F-117 개발에 참여한 엔지니어 데니스 오버홀저가 86세로 별세

[위종민]

F-117 나이트호크 개발에 참여한 록히드 마틴의 엔지니어 데니스 오버홀저가 4월 28일 향년 86세의 나이로 별세하셨네요. 삼가 고인의 명복을 빕니다. 

켈리 존슨은 RCS를 줄이는 다면체 항공기라는 개념(혹은 다면체가 RCS를 줄인다는 개념?) 자체를 믿지 않았고 기회가 될 때마다 개발엔 반대했다고 합니다. 아무래도 공력학적으로는 날아다니는 게 신기한 기체라서 그랬던 걸까요? ㅎㅎㅎ

노스롭의 (아마도 B-2처럼 곡면과 톱니로 이뤄졌을) 시제기는 정면 방향 스텔스 성능이 더 뛰어났지만 록히드의 시제기가 전반적인 스텔스 성능이 더 뛰어났다고도 하네요. 

록히드 마틴 스컹크웍스 엔지니어 Denys Overholser가 최초의 실전 스텔스 공격기 F-117 개발로 이어진 업적과 관련해 나이트호크 앞에서 포즈를 취하고 있다. 촬영 시점 미상. 사진 제공: Lockheed Martin

F-117 개발로 이어진 업적의 스텔스 개척자 Denys Overholser, 86세로 별세
2026년 5월 1일 | 작성자 John A. Tirpak

레이더 반사 단면적(RCS) 수학 이론에 대한 통찰을 통해 최초의 실전 스텔스 공격기 개발로 직접 이어졌고, 전투기 설계와 전술을 영구적으로 바꾼 록히드 마틴 엔지니어 Denys Overholser가 4월 28일 향년 86세로 별세했다. 

Overholser는 “Hopeless Diamond”라 불리는 다면체 스텔스 항공기 개념을 고안했고, F-117 나이트호크 스텔스 공격기의 특허를 작성했으며, 미국 레슬링 명예의 전당에도 이름을 올렸다. 록히드와 다른 방산 기관에서 수행한 그의 작업 상당수는 여전히 기밀 상태다.

1975년부터 1991년까지 록히드 스컹크웍스 첨단 프로젝트 부서를 이끌었던 항공우주 엔지니어 Ben Rich는 1990년대 초 인터뷰에서 Overholser—“젊은 엔지니어 중 한 명”—가 새로운 스텔스 접근법 아이디어를 들고 찾아왔다고 회상했다. Overholser는 러시아 수학자 표트르 우핌체프(Pyotr Ufimtsev)가 1962년에 작성한 레이더파 산란, 즉 회절에 관한 잊혀진 논문을 읽고 있었다. 정작 러시아군은 이 논문을 무시했으며, 미 공군 해외기술부대가 1971년에 이를 번역했다.

회고록 『Skunk Works』에서 Rich는 “그 논문은 너무 난해하고 이해하기 어려워서 진짜 괴짜 중의 괴짜만이 끝까지 읽을 수 있었다”고 썼다. 인터뷰에서 Rich는 Overholser에게 “자유시간에 이런 걸 하는 건가?”라고 물었다고 말했다.

1970년대 이전까지 레이더 반사 단면적 감소 노력은 SR-71 정찰기와 D-21 정찰 드론에 적용된 것처럼 레이더 흡수 재료와 내부 구조에만 제한되어 있었다.

우핌체프의 연구는 형상 설계만으로도 물체의 레이더 반사를 크게 줄일 수 있음을 보여주었으며, 동시에 물체의 레이더 반사 단면적—즉 레이더 반사도—를 계산하는 기초도 제공했다. 항공기의 RCS를 줄이면 레이더에 탐지되기 전에 목표에 상당히 가까이 접근할 수 있으며, 경우에 따라 전혀 탐지되지 않을 가능성도 있었다.

