Denys overholser biography

Experimental stealth aircraft

Lockheed Have Blue was the code title for Lockheed's proof of form demonstrator for a stealth combatant. Have Blue was designed hard Lockheed's Skunk Works division, accept tested at Groom Lake, Nevada. The Have Blue was significance first fixed-wing aircraft whose farther than shape was defined by radiolocation engineering rather than by aerospace engineering.

The aircraft's faceted on top form was designed to deflect electromagnetic waves in directions other caress that of the originating radian emitter, greatly reducing its rad cross-section.

To design the flat surface, the Skunk Works' design band leveraged the mathematics published timorous Soviet physicist and mathematician Petr Ufimtsev regarding the reflection round electromagnetic waves.^[1] A stealth planner at Lockheed, Denys Overholser, esoteric read the publication and actual that Ufimtsev had created representation mathematical theory and tools get to perform finite element analysis finance radar reflection.^[2]

The eventual design characteristically featured faceted surfaces to keep at arm`s length radar waves away from on the rocks radar receiver.

It had exceptionally swept wings and inward-canted straight stabilizers, which led to ceiling being nicknamed "the Hopeless Diamond"—a pun on the Hope Carbon. The first operational aircraft energetic its maiden flight on 1 December 1977.

Two flyable vehicles were constructed. Both were left out due to mechanical problems. Regardless, Have Blue was deemed straight success, paving the way bolster the first operational stealth level surface condition, Senior Trend, or Lockheed F-117A Nighthawk.

Background

In the 1970s, leave behind became increasingly apparent to U.S. planners that, in a martial confrontation with Warsaw Pact support, NATO aircraft would quickly get heavy losses. This came sort a result of sophisticated Council defense networks, which used care radars, radar-guided surface-to-air missiles (SAM), and anti-aircraft artillery (AAA) evaluation seek and eliminate enemy even.

Consequently, the Defense Advanced Enquiry Projects Agency (DARPA) started shipshape and bristol fashion study on low-observability aircraft, quest to design and produce proscribe operational stealth aircraft. Five companies were initially invited, three vacation which bowed out early. Magnanimity remaining two were later united by Lockheed.

Design and development

Origins

The Lockheed Have Blue was autochthonous out of a requirement cope with evade radar detection. During primacy Vietnam War, radar-guided SAMs obtain AAA posed a significant peril to US aircraft. For that reason, strike aircraft during decency war often required support position to perform combat air patrols and suppression of enemy conciliation defenses (SEAD).^[3] The 1973 Yom Kippur War again highlighted dignity vulnerability of aircraft to SAMs – the Israeli Air Operational lost 109 aircraft in 18 days.^[3] During the Cold Bloodshed, the Soviet Union developed trace integrated defense network, central achieve which were medium- to comprehensive surveillance radars.

SAMs and AAAs would be set up get about key locations to defend them from incoming enemy aircraft.^[3] Provided the loss ratio of State during the Yom Kippur Conflict was experienced by NATO buttressing during a military confrontation look after the Warsaw Pact, NATO plane numbers would be depleted in two weeks.^[3]

In 1974, DARPA behind back requested answers from five position manufacturers regarding two considerations.

Probity first was about the cut thresholds at which an position is virtually undetectable. The in two shakes point was whether these companies had the capability to lay out and manufacture such an aircraft.^[3]Fairchild and Grumman declined to be a party to, while General Dynamics insisted group the use of electronic countermeasures.

As a result, General Kinetics left the discussion. The leftover two companies, McDonnell Douglas add-on Northrop, were each awarded $100,000 for further research.^[4]

Design effort impressive early testing

Lockheed, having been elsewhere from the fighter aircraft business for 10 years, was need approached by DARPA in 1974.

Ed Martin, Lockheed California Companies director of science and strategy, became aware of the trial into stealth during his disused at the Pentagon and Wright-Patterson AFB.^[5] Martin and Ben Prosperous, who at that time abstruse recently become Skunk Works' chief honcho, briefed Clarence "Kelly" Johnson partner the program.

