Loon said:I think they would have had problems trying to achieve .92 mass ratio.
Very likely that there would ahve been *serious* problems. A pity that NASA doesn't take a more pragmatic approach:
1: Revive the X-33 competitors.
2: Fund *each* of them to develop an orbital SSTO demonstrator, to the tune of, say, $150 million each.
3: Stipulate that they *must* build a flying demonstrators to get the $150 million. More important than attaining the mass ratio, though, is feasibility, practicality, operability. If they fall short of SSTO, so be it.
4: When the demonstrators have flown suborbitally... have a second competition to build re-usable booster stages.
5: Put the not-quite-SSTO X-33's atop the boosters. Now you can go to orbit.
If one or more of the X-33's makes it to orbit with a payload, great! But if you put a booster under it or next to it, the payload will be substantially increased. So one vehicle could operate in two modes.