Rich는 메모장을 들어 보이며 우핌체프 연구 일부를 설명했다. 그는 “이걸 이렇게 수직으로 들면 하나의 RCS 값이 나온다. 하지만 45도로 돌려 다이아몬드나 연 모양으로 기울이면 레이더가 모서리를 따라 이동하는 방식 때문에 RCS를 절반 이상 줄일 수 있다”고 말했다.

공군이 새로운 기밀 기술에 관심을 갖게 만들 방법을 찾던 Rich는 Overholser에게 다면체 설계를 항공기에 적용하는 방법과, 당시 컴퓨터 성능으로 정확한 RCS 측정 방법을 개발하는 일을 맡겼다. 당시 36세였던 Overholser는 미래 전투기를 위한 핵심 연구를 이끌게 되었다. 이는 또한 용기 있는 작업이었다. Rich에 따르면 그의 전임자인 전설적 엔지니어 Kelly Johnson은 이러한 개념 자체를 믿지 않았고 기회가 있을 때마다 반대 의사를 밝혔다.

Overholser는 “Echo 1”이라는 컴퓨터 프로그램을 개발했다. 이 프로그램은 일련의 평평한 면(facet)으로 구성된 항공기 일부의 RCS를 계산할 수 있었다. 이후 각각의 계산 결과를 합쳐 전체 설계의 총 RCS를 산출했다. 그는 이어 “Hopeless Diamond”라는 다면체 항공기 개념을 설계했으며, 이 기체는 록히드 D-21보다 1,000배 낮은 레이더 반사도를 가질 것이라고 주장했다. 그는 Rich에게 실전 전투기 크기의 항공기도 “독수리 눈알 수준”의 레이더 반사를 가질 수 있다고 말했다.

이 연구는 곧 “Experimental Survivable Testbed”를 의미하는 XST라는 공군 프로그램으로 이어졌다. 록히드와 노스럽—다른 방식의 스텔스를 추구하고 있었다—은 개념 입증용 소형 저피탐 항공기 설계를 위한 비밀 계약을 받았다. 노스럽은 곡면과 모서리 형상에 따른 RCS를 연구하는 접근법을 사용했으며 정면 방향 성능이 더 뛰어났지만, 당시 기준으로는 록히드 접근법이 전반적으로 더 우수했다. 록히드는 경쟁에서 승리해 “Have Blue” 시제기 두 대를 제작했다. 두 기체 모두 추락했지만, 어느 사고도 스텔스 기술 때문은 아니었으며, 이후 록히드는 실전 시제기 개발 계약을 수주했다. 그것이 YF-117이 되었고, 이어 F-117로 발전했다. F-117은 1991년 걸프전과 이후 일부 분쟁에서 놀라운 성공을 거두었다.

F-117 나이트호크는 레이더를 회피하고 탐지되지 않은 채 침투해 강력히 방어된 목표를 파괴할 수 있는 새로운 군용 항공기 시대를 열었다. Staff Sgt. Aaron D. Allmon II

슈퍼컴퓨터 성능이 향상되면서 전체 항공기의 RCS를 한 번에 계산하는 것이 가능해졌다. Overholser가 수학 이론에서 도입한 기본 원리들은 오늘날 현대 스텔스 기술의 기반으로 계속 사용되고 있다.

Overholser는 텍사스에서 성장했으며 오리건주립대학교에서 수학과 전기공학 학위를 취득했다. 이후 시스템공학과 운용연구 학위도 추가로 취득했다. 그는 보잉에서 미사일 프로젝트에 참여했으며, 컴퓨터 교육을 받은 초기 엔지니어 중 한 명이었다. 대부분의 항공우주 계산이 여전히 계산자를 사용하던 시절, 컴퓨터 경험을 갖고 있다는 이유로 1964년 스컹크웍스에 채용되었다.

스컹크웍스가 속한 록히드 마틴 항공 부문 사장 Greg Ulmer는 4월 29일 직원들에게 보낸 성명에서 Overholser의 작업이 “스텔스 기술의 문을 열었다”고 밝혔다.