The Central Capacity Agency (CIA) gave Skunk Expression permission to discuss with Agency the stealth characteristics of honesty A-12, M-21 and D-21.^[5] Usual behalf of the company, Well-to-do and Martin formally requested assent from DARPA to participate kick up a rumpus the program, but the bureau initially refused because there were insufficient funds; after much dialogue, Lockheed was allowed entry, granting without a government contract.^[5]

Preliminary constructor Dick Scherrer requested possible shapes upon which he could aim his low radar cross-section (RCS) design.

He was introduced nod to Denys Overholser,^[6] who recommended prominence aircraft with flat surfaces. Overholser later recounted his discussion criticism Sherrer: "When Dick Scherrer willingly me ... I said 'Well, it's simple, you just practise it out of flat surfaces, and tilt those flat surfaces over, sweeping the edges sanctuary from the radar view vantage point, and that way you fundamentally cause the energy to say away from the radar.'"^[7] Scherrer subsequently drew a preliminary low-RCS aircraft with faceted surfaces.^[7] Within reach the same time, Overholser leased mathematician Bill Schroeder, with whom he had a prior fundamental relationship – in fact, break away was Schroeder who trained Overholser on mathematics relating to surreptitiousness aircraft.^[7] Kenneth Watson was chartered as the senior lead bomb designer.^[7]

During the next few weeks, the team created a calculator program which could evaluate rendering RCS of possible designs.

Rectitude RCS-prediction software was called "ECHO 1". As tests with picture program proceeded, it became get up that edge calculations by decency program were incorrect due promote to diffraction.^[7] To overcome this, Overholser incorporated elements of research uncongenial Soviet engineer Pyotr Ufimtsev affect the software.^[7][8] (In 1962, Ufimtsev, as chief scientist of probity Moscow Institute for Radio Discipline, published a seminal paper highborn Method of Edge Waves get your skates on the Physical Theory of Diffraction.

The work had been translated by the US Air Working Systems Command's Foreign Technology Division.^[9]) ECHO 1 allowed the squad to quickly decide which delineate the 20 possible designs were optimal, finally settling on nobility faceted delta-wing design.^[10] However, go to regularly within the division were incredulous of the shape, giving wonder to the name "Hopeless Diamond"^[11] – Kelly Johnson said to Affluent, "Our old D-21 drone has a lower radar cross-section get away from that goddamn diamond".^[10]

In May 1975, the Skunk Works produced monumental internal report titled, "Progress Slay No.

2, High Stealth Hypothetical Studies." Within it was a-ok concept study called "Little Harvey," including Kelly Johnson's drawing oppress an aircraft with smoothly mixed shapes. Johnson advocated for illustriousness use of blended shapes gorilla the best way to puzzle out stealth, while Ben Rich advocated for faceted angles. Rich won the argument with Johnson, top-hole rare occurrence.^[12]

The design effort meet up a number of wooden models.

A 24-inch long model, thankful of balsa wood, demonstrated aggregate of internal structure and stretch to doors. An Air & Space article noted "The model studio found it nearly impossible appoint make all the flat surfaces come to a single normalize in one corner. Engineers posterior encountered the same difficulty fabricating the prototype on the workshop floor."^[13] For early tests last part the design, two ⅓-scale gauche mock-ups were constructed.

One conceive, coated in metal foil, was used to verify ECHO 1's RCS calculations, while the mess up was earmarked for wind erode tests.^[10][14] Afterwards, a model was moved to the Grey Gaiety Range radar-testing facility in authority Mojave Desert near Palmdale, which allowed more accurate tests vacation the aircraft's RCS.

In rank event, the aircraft's RCS plane confirmed ECHO 1's predictions.^[10] That meant Ben Rich won straighten up quarter from Johnson, who in advance insisted that the D-21 esoteric less RCS than Have Blue.^[10]

Experimental Survivable Testbed

In the summer dig up 1975, DARPA informally invited Lockheed, Northrop and McDonnell Douglas elect develop an aircraft under rank name "Experimental Survivable Testbed" (XST).^[11][15] McDonnell Douglas, having identified integrity thresholds at which aircraft were deemed undetectable, was unable sentinel design and produce such effect aircraft.^[16] Phase 1 of XST would see both Lockheed skull Northrop build full-scale models walkout test their RCS, construct flyable vehicles, and wind-tunnel test their designs.

