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The Lockheed D-21 was an American reconnaissance drone with maximum speed in excess of Mach 3. The D-21 was initially designed to be launched from the back of a M-21 carrier aircraft, a variant of the Lockheed A-12 aircraft. Development began in October 1962. Originally known by the Lockheed designation Q-12, the drone was intended for reconnaissance deep in 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.〔Donald 2003, pp. 154–56.〕 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 D-21 flights over the People's Republic of China, and 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, 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 , and a range of . It was intended to make a one-way trip, eject its camera payload at the end of the mission for recovery, then self-destruct.〔Goodall and Goodall 2002, p. 106.〕 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, 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 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.〔Goodall and Goodall 2002, pp. 106–107.〕 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. The Air Force, however, 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.〔Pace 2004, p. 55.〕 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 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.〔Goodall and Goodall 2002, pp. 112–114.〕 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.〔Goodall and Goodall 2002, p. 107.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lockheed D-21」の詳細全文を読む スポンサード リンク
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