Ulmer는 Overholser가 오랫동안 대중의 주목을 받지 못했지만 “기밀 프로그램 세계에서는 그것이 바로 목적이었다”고 말했다. 그는 “탁월함과 규율, 그리고 드문 수준의 인격을 요구하는 작업을 통해 수십 년간 역사 형성에 기여했다”고 말했다. 또한 그의 스텔스 연구는 “공군력을 영원히 바꿔놓았으며”, “스텔스의 로제타 스톤”이었다고 평가했다.

Overholser는 국가방위산업협회의 첫 “전투 생존성” 상을 수상했으며, 군사 기술 발전에 기여한 공로로 공군장관과 국방장관으로부터 훈장을 받았다.

Ulmer는 Overholser가 “복잡한 개념을 쉽게 설명하고, 다른 사람들이 스스로 해결할 수 없다고 생각했던 문제를 해결할 수 있다고 느끼게 만드는” 보기 드문 교육자였다고 말했다. 말년에는 국방부와 MIT 링컨연구소의 자문 엔지니어로 활동했다.

Ulmer는 “우리의 마음은 그의 가족과 사랑하는 사람들, 그리고 그를 알 수 있었던 모든 사람들과 함께한다”며 “우리는 그의 삶과 봉사, 그리고 그가 남긴 특별한 유산에 깊이 감사한다”고 말했다.

2003년부터 2007년까지 공군 신속능력실(RCO) 실장을 지낸 David Hamilton은 “Denys는 훨씬 젊은 엔지니어들에게 셀 수 없이 많은 시간 동안 지도와 멘토링을 제공했다”며 “그는 항공기 생존성 분야의 새로운 방법을 개척할 후속 세대를 키워냈다”고 말했다. 그는 이어 “다른 사람들을 돕기 위해 손을 내민 그의 태도가, 거친 아이디어를 현실화하고 국가를 위한 실전 능력으로 전환해야 했던 엔지니어와 프로그램 관리자들 사이에서 그를 진정한 영웅으로 만들었다”고 말했다. “그는 훌륭한 인물이었으며 항공 전투 생존성 공동체에서 크게 그리워질 것이다.”

Overholser는 또 다른 특별한 이력도 갖고 있었다. 그는 미국 레슬링 명예의 전당에도 헌액되었다. 고등학교와 대학 시절 레슬링 선수로 활동했지만, 그 영예는 주로 항공우주 기술 발전에 기여한 공로 때문이었다.

Stealth Pioneer Denys Overholser Dies At 86

Stealth Pioneer Denys Overholser Dies At 86

Denys Overholser, the Lockheed Martin Skunk Works engineer whose work led to the first operational stealth attack airplane, the F-117, poses in front of a Nighthawk in this undated photo. Courtesy of Lockheed Martin

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Denys Overholser, Stealth Pioneer Whose Work Led to the F-117, Dies at 86

May 1, 2026 | By John A. Tirpak

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Denys Overholser, the Lockheed Martin engineer whose insights on the mathematics of radar cross section led directly to the first operational stealth attack airplane and permanently reshaped combat aircraft design and tactics, died April 28 at the age of 86.

Overholser came up with the idea of the “Hopeless Diamond” faceted stealth aircraft, wrote the patent for the F-117 Night Hawk stealth attack aircraft, and also earned a place in the National Wrestling Hall of Fame. Much of his work at Lockheed and other defense industrial organizations remains classified.

Ben Rich, the aerospace engineer who headed Lockheed’s Skunk Works advanced projects unit from 1975-1991, recalled in an early 1990s interview that Overholser—“one of my young guys”—came to him with the idea for a new approach to stealth. Overholser had read a forgotten 1962 paper on radar wave scattering, or diffraction, by the Russian mathematician Pyotr Ufimtsev; a paper that the Russian military itself had ignored. The Air Force’s foreign technology unit had translated the paper in 1971. 

