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The D-21 was designed to carry a single high-resolution photographic camera over a preprogrammed path, then release the camera module into the air for retrieval, after which the drone would self-destruct.[1] Following a fatal accident when launched from an M-21, the D-21 was modified to be launched from a Boeing B-52 Stratofortress. Several test flights were made, followed by FOUR UNSUCCESSFUL OPERATIONAL FLIGHTS OVER THE PEOPLE'S REPUBLIC OF CHINA, before the program was canceled in 1971. (emphasis mine)
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As Chris mentioned, there was never a weapons system involved with D-21...is there a timeline for your return from Fantasyland?
Link: https://en.wikipedia.org/wiki/Lockheed_D-21