During the early 1960s, Lockheed’s Clarence “Kelly” Johnson began investigating potential design outgrowths of the A-12 OXCART reconnaissance aircraft. One idea involved an unmanned drone capable of carrying a camera package to altitudes above 90,000 feet while flying at speeds in excess of Mach 3. The ramjet-powered drone, codenamed TAGBOARD, was designed to be launched from an OXCART-type aircraft called the M-21.The mated combination was called MD-21.
Several test launches of D-21 drones over the Pacific Missile Range proved the viability of the system, but a fatal accident in July 1966 resulted in cancellation of further use of the MD-21. In a project called SENIOR BOWL, two Boeing B-52H bombers were configured to serve as launch platforms for a modified version of the drone, designated D-21B, which was propelled to ramjet ignition speed by a Lockheed Missiles and Space Company DZ-1 solid-propellant booster.
The drone was designed to withstand surface temperatures that rapidly went from -58° F at launch to 428° F at cruise. The ramjet was programmed to ignite at 74,000 feet. After a booster burn time of about 90 seconds, and at an altitude of about 80,000 feet, explosive bolts separated the D-21B from the booster, and the drone began its programmed sortie. Following completion of the mission the D-21B flew to friendly territory and jettisoned its camera package for midair recovery. The drone itself then self-destructed.
Between 6 November 1967 and 20 March 1971, 12 test missions and four operational sorties were flown with D-21B drones. Each mission cost approximately $5.5 million and the operational missions failed to produce the expected results because the camera packages were not recovered. On 23 July 1971 the program was cancelled and all remaining drones were placed in storage.
Article 525, the 25th TAGBOARD airframe built, never flew a mission. Following termination of the program, it was stored at Norton AFB, California, and eventually transferred to Davis-Monthan AFB, Arizona, in 1976. Article 525 was delivered to NASA Dryden Flight Research Center, Edwards, California, on 1 June 1994 and loaned to Blackbird Airpark in October 1994.
Timeline and Summary of Significant Events:
- 25th TAGBOARD airframe built – never flew a mission
- Following termination of the program, it was stored at Norton AFB, California, and eventually transferred to Davis-Monthan AFB, Arizona, in 1976
- Was delivered to NASA Dryden Flight Research Center, Edwards, California, on 1 June 1994
- Loaned to Blackbird Airpark in October 1994, by NASA
Information provided by Peter. W. Merlin, an aerospace historian
M-21 photo courtesy of cia.gov