Even more Top Secret than the Lockheed SR-71, the D-21 drone was a promising Cold War idea that could have eliminated the need for manned overflights, although it was mostly unsuccessful. After the ...
Modern Engineering Marvels on MSN
Lockheed’s D-21 drone tried to replace risky spy flights and paid a strange price
The D-21 was designed to fly at an approximate speed of Mach 3.3 above 90,000 feet not as a demonstration piece, but as a way around a very particular issue: Since the 1960 shootdown of U-2s, the ...
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