The latest U-2 version in Air Force service is the TR-1, for “tactical reconnaissance.” It was named on the spot by USAF Gen. David C. Jones, then Chairman, Joint Chiefs of Staff. “We have to get the U-2 name off the plane.” Even the military is sensitive to that “Spy Plane” image. “We’ll call it the TR-1, tactical reconnaissance one.”
The TR-1 entered service with the Air Force in 1981. Both the TR-1 and ER-2, latest U-2 versions, are 40 percent larger than the original. Wing span is 103 feet; fuselage, 63 feet long. The contract for both was a cooperative effort by the USAF and NASA. The ER-2 is equipped with interchangeable noses for varying missions. Without penetrating foreign territory, the TR-1 with highly sophisticated sensors operating from very high altitude can identify targets and threats behind enemy lines.
Development of the latest long-endurance capability, operating now in the TR-1, occupied us for many years. There are many more things we can do now that we could not do when the plane first was developed—nearly 30 years ago! There are many new technologies—silicon chips, optical fibers, various composite materials. But I don’t think anything is going to fly higher subsonically. And that, of course, is why we went to our next project, the SR-71, to get more altitude and speed. It was under design as soon as the U-2 became operational.
“About a year after that first flight in 1956,” Bissell has said. “I came to the conclusion that we should start working on the successor to the U-2, because it was clear to me that sooner or later the U-2 would be vulnerable to interception.”
14
Blackbirds Fly Stealthily—Three Times the Speed of Sound
FEBRUARY 29, 1964. PRESIDENT REVEALS SECRET AIRCRAFT:
“The United States has successfully developed an advanced experimental jet aircraft, the A-11, which has been tested in sustained flight at more than 2,000 mph and at altitudes in excess of 70,000 feet,” President Lyndon Johnson announced today.…
“The performance of the A-11 far exceeds that of any other aircraft in the world today.…
“The project was first started in 1958…. The Lockheed Aircraft Corporation at Burbank, California is the manufacturer of the aircraft. The aircraft engine, the J-58, was designed and built by the Pratt & Whitney Division, United Aircraft Corporation. The experimental fire control and air-to-air missile system for the A-11 was developed by the Hughes Aircraft Company.
“In view of the continuing importance of these developments to our national security, the detailed performance of the A-11 will remain strictly classified and all individuals associated with the program have been directed to refrain from making any further disclosure.…”
JULY 24, 1964. PRESIDENT ANNOUNCES NEW SPY PLANE
President Lyndon Johnson at a press conference: “I would like to announce the successful development of a major new strategic manned aircraft system which will be employed by the Strategic Air Command. This system employs the new SR-71 aircraft and provides a long-range advanced strategic reconnaissance plane for military use capable of world-wide reconnaissance for military operations.…
“The SR-71 aircraft reconnaissance system is the most advanced in the world. The aircraft will fly at more than three times the speed of sound. It will operate at altitudes in excess of 80,000 feet. It will use the most advanced observation equipment of all times in the world … an outstanding reconnaissance capability.… The SR-71 uses the same J-58 engine as the experimental interceptor previously announced but it is substantially heavier and it has a longer range. The considerably heavier gross weight permits it to accommodate the multiple reconnaissance sensors needed by the Strategic Air Command to accomplish the strategic reconnaissance mission in a military environment.
“This billion dollar program was initiated in February 1963. The first operational aircraft will begin flight testing in early 1965, and deployment of production units to the Strategic Air Command will begin shortly thereafter.…”
DECEMBER 23, 1964. DEPARTMENT OF DEFENSE NEWS ANNOUNCEMENT
“First flight of the U.S. Air Force SR-71, the new long-range strategic reconnaissance aircraft, took place yesterday at Palmdale, California.
“The Lockheed-built aircraft, flown by company test pilot Robert Gilliland, was in the air approximately one hour.
“… All test objectives were met.
