Airplane-like first stage

Derek Lyons wrote:

Considering they used the drone's engines for takeoff boost and to
help take the whole thing to launch speed...


Not takeoff boost (you are probably thinking of Hound Dog on the B-52
where the two missiles turbojets were used during takeoff).
The D-21's ramjet couldn't be lit till it was traveling at several
hundred MPH.
On the M-21/D-21 flights the ramjet was ignited at Mach 1.24.

Pat