I just got bitten by the 'Boeing 797' hoax, but discovered that there is a germ of truth to it. See
http://en.wikipedia.org/wiki/Blended_wing_body
This design comes close to what I have envisioned for the carrier wing, although the engines would have to be under the vehicle, not on top at the rear.
I find the obsession with exotic propulsion technology, such as the scram jet, to be a little discouraging. Good old fashioned rockets will work, quite well, actually, and they are available right now. It is not that I am against new technology, but I am anxious to see us regain our ability to reach space, and waiting for something like the scram jet to be perfected could delay that process by 20 years or more.
What many people don't seem to understand is that research and development will increase dramatically once we establish a commercial presence in space. It is all very well to talk about building single-stage to-orbit vehicles, and Mars exploration craft, and such, but those kinds of things will be enormously expensive, and getting someone to foot the bill will be hard unless we are already reaping benefits from space exploration that can be measured in dollars.
Think of the first transcontinental railroad. Most people believe that it was built to make transportation to California quick and affordable, and that was the justification given to the public at the time. But the real reason was the granting of all the land on either side of the right-of-way for 5 miles to the railroad companies. They got a swath of land ten miles wide for hundreds of miles. All of the gold that came out of California was worth a fraction of the worth of that land.
Once a way is found to get people into space cheaply and reliably, the launch industry will see a huge increase in business, as large corporations put their private space stations into orbit. Dow Chemical, General Electric, Westinghouse, DuPont, and a long list of names most people would not recognize, are anxious to begin experimenting in zero gravity. But they need to get their people up there. They are not interested in making discoveries which will become public property, which is the case with the International Space Station. They are not interested in having some astronaut conducting their research. These companies want their people aboard their space stations to make the breakthroughs, secure the patents, and beat the competition in the race to bring new products to market.
Once we reach that stage, the future of space exploration is assured. When wealth is being created by new products which can only be made in space, the money for development of advanced propulsion systems will go from a trickle to a waterfall. As we open up the Moon for development, money for missions to other planets will become abundant. But we have to get business up and running in space to be certain that space will not be abandoned. Relying on government funding for missions to the Moon or to Mars is a recipe for failure. When we give the private sector a reason to want to travel between the planets, progress will be rapid.
This may seem crass and cynical, but it is the reality as I see it.