The Secret Ways of A Speedy Blackbird

In the 4 1/2 years since Lyndon Johnson told the world of a new U.S. spy plane faster and higher-flying than the old U2, the SR-71 has remained wrapped in secrecy as dark as its dull black paint. Travelers have caught tantalizing glimpses of the mysterious jet at Thailand's Udorn airbase, from which it has flown over Red China and North Viet Nam; there has been talk of speed "faster than a bullet" and a ceiling of 100,000 ft. An occasional unrevealing photograph has been declassified by cautious military censors. But only recently have any more significant details of the "Blackbird's" equipment, performance and capabilities been released. They strongly suggest that the SR-71 is--both literally and figuratively--the world's hottest aircraft.

Too Hot to Touch. More than 30 of the superplanes have been built in Lockheed Aircraft's fabled "Skunk Works" under the supervision of Aeronautical Engineer Clarence ("Kelly") Johnson, the man who also designed the U2. The Air Force admits to one squadron, stationed at California's Beale AFB, but the planes are also known to fly out of Okinawa, the Philippines and Thailand. Although a few other aircraft can challenge the SR-71 in a brief dash, the Blackbird can fly 2,000 m.p.h. at 120,000 ft. for as long as an hour, far outdistancing any rival.

At that speed, combustion chambers in the SR-71's two huge Pratt & Whitney J58 engines reach a temperature of 2,800DEG--hotter than any other operational engine. They gulp special kerosene-based "Lockheed Lighter Fuel, 1-A" at a ravenous rate.

The fuel probably gets an extra kick from a high-energy chemical additive, and the mighty engines can drive the SR-71 in a missile-like ballistic curve that takes the plane above 97% of the earth's atmosphere. Yet even in the rarefied upper atmosphere, the surface temperature of the plane's leading edges hits 630DEG, enough to heat the Blackbird's titanium skin to cherry-red incandescence. An intricate system of pumps and pipelines circulates fuel near enough to the skin to absorb heat and carry it to cooler parts of the plane where it is radiated away. Even so, if the space-suited two-man crew cannot take time to cool off the craft thoroughly before it descends, the SR-71 remains too hot to touch for an hour after landing.

Bag of Tricks. The plane's micro-miniaturized gear includes "side-looking" radar to peer through clouds and map terrain far from its path. New cameras use "folded optics" to produce telescopic closeups in black-and-white or on new, grainless color film--which can be dropped in pods and parachuted to waiting intelligence officers. When sensitive receivers detect incoming radar pulses, the Blackbird can dip into its bag of tricks and give itself "electronic invisibility." There is even a top-secret method of masking the SR-71's heat emissions to confuse enemy infrared tracking. Put together in one package, the sophisticated gadgetry makes the Blackbird all but invulnerable--the next best thing to a manned, orbiting spy in the sky.

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