Predecessor models

The A-12 Oxcart, designed for the CIA by Kelly Johnson at the Lockheed Skunk Works, was the precursor of the SR-71. Lockheed used the name "Archangel" for this design, but many documents use Johnson's preferred name for the plane, "the Article". As the design evolved, the internal Lockheed designation went from A-1 to A-12 as configuration changes occurred, such as substantial design changes to reduce the radar cross-section. The first flight took place at Groom Lake, NV, on April 25, 1962. It was an Oxcart labeled the A-11 configuration since it was equipped with less powerful Pratt & Whitney J75s because development of the Pratt & Whitney J58s intended for the Oxcart was delayed. When the J58s finally arrived at the "Ranch" (Groom Lake's Area 51) and were installed, the Oxcart configuration number was changed to its final A-12 nomenclature (the J58s became the standard power-plant for all subsequent A-12s). Eighteen aircraft were built in three variations, of which three were YF-12As, prototypes of the planned F-12B interceptor version, and two were the M-21 variant (see below).

The Air Force reconnaissance version was originally called the R-12 (see the opening fly page in Paul Crickmoore's book SR-71, Secret Missions Revealed, which contains a copy of the original R-12 labeled plan view drawing of the vehicle). However, during the 1964 presidential campaign, Senator Barry Goldwater continually criticized President Lyndon B. Johnson and his administration for falling behind the Soviet Union in the research and development of new weapon systems. Johnson decided to counter this criticism with the public release of the highly classified A-12 program and later the existence of the reconnaissance version.

Name and designation

The USAF had planned to redesignate the A-12 aircraft as the B-71 as the successor to the B-70 Valkyrie, which had two test Valkyries flying at Edwards AFB, California. The B-71 would have a nuclear capability of 6 bombs. The next desination was RS-71 (Reconnaissance-Strike) when the strike capability became an option. However, then USAF Chief of Staff Curtis LeMay preferred the SR designation and wanted the RS-71 to be named SR-71. Before the Blackbird was to be announced by President Johnson on February 29, 1964, LeMay lobbied to modify Johnson's speech to read SR-71 instead of RS-71. The media transcript given to the press at the time still had the earlier RS-71 designation in places, creating the myth that the president had misread the plane's designation.

This public disclosure of the program and its designation came as a shock to everyone at Skunk Works and Air Force personnel involved in the program; at this time all of the printed Maintenance Manuals, Flight Crew Handbooks (the source of Paul Crickmoore's page), training vufoils, slides and materials were still labeled "R-12" (The June 18, 1965 Certificate of Completion issued by the Skunkworks to the first Air Force Flight Crews and their Wing Commander are labeled: "R-12 Flight Crew Systems Indoctrination, Course VIII" and signed by Jim Kaiser, Training Supervisor and Clinton P. Street, Manager, Flight Crew Training Department). Following Johnson's speech, the designation change was taken as an order from the Commander-in-Chief, and immediate republishing began of new materials retitled "SR-71" with 29,000 blueprints altered.

Variants

One notable variant of the basic A-12 design was the M-21. This was an A-12 platform modified by replacing the single seat aircraft's Q bay (which carried its main camera) with a second cockpit for a launch control officer. The M-21 was used to carry and launch the D-21 drone, an unmanned, faster and higher flying reconnaissance device. This variant was known as the M/D-21 when mated to the drone for operations. The D-21 drone was completely autonomous; having been launched it would overfly the target, travel to a rendezvous point and eject its data package. The package would be recovered in midair by a C-130 Hercules and the drone would self destruct.

The program to develop this system was canceled in 1966 after a drone collided with the mother ship at launch, destroying the M-21 and killing the Launch Control Officer. Three successful test flights had been conducted under a different flight regime; the fourth test was in level flight, considered an operational likelihood. The shock wave of the M-21 retarded the flight of the drone, which crashed into the tailplane. The crew survived the mid-air collision but the LCO drowned when he landed in the ocean and his flight suit filled with water.

The only surviving M-21 is on display, along with a D-21B drone, at the Museum of Flight in Seattle, Washington. The D-21 was adapted to be carried on wings of the B-52 bomber.