NORTH AMERICAN & GENERAL DYNAMICS PHASE B SHUTTLE 
This illustration depicts an early shuttle Phase-B design by North American / General Dynamics. NASA awarded two $8-million Phase-B contracts to consortiums led by North American Rockwell and McDonnell-Douglas in May 1970. The booster (model B8D) was based on an earlier General Dynamics Phase-A study while the low-crossrange straight-wing “NAR-130” orbiter was designed by North American Rockwell.
North American “NAR-130” low crossrange orbiter reentry. The straight-wing design would remain a secondary option until late 1971 mostly due to internal NASA politics although nobody seriously believed it would ever be built.
North American / General Dynamics shuttle on the launch pad. When NASA awarded the shuttle Phase-B study contracts, it was still requesting funding for simultaneously developing its 12-man space station and the shuttle. Each project would have cost $5 billion in FY 1971-77 but sceptics in Congress regarded them as a precommitment to a $50-100 billion manned mission to Mars.
GD booster / NAR orbiter orbiter separation at 70km altitude and 3,130m/s velocity. The orbiter version depicted here is the elegant “NAR-134-B” delta wing high-crossrange version. It would have weighed 98,762kg empty and a 9,072kg payload could be accomodated. For some reason, the Phase B contract only called for a 6,804-kg payload capability to a 500-km 55 de.g orbit. This was similar to Max Faget's “DC-3” specifications, although the US Air Force wanted much more. But the system had considerable growth potential since the orbiter/booster landing jets might be removed on some missions. NASA still had not decided if the shuttle would make powered or unpowered glide landings, but there was considerable evidence that dead-stick glide landings were feasible although the jet engines were retained for now.
”Space Shuttle” -- Dennis R. Jenkins, 1981, ISBN: 0963397451
"Spaceflight and Rocketry -- a Chronology”, David Baker:, Facts on File Inc, 1996, ISBN 0-8160-1853-7
”The Space Shuttle Decision” -- T.A. Heppenheimer, NASA History Office, NASA SP-4221, 1999