“The aircraft will be assigned to the Strategic Air Command at Beale Air Force Base, Marysville, California, in 1965.”
Almost as soon as the U-2 was in operation, we began to plan its successor.
Efforts to improve the U-2 had yielded very little gain. A new design would be necessary. We set up our own requirements. There were none officially yet—just the need. We knew we needed more altitude and, especially, more speed.
Vulnerability studies led us to the decision that the next airplane should operate at altitudes well over 80,000 to 85,000 feet, fly at speeds well over Mach 3, and be able to out-maneuver any SA-2 missile the Russians might develop. It had to be stable enough in flight to take a good photograph from altitudes above 90,000 feet. It had to retain the characteristics of the U-2—be able to photograph very, very small targets on the ground—while flying four to five times as fast. We wanted it to have global range—with multiple midair refuelings from the KC-135 aerial tankers. The aircraft also should present an extremely low radar cross-section—be very difficult to detect.
The decision to assign this project to Lockheed was arrived at only after consideration of several design proposals from other companies. From April 21, 1958, through September 1, 1959, I made a series of proposals for Mach 3-plus reconnaissance aircraft to Richard Bissell of the CIA and to the USAF Bissell, as chairman of the review committee, was reluctant to award the contract for its successor to the same company that had built the U-2 without a design competition.
Some of the other entries were interesting.
A Navy in-house concept proposed an inflatable rubber vehicle which could be carried to altitude by a balloon, then boosted by rocket power to a speed where its own ramjets could take over. This rapidly was demonstrated to be unfeasible. The balloon would have had to be a mile in diameter to lift the unit, which itself had a proposed wing area of one-seventh of an acre.
Convair proposed a ramjet-powered Mach 4 aircraft, which also had to be carried aloft by another vehicle and launched at supersonic speeds where the ramjet power could take over. Unfortunately, the launch vehicle was the B-58, which could not attain supersonic speed with the bird in place. Even if it could, the survivability of the piloted vehicle was in question because of probable ramjet blowout in maneuvers.
The total flight time for the Marquardt ramjet at the time was not over seven hours, obtained mainly on the ramjet test vehicle for the Boeing Bomarc missile. This test vehicle, the X-7, had been built and operated by the Skunk Works.
On August 29, 1959, our A-12 design, the twelfth in the series, was declared the winner and Bissell gave us a limited go-ahead. We were to conduct tests on models, build a full-scale mockup, and investigate specific electronic features of the airplane over a four-month period.
On January 30, 1960, we were given a full go-ahead for design, manufacture, and test of 12 aircraft.
The code name was Oxcart, a name selected from a list of deliberately deceptive identifications. Obviously an oxcart is a slow-moving body. This CIA program led to other versions of the design for the U.S. Air Force. The next would be a long-range fighter for the Air Defense Command, first discussed with Gen. Hal Estes on March 16 and 17 of that same year. It became the YF-12A.
In January 1961, I made a proposal for a strategic reconnaissance airplane to Air Force Secretary Dr. Joseph Charyk, U-2 project officer Col. Leo Geary, and Lew Meyer, an Air Force finance officer. This encountered initial opposition in some quarters where it was seen as competition for funds for the North American B-70 program, then the object of considerable controversy. But it became the SR-71, the prime reconnaissance airplane for the Air Force today. There also would be a fo
urth verson—the D-21, an unmanned drone.
The aircraft that were to become the “Blackbirds” were the first to use the “Stealth” technology we developed for radar avoidance. We had tried to work it into the U-2 as a modification after the aircraft already were in operation and got nowhere. To be “stealthy,” aircraft must have certain features incorporated in design from the very beginning, not added later. “Stealth” must be designed into the airplane from the first three-view drawing to be effective. This is what we did with the Mach 3-plus aircraft.
