How about Dyna-Soar?
Were there any serious technical issues that would keep it from happening?
http://www.astronautix.com/craft/dynasoar.htm
http://www.aero.org/publications/crosslink/winter2004/01.html
Some day I forsee rich space enthusiasts recreating Dyna-Soar and MOL and all those other projects that never flew and giving them their Day in Space with exact, working replicas. The same for models that did fly such as Mercury and Gemini.
http://www.astronautix.com/articles/youelled.htm
Oh man, imagine a recreation of the Soviet manned lunar program as it was designed to happen.
http://www.fas.org/spp/eprint/lindroos_moon1.htm