In his memoir, “Skunk Works,” Rich said “the paper was so obtuse and impenetrable that only a nerd’s nerd would have waded through it.” In the interview, Rich said he asked Overholser, “is this what you do with your free time?”  

Until the 1970s, the effort to reduce radar cross section had been limited to radar-absorbing materials and internal structure, as used on the SR-71 reconnaissance airplane and the D-21 reconnaissance drone.  

Ufimtsev’s research showed that shaping could dramatically attenuate the radar return of an object, and the work also provided the basis for calculating the radar cross section—radar reflectivity—of objects. Reducing the RCS of an aircraft could allow it to get quite close to a target before being detected by radar, and potentially, the aircraft might not be detected at all. 

Holding up a legal pad, Rich summarized some of Ufimtsev’s findings, saying “if I hold it straight up and down like this, it’s one RCS (value). But if I rotate it 45 degrees,” creating a diamond, or kite shape, and tilting it, “I cut RCS by more than half, because of the way radar travels along the edges.” 

Looking for ways to get the Air Force interested in new, classified technologies, Rich put Overholser to work on developing ways “faceting” could be applied to aircraft, as well as methods to accurately measure RCS with the computer power then available. Overholser, at 36, was heading up seminal work on the combat aircraft of the future. It was also brave work because Rich said his predecessor, the legendary Kelly Johnson, was not a believer in the whole idea and said so at every opportunity.  

Overholser came up with a computer program he called “Echo 1” that could calculate RCS for a portion of an aircraft covered by a series of flat surfaces, or facets.  These could then be added to other calculations to obtain an overall RCS for the design. He then drafted the “Hopeless Diamond,” a faceted aircraft concept which Overholser said would have 1,000 times less radar reflectivity than Lockheed’s D-21. A full-size combat aircraft, he told Rich, could have the radar return “of an eagle’s eyeball.” 

The work soon led to an Air Force program called XST, for “Experimental Survivable Testbed.” Lockheed and Northrop—which was pursuing stealth along a different path—were given secret contracts to design small, low-observable aircraft to prove out the concept. Northrop’s approach had been to assess RCS of compounds curves and edge shape, and worked better in a forward view, but Lockheed’s approach worked better overall at that point. Lockheed won and built two demonstrators called “Have Blue.” Although both crashed, neither accident was due to stealth, and Lockheed received an Air Force contract to build an operational prototype, which became the YF-117. That in turn led to the F-117, which was phenomenally successful in the 1991 Gulf War and in some later conflicts. 

The F-117 Nighthawk ushered in a new era in military aviation: aircraft that could evade radar and penetrate unseen to destroy highly protected targets. Staff Sgt. Aaron D. Allmon II

As supercomputers became more powerful, it became possible to calculate RCS for an entire aircraft at once. The basic principles Overholser ported over from the mathematical theory continue to serve as the basis for modern stealth.   

Overholser grew up in Texas and earned degrees in mathematics and electrical engineering from Oregon State University, later adding degrees in systems engineering and operations research. He worked on missile projects for Boeing and was one of the first engineers in that company to be chosen for training on computers. He moved to Skunk Works in 1964, hired because he was familiar with computers at a time when most aerospace math was still done on slide rules.   

Greg Ulmer, president of Lockheed Martin Aeronautics—of which Skunk Works is a division—issued a statement to employees on April 29 saying Overholser’s worked “unlocked stealth technology.” 

Overholser went largely unsung and “in the world of classified programs, that was exactly the point,” Ulmer said. “He spent decades shaping history far from public view through work that demanded brilliance, discipline, and a rare depth of character.” His work on stealth “would reshape airpower forever,” Ulmer said., adding that Overholser’s work was “the Rosetta stone” of stealth. 

Overholser received the first-ever award of the National Defense Industrial Association for “Combat Survivability,” and was decorated by the Secretaries of the Air Force and Defense for his contributions to military technology. 

Ulmer said Overholser had the rare knack of being a teacher who could “demystify complex concepts and make others feel capable of solving problems they never thought they could.” In later years, Overholser was a consulting engineer for the Pentagon and MIT’s Lincoln Laboratories.  

