[1] A stealth engineer at Lockheed, Denys Overholser, had read the publication and realized that Ufimtsev had created the mathematical theory and tools to perform finite element analysis of radar reflection.

In the 1970s, it became increasingly apparent to U.S. planners that, in a military confrontation with Warsaw Pact forces, NATO aircraft would quickly suffer heavy losses.

This came as a result of sophisticated Soviet defense networks, which used surveillance radars, radar-guided surface-to-air missiles (SAM), and anti-aircraft artillery (AAA) to seek and eliminate enemy aircraft.

[3] During the Cold War, the Soviet Union developed an integrated defense network, central to which were medium- to long-range surveillance radars.

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.

[5] 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.

[5] On behalf of the company, Rich and Martin formally requested permission from DARPA to participate in the program, but the agency initially refused because there were insufficient funds; after much debate, Lockheed was allowed entry, albeit without a government contract.

[7][8] (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.

Within it was a concept study called "Little Harvey," including Kelly Johnson's drawing of an aircraft with smoothly blended shapes.

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.

One model, coated in metal foil, was used to verify ECHO 1's RCS calculations, while the other was earmarked for wind tunnel tests.

[10][14] 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.

[10] In the summer of 1975, DARPA informally invited Lockheed, Northrop and McDonnell Douglas to develop an aircraft under the name "Experimental Survivable Testbed" (XST).

[18] 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.

[16] To test the design's radar returns, Lockheed erected a $187,000 specially built pole upon which the model would be perched.

[clarification needed][20] DARPA, having realized the progress accumulated throughout the study, urged the Northrop team to remain together.

[21] Skunk Works now had to design, construct and flight test two crewed demonstrators as part of Phase 2, or Have Blue.

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".

[23] 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).

As a result, a quadruple redundant fly-by-wire (FBW) flight control system was integrated into the aircraft to give it normal flying characteristics.

[28] 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.

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.

The scheme, consisting of three colors, each with three tones, was used to deceive any casual onlooker from recognizing the design's characteristic faceting.

[33] Dyson, an F-15 Eagle pilot, was previously approached by United States Air Force personnel about the project in 1976.

The aircraft pitched up just as it made contact with the ground which forced the pilot, Bill Park, to abort the landing and make a second attempt.

Efforts to lower the gear were unsuccessful and Bill Park was forced to climb again, and eject when his fuel ran out.

Just a month later, on the day HB1001 was transported to Groom Lake, the Air Force awarded the company a contract under the code name Senior Trend.