#FDL-8A

[lonestarflight]

"Rockwell concept for an air-launched spaceplane produced as part of the Advanced Military Spaceflight Capability study."

"In December 1980, Don Hart of the Air Force Rocket Propulsion Laboratory at Edwards Air Force Base wrote a memo describing a proposed Air Force Space Sortie Vehicle that would be launched from the back of a 747. Ehrlich says that he knew Hart at the time, and that it is possible that Hart got the idea of the Space Sortie Vehicle concept from some work that Rockwell was then engaged in. “I’m not sure which came first, Don’s or ours, or they may even have been shared concepts,” Ehrlich remembers. He said that around 1978 or ’79 the Air Force was interested in a concept that they then called 'On-Demand Launch.' Rockwell learned of the Air Force interest and began working on several concepts. In 1979, the Air Force initiated an Advanced Military Spaceflight Capability Technology Identification Study (known as AMSC) and Rockwell was ready for it. The AMSC study actually preceded and ran concurrently with the Air Force Space Sortie Vehicle outlined in Hart’s December 1980 memo.

Ehrlich had taken his lifting body knowledge with him to Rockwell. The FDL-5A shape seen pulled out of the C-5 in the artist impression is the more angular version, with the single tail. But when Rockwell started working on the AMSC, they considered a spacecraft with drop tanks and mounted above a 747. The shape they used in that study was the more rounded version, with winglets. 'Different mission, different shape, but retaining the critical aerodynamic features which were key,' Ehrlich explained. The craft could be wider because it did not have to fit inside an aircraft. The Rockwell craft also had three rocket engines in its tail.

The Rockwell approach was to use the V-shaped drop tank only for hydrogen. The spacecraft itself would carry both oxygen and a little bit of hydrogen for the final push into orbit. This simplified the tank design, and since the tank was the expendable part of the spacecraft that reduced cost.

But Rockwell ran into the same limitations experienced by other companies that looked into the Sortie Vehicle Concept. Such a craft could only carry a relatively small payload. But it also required drop tanks, and that increased the expense. The Air Force wanted a cheaper vehicle and the only way to achieve that would be to develop one that was fully reusable."

Date: late 1970s/early 1980s

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