Origins The Lockheed
Have Blue was born out of a requirement to evade radar detection. During the
Vietnam War, radar-guided SAMs and AAA downed many US aircraft, leading planners to accompany strike aircraft with support aircraft to perform combat air patrols and
suppression of enemy air defenses (SEAD). The 1973
Yom Kippur War again highlighted the vulnerability of aircraft to SAMs; the
Israeli Air Force lost 109 aircraft in 18 days.
Design effort and early testing Lockheed, having been absent from the fighter aircraft industry for 10 years, was not approached by DARPA in 1974. Ed Martin, Lockheed California Companies director of science and engineering, became aware of the research into stealth during his work at
the Pentagon and
Wright-Patterson AFB. Martin and
Ben Rich, who at that time had recently become
Skunk Works' president, briefed
Clarence "Kelly" Johnson on the program. The
Central Intelligence Agency (CIA) gave Skunk Works permission to discuss with DARPA the stealth characteristics of the
A-12, M-21 and D-21. who recommended an aircraft with flat surfaces. Overholser later recounted his discussion with Sherrer: "When Dick Scherrer asked me ... I said 'Well, it's simple, you just make it out of flat surfaces, and tilt those flat surfaces over, sweeping the edges away from the radar view angle, and that way you basically cause the energy to reflect away from the radar.'" Scherrer subsequently drew a preliminary low-RCS aircraft with faceted surfaces. (In 1962, Ufimtsev, as chief scientist of the Moscow Institute for Radio Engineering, published a seminal paper titled
Method of Edge Waves in the Physical Theory of Diffraction. The work had been translated by the US
Air Force Systems Command's Foreign Technology Division.) ECHO 1 allowed the team to quickly decide which of the 20 possible designs were optimal, finally settling on the faceted delta-wing design. However, many within the division were skeptical of the shape, giving rise to the name "Hopeless Diamond" – Kelly Johnson said to Rich, "Our old
D-21 drone has a lower radar cross-section than that goddamn diamond". The design effort produced a number of wooden models. A 24-inch long model, made of
balsa wood, demonstrated placement of internal structure and access doors. An
Air & Space article noted "The model shop found it nearly impossible to make all the flat surfaces come to a single point in one corner. Engineers later encountered the same difficulty fabricating the prototype on the factory floor." For early tests of the design, two ⅓-scale wooden mock-ups were constructed. One model, coated in metal foil, was used to verify ECHO 1's RCS calculations, while the other was earmarked for wind tunnel tests. Afterwards, a model was moved to the
Grey Butte Range radar-testing facility in the
Mojave Desert near
Palmdale, which allowed more accurate tests of the aircraft's RCS. In the event, the aircraft's RCS level confirmed ECHO 1's predictions. McDonnell Douglas, having identified the thresholds at which aircraft were deemed undetectable, was unable to design and produce such an aircraft. Phase 1 of XST would see both Lockheed and Northrop build full-scale models to test their RCS, construct flyable vehicles, and wind-tunnel test their designs. Following Phase 1, a sole contractor would be selected to continue with the construction and flight testing of two demonstrators as part of Phase 2. On 1 November 1975, Lockheed and Northrop were each awarded $1.5-million contracts to proceed with Phase 1 of XST. During a four-month period, the two companies were each required to construct full-scale wooden mock-ups, which would then be evaluated at the USAF's
Radar Target Scatter (RATSCAT) test facility at
White Sands, New Mexico. because the Northrop XST had a much higher side hemisphere RCS. DARPA, having realized the progress accumulated throughout the study, urged the Northrop team to remain together. The agency would later initiate the
Battlefield Surveillance Aircraft-Experimental (BSAX), which evolved into the
Tacit Blue and, ultimately, the
B-2 bomber.
Construction and further tests Skunk Works now had to design, construct and flight test two crewed demonstrators as part of Phase 2, or
Have Blue. To build the demonstrators, Ben Rich had to raise $10.4 million from the Lockheed management, which was secured by June. Phase 2 encompassed three main objectives, which were the validation of: reduced visibility in the
radio wave,
infrared, and
visual spectrums and reduced
acoustical observability; acceptable flying qualities; and the "modeling capabilities that accurately predict low observable characteristics of an aircraft in flight". On 1 September, however, with HB1001 partially complete, Lockheed machinists went on a four-month strike. A group of managers took over the job of assembly, which was completed in six weeks, with ground tests beginning on 17 October. While superficially similar to the later F-117, the
Have Blue prototypes were smaller aircraft, about one quarter the weight of the F-117, with a
wing sweep of 72.5° and inward-canted vertical tails (inverse
V-tail).
Radar-absorbent material (RAM), developed in a Lockheed laboratory, was applied to the aircraft's flat surfaces – for the windscreen, special coatings were applied to give them metallic characteristics. The aircraft's gross weight of 9,200–12,500 lb (4,173–5,669 kg) enabled the aircraft to use the landing gear from the
Northrop F-5 fighter. Because stealth took precedence above all else, the aircraft was inherently
unstable. As a result, a quadruple redundant
fly-by-wire (FBW) flight control system was integrated into the aircraft to give it normal flying characteristics. The flight control system was borrowed from the
F-16. The overwing engine inlet was covered by a low-RCS grid; blow-in doors were constructed at the upper fuselage to admit additional airflow during takeoffs, when more air is needed. Throughout the one and a half months after the start of ground tests, HB1001, the first of two demonstrators, underwent tests in preparations for the first flight. Flight instrumentation was checked first, followed by a thorough
shakedown of the aircraft. In early November, two
semi-trailers were parked parallel to each other outside Building 82; a camouflage net was thrown over the top to cover the demonstrator during outdoor engine runs. During the engine tests, a local resident complained about the noise, but
Have Blue retained its secrecy. After four taxi tests, HB1001 was ready for test flights. == Operational history ==