Lockheed A-12
The Lockheed A-12 is a retired high-altitude, Mach 3+ reconnaissance aircraft built for the United States Central Intelligence Agency by Lockheed's Skunk Works, based on the designs of Clarence "Kelly" Johnson. The aircraft was designated A-12, the twelfth in a series of internal design efforts for "Archangel", the aircraft's internal code name. In 1959, it was selected over Convair's FISH and Kingfish designs as the winner of Project GUSTO, and was developed and operated under Project Oxcart.
The CIA's representatives initially favored Convair's design for its smaller radar cross-section, but the A-12's specifications were slightly better and its projected cost was much lower. The companies' respective track records proved decisive. Convair's work on the B-58 had been plagued with delays and cost overruns, whereas Lockheed had produced the U-2 on time and under budget. In addition, Lockheed had experience running a highly classified "black" project.
The A-12 was produced from 1962 to 1964 and flew from 1963 to 1968. It was the precursor to the twin-seat U.S. Air Force YF-12 prototype interceptor, M-21 launcher for the D-21 drone, and the SR-71 Blackbird, a slightly longer variant able to carry a heavier fuel and camera load. The A-12 began flying missions in 1967 and its final mission was in May 1968; the program and aircraft were retired in June. The program was officially revealed in the mid-1990s.
A CIA officer later wrote, "Oxcart was selected from a random list of codenames to designate this R&D and all later work on the A-12. The aircraft itself came to be called that as well." The crews named the A-12 the Cygnus, suggested by pilot Jack Weeks to follow the Lockheed practice of naming aircraft after celestial bodies.
Design and development
With the failure of the CIA's Project Rainbow to reduce the radar cross-section of the U-2, preliminary work began inside Lockheed in late 1957 to develop a follow-on aircraft to overfly the Soviet Union. Designer Kelly Johnson said, "In April 1958 I recall having long discussions with Richard M. Bissell Jr. over the subject of whether there should be a follow-on to the U-2 aircraft. We agreed... that there should be one more round before satellites would make aircraft reconnaissance obsolete for covert reconnaissance."Under Project Gusto the designs were nicknamed "Archangel", after the U-2 program, which had been known as "Angel". As the aircraft designs evolved and configuration changes occurred, the internal Lockheed designation changed from Archangel-1 to Archangel-2, and so on. These names for the evolving designs soon simply became known as "A-1", "A-2", etc. The CIA program to develop the follow-on aircraft to the U-2 was code-named Oxcart. A-4 through A-6 concepts applied blended wing/fuselage configurations with combinations of turbojet, ramjet, and rocket propellant. However, these concepts never met the required range. Concepts A-7 thru A-9 used a single J58 afterburning turbojet plus two Marquardt XPJ-59 ramjets burning JP-150 fuel.
Design concept A-10 featured two General Electric J93-3 turbojets with 2-D underwing inlets and had better mission radius than concepts A-4 thru A-9. These designs had reached the A-11 stage when the program was reviewed. The A-11 was competing against a Convair proposal called Kingfish, of roughly similar performance. However, the Kingfish included a number of features that greatly reduced its RCS, which was seen as favorable to the board. Lockheed responded with a simple update of the A-11, adding twin canted fins instead of a single right-angle one, and adding a number of areas of non-metallic materials. This became the initial A-12 design. On 26 January 1960, the Central Intelligence Agency officially ordered 12 A-12 aircraft with the contract signed on February 11, 1960. Lockheed charged $96.6 million for design, manufacture and testing of 12 aircraft.
New materials and production techniques
Because the A-12 was well ahead of its time, many new technologies had to be invented specifically for the Oxcart project with some remaining in use to present day. One of the biggest problems engineers faced at the time was working with titanium.In his book Skunk Works: A Personal Memoir of My Years at Lockheed, Ben Rich stated, "Our supplier, Titanium Metals Corporation, had only limited reserves of the precious alloy, so the CIA conducted a worldwide search and using third parties and dummy companies, managed to unobtrusively purchase the base metal from one of the world's leading exporters – the Soviet Union. The Soviets never had an inkling of how they were actually contributing to the creation of the airplane being rushed into construction to spy on their homeland." 93% of A-12's structure was titanium.
