Slide 14 of 100
Other companies besides Douglas were also investigating large military reusable launch vehicles. North American Aviation's air-augmented vertical takeoff & landing single-stage-to-orbit RLV from 1963 would have used external burning ramjets which, according to preliminary studies may reduce the gross liftoff mass of a VTVL SSTO by up to 30%. The sensitivity to air-augmentation system weight would however be quite high. A pure rocket-powered version would have a gross liftoff mass of 13,607t including a 453.6-tonne useful payload. The maximum diameter was 48.8m and the length without payload fairing was 53m. This design was initially classified by the US Department of Defense before being resurrected for Rockwell's and NASA's solar power satellite launch studies in the late 1970s.
”Advanced Launch Vehicle Systems and Technologies” -- Bell, SPACEFLIGHT 1978/p.135; AAS 1977/vol.36/p.117
"Spaceflight and Rocketry -- a Chronology" -- David Baker:, Facts on File Inc, 1996, ISBN 0-8160-1853-7