There is a scale Space Shuttle that belongs to Henry Kin, one of the members of my local RC club, Greater Cincinnati Radio Controlled Club. Here is a link to video of one of the flights. [link=http://www.gcrcc.net/Videos/Shuttle_Maiden.wmv]Maiden Shuttle Flight [/link]

It is rocket-powered though, and Henry is working to improve controlability. One of the latest improvements is to launch it from a large airplane that carries it to altitude.

Here are a few pictures of the Shuttle mounted to it's carrier plane. [link=http://www.gcrcc.net/img/club_mtg_pics.html]March 2007 Meeting Pictures[/link]

It is hard to imagine how you could make a Shuttle look scale, with any intake opening large enough to fly the plane. Perhaps you should consider powering it with a rocket motor too?