Posted on 04/24/2012 6:41:06 PM PDT by DogByte6RER
How Lockheed’s Skunk Works Got into the Stealth Fighter Business
How Lockheed’s Skunk Works Got into the Stealth Fighter Business
How do you hide an airplane behind a bird? Very skillfully. Lt. Col. William B. O'Connor (ret.) flew the F-117 Nighthawk during the Bosnia Conflict, and in Stealth Fighter, he explains the history, operation, and soul America's most advanced stealth jet.
While the United States had never embraced a defensive mindset and had only fielded one strategic SAM system to that point, the Nike-Hercules dating from the 1950s, and one real medium-range tactical system, the HAWK (homing all the way killer), the Soviets had fielded over fifteen different systems. One Soviet SAM system was even armed with nuclear warheads.
It had become clear that there had to be a better way. So in 1974, the U.S. Defense Advanced Research Projects Agency (DARPA) initiated a program known as Project Harvey (named after the 6 feet 3 1/2 inches tall invisible white rabbit from the play of the same name). The ultimate goal was to develop a combat aircraft with as low a radar signature as possible. Five aerospace corporations had been contracted a million dollars each to give it their best shot. Surprisingly, Lockheed hadn't been among them. It was only an accidental tip-off that allowed Lockheed's Ben Rich to lobby for inclusion. Rich had been an engineer on the secret U-2 and SR-71 reconnaissance aircraft and had by then advanced to become Lockheed's successor to the famous Kelly Johnson as director of the Skunk Works. The "Skunk Works" is the official alias for the department responsible for all of Lockheed's highly secret advanced development projects. It was formed in 1943 to build America's first jet fighter, the P-80, and numerous other projects that belong to the shadow world of military operations.
By the time Rich had gotten wind of Project Harvey, there was no money left for another developmental contract. So Lockheed was offered a shot-for a dollar. But Rich wanted in and wisely turned down the token dollar. He knew that any new technologies developed with company funds would then be proprietary. Lockheed was famous for building small fleets of extremely advanced aircraft-often used for highly secretive missions. During World War II, they had built the United States' first operational subsonic jet fighter, the P-80. They skipped the Mach-1 era altogether and jumped right to fielding the United States' first fighter capable of speeds in excess of Mach 2, the F-104 Star Fighter. Along the way came the high-flying U-2, the higher-flying SR-71, the hypersonic D-21 drone (which would ride piggyback on an SR-71 until released), and other things not yet named.
In Rich's own words, the unsung hero of Lockheed's effort was an anonymous staff mathematician and electrical engineer named Denys Overholser. Overholser and his mentor, another mathematician named Bill Schroeder, had discussed the possibilities of utilizing some of the equations associated with optical scattering (how electromagnetic waves bounce off variously shaped objects) on this project. Both had the rather odd hobby of reading obscure Russian mathematics papers and had made the ultimate "nerd's nerd" discovery. They had stumbled across a paper published in Moscow a decade earlier titled "Method of Edge Waves in the Physical Theory of Diffraction." It had been written by Pyotr Ufimtsev, the Soviet's chief scientist at the Moscow Institute of Radio Engineering and the last in a long line of scientists developing a long series of wave equations originally derived centuries ago by the Scottish physicist James Clerk Maxwell.
The U.S. intelligence community had helped translate this research and brought it to the West. The paper was in no way classified or related to weapons development at all. It was purely theoretical math. Years later, Ufimtsev immigrated to the United States to teach at the University of California, Los Angeles, and only then discovered his inadvertent contribution to the development of stealth aircraft.
The equations that Ufimtsev had developed made the reflections of radio waves off hard surfaces predictable. Not invisible, transparent, or tactical in any way-just predictable. The problem for Lockheed was that the calculations were so ferociously difficult that the most advanced supercomputers in the world at the time could only compute results for flat surfaces. Any attempt to perform the calculations for the curved surfaces you would find on a conventional aircraft-well, those machines would still be grinding away toward a solution today.
Schroeder recognized how these equations could be applied to Lockheed's current project. The solution was not even to attempt to design an aircraft with any curved surfaces, but to build one with dozens, or perhaps hundreds, of individual flat triangular and rectangular plates. Then the challenge was to compute the reflection from each and every flat surface before adding them all together to build a picture of the aircraft's total radar signature. Once you knew where every bit of radar reflection was coming from, you could then reorient those individual plates so that the reflection would go off in a direction away from the radar looking at it.
The process became known as "faceting." And that became the real secret-not to absorb all the radar or make the plane somehow transparent, but to make the plane's signature predictable. That predictability could then be used to shape a tactically useful aircraft. The jet would also be covered in thin sheets of RAM, but the bulk of the stealth effect was achieved by its shape.
Traditionally, a single engineering specialty will take the lead during the design of a new aircraft. An aerodynamicist may be in charge of pushing through a new wing or fuselage shape, as happened with the early delta wings and area-ruled fuselages of the "Century Series" of interceptors. Sometimes it may be the power-plant guy: "Here's the engine we're going to use, build us a jet fighter for it." This is how the P-80 came about. Occasionally it may be the armaments people- the A-10 is fundamentally a massive 30mm Gatling cannon with a plane built around it. In this particular case, this was the first time the lead was owned by an electrical engineer.
