Lockheed D-21 - Design and Development

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 downing of Gary Powers's U-2 in 1960, a number of 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 US Air Force 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.

Johnson wanted to power the Q-12 with a ramjet engine built by Marquardt 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. In contrast, 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 as the 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. However, 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. In contrast, the Air Force 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.

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 Air Force to recover film canisters from satellites. If the C-130 missed, the hatch was equipped with flotation devices so it could be recovered by ship. 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 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.