Commercial HLV and R&D

[Ben the Space Brit]

I saw a 'concept' design once - I think it was originally an Orbital concept.  The carrier aircraft was a Lockheed C-131 Stratolifter with the cargo bay "hollowed out" into a 'bomb bay' for a rocket.  IIRC, it was an EELV-class payload.  The aircraft had a massively augmented wing, actually joined to the horizontal stabilisers at the tips, to increase lift.  I think that we can agree that no existing aircraft can be the lifter for an HLV-class payload.

However, the point is that the carrier aircraft doesn't have to be supersonic if you make it a 3STO with a high-thrust starter stage to get it through the sound barrier.  The real critical need is to get the rocket high enough to reduce the weight of the starter booster.