Scamjet? That is hilarious. I know that was probably a typo - but it's synchronistically very funny. A little about the workings of a Scramjet, or Supersonic Combustion Ramjet:
A turbojet has 5 basic stages - an inlet stage, a compressor stage, a combustor stage, a turbine stage - and an expansion nozzle. The inlet stage is self-explanatory - it actually is more complex at supersonic speeds but we won't worry about that for the purposes of this short explanation. The compressor stage is the fan blades you see when you look in the front of any engine. It's job in life is to compress the air coming in to raise the temperature and pressure before combustion. For reasons of thermodynamics, this is necessary to get more bang for the fuel buck. After the air flow is ignited by the combustor stage, it goes to the turbine stage - which is a parasitic stage in that its job in life is to get the energy out of the airflow so it can drive the combustor stage up front. After that, the air is free to go and expands in the expansion nozzle to basically push against the walls to drive the craft forward.
A scramjet is a marvelously simple device that does all the above. At Mach 4 or higher - the underside of the aircraft nose acts like a compressor in that it is sloped as a "compressor ramp" - such that the air volume is constricted as it moves down the ramp into the smaller inlet. Cramming 10 pounds of air into a 5-pound bag compresses the air. Voila! Get rid of the compressor stage. Well...if you don't have a compressor stage, why the hell do you need a turbine stage? So th turbine stage is pink-slipped too. What do you have left? A hollow tube with some "butane" torches sticking out of the walls.
Regarding the tiles. I do not hold it against the Shuttle that it uses aerobraking - using air friction to decelerate. It is really the only way to slow down. Carrying the fuel necessary to decelerate using retrorockets would basically double the fuel requirements of any orbital vehicle. That said, however, the tile concept as heat dissipator/absorber needs to be much improved - and that will take some serious materials science technology advancements. So be it. I'd be the last one to say that the next improvement to the Shuttle is technologically here already. It isn't. That's why the replacement will be VERY expensive - lots of new technology will have to be developed. However, in terms of what it will mean to future access to space - it will be well worth it.
It's the external boosters that's bringing down shuttles, I think -- not the tiles.