“Our hearts are with his family, loved ones and all who had the privilege of knowing him,” Ulmer said. “We are profoundly grateful for his life, his service, and the extraordinary legacy he leaves behind.” 

David Hamilton, who was director of the Air Force’s Rapid Capabilities Office from 2003-2007, said “Denys freely gave countless hours of tutoring and mentoring to many other engineers far more junior. He helped ferment the follow-on generations who continue to pioneer new methods in aircraft survivability. It was his reaching out to help others that elevated him to true unique hero status within the class of engineers and program managers who had the task to bring wild ideas to reality and into operational capabilities for the nation. He was a class act who will be severely missed by the aviation combat survivability community.” 

Overholser enjoyed another distinction, having been elected to the National Wrestling Hall of Fame. He wrestled in high school and college, but the honor stemmed mainly from his contributions to aerospace technology.  

Denys Overholser, the Lockheed Martin Skunk Works engineer whose work led to the first operational stealth attack airplane, the F-117, poses in front of a Nighthawk in this undated photo. Courtesy of Lockheed Martin

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Denys Overholser, Stealth Pioneer Whose Work Led to the F-117, Dies at 86

May 1, 2026 | By John A. Tirpak

Denys Overholser, the Lockheed Martin engineer whose insights on the mathematics of radar cross section led directly to the first operational stealth attack airplane and permanently reshaped combat aircraft design and tactics, died April 28 at the age of 86.

Overholser came up with the idea of the “Hopeless Diamond” faceted stealth aircraft, wrote the patent for the F-117 Night Hawk stealth attack aircraft, and also earned a place in the National Wrestling Hall of Fame. Much of his work at Lockheed and other defense industrial organizations remains classified.

Ben Rich, the aerospace engineer who headed Lockheed’s Skunk Works advanced projects unit from 1975-1991, recalled in an early 1990s interview that Overholser—“one of my young guys”—came to him with the idea for a new approach to stealth. Overholser had read a forgotten 1962 paper on radar wave scattering, or diffraction, by the Russian mathematician Pyotr Ufimtsev; a paper that the Russian military itself had ignored. The Air Force’s foreign technology unit had translated the paper in 1971. 

In his memoir, “Skunk Works,” Rich said “the paper was so obtuse and impenetrable that only a nerd’s nerd would have waded through it.” In the interview, Rich said he asked Overholser, “is this what you do with your free time?”  

Until the 1970s, the effort to reduce radar cross section had been limited to radar-absorbing materials and internal structure, as used on the SR-71 reconnaissance airplane and the D-21 reconnaissance drone.  

Ufimtsev’s research showed that shaping could dramatically attenuate the radar return of an object, and the work also provided the basis for calculating the radar cross section—radar reflectivity—of objects. Reducing the RCS of an aircraft could allow it to get quite close to a target before being detected by radar, and potentially, the aircraft might not be detected at all. 

Holding up a legal pad, Rich summarized some of Ufimtsev’s findings, saying “if I hold it straight up and down like this, it’s one RCS (value). But if I rotate it 45 degrees,” creating a diamond, or kite shape, and tilting it, “I cut RCS by more than half, because of the way radar travels along the edges.” 

Looking for ways to get the Air Force interested in new, classified technologies, Rich put Overholser to work on developing ways “faceting” could be applied to aircraft, as well as methods to accurately measure RCS with the computer power then available. Overholser, at 36, was heading up seminal work on the combat aircraft of the future. It was also brave work because Rich said his predecessor, the legendary Kelly Johnson, was not a believer in the whole idea and said so at every opportunity.  

Overholser came up with a computer program he called “Echo 1” that could calculate RCS for a portion of an aircraft covered by a series of flat surfaces, or facets.  These could then be added to other calculations to obtain an overall RCS for the design. He then drafted the “Hopeless Diamond,” a faceted aircraft concept which Overholser said would have 1,000 times less radar reflectivity than Lockheed’s D-21. A full-size combat aircraft, he told Rich, could have the radar return “of an eagle’s eyeball.” 

