Stealth and Speed: America's SR-71 Blackbird Might Be Old (But Still the World's Fastest Plane)
The Blackbird’s design reflected the fact that it was pushing the limits. The crew wore pressure suits like those used on space missions to withstand the high altitudes they were flying at, and were treated to a medical exam and a high-protein steak and egg meals before each mission. The SR-71’s J58 engines could only start through use of two vehicle-mounted V8 starter engines, and the triethylborane used in the fuel would belch green flames during ignition. The J58s would switch to a partial ramjet mode at high speeds, such that the SR-71 actually became more fuel efficient when it went faster.
The sleek and sinister SR-71 Blackbird looks like it belongs in a science fiction movie, though in fact the jet black spy plane proved far more successful at outrunning enemy missiles than any of the spaceships depicted in Star Wars. Though retired in the 1990s in favor of spy satellites and recon drones, it doesn’t look like any modern designs are likely to challenge the Blackbird’s record as the fastest manned aircraft ever.
As Cold War tensions heightened during the 1950s, the CIA began flying the U-2 spy plane to keep tabs on the Soviet Union’s fast expanding nuclear weapons capabilities. Ungainly and relatively slow-moving, the U-2 relied upon its ability to fly at extremely high altitudes to avoid enemy fighters and early surface-to-air missiles.
The intelligence provided by U-2s in 1962 uncovered the Soviet nuclear missiles deployed to Cuba, leading to the dramatic events of the Cuban Missile Crisis. But the U-2s also provoked diplomatic incidents because they simply couldn’t fly high enough to avoid Russian missiles SA-2 surface-to-air missiles. A U-2 was shot down in 1960, and its pilot, Gary Powers, captured, triggering an embarrassing diplomatic row. Another U-2 was shot down during the Cuban Missile Crisis, killing the pilot and escalating tensions between Moscow and Washington at a critical moment. Five Taiwanese U-2s were shot down over China.
American engineers realized altitude was no longer an adequate defense and in 1957 began working on a plane for the CIA that they hoped Soviet radars would be unable to detect, and that could outrun any missiles fired at it. The Lockheed Skunkworks factory ultimately developed the A-12, codenamed “Archangel.” The prototype was first tested in Area 51 in 1962, and in the end fifteen A-12s were produced.
CIA A-12s flew a total of 29 spy missions over North Korea and Vietnam through 1968 in Operation Black Shield, losing six aircraft to accidents. Intelligence gathered by A-12 helped the CIA to map out North Vietnamese air defenses and located the U.S.S. Pueblo after it was hijacked by North Korea.
The Air Force developed prototypes of an interceptor version, the YF-12, and later considered a high speed bomber, the B-71 (coming numerically after the XB-70 Valkyrie bomber that never entered production). There was even a bizarre M-21 drone carrier that launched a D-21 spy drone off its back. However, none of these spinoffs entered service, and the A-12 was retired in favor of an Air Force operated variant, the SR-71.
The A-12 mounted a single high-resolution camera that recorded a broad swath of terrain directly underneath the aircraft. The Air Force wanted a longer-range version of the A-12 with better sensors that didn’t need to fly directly over hostile territory, particularly as an agreement reached with the Soviet Union that banned territorial overflight. This led to the two-seat SR-71A—the “SR” standing for Strategic Reconnaissance.
The SR-71 was actually slightly less stealthy and high-flying than the A-12, but had different intelligence-gathering technology. It mounted a side-looking airborne radar that mapped the ground below it, and also used two cameras that took images to either side, though at lower-resolution than the A-12’s larger camera. The Reconnaissance Systems Officer in the back seat operated the radar and assisted with navigation. Additionally, the Blackbird had an Electro-Magnetic Reconnaissance system that could detect and record signals traffic.
A total of 32 SR-71s were produced, including two SR-71B trainers and a single SR-71C prototype nicknamed “the Bastard” because of its unstable handling.
The Blackbird could sustain speeds above Mach 3, with a so far unbroken manned-flight record of Mach 3.3 or 3.5. (The 3.3 record is confirmed, while Mach 3.5 is claimed by pilot Brian Shul to have been achieved while outrunning a missile over Libya in 1986.) That speed is actually even more impressive than it seems, because while later Soviet MiG-25 and MiG-31 fighters could attain Mach 3, they could only do so for brief periods on afterburners, the aerial equivalent of an energy-burning sprint. The SR-71 could sustain Mach 3 flight for 90 minutes, at which points it required in-flight refueling. A Blackbird once set the record for flying from New York to London in 1 hour and 54 minutes.
In effect, by the time it took a SAM system could lock onto an SR-71 traveling at Mach 3 and launch a missile, the Blackbird was already moving beyond the effective range of the missile.
But Lockheed wasn’t just counting on speed to evade enemy missiles. The Blackbird was the first operational airplane intentionally designed with a reduced radar cross-section to minimize the chance of detection. The Blackbird’s chines—the knife-like tapered edges of the fuselage—were even coated with early radar-absorbent iron-ferrite paint to help lower radar detection ranges. The chines were also found to provide additional lift and greater aerodynamic stability.