The computer program designed by Overholser's team to make these calculations was called Echo- 1. Armed with that tool, the first test subject, the Hopeless Diamond, was built. It was described as a diamond for obvious reasons and "hopeless" for its aerodynamic qualities (or rather, its complete lack thereof).
Early radar testing of the Hopeless Diamond turned out to be staggeringly successful. The White Sands experimental radar range near Holloman AFB was used. When the radar was fired up for the initial testing, the only thing that showed up was the reflection of the pole on which the test model was supposed to be mounted. Assuming that the model had fallen off the pole, the radar operators sent technicians downrange to fix the problem. To their surprise, the ten-foot model was still in place.
To test the model at all, Lockheed then had to design an invisible "stealth pole" to mount the model utilizing the same technology as the proposed fighter. The results were once again astounding, and incredulous USAF officials were called in to witness and verify the data.
The first opportunity to impress these officials almost resulted in embarrassment. When the radars were turned on, the reflections, while still very small by airplane standards, were orders of magnitude larger than what the USAF officials had been led to expect. They could still clearly see a small radar return from where the model was mounted.
While the Lockheed engineers were trying to explain this discrepancy, a radio call came in from a technician downrange. He reported that a bird was perched on the ten-foot model. The quick reply was an order to blow the horn of the pickup truck the guy was sitting in. As the startled bird flew away, the radar reflection on the test scope disappeared.
The very idea that a combat aircraft could be made so invisible as to hide behind a bird was an opportunity that couldn't be passed up. Everything associated with the program became classified at the highest levels. The program was transferred from DARPA to the USAF special projects office. The word "stealth" was forbidden to be mentioned in any unclassified document. And in April 1976, the Ford administration gave Lockheed the go-ahead for a full-scale aircraft. The Skunk Works was officially in the stealth fighter business.
What is that?
Impressive.
F-117 Nighthawk
The P-80 wasn’t the first US jet fighter. P-59 Airacomet would be the first.
Looks like a 117 to me. They are impressive.
/johnny
I saw an F-117 at an airshow back in 1998 or 1999. I walked two or three times around it trying to figure out where the exhaust was. When I finally zeroed in on the answer, I couldn’t believe my eyes.
Thanks for this history lessen! Good interesting read.
Anyone interested in this should hit Amazon ASAP for the book “Skunk Works” by Lockheed’s Ben Rich. It’s an amazing look at a piece of our history.
GREAT article - thanks for posting!
I concur... Not only for the F-117, but the SR-71 as well... The explanation of the “plunger” in the engine intake that allowed the aircraft to operate at high speeds and altitudes is incredible. Skunk Works is a book for anyone interested in military/aviation history.
The 71 is my favorite thing in existence. My daughter worked on the 117 and said it’s more incredible than people will ever know ;)
Well, make that a century and a half. Maxwell's first paper on it was in 1864, IIRC. Oliver Heaviside recast them into modern form twenty years later.
One of the great breakthroughs in the history of Science occurred when Maxwell intuitively inserted a term into one of his equations (the one for the magnetic field) to be symmetrical with the other one (for the electric field). He did this on aesthetic grounds, without any immediate empirical evidence for its inclusion.
However, it gave him a pair of equations that allowed him to predict the existence of a wave, traveling through space, that was composed of both electric (electrostatic) and magnetic fields which reinforced each other and therefore sustained the wave for indefinite distances.
The equations included two constants for the characteristics of the medium through which the wave was travelling; and the speed of the wave was dependent on these two characteristics. (Technically, they are known as the 'dielectric permittivity' and the 'magnetic permeability.')
These had been previously been determined for a vacuum. When they were substituted into Maxwell's equation for the velocity of his hypothetical 'electromagnetic' wave, it gave another value that was already empirically known: the speed of light.
So, on the basis of Maxwell's inspired guess as to the form of his equations, he was soon able to postulate with some confidence that light itself was an electromagnetic wave.
And soon after Heaviside reformulated Maxwell's equations, a young Heinrich Hertz demonstrated how to produce and detect EM waves of practical dimensions much longer than those of light: Radio waves.
When I first saw one in a static display, they had black painted plywood sheets over the exhaust. Armed guards and roped off too.
That’s the F117!
Kind of a side note but the last year they were at Holloman I got to take a tour of the ‘test cells’ where they work on the engines. Being a gearhead it was like going to Nirvana.
Imagine ‘walls’ of Snap-On tool rack/cabnets and clean room style working conditions. I quickly understood why that little toy cost so much. But the really funny part was the drawers full of ‘modified’ tools the crew came up with to actually get work done ;)
That’s pretty awesome... Flying math... Sat through a lecture during open cockpit day at Castle AFB with a sled-driver... Stellar bird! It had not dawned on me until then that max speed and altitude where a function of weight. Thrust levers were essentially at the detents and as fuel was consumed, the aircraft climbed and increased in speed. They essentially ran out of fuel before they ever hit the maximum possible speed and altitude.
I think it’s interesting that so much of that plane’s abilities are still classified.
“Sled Driver”...now there’s a book I want in the worst way. I love the stories on that plane posted here on FR from time to time and available on the net. The story about the ‘altitude check’ is hilarious.
Also, My daughter and I stopped at the Tucson museum on a trip. She had never seen a 71 in real life. For all her time with the 117, she still stood there slack jawed when she realized that they built that thing with slide rules and 1950s tech.
Thanks all.
God,I’d love to go out for a “spin” in that.
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