Before the A-12, titanium was used only in high-temperature exhaust fairings and other small parts directly related to supporting, cooling, or shaping high-temperature areas on aircraft like those subject to the greatest kinetic heating from the airstream, such as wing leading edges. The A-12, however, was constructed mainly of titanium. Titanium is rigid and difficult to machine, which made it difficult to form into curves given available techniques. This made it difficult to form the leading edges of the wing and similar surfaces. The solution was found by machining only small "fillets" of the material with the required shape and then gluing them onto the underlying framework which was more linear. A good example is on the wing: the underlying framework of spars and stringers formed a grid, leaving triangular notches along the leading edge that were filled with fillets.
With the move to the A-12, another improvement in RCS was made by replacing the fillets with new radar-absorbing composite materials made from iron ferrite and silicon laminate, both combined with asbestos to absorb radar returns and make the aircraft more stealthy.
To further reduce the detectability of the aircraft's afterburner plumes a special cesium additive nicknamed "panther piss" was added to the fuel.
Flight testing
After development and production at Skunk Works, in Burbank, California, the first A-12 was transferred to Groom Lake test facility. On 26 April 1962 it was taken on its first flight with Lockheed test pilot Louis Schalk at the controls. The first official flight took place on 30 April and subsequent supersonic flight on 4 May 1962, reaching speeds of Mach 1.1 at.In 1962, the first five A-12s were initially flown with Pratt & Whitney J75 engines capable of thrust each, enabling the J75-equipped A-12s to obtain speeds of approximately Mach 2.0. On 5 October 1962, with the newly developed J58 engines, an A-12 flew with one J75 engine, and one J58 engine. By early 1963, the A-12 was flying with J58 engines, and during 1963 these J58-equipped A-12s obtained speeds of Mach 3.2.
In 1963 the program experienced its first loss when, on 24 May, "Article 123" piloted by Kenneth S. Collins crashed near Wendover, Utah. Collins safely ejected and was wearing a standard flight suit, avoiding unwanted questions from the truck driver who picked him up. He called Area 51 from a highway patrol office. The reaction to the crash illustrated the secrecy and importance of the project. The CIA called the aircraft a Republic F-105 Thunderchief in news articles and official records. Two nearby farmers were told that the aircraft was carrying atomic weapons to dissuade them from approaching the crash site; and local law enforcement and a passing family were strongly warned to keep quiet about the crash. Each was also paid in cash to do so; the project often used such cash payments to avoid outside inquiries into its operations.
In June 1964, the last A-12 was delivered to Groom Lake, from where the fleet made a total of 2,850 test flights. A total of 18 aircraft were built through the program's production run. Of these, 13 were A-12s, three were prototype YF-12A interceptors for the U.S. Air Force, and two were M-21 reconnaissance drone carriers. One of the 13 A-12s was a dedicated trainer aircraft with a second seat, located behind the pilot and raised to permit the instructor pilot to see forward. The A-12 trainer, known as "Titanium Goose", retained the J75 power plants for its entire service life.
Three more A-12s were lost in later testing. On 9 July 1964, "Article 133" crashed while making its final approach to the runway when a pitch-control servo device froze at an altitude of and airspeed of causing it to begin a smooth steady roll to the left. Lockheed test pilot Bill Park could not overcome the roll. At about a 45-degree bank angle and altitude he ejected and was blown sideways out of the aircraft. Although he was not very high off the ground, his parachute opened and he landed safely.
On 28 December 1965, the third A-12 was lost when "Article 126" crashed 30 seconds after takeoff when a series of violent yawing and pitching actions was followed very rapidly with the aircraft becoming uncontrollable. Mel Vojvodich was scheduled to take aircraft number 126 on a performance check flight which included a rendezvous beacon test with a KC-135 tanker and managed to eject safely above the ground. A post-crash investigation revealed that the primary cause of the accident was a maintenance error; a flight-line electrician had mistakenly swapped the connections of the wiring harnesses linking the yaw- and pitch-rate gyroscopes of the Stability Augmentation System to the control-surface servos, meaning that control inputs commanding pitch changes counterintuitively caused the aircraft to yaw and control inputs commanding left or right yaw instead changed the aircraft's pitch angle. The investigation criticized the electrician's negligence but also noted as contributory causes failures in the supervision of maintenance activity and the fact that the aircraft's design allowed for the swapped connection in the first place.