The original concept for the bladed launch vehicle was based on a small system with a small payload. Once the market moved out from under us to larger payloads, and a full-up rocket engine in the tail was required, frankly the blades weren't that good an idea any more, but it's a long story.

I still think the concept has potential in its original form, but there are still a lot of problems to iron out, including screwing a propeller through max Q, figuring out some touchy reentry problems, and a few others.

I could do volumes on the history and theory of SSTO, but suffice it to say it is feasible, and without enormous advances in technology. The old Atlas is practically an SSTO all by itself, staging only its outboard engines. And it isn't even LOX-hydrogen.

One key is not to try and get a Shuttle-sized payload out of the deal, which is one area where the Venturestar/X-33 concept hit the wall.