Slide 16 of 100
The AACB Class III concept was based on a airbreathing HTHL TSTO design investigated by Lockheed in 1965-66. The giant hypersonic booster aircraft would have been powered by turbofan-ramjet-scramjet engines. It would have weighed 306,175kg at liftoff and carried a smaller 131,542-kg orbiter rocketplane plus 15,876kg payload. The panel concluded thetechnology did not yet exist to develop this concept, so it was only regarded as an option by 1982 at the earliest.
”Space Shuttle” -- Dennis R. Jenkins, 1981, ISBN: 0963397451