The Lockheed D-21 was one of the most ambitious spy aircraft ever conceived—a pilotless reconnaissance drone designed to fly faster than Mach 3, cruise at the edge of space, penetrate the world’s most heavily defended airspace, and photograph China’s secret nuclear facilities without risking a single American pilot.
Born in the aftermath of the U-2 incident that brought down Francis Gary Powers, the D-21 represented the cutting edge of Cold War technology, combining Blackbird-inspired stealth, extreme speed, and revolutionary unmanned flight. But turning that vision into reality proved far more dangerous than anyone expected.
A catastrophic midair collision claimed the life of a test crewman, repeated operational missions ended in bizarre failures, priceless intelligence sank to the bottom of the Pacific, and one of the world’s most advanced drones ultimately crashed inside enemy territory, where Soviet engineers quietly studied its secrets.
At one point, Pentagon officials even considered converting the aircraft into a nuclear strike platform before changing technology and Cold War politics rendered the project obsolete. This is the extraordinary story of the Lockheed D-21, the secret drone that was decades ahead of its time, the remarkable engineers who built it, and the mission that foreshadowed the future of unmanned warfare.
The Lockheed D-21 is an American supersonic reconnaissance drone. The D-21 was initially designed to be launched from the back of an M-21 carrier aircraft, a variant of the Lockheed A-12 aircraft. The drone had maximum speed in excess of Mach 3.3 (2,200 miles per hour; 3,600 kilometers per hour) at an operational altitude of 90,000 feet (27,000 meters).
Development began in October 1962. Originally known by the Lockheed designation Q-12, the drone was intended for reconnaissance deep into enemy airspace.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.
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 successful test flights were made, followed by at least four unsuccessful operational D-21 flights over China, before the program was canceled in 1971.
Design and Development
In the 1960s, Lockheed’s secret Skunk Works developed the Mach 3 A-12 reconnaissance aircraft for the Central Intelligence Agency (CIA). After the shooting down of the U-2 piloted by Gary Powers in 1960, several different concepts were proposed as alternatives. Kelly Johnson, the leader of Skunk Works, developed the concept of a long-range drone that used much of the A-12’s technology.
In October 1962, the CIA and the United States Air Force (USAF) instructed Lockheed to study a high-speed, high-altitude drone concept. Johnson specified speeds of Mach 3.3–3.5, an operational altitude of 87,000–95,000 feet (27,000–29,000 m), and a range of 3,000 nautical miles (3,500 mi; 5,600 km). It was intended to make a one-way trip, eject its camera payload at the end of the mission for recovery, then self-destruct. It had a double-delta wing similar to the A-12’s wing design. The Q-12 was to be air-launched from the back of an A-12, and used key technology from the A-12 project, including titanium construction and radar cross-section reduction design features.
M-21 carrying D-21 in flight
Johnson wanted to power the Q-12 with a ramjet engine built by the Marquardt Corporation for the Boeing CIM-10 Bomarc long-range surface-to-air missile. Marquardt and Lockheed had already collaborated on several programs and had a close working relationship. The engine, the RJ43-MA-11, required modification, since it was only designed to burn as long as the missile needed to hit a target, while the Q-12’s engine needed to operate at high temperatures for at least an hour and a half at high altitudes. The modified engine was designated RJ43-MA20S-4.
A full-scale mockup of the Q-12 was ready by 7 December 1962, and had already undergone preliminary tests to measure its radar cross-section. Marquardt had also successfully tested the modified RJ-43 in its wind tunnel in the meantime. The CIA was not enthusiastic about the Q-12, mostly because the agency was overextended at the time with U-2 missions, getting the A-12 up to speed and covert operations in Southeast Asia. The USAF was interested in the Q-12 as both a reconnaissance platform and a cruise missile and the CIA finally decided to work with the USAF to develop the new drone. Lockheed was awarded a contract in March 1963 for full-scale development of the Q-12.
A modified D-21 carried on the wing of a B-52
The camera and its film magazines with an inertial navigation system were carried in a cramped “Q-bay” below the drone’s air intake. These components were built into a module that fit into the bay and was known as a “hatch”. The hatch would be ejected at the end of the mission and then snagged out of the air by a JC-130 Hercules, a technique that had been developed by the USAF to recover film canisters from balloons and satellites.
If the C-130 missed, the hatch was equipped with flotation devices so it could be recovered by ship if released over water. Honeywell built the avionics systems; new construction techniques and materials had to be developed for the systems to withstand the high temperatures, extreme vibrations and lack of space in the D-21.
In late 1963 the project was named Tagboard; the Q-12 was re-designated D-21 while the A-12 version launcher became M-21 (D- for “daughter” and M- for “mother”). Two of the original 18 A-12 aircraft were designated as M-21s with serial numbers 60-6940 and 60-6941. The M-21 was a two-seat version of the A-12, with a pylon on the fuselage centerline between the vertical stabilizers to carry the drone in a nose-up attitude.
Top Photo: Lockheed D-21B at the National Museum of the United States Air Force
Sources: YouTube; Wikipedia