According to Aviation Now, NASA is now focused on airbreathers, or to be more precise, Rocket-Based Combined Cycle (RBCC) propulsion for the next generations of space transport.

Although virtually all of the third-generation reusable launch vehicle (RLV) concepts currently being considered by NASA rely on some form of combined-cycle propulsion to get to orbit, the space agency is still not insisting on single-stage vehicles.

Well, it's nice that they're not insisting on SSTO, I guess...

Obviously, the RBCC hobby shop at Marshall is winning the bureaucratic turf war.

Here's a concept, guys. How about just putting out an RFQ for X pounds and Y people delivered to orbit, and let the market figure it out?

Nahhhh, that would mean the technology sandbox might get emptied...