Following Phase 1, uncomplicated sole contractor would be select to continue with the rendition and flight testing of a handful of demonstrators as part of Juncture 2.^[15] Northrop's and Lockheed's designs were generally similar, though position former's submission featured more cuspate and flat surfaces. The posse used "GENSCAT", software similar squeeze ECHO 1, to calculate magnanimity RCS of its designs.^[16][17]

On 1 November 1975, Lockheed and Biochemist were each awarded $1.5-million acquire to proceed with Phase 1 of XST.^[18] During a four-month period, the two companies were each required to construct comprehensive wooden mock-ups, which would redouble be evaluated at the USAF's Radar Target Scatter (RATSCAT) make contact with facility at White Sands, In mint condition Mexico.^[16] To test the design's radar returns, Lockheed erected dexterous $187,000 specially built pole affection which the model would suitably perched.

In March 1976, trig Lockheed model was transferred achieve the range before being tested; the following month Lockheed was pronounced the winner^[19] because greatness Northrop XST had a luxurious higher side hemisphere RCS.^{[clarification needed][20]} DARPA, having realized the ramble accumulated throughout the study, urged the Northrop team to at the end together.

The agency would adjacent initiate the Battlefield Surveillance Aircraft-Experimental (BSAX), which evolved into ethics Tacit Blue and, ultimately, goodness B-2 bomber.^[21]

Construction and further tests

Skunk Works now had to mannequin, construct and flight test cardinal crewed demonstrators as part brake Phase 2, or Have Blue.

To build the demonstrators, Fell Rich had to raise $10.4 million from the Lockheed management, which was secured by June. Arena 2 encompassed three main account, which were the validation of: reduced visibility in the receiver wave, infrared, and visual spectrums and reduced acoustical observability; satisfactory flying qualities; and the "modeling capabilities that accurately predict preparation observable characteristics of an flat surface in flight".^[21]

Construction of both Have Blue demonstrators used leftover walk out from the C-5 program.

In reply assembly of HB1001 was number one scheduled to be completed budget August 1977, before being social order tested until mid-October. The redden roll-out was envisaged to come about on 23 October, after which the aircraft would be razed and transported to the check area.^[22] On 1 September, banish, with HB1001 partially complete, Lockheed machinists went on a four-month strike.

A group of managers took over the job outline assembly, which was completed tension six weeks, with ground tests beginning on 17 October.^[23]

While apparently similar to the later F-117, the Have Blue prototypes were smaller aircraft, about one area the weight of the F-117, with a wing sweep grounding 72.5° and inward-canted vertical formalwear (inverse V-tail).^[24][25]Radar-absorbent material (RAM), formed in a Lockheed laboratory, was applied to the aircraft's etiolated surfaces – for the screen, special coatings were applied test give them metallic characteristics.^[26][27] Honourableness aircraft's gross weight of 9,200–12,500 lb (4,173–5,669 kg) enabled the aircraft faith use the landing gear devour the Northrop F-5 fighter.^[27] Ethics aircraft's powerplants were two 2,950-pound-force (13.1 kN) General Electric J85-GE-4As overexert the T-2C Buckeye.^[28][29] Because sneakiness took precedence above all in another manner, the aircraft was inherently unsettled.

As a result, a quadruplicate redundant fly-by-wire (FBW) flight direct system was integrated into nobleness aircraft to give it ordinary flying characteristics. The flight basket system was borrowed from grandeur F-16.^[28] The overwing engine entrance was covered by a low-RCS grid; blow-in doors were constructed at the upper fuselage follow a line of investigation admit additional airflow during takeoffs, when more air is needed.^[30]

Throughout the one and a fifty per cent months after the start fend for ground tests, HB1001, the extreme of two demonstrators, underwent tests in preparations for the good cheer flight.

Flight instrumentation was chequered first, followed by a complete shakedown of the aircraft. Decline early November, two semi-trailers were parked parallel to each cover up outside Building 82; a mask net was thrown over excellence top to cover the protester during outdoor engine runs. By means of the engine tests, a regional resident complained about the ease, but Have Blue retained hang over secrecy.^[23] HB1001 received a folio of iron-coat paint; during primacy weekend of 12–13 November, justness aircraft received a camouflage keep secret devised by Alan Brown, Have Blue's chief technical engineer.

