Paul Crickmore
Lockheed A-12: The CIA's Blackbird and other variants
INTRODUCTION
Sir Sydney Camm, the renowned British aerospace design engineer, once remarked, “All modern aircraft have four dimensions: span, length, height and politics.” In this particular instance, he was referring to the British-built BAC TSR-2; but this fourth, political, dimension exerted an almost exponential influence throughout the development and operational life of Lockheed’s aviation icon.
Built by Lockheed to replace their earlier, high-flying, subsonic, reconnaissance-gathering U-2, the A-12 and its stablemate, the SR-71, catapulted high performance into a different orbit. They remain the fastest and highest-flying jet-propelled operational aircraft ever, cruising in afterburner at the designed speed of Mach 3.2 (that’s 1.8 miles per second) and at altitudes in excess of 16 miles. However, the political sensitivity surrounding the “Black World” strategic reconnaissance mission caused US President Dwight Eisenhower to insist that such vital covert business should be conducted by an aircraft not only immune from interception, but also blind to hostile radar detection. This necessitated the development of a range of radar “camouflaging” techniques that today we have all come to know as “stealth.” But when CIA U-2 pilot Francis Gary Powers was shot down by a surface-to-air missile (SAM) whilst in the middle of a deep-penetration reconnaissance sortie of the Soviet Union on May 1, 1960, politics came to the fore and the fallout would have a profound impact on all such future US aviation programs.
DESIGN AND DEVELOPMENT
During the early-to-mid Cold War years, western leaders had to rely primarily upon reconnaissance aircraft to gather photographic intelligence (PHOTINT), electronic intelligence (ELINT), and communications intelligence (COMMINT) about the activities of the Soviet Union, her allies in the Warsaw Pact, and Communist China. This was in part due to the closed nature of these societies, but also to the size of the land mass and the level of technical ability prevailing at that time. The violation of a sovereign state’s airspace is contrary to international law. As a result, such planned incursions required prior clearance from the very top; and in the case of the United States, that meant the President. Routes and the number of sorties were highly regulated and the flights themselves were conducted under conditions of great secrecy. The name of the game was to acquire the requisite raw data, but avoid at all costs getting caught in the act.
Lockheed’s custom-built strategic reconnaissance-gathering aircraft, the U-2, undertook the first in a series of vital but hazardous overflights of “denied territory” on June 20, 1956. Designed by Clarence L. “Kelly” Johnson, President of Lockheed’s legendary Skunk Works, and operated by the Central Intelligence Agency (CIA), the program went under the classified cryptonym of Aquatone (later redesignated Chalice). Photographic results gained by the project were sensational. Flying at altitudes in excess of 70,000ft, the frail, subsonic, glider-looking aircraft was immune from fighter interception. But President Eisenhower was concerned that the U-2 should also escape detection and tracking by Soviet radars.
On July 10, 1956, after just five incursions, the Soviets delivered their first protest note about the flights and Eisenhower ordered their immediate suspension. However, those missions had generated a vast amount of intelligence, revealing for the first time many aspects of Soviet military and industrial capability. During a meeting on July 19, and despite pleas to the President from the CIA’s Director of Central Intelligence (DCI), Allen Dulles, that Aquatone should be allowed to continue such overflights on the basis that the quality of intelligence gained far outweighed any potential damage to international relations, Eisenhower remained resolute and the ban stood — at least for the immediate future.
On August 16, 1956, the DCI’s Special Assistant for Planning and Coordination, Dr Richard Bissell, convened a meeting with Kelly Johnson and a number of prominent scientists — the meeting’s objective was to agree on a plan to develop some form of “electronic camouflage” that would render the U-2 invisible to Soviet radars, thereby addressing Eisenhower’s concerns. The meeting lasted into the early hours and resumed again at 0700hrs the next day, and by midday they had devised a program to apply radar-canceling devices to a U-2, codename Project Rainbow. It was the first attempt to make an operational aircraft “stealthy.” Dr Edwin Land, of the Massachusetts Institute of Technology (MIT), chaired the project and via Marshall Holloway, Director of the MIT Lincoln Laboratory, in Lexington, Massachusetts, recruited a small number of radar experts into the program. They were based in a secure building on the roof of the Lincoln Laboratory and included Frank Rodgers, associate head of the Radar Division.
A major problem facing the team was that during the course of a U-2 overflight, the aircraft would first need to remain invisible to Soviet long-range, low-frequency, early warning radars operating in the 65/86 MHz range. Then, upon penetrating deeper into the USSR, high- frequency S-band and X-band target acquisition radars operating in the 2–4 GHz and 8–12 GHz bands respectively, would need to be dealt with. This required the development of different methods and materials to defeat the different radar systems illuminating the target.
By the summer of 1957, the team had developed a number of innovative solutions. To reduce low-frequency returns, the U-2 utilized a system of wires and ferrite beads mounted on the aircraft’s vertical tail surface, which were also arranged to frame the aircraft’s planform. Known as “Trapeze” and “Wires,” this arrangement reduced the U-2’s radar return by about 12dB, which in practical terms meant that long-range detection was halved. To reduce returns in the high-frequency bands, radar-absorbent material (RAM) was applied to the underside of the aircraft’s fuselage. Operating on the principle of a Salisbury screen, the coating consisted — from the inside out — of fiberglass, a honeycomb spacer, a graphite-impregnated layer, a protective layer for durability, and finally a layer of paint. This treatment was nicknamed “Wallpaper” and aircraft equipped with these devices were known as “Dirty Birds.” However, one of the problems resulting from these measures was that they added both weight and drag to the U-2, reducing its maximum altitude by some 5,000ft and its range by about 20 percent.
During a meeting at the White House in early May 1957, preliminary approval was granted for more Soviet overflights, despite the fact that phase one of Project Rainbow hadn’t yet been completed. So in June one Dirty Bird was deployed to each of the three U-2 Operating Locations (OLs). Two penetration flights of the Soviet Union were made from Turkey on July 21 and 30 to evaluate the effectiveness of the treatment. But despite “Trapeze,” “Wires,” and “Wallpaper,” subsequent analysis of the U-2’s System 5 (a multi-band radar recorder) revealed that Soviet radars had been alerted to the aircraft’s presence when it was flying directly toward or directly away from the radar head. This led to the conclusion that the source of the radar returns had emanated from the U-2’s inlets, cockpit, and exhaust — none of which could be treated with what had been developed thus far. Clearly, a more radical approach to solving the problem was required.