From: utzoo!decvax!cca!John@sri-unix Newsgroups: net.space Title: rocket planes Article-I.D.: sri-unix.1847 Posted: Tue Jun 22 10:27:54 1982 Received: Sun Jun 27 02:25:54 1982 The 4000 mph that the X-15 could do is a long way from the 18,000 mph needed for earth orbit. At that speed the X-20 would have faced the same problem that the shuttle has: how to protect the craft from the heat of re-entry. The Boeing designers could have used Von Braun's solution, ablative shields, but with expendable shields and expendable boosters the only reusable part of the craft would be the cockpit. The only advantage I can see to that sort of design is being able to land it at different locations. This was more useful for military programs than civilian ones, which is probably why they ultimately decided not to bother. --------