Problems with the U-2 Before the U-2 became operational in June 1956, CIA officials had estimated that improvements in Soviet air defences meant it would only be able to fly safely over the
Soviet Union for between 18 months and two years. After overflights began and the Soviets demonstrated the ability to track and attempt to intercept the U-2, this estimate was adjusted downward. In August 1956,
Richard Bissell reduced it to six months. To extend the life of the U-2, the CIA implemented
Project Rainbow, which added various countermeasures to confuse Soviet radars and make interception more difficult. There were two anti-radar methods. First, a diffusing coating for the fuselage; second, a series of wires strung along the fuselage and the wing edges intended to cancel radar reflections from the airframe by transmitting a similar return but out-of-phase. Several Rainbow-equipped flights were made, but the Soviets were able to track the aircraft. The weight of the equipment lowered the aircraft's maximum cruise altitude, making it more vulnerable to interception. Rainbow was cancelled in 1958.
Replacing the U-2 As early as 1956 Bissell had already started looking for an entirely new aircraft to replace the U-2, with an emphasis on reducing the
radar cross-section (RCS) as much as possible. High-altitude flight would still be useful to avoid interception by aircraft, but did little to help against missiles. By reducing the RCS, the radars guiding the missiles would have less time to track the aircraft, complicating the attack. In August 1957 these studies turned to examining
supersonic designs. It was realized that supersonic aircraft were very difficult to track on radars of that era. This was due to an effect known as the
blip-to-scan ratio, which refers to the "blip" generated by an aircraft on the
radar display. In order to filter out random noise from the display, radar operators would turn down the amplification of the radar signal so that fleeting returns would not be bright enough to see. Returns from real targets, like an aircraft, would become visible as multiple radar pulses all drawn onto the same location on the screen, and produced a single, brighter spot. If the aircraft was moving at very high speeds, the returns would be spread out on the display. Like random noise, these returns would become invisible.
Project Gusto By 1957 so many ideas had been submitted that Bissell arranged for the formation of a new advisory committee to study the concepts, led by
Edwin H. Land under the designation
Project Gusto. The committee first met in November to arrange for submissions. At their next meeting, on 23 July 1958, several submissions were studied.
Kelly Johnson of Lockheed presented the Archangel I design, which could cruise at Mach 3 for extended periods to take advantage of blip/scan spoofing, although it was not designed for reduced RCS. Convair proposed a
parasite aircraft that was launched in the air from a larger version of their
B-58 Hustler that was then being studied, the B-58B. The Navy introduced a submarine-launched inflatable rubber vehicle that would be lifted to altitude by a balloon, boosted to speed by rockets, and then cruise using
ramjets. Johnson was asked to provide a second opinion on the Navy design, and the committee arranged to meet again shortly. At the next meeting, in September 1958, the designs had been further refined. Johnson reported on the Navy concept and demonstrated that it would require a balloon a mile wide for launching. The submission was then dropped.
Boeing presented a new design for a
liquid hydrogen powered inflatable design. Lockheed presented several designs; the
Lockheed CL-400 Suntan looked like a scaled-up
F-104 Starfighter powered by wingtip-mounted hydrogen-burning engines, the G2A was a subsonic design with a low radar cross-section, and the A-2 was a
delta wing design using ramjets powered by
zip fuel. Convair entered their parasite design, slightly upgraded and intended to fly at Mach 4. == FISH ==