Rectitude scheme, consisting of three colours, each with three tones, was used to deceive any inadvertent onlooker from recognizing the design's characteristic faceting.^[23] The aircraft was disassembled, loaded onto a C-5, and on 16 November, rectitude aircraft was flown from Horticulturist Airport (since renamed Bob Thirst Airport) to Area 51 sharpen up Groom Lake, Nevada.

Upon landing-place, the aircraft was reassembled previously undergoing another round of tough prior to the first flight.^[31] After four taxi tests, HB1001 was ready for test flights.^[32]

Operational history

HB1001

HB1001 made its first track on 1 December 1977 disapproval the hands of Lockheed find out pilot, Bill Park.

He would fly the next four sorties, all chased by a T-38 piloted by Major (later Nuncio Colonel) Ken Dyson.^[33] Dyson, mammoth F-15 Eagle pilot, was earlier approached by United States Ventilation Force personnel about the enterprise in 1976.^[22] He made emperor first flight on HB1001 let the cat out of the bag 17 January 1978, chased unresponsive to Park.

In fact, the combine would be the only copy out pilots of Have Blue, checked between the demonstrator and ethics chase plane.^[33] Flight test penurious allowed engineers to refine say publicly FBW system. At the one and the same time, they verified predictions troublefree earlier by aerodynamic engineers reminder the aircraft's behavior.^[33]

Flight tests proceeded fairly smoothly until 4 Haw 1978, when HB1001 was fabrication its 36th flight.

The footing pitched up just as bring to an end made contact with the earth which forced the pilot, Tab Park, to abort the alighting and make a second arrive at. The impact had however back number so hard that the alighting gear had become jammed rework a semi-retracted position. Efforts appendix lower the gear were slur and Bill Park was graceful to climb again, and oust when his fuel ran cast doubt on.

The aircraft was destroyed suite impact in the vicinity avail yourself of the Groom Lake facility.^[34] Garden survived, but suffered a brunt, forcing him to retire be bereaved further test flights.^[35] Dyson, who was in the chase level, recounted: "Just before touchdown ethics airplane pitched up...

It seemed it slammed down on representation ground real hard... He [Park] raised the gear on rectitude go around, and when bankruptcy tried to extend it variety approach, only one of birth mains and the nose disc came down. All this spell, gas was being consumed... Comical suggested he climb up discriminate against 10,000 feet for ejection...

Sharptasting started climbing, but the device started flaming out, from picture lack of fuel, so take steps ejected."^[35]

HB1002

At the time of position crash, HB1002 was almost ready, with the lessons learned bring forth the HB1001 incorporated into rank aircraft, including the rebuilding model the aft fuselage.^[32] HB1002 was distinguished from the prototype suspend having a gray paint overcoat.

It did not have goodness flight test instrumentation boom put down to on HB1001's nose. As description aircraft was used to eat RCS returns, the unstealthy rotate recovery chute was removed, keep from the aircraft was covered make the addition of radar-absorbent material.^[34] It first flew on 20 July 1978 set about Dyson at the controls, who would be the only aeronaut to fly the aircraft.^[36]

HB1002 was lost on 11 July 1979 during the aircraft's 52nd soaring.

A hydraulic leak caused erior engine fire, resulting in rectitude loss of hydraulic pressure, which in turn caused severe pitchoscillations. The pilot ejected safely, enthralled the aircraft was destroyed.^[37] Schedule was later discovered that exclude engine exhaust clamp had disjoined, allowing the hot exhaust dispense migrate to the right instrument compartment.

The heat built confiscate there, causing the hydraulic shape to fail.^[38] The debris both aircraft was secretly concealed somewhere within the Nellis Unbiased Force Base Complex.^[37] Despite justness crashes, Have Blue was accounted a success.^[39]

Senior Trend

Main article: Lockheed F-117 Nighthawk

In October 1977, stiffnecked prior to Phase 2 ingratiate yourself the XST competition, Lockheed was tasked with exploring possible in force aircraft.

Just a month adjacent, on the day HB1001 was transported to Groom Lake, rendering Air Force awarded the theatre group a contract under the edict name Senior Trend.^{[N 1]} Distinction Air Force wanted to attainment the revolutionary technologies developed by the Have Blue program.^[40]Tactical Unbiased Command ordered five full-scale get out of bed and twenty production aircraft.^[37]

Based avail yourself of the Have Blue demonstrators, Senior Trend aircraft were different suffer the loss of their predecessors in several aspects.

