The OXCART "Family"
The A-12’s unique design and characteristics became the foundation for three other versions of supersonic aircraft that Lockheed built for CIA and the Air Force: the YF-12A, the M-21, and the SR-71.
In October 1962, the Air Force ordered three interceptor variants to replace the cancelled F-108A Rapier. The modified A-12, first designated the AF-12 and then the YF-12A, was designed and built under a project codenamed KEDLOCK. The aircraft’s mission was to intercept new Soviet supersonic bombers long before they reached the United States. It carried three air-to-air missiles and a second crewman who worked the fire control system. The Air Force initially envisioned a fleet of as many as 100, but only three were built and delivered during 1963-64. Secretary of Defense Robert McNamara cancelled KEDLOCK in early 1968 as a cost-cutting measure, and the aircraft were never deployed operationally. CIA was involved with the project only in giving up three A‑12 airframes and helping write “black” contracts. The Air Force bore all the costs of the YF-12A, which was superseded by the F-111. Two of the aircraft were given to the National Aeronautics and Space Administration for research, and one was converted into a trainer for the SR-71 program.
TAGBOARD: The M-21 and D-21
In October 1962, CIA authorized the Skunk Works to study the feasibility of modifying the A-12 to carry and deploy a reconnaissance drone for unmanned overflight of denied areas. The project was codenamed TAGBOARD. The mother ship, redesignated the M-21 to avoid confusion with the A-12, was fitted with a second seat for a launch control officer (LCO) for the drone, called the D‑21. It was 43 feet long, weighed over five tons, had a ramjet engine, could reach a speed of over Mach 3.3 at 90,000 feet, fly over 3,000 miles, and had the smallest RCS of anything Lockheed had yet designed. The drones would be launched well away from targets, fly their missions, and return to a preprogrammed location in international waters. There they would jettison a payload that a C-130 would snag in midair, and then self-destruct with a barometrically activated explosive device. In June 1963, the Air Force took over the project because it had overall charge of unmanned reconnaissance aircraft. Lockheed eventually built two M-21s and 38 drones, and its test pilot Bill Park flew all the M-21 flights. On the fourth TAGBOARD test on 30 July 1966, a launch mishap caused the mother ship to crash, killing LCO Ray Torick and prompting Kelly Johnson to end the program. Afterward the Air Force used B-52s to launch the drones against Communist Chinese targets in a project called SENIOR BOWL. Four missions were flown starting in November 1969. None was completely successful, and SENIOR BOWL was cancelled in July 1971.
The best known version of the A-12 (above right) is the SR‑71 Blackbird (above left), whose nickname has become eponymous with the entire set of OXCART variants. In December 1962, the Air Force ordered six “reconnaissance/strike” aircraft for high-speed, high-altitude flights over hostile territory after a nuclear attack—hence its original designator RS. Compared to the A-12, the SR-71 was about six feet longer, weighed 15,000 pounds more fully loaded, had more prominent nose and body chines and a two-seat cockpit, and carried additional optical and radar imagery systems and ELINT sensors in interchangeable noses.
With the added weight, the aircraft flew slower and lower than the A-12 or the YF-12A, but it carried more fuel and had a longer range. After an initial contract for six RS-71s, the Air Force ordered 25 more in August 1963. When President Johnson disclosed the aircraft’s existence in July 1964, he mistakenly transposed the designator letters. Air Force officials let the error stand and came up with the Strategic Reconnaissance (SR) category instead. The fleet, based in the United Kingdom, Okinawa, and California, flew over
3,500 sorties from March 1968 until November 1989, when it was deactivated. In September 1994 Congress allocated funds to reactivate three SR-71s. Two aircraft and crews became operational during 1995 and 1996. In October 1997, President Bill Clinton vetoed further funding, and in June 1999 the SR‑71 program was shut down again.