The Real X-Jet
From Transformers to the X-Men, the Blackbird is still Hollywood's favorite futuristic jet. Here's the real story of its birth.
- By William E. Burrows
- AirSpaceMag.com, March 01, 1999
On May 1, 1960, Soviet air defense missiles downed a U-2 flown by Francis Gary Powers, and, with 24 missions flown, overflights of the Soviet Union were halted. America’s first purpose-built spyplane had, until that day, avoided such a fate by flying extremely high, but the U-2 was slow, and U.S. officials had always known its days were numbered. If the airplane’s follow-on was to be less vulnerable, and assuming the high-altitude requirement persisted, as it had to, then only one area of performance remained: speed.
Under a project code-named Gusto, the Lockheed Skunk Works, headed by the legendary Kelly Johnson, and the Convair division of General Dynamics completed designs for a successor to the U-2 in the summer of 1959. Convair proposed a manned, ramjet-powered parasite reconnaissance airplane that would be launched from a special version of the B-58B Super Hustler bomber flying at Mach 2.2 above 35,000 feet. The parasite would reach Mach 4.2 and 90,000 feet, according to Convair. The project, named Fish, was terminated because the Air Force canceled the B-58B and ramjet technology was unproven. Convair later came back with the ground-launched Kingfish, based on its F-106 Delta Dart interceptor and the B-58, but it too was doomed.
That left the Skunk Works entry, which had evolved from A-1 (for “Archangel”) to A-11 and then A-12, which in turn evolved into the Air Force’s SR-71. There is disagreement even today at the Skunk Works on whether the CIA’s version was the A-11 or the A-12. Garfield J. Thomas, vice president of Reconnaissance Systems at what is now Lockheed Martin, says it was the A-11. Albert T. “Bud” Wheelon, who was head of the CIA’s Directorate of Science and Technology in the early 1960s, agrees. Engineers at Pratt & Whitney who designed its engine claim it was really the A-12. They’re all correct. Two Johnsons—Kelly in private and Lyndon Baines in public—called it the A-11. And the basic airplane was the A-11. It became the A-12 when its metal vertical tail, engine inlets, and the forward edges of its nacelles were changed to a kind of composite plastic to foil enemy radar. One thing is certain: Both aircraft were in a program code-named Oxcart. In January 1960, the Skunk Works got an order for 12.
Oxcart was to cruise at 90,000 feet and Mach 3.2—faster than a rifle bullet. At that speed, the friction of the air would create tremendous heat, but airframe heating in itself was not insurmountable. North American’s X-15 almost routinely exceeded Mach 3 and in October 1967 would set a world record of Mach 6.7. But the X-15 flew supersonically for mere minutes, not for the many hours required of a long-range reconnaissance aircraft. The F-106, the nation’s premier operational interceptor at the time and for years to come, could fly at Mach 2 for only 15 minutes at a time.
The heat that would be created by flying at Mach 3+ for long periods bedeviled engineers and required unparalleled inventiveness. As Kelly Johnson said, “Everything on the aircraft, from rivets and fluids, including materials and power-plants, had to be invented from scratch.” Long before the A-12 flew, its designers calculated that their creation’s leading edges would get hotter than a soldering iron, and without adequate cooling in the cockpit, it would literally get hot enough to bake a cake.
In early 1991, with the cold war over and much of the SR-71 declassified, the Graduate Aeronautical Laboratories at the California Institute of Technology presented a course entitled “Ael07, Case Studies in Engineering: The SR-71 Blackbird.” The course was based on a detailed three-inch-thick engineering summary, and virtually every section of the book, whether the subject was grease, hydraulic fluid, engines, oil, electrical plugs, or tires, shared one word: heat.
To cope with both altitude and heat, a fuel called JP-7 was developed with an exceptionally high flash point: A lighted cigarette tossed into a pail of JP-7 would go out. This tolerance for high temperatures allowed it to be the airplane’s primary heat sink. And there was a lot of it: The fuselage and inner wings formed fuel tanks with a capacity of 40 tons, and they were unlined, since no plastic liner could survive.
B.F. Goodrich came up with main landing gear tires that were compounded with aluminum powder to produce a silvery rubber that reflected heat from the airframe. And they were filled with nitrogen, not air, because oxygen would only incite combustion. The tires, which had a 22-ply rating, cost $2,300 apiece and were good for between 15 and 20 landings, depending on the pilot’s touch. The wheel wells into which they retracted were shielded and surrounded by tanks of fuel that performed double duty as a massive cooling system. The heat sink worked by routing the fuel to a pump that raised its pressure to 45 pounds per square inch and sent it to several valves and heat exchangers, where it cooled subsystems before being returned to the tanks to be consumed in the engines. The JP-7 circulated throughout the fuselage and wings the way blood does in animals.
