The D-21 was also launched from from the back of a M-21, which is a variant of the SR-71Lockheed D-21 reconnaissance drones were launched from B-52Hs.
Tagboard Flyers: the story of the B-52 bombers that carried the D-21 Mach 3 ramjet-powered reconnaissance drones - The Aviation Geek Club
Tagboard Flyers: the story of the B-52 bombers that carried the D-21 Mach 3 ramjet-powered reconnaissance dronestheaviationgeekclub.com
I guess it does make more sense to drop it from under the wing rather than on the back, it’s a lot simple, and safer.That proved to be dangerous in flight tests. In actual D-21 reconnaissance missions, B-52Hs were used as carrier aircraft.
M-21 was developed from A-12, the precursor to SR-71.