ap08, the radiation discussion is tangential - if you want to continue it then jetblast is probably the place to do so.
What surprises me is the velocities projected on that flight profile diagram posted above. Running mach 4 at various altitudes between 20 and 50 kilometers through an online atmospheric properties calculator, it appears that some parts of the vehicle skin may be exposed to total air temperatures exceeding 700 degrees C. Not your typical Long-EZ!
For the original spaceshipone the max velocity (about 960m/s) was at burnout, altitude about 55km. Peak heating was a little lower and the max temperature was just over 600C.
Does the craft have any form of reacrion controls, oris the whole thing ballistic once the conventional controls don't work?
Because it doesn't go much out of the atmosphere the conventional controls should be functional for most of the flight. It wil lhave a reaction control system fitted, though.