed for larger payloads of 9,072kg. The VTHL TSTO design (left) would have had a gross liftoff weight of 745,479kg. It was expected to cost $3 billion to develop but only $4 million to operate per flight. An alternatively 598,742-kilogram HTHL TSTO design (right) would have cost $4 billion but otherwise offer similar capabilities. These concepts would have been available in 1978- but would have required high flight rates to make economic sense vs. Class I.
Dennis R. Jenkins, 1981, ISBN: 0963397451