If you reread what I wrote, you'll see that I said:

Perhaps a better approach would be to use a TSTO design with a mother ship (similar to DARPA's SCAMP [sic] concept) to carry a booster with the payload as high and as fast as possible. SCAMP [sic] is taking about launching the booster at around Mach 3 and over 100,000 feet high. An air breathing rocket engine might be able to get it a lot faster and perhaps higher before release, increasing the payload to orbit.

The key phrase is "similar to DARPA's SCAMP concept", only I meant to say RASCAL. An air breathing rocket could probably achieve much higher performance than RASCAL's mothership (for lack of a better term), although it would have to contend with higher thermal loads, too.