XB-70

During the course of the X-15 program, various drawings and artist concepts were released that showed the research airplane-particularly the proposed delta-wing version-carried by a North American XB-70 bomber. The use of this Mach 3+ capable aircraft would have greatly extended the performance envelope of the X-15. However, given the theoretical uncertainties of launching an object from the back of a larger aircraft traveling at Mach 3, it is unlikely that the Air Force or NASA ever seriously considered this concept. After the fatal crash on 30 July 1966 of a Lockheed M-21 Blackbird while launching a D-21 drone from a similar configuration, it became even more unlikely. Nevertheless, sometime during 1966 North American conducted a study (logically called "XB-70/X-15"); unfortunately, however, no copy could be found in any archive, so its contents and conclusions are unknown.-1228

The use of the Mach 3+ capable XB-70A as a carrier aircraft would have greatly extended the performance envelope of the X-15. However, given the theoretical uncertainties of launching an object from the back of a larger aircraft traveling at Mach 3, coupled with the fact that only two Valkyries were manufactured, it is unlikely that the Air Force or NASA ever seriously considered this concept. (North American Aviation)