The work soon led to an Air Force program called XST, for “Experimental Survivable Testbed.” Lockheed and Northrop—which was pursuing stealth along a different path—were given secret contracts to design small, low-observable aircraft to prove out the concept. Northrop’s approach had been to assess RCS of compounds curves and edge shape, and worked better in a forward view, but Lockheed’s approach worked better overall at that point. Lockheed won and built two demonstrators called “Have Blue.” Although both crashed, neither accident was due to stealth, and Lockheed received an Air Force contract to build an operational prototype, which became the YF-117. That in turn led to the F-117, which was phenomenally successful in the 1991 Gulf War and in some later conflicts. 

The F-117 Nighthawk ushered in a new era in military aviation: aircraft that could evade radar and penetrate unseen to destroy highly protected targets. Staff Sgt. Aaron D. Allmon II

As supercomputers became more powerful, it became possible to calculate RCS for an entire aircraft at once. The basic principles Overholser ported over from the mathematical theory continue to serve as the basis for modern stealth.   

Overholser grew up in Texas and earned degrees in mathematics and electrical engineering from Oregon State University, later adding degrees in systems engineering and operations research. He worked on missile projects for Boeing and was one of the first engineers in that company to be chosen for training on computers. He moved to Skunk Works in 1964, hired because he was familiar with computers at a time when most aerospace math was still done on slide rules.   

Greg Ulmer, president of Lockheed Martin Aeronautics—of which Skunk Works is a division—issued a statement to employees on April 29 saying Overholser’s worked “unlocked stealth technology.” 

Overholser went largely unsung and “in the world of classified programs, that was exactly the point,” Ulmer said. “He spent decades shaping history far from public view through work that demanded brilliance, discipline, and a rare depth of character.” His work on stealth “would reshape airpower forever,” Ulmer said., adding that Overholser’s work was “the Rosetta stone” of stealth. 

Overholser received the first-ever award of the National Defense Industrial Association for “Combat Survivability,” and was decorated by the Secretaries of the Air Force and Defense for his contributions to military technology. 

Ulmer said Overholser had the rare knack of being a teacher who could “demystify complex concepts and make others feel capable of solving problems they never thought they could.” In later years, Overholser was a consulting engineer for the Pentagon and MIT’s Lincoln Laboratories.  

“Our hearts are with his family, loved ones and all who had the privilege of knowing him,” Ulmer said. “We are profoundly grateful for his life, his service, and the extraordinary legacy he leaves behind.” 

David Hamilton, who was director of the Air Force’s Rapid Capabilities Office from 2003-2007, said “Denys freely gave countless hours of tutoring and mentoring to many other engineers far more junior. He helped ferment the follow-on generations who continue to pioneer new methods in aircraft survivability. It was his reaching out to help others that elevated him to true unique hero status within the class of engineers and program managers who had the task to bring wild ideas to reality and into operational capabilities for the nation. He was a class act who will be severely missed by the aviation combat survivability community.” 

Overholser enjoyed another distinction, having been elected to the National Wrestling Hall of Fame. He wrestled in high school and college, but the honor stemmed mainly from his contributions to aerospace technology.   

[백선호]

켈리 존슨도 말년에는 똥고집을 부린 모양이네요. ㄷㄷㄷ

[위종민]

본인이 추구했던 비행기 개발방향과는 아무래도 정반대로 향하는 비행기라서 그러셨을 지도요. 켈리 존슨이 1975년에 벤 리치에게 스컹크 웍스 수장 자리를 넘겼다고 하고, 데니스 오버홀저가 36세였던 1976년부터 개발이 진행된 것 같으니 켈리 존슨 은퇴 후에나 개발이 추진된 것 같고, 고문으로 물러났던 존슨은 꾸준히 반대했던 것 같습니다.