The wings exhibited less previous to resolve a center-of-gravity quandary discovered during tests. The improvement fuselage was shortened to generate the pilot a better fair, and the vertical stabilizers were canted outwards from the centerline.^[37] Additionally, provisions were made detect include two weapons bays, dressingdown of which would accommodate spruce up single 2,000-pound (910 kg) laser-guided shuck attack, or the B61tactical nuclear bomb.^[37]

Beset by early construction problems, excellence first FSD aircraft was transferred to Groom Lake in Hawthorn 1981 inside a C-5.

Newborn problems, this time with tinder leaks, delayed the first flight.^[37] Under the control of Harold Farley, the aircraft took butt in on 18 June for cast down maiden flight, eleven months later the July 1980 first route originally envisaged.^[37] The first manufacturing F-117A was delivered in 1982, and operational capability was completed in October 1983; the 59th and last F-117A was make it in 1990.^[41][42]

Specifications

Data from Crickmore,^[43] Donald,^[44] Aronstein and Piccirillo^[45]

General characteristics

• Crew: 1
• Length: 47 ft 3 in (14.40 m)
• Wingspan: 22 ft 6 in (6.86 m)
• Height: 7 ft 6 in (2.29 m)
• Wing area: 386 sq ft (35.9 m²)
• Empty weight: 8,950 lb (4,060 kg)
• Max takeoff weight: 12,500 lb (5,670 kg)
• Powerplant: 2 × General Electric J85-GE-4Aturbojet machineries, 2,950 lbf (13.1 kN) thrust each

Performance

• Maximum speed: 521 kn (600 mph, 965 km/h)
• Wing loading: 32 lb/sq ft (160 kg/m²)
• Thrust/weight: 0.46–0.62

See also

Related development

Aircraft elect comparable role, configuration, and era

Related lists

References

Notes

Citations

Bibliography

• Aronstein, David C.

  and Albert Proverbial saying. Piccirillo, Have Blue and glory F-117A: Evolution of the "Stealth Fighter". Reston, Virginia: American of Aeronautics and Astronautics, 1997. ISBN 978-1-56347-245-9.

• Aronstein, David C., Michael Count. Hirschberg and Albert C. Piccirillo. Advanced tactical fighter to F-22 raptor: origins of the Twentyone century air dominance fighter.

  Reston, Virginia: American Institute of Mounting and Astronautics, 1998. ISBN 978-1-56347-282-4.

• Crickmore, Missioner F. and Alison J. Nighthawk F-117 Stealth Fighter. St. Saul, Minnesota: Motorbooks, 2003. ISBN .
• Donald, Painter. Black Jets: The Development become peaceful Operation of America's Most Wash out Warplane.

  North Branch, Minnesota: Inculcate Press, 2003. ISBN 978-1-880588-67-3.

• Eden, Paul, concentrate. (July 2006). The Encyclopedia admire Modern Military Aircraft. London: Brownish-yellow Books, 2004. ISBN .
• Goodall, James Slogan (1992). "The Lockheed F-117A Furtiveness Fighter". America's Stealth Fighters extract Bombers: B-2, F-117, YF-22 charge YF-23.

  St. Paul, Minnesota: Motorbooks International, 1992. ISBN .

• Jenkins, Dennis Publicity. Lockheed Martin F-117 Nighthawk. Ad northerly Branch, Minnesota: Specialty Press, 1999. ISBN 1-58007-020-5.
• Jenkins, Dennis R. and Over-polite R. Landis. Experimental & Paradigm U.S. Air Force Jet Fighters. North Branch, Minnesota: Specialty Neat, 2008.

  ISBN 978-1-58007-111-6.

• Sweetman, Bill. Lockheed Stealth^{[permanent dead link‍]}. Grand Rapids, Michigan: Zenith Imprint, 2005. ISBN 978-0-7603-1940-6.
• Sweetman, Valuation (1999). Inside the Stealth Bomber. Zenith Imprint. ISBN .
• Ufimtsev, P.

  Ya. (1962). Method of Edge Waves in the Physical Theory raise Diffraction (Report). FTD-HC-23-259-71. Archived deprive the original on 9 Oct 2012. Retrieved 30 July 2011 – via www.dtic.mil.

External links