This week, the National Reconnaissance Office declassified a trove of documents pertaining to the long defunct “Tagboard” drone program, a reconnaissance effort so ahead of its time that it seemed like science fiction until only recently. In the 1960s, the United States found itself in a unique position: Nuclear programs in both China and the Soviet Union posed a clear threat to American security, and a number of burgeoning technologies promised to potentially lift the veil of secrecy created by the vast distances separating American experts from adversary programs.

After a U-2 spy plane piloted by Gary Powers was shot down over the Soviet Union in 1960, there was a growing emphasis on finding ways to get eyes on enemy programs without placing American pilots at risk. The A-12 “Oxcart,” predecessor to the legendary SR-71 Blackbird, promised to make photographic surveillance a less-risky venture, and early national reconnaissance satellites launched in 1960 offered more capabilities than ever before, but U.S. Department of Defense officials soon recognized that even the capabilities afforded by these two new technological marvels weren’t enough to keep America’s fingers on the pulse of the world’s nuclear developments.

U-2 Spy Plane (USAF)

“In view of the political sensitivity to overflight of certain denied areas, such as China, by manned collection systems and the technical and other limitations of the current satellite program, the Tagboard operational capability has been developed to collect against objectives of national interest located in areas where manned operations could provoke incidents potentially embarrassing to the United States,” a memo from the Joint Chiefs of Staff, penned in 1969, reads.

And thus, Lockheed’s D-21 Mach 3-capable drone was born. Built largely out of titanium and boasting a 19-foot wingspan, the D-21 was a 12-ton drone originally designed to ride atop the A-12. Once deployed, the D-21 could fly more than 3,000 miles, capturing a swath of territory 16 miles wide for the entirety of its flight before ejecting its 5,600-exposure film cartridge and self-destructing. From there, a specially equipped JC-130 would scoop the canister out of mid-air as it descended by parachute, or, failing that, a Navy ship could fish it out of the ocean.