We had achieved Mach 4 flight earlier for a few seconds with the X-17, our ramjet test vehicle—before that the X-7. The idea of attaining and staying at Mach 3.2 over long flights was the toughest job the Skunk Works ever had and the most difficult of my career. Early in the development stage, I promised $50 to anyone who could find anything easy to do. I might as well have offered $1,000 because I still have the money.
Aircraft operating at those speeds and altitudes would require development of special fuels, structural materials, manufacturing tools and techniques, hydraulic fluid, fuel-tank sealants, paints, plastics, wiring and connecting plugs, as well as basic aircraft and engine design. Everything about the aircraft had to be invented. Everything.
In the search for a suitable fuel we considered initially such exotic candidates as liquid hydrogen, coal slurries, and boron slurries.
Design of a liquid hydrogen powered airplane actually was carried to the point approaching a production contract for a substantial number of them. The concept had seemed promising. While the airplane was very large, it was very light in weight. Powered by special engines developed by Pratt & Whitney, it would have a cruising altitude well above 100,000 feet—higher than the Blackbirds later achieved, although with less speed and range. But the further we went into development, the worse the problems we perceived.
The CL-400 was essentially a big flying vacuum bottle, with the liquid hydrogen heavily insulated to keep it at very low temperatures and as close to absolute zero as possible. The problems of transporting this fuel from a plant in the United States to wherever the airplane could be based would have been prohibitive. It would have required a whole fleet of C-124s to keep just a few liquid hydrogen planes flying. No foreign nation was likely to approve our flying in with such quantities of it nor to allow us to put a ship in their harbors and liquefy it on the site.
We had engaged the Pomeroy Company to design a hydrogen liquefaction plant that was to have been erected near our aircraft plants and the Palmdale Airport in the Mojave Desert. It would have used ten percent of the natural gas input to the city of Los Angeles in 1972 and ’73!
One day we were visited at Lockheed by Assistant Air Force Secretary James Douglas and Gen. Clarence Irvine of the Air Force. Their question was, “How much stretch have you got in this thing, Kelly?”
“Let’s take a look at it,” I said. “Here’s the inboard view. You can see it’s totally liquid hydrogen from one end to the other except for a small cockpit up front.”
You do not put liquid hydrogen in nooks and crannies and odd-shaped tanks. The container has to be cylindrical—and very well insulated. With this airplane, we didn’t have the condition we’ve always had with other aircraft, both piston-powered and jets, where extra fuel could be added for a little more power and range. The Constellation gross weight, for example, doubled in its lifetime. We were able to do the same with most of the fighters, too. But with the liquid hydrogen airplane, once you set down the tank volume, that’s it. You could carry external tanks, but it would be difficult, and the airplane would carry added drag because of air resistance.
So the Secretary and the General turned to Perry Pratt, head of Pratt & Whitney engine design. “Maybe there’s something in the engine. Perry, how much stretch do you have in this engine?”
“Perhaps three to four percent in five years,” was the answer.
Overall, it wasn’t a very good forecast. We all agreed to cancel that effort without any more expenditure of funds. And had we proceeded, we would have run right into the energy crunch of the 1970s.
Coal slurries—finely-ground-up coal mixed with a light oil base and water—were a possible power source, injected into the engines as fuel. But the tiny coal cinders tended to ruin the turbine blades.
Boron compounds—in slurries—were tried, too. But these were difficult to use and plugged up the injector nozzles, not only in the engine but afterburners as well.
We decided to stick with liquid petroleum as fuel. It would have to be a very special fuel, though, for those operating altitudes and temperatures—from – 90°F for midair refueling at high altitude to + 650°F in supersonic flight.
We put the problem to our old friend, Jimmy Doolittle, now a top executive with Shell Oil. That company had come up with what we called LF-1A, “Lockheed Lighter Fluid 1 for the U-2; and it was a good fuel for that airplane. Shell came through again, with cooperation from the Ashland and Monsanto companies and Pratt & Whitney, with a new chemical lubricant and fuel for the Mach 3-plus aircraft. This we call LF-2A. The Air Force has its own designations, of course.
