Apr 152012
The proposed X-15A-3 was a stretched, delta-winged version intended for extended duration flight at Mach 6+. As with the X-15 and X-15A-2 versions, the plan was to launch the X-15A-3 from a B-52 underwing pylong. However, North American Aviation proposed launching it from atop a B-70 bomber. The theory was that the B-70 could get the X-15 up to around Mach 3 prior to separation, thus greatly improving the rocketplanes performance. However, launchign winged vehicles from the back of supersonic aircraft is non-trivially difficult… as the M-21/D-21 crash demonstrated.
A high-rez of this can be downloaded HERE.