Somewhere over the Nevada desert in the spring of 1966, a shape detached itself from the back of what appeared to be an impossibly stretched SR-71 Blackbird. For a fraction of a second, the shape hung in the slipstream like a remora leaving a shark — and then the ramjet ignited. The D-21 drone, forty-three feet of titanium and composite wrapped around a Marquardt RJ43-MA-11 ramjet, punched through Mach 3 and climbed toward the stratosphere. Below it, the M-21 mothership banked away, its pilot Bill Park squinting into the sun. Nobody on the ground saw a thing. Nobody was supposed to. This was Project Tagboard, one of the most classified programs in Cold War aviation history — and certainly the strangest. The CIA and Lockheed's Skunk Works had built a Mach 3+ reconnaissance drone designed to ride piggyback on a modified A-12 spy plane, launch at supersonic speed, fly a pre-programmed route over enemy territory, eject its camera film for mid-air retrieval, and then self-destruct. It was, by any measure, completely insane. And it very nearly worked.

Kelly Johnson's Most Secret Creation

Development began in October 1962, when CIA director John McCone asked Kelly Johnson whether the Skunk Works could build an unmanned version of the A-12 Oxcart spy plane. The idea was born of necessity: after the Gary Powers U-2 shootdown in 1960, overflying the Soviet Union and China with manned aircraft had become politically untenable. But the need for photographic intelligence over Chinese nuclear test sites had never been more urgent. Johnson, who had designed the U-2 and the A-12, accepted the challenge. His team produced the Q-12 — later renamed D-21 ("D" for daughter) — while the A-12 launch platform became the M-21 ("M" for mother). The drone would ride atop the M-21, launch at Mach 3.2 and 80,000 feet, fly its reconnaissance route, and then eject a hatch containing the camera and exposed film. A JC-130 aircraft would snag the film package in mid-air using a trapeze system. After film ejection, the D-21 would self-destruct. In his memoir, Skunk Works director Ben Rich recalled that Kelly Johnson was so shaken by the loss of Ray Torick that he immediately cancelled the M-21 launch programme, unwilling to risk another life launching a drone from the back of a Blackbird.

Senior Bowl: The B-52 Era

Johnson refused to give up on the concept, but he was done risking two-man crews. The D-21 was redesigned as the D-21B, fitted with a solid-rocket booster for launch from under the wing of a B-52 Stratofortress. The new program was codenamed Senior Bowl. After a series of test flights, four operational missions were launched over China between November 1969 and March 1971. All four targeted the Lop Nur nuclear test site in western China. The results were uniformly disappointing: the first drone strayed off course and crashed in Soviet Siberia — handing Moscow an unexpected look at some of America’s most advanced technology; the second flew its route but the film canister was lost at sea; the third’s film sank during a botched sea recovery; and the fourth crashed in China’s Yunnan province, where its wreckage is displayed to this day.

Legacy of a Mach 3 Ghost

The D-21 program was cancelled on July 23, 1971. The remaining drones were put into storage at Davis-Monthan Air Force Base in Arizona, where they sat in the desert sun for decades, their existence still classified. The Soviets, meanwhile, made good use of the D-21 that had crashed in Siberia. They reverse-engineered elements of its design for the Tupolev Voron reconnaissance drone program. The Chinese, too, recovered D-21 wreckage from a crash in Yunnan province and studied it closely — the remains are now displayed at the China Aviation Museum in Beijing. The D-21 was decades ahead of its time. In an era when "drone" meant a radio-controlled target, Lockheed had built an autonomous, Mach 3+ reconnaissance platform that could operate at 90,000 feet. Today's high-altitude, long-endurance drones owe a quiet debt to Kelly Johnson's most secret creation.

Sources: Lockheed Martin, National Museum of the USAF, Ben Rich "Skunk Works," The Aviation Geek Club, CIA FOIA archives