Development of that fuel took a lot of doing. It was very expensive, but it’s an excellent fuel.
The fuel in this design also acts as an insulating element. The fuel tanks not only contain the fuel but are constructed to protect the landing gear. The gear retract up into the middle of the tanks. With radiant cooling to the fuel, the rubber tires are insulated against the very high temperatures the plane encounters during hour after hour of flight. And the plane doesn’t land with the tires ready to blow out.
In selection of structural materials for a Mach 3-plus airplane, aluminum automatically was ruled out. It would not withstand the ram-air temperatures of 800°F over the body of the plane. High-strength stainless steel alloys or titanium would be required for the basic structure. And high-temperature plastics would have to be developed for radomes, cockpits, and certain other areas.
Stainless steel actually is a better high-temperature material than titanium. But visiting the Lockheed-Georgia plant, which was building parts for the supersonic B-70 bomber, I saw what it took to make basic honeycomb panels for the fuselage: a “clean-room” environment—what was essentially a big pressurized airbag—with pressure locks for entrance and exit, everyone in white clean-room suits, and all the controls necessary to observe sterile conditions.
I reverted to my old Skunk Works axiom, “Keep it simple, stupid.” The more complexity, the more potential for problems. This is too sophisticated for the Skunk Works, I decided. We’ll use the material we’ve worked on experimentally for ten years, the new advanced titanium in conventional structure.
The shape of the airplane itself was determined after a great many wind-tunnel and other tests. The result, head on, looks like a snake swallowing three mice. And for good reason. We added chines on the fuselage to get aerodynamic lift, among other things. We had some without them, but a terrific amount with them.
Before we got into high gear on production, we thought it advisable to build several test samples of the most complex sections: the nose and the basic wing structure.
The first wing section was a catastrophe. When we put it in a “hot box” to simulate high in-flight temperatures, it wrinkled up like an old dishrag. The solution was to divorce the skin panels from the wing spars in each direction and put corrugations and dimples in the skin—the wing surface. When the titanium got really hot, the corrugations merely deepened. I was accused of making a Mach 3 Ford Trimotor—that was made all of corrugated aluminum. But it was a very effective solution to a really difficult problem.
The nose section of the airplane presented other problems. We put it in the hot box to study cooling requirements for the pilot and the gear. We produced 6,000 parts; and of them fewer than ten percent were any good. The material was so brittle that if you dropped a piece on the floor it would shatter.
Obviously, we were doing something wrong. We queried Tit
anium Metals Corporation on why we had hydrogen embrittlement from our processes. They didn’t know. So we threw out our entire titanium processing system and replaced it with the same methods TMC used in making the original sheets and forgings at their factory.
After the initial shambles on the nose segment heat treat tests, we put into effect a quality-control program that I believe was and is unequaled anywhere. For every ten parts manufactured, we made three sample parts. These would be heat-treated and otherwise tested before any of the others of the batch would be put in storage for future use. One sample went into a tensile strength test machine to find out how strong the material itself was. In the second, we made a short cut—about one-quarter inch long—and bent the sample at that cut around a form with a very small radius—as small as 32 times the thickness of the sheet—to see if it would crack. The third sample was used in case a re-heat-treat test was necessary. We didn’t want to throw away the whole batch needlessly; it was too darned expensive.
We could trace back to the mill and know the direction of the sheet rolling, and whether the part was cut with or against the grain. Before we would do all the expensive machining to cut landing gears from the huge heavy extrusions we would cut twelve samples, and unless everyone met the test we devised for them, we would not use that extrusion to make a landing gear. We’ve had no landing gear failures on the birds despite the hard landings that go with in-service flying.
There were times when I thought we were doing nothing but making test samples. But the test effort was worth it. By the early 1980s, we had made more than 13,000,000 titanium production parts for all of our Skunk Works airplanes and also for the Lockheed L-1011 commercial transport and the company’s big military cargo aircraft.
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