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Comments (9)
Bouroughs did a great job of describing the machine development. However he did overlook the J-58 engine's need for a ground based Starter Cart (2 Buick Wildcat V-8s) and that the JP-7 required an "exotic" igniter called TEB ( Tri-Ethyl-Borate).
To see some of the personal experiences on the A-12, go to the following web sites:
http://www.habu.org/a-12/06932.html
http://www.wvi.com/~lelandh/m21_Crash.html
http://www.roadrunnersinternationale.com/oxcart_pilot_training.html
There are a number of pilot's stories under the Roadrunners...
Posted by Edward Power on June 11,2011 | 12:26 PM
This is a very interesting piece. I am a retired Navy Civil Servant. I was an electronics engineer for 25 yrs with the Navy Civil Service. My Dad worked for Lockheed during the Kelly Johnson years. He was superintendant over the skunk works tooling dept, 3rd under Kelly Johnson. His name was Edwin C. Mort. He passed away early January of 1989.
This piece answers many questions I have had about the "Black Bird".
Posted by Richard E. Mort on June 11,2011 | 08:58 PM
My father worked for General Electric from 1945-84
and did work with a lot of other companies during
that time.
One such company was the Skunk Works during Kelley Johnson's time and I remember the Blackbird being
refered to as the YF-12A.
My father worked with a lot of space exploration programs(Including the X-15 during Harrison "Stormy" Storms time)
defense projects and commercial aviation jobs(The SST program with Boeing until President Nixon axed it in 1971)
I've always been interested in what my father did BUT just
didn't have the math or science knowledge to persue it. I
still read LOTS of science fiction. Sir Arthur C Clarke
was both our favorite author.
My father lived from 1919-1995 and I was born in 1949.
Thanx! for letting me ramble on a bit.
Great piece on the Blackbird...
06 16 11
Posted by Don Ducker Jnr on June 16,2011 | 09:11 AM
Now 12 years later Annie Jacobsen has written Area 51, and in there is a lot of information about Oxcart, the Skunkworks and other formerly classified projects.
Posted by PeterK on June 23,2011 | 05:54 PM
The SR-71 also served as the artistic inspiration for a cover illustration (http://www.isfdb.org/wiki/images/a/a9/ANLGJUL68.jpg) for a novella by Dean McLaughlin in the July 1968 issue of Analog Magazine. The artist was the late Frank Kelly Freas who depicts an SR-71-like aircraft looming over WWI fighters as a result of the 20th Century airplane arriving unexpectedly over France in 1918. The story somewhat humorously depicts the frustration of the modern airplane's sole pilot who discovers that his modern missiles can't shoot down wood and fabric biplanes with tiny radial engines.
Posted by Diana Powe on June 24,2011 | 05:33 AM
Excellent work Mr.Burrows. Nothing captures my imagination like the Blackbird. Not even my beloved Corsair.
Marines are the reason I don't speak Japanese.
Soldiers are the reason I don't speak German.
Texans are the reason I don't speak Spanish.
Semper Fi
If it were not for the United States Military,
There would not be a United States of America.
Freedom comes at a price. Remember those who paid it.
Posted by Hank Armstrong on June 24,2011 | 10:19 AM
It is just breathtaking to think of the 'Murderers' Row' of engineering, design, and fabrication talent that Kelly Johnson surrounded himself with in the 50's and 60's at Lockheed's SkunkWorks. Of course, the Cold War-driven unlimited budgets and different gov't/defense contractor relationships of that time enabled a lot of innovation, but to imagine the history-altering aircraft these guys dreamed up and built is just amazing. With slide rules and calipers and feeler gauges . . . .
Like Ben Rich spoke about in his book, SKUNK WORKS, these groups of guys in white shirts and ties and pocket protectors, justifying their blueprints over cigarettes and coffee and slide rules to crusty, seen-everything fabricators whose experience tempered their ideas must have been an intoxicating atmosphere. I often think THAT's why it was buried behind layers of Black World secrecy: They were just having too much fun making history, one rivet at a time.
Posted by Joey Wilson on July 8,2011 | 01:20 AM