While the U-2 was given a very simple ECM system, says Thomas, the SR-71’s electronic bays were crammed. All of the ECM equipment, plus the SR-71’s nose-mounted high-resolution optical bar camera and its side-looking radar and other sensors, were operated by the reconnaissance systems officer, or RSO, who sat behind the pilot. The CIA’s A-12 had one pilot who ran everything, but the Air Force decided that the load was too great, so it had the Skunk Works make room for the RSO.
That change and others created real differences in both airplanes’ performances. The A-12 actually flew up to 5,000 feet higher than the SR-71, was a bit faster, and had cameras that could cover three times as much territory with better resolution. The penalty for adding a crewman was a smaller camera. “The A-12 was like the U-2,” says Bob Murphy, the SR-71 plant manager. “It had a massive camera, a very, very large camera, whereas in the SR-71, the second guy sits where the massive [Type I] camera went in the A-12.”
Whatever its limitations relative to the A-12’s camera, the SR-71’s was by all accounts good enough. According to Ben Rich, it could peer more than 130 miles into a targeted territory. It is still used on U-2s and remains classified. The SR-71’s performance was also somewhat reduced by the side-looking radar it carried, plus gear that collected electronic and communication intelligence by sniffing out radars and listening to radio transmissions.
The CIA’s contract for the A-12 specified that it have very-low-observable qualities but not that it be completely stealthy. Still, the low-observable specification was a problem that had to be solved before the contract was finally signed in February 1960. Its blended body reduced its radar reflectivity dramatically. Its overall shape, including the two vertical tails that cant inward plus lots of curves, helped to hide it. So did special radar-absorbing plastic panels made of silicone and asbestos that had to be formulated to withstand temperatures of roughly 550 degrees.
What was more difficult, according to Thomas, was shaping the surfaces so that they intercepted, captured, and absorbed or redirected radar signals. The trick was to guide the radar signal around the aircraft before either dissipating it or redirecting it. He describes the plastic panels as a series of gradually phased “steps” that accomplished this with exquisite nuance. “An enormous amount of invention had to go into this thing,” Thomas says, “and it was all done simultaneously in a matter of 31 months.” And, as almost everyone who was involved likes to point out, nearly all the engineering was done with slide rules and calculators rather than computers.
Besides creative genius, Kelly Johnson had an aggressive and practical business sense. When he thought up the A-12, he saw the airframe as the equivalent of a basic automobile chassis that could be assembled as a sedan, a convertible, or a station wagon. The key was to use different forward fuselages on the same basic body, wing, and tail. The separation point was at Frame 715, which connected the wings at the roots of their leading edges. Everything behind 715, including the nacelles and their inlets and engines, remained essentially the same while the forward fuselages differed. The basic design was therefore turned into a long-range missile toting interceptor called the YF-12. Another version, the M-12, carried a ramjet-powered, camera-carrying drone called the D-21 on its back. “M” stood for mother; “D” for daughter. The thing was used briefly over China with mixed results and one of the D-21s destroyed the M-12 that carried it when it slammed into the aircraft during separation.
There were even plans that never materialized for a penetrator version that could have carried nuclear missiles. Pratt & Whitney’s Joseph Daley says that the Soviets at the Strategic Arms Limitation Talks in the late 1960s insisted that it not be built because “if it was used offensively, there was no way in the world you could defend against it.”
And there was yet another permutation—a bizarre one. SR-71 lore has it that the airplane was really designated RS, for Reconnaissance Strike, but that President Johnson mistakenly called it the SR when he announced it in 1964; the name stuck and it became Strategic Reconnaissance.
In fact, the SR-71’s stated mission when it was created was not to collect routine intelligence but to do “post-strike reconnaissance” a few days after World War III began. With air bases and much of the United States reduced to radioactive rubble, the Pentagon’s war planners would have wanted to locate Soviet targets that were still standing, according to Daley, as part of the ultra-secret Single Integrated Operating Plan by which the war was supposed to have been fought.
The Strangelovian plan called for moving two SR-71s and a C-141 transport full of support equipment and photo-interpreters to remote bases like Mozambique or Diego Garcia. With the first missile and bomber exchanges over, the SR-71s would scour the U.S.S.R. for remaining targets and get the information to the Navy’s missile submarines so they could continue the ballistic beating. The pilots would have been provided with eye patches, Daley adds, “so when the things [submarine-launched missiles] go off, you still have one eye that can see.” With what remained of the 15 A-12s mothballed, and with World War III averted, the 31 expensive SR-71s were put on regular reconnaissance duty until they were finally retired in January 1990, only to be revived in on-again, off-again directives from Congress.