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The Unmatched Speed and Stealth of the SR-71 Blackbird: Why the MiG-25 Couldn’t Keep Up

The still-unmatched wonder, even to this day, in the annals of aviation history is Lockheed’s SR-71 Blackbird, which was retired almost a quarter-century ago. To date, no aircraft has threatened the title held by this jet as the fastest ever flown with a human crew title earned 59 years after its maiden flight. During its thirty years of service, the Blackbird famously outran more than 4,000 missiles.

But the SR-71 was by no means invulnerable. From an impressive Soviet crop of interceptors, such as the MiG-25 with a possible Mach 3.2, to surface-to-air missiles like the SA-2 with a possible Mach 3.5 plus, serious threats did exist. And with a reported top speed for the SR-71 of Mach 3.2, the difference between itself and its pursuers was not exactly phenomenal. But in actuality, it had little to do with speed regarding how the SR-71 was able to avoid interception.

The SR-71 was the product of a legendary aeronautical engineer-Kelly Johnson-methodical mission planning, early stealth technology, and just raw power. Johnson himself had already made quite the name with designs such as the P-38 Lightning and the U-2 spy plane when he was developing the SR-71 under the Archangel program. It was in a class of its own, with sustainable speeds that only a few other aircraft could ever dream of.

The publicized Mach 3.2 top speed of the SR-71 generally gets the headlines, but in reality, it could sustain such a speed for hours on end, which was what made the plane truly unique. For example, the rocket-powered North American X-15 would reach Mach 6.7 but required extensive maintenance after extremely short flights, while the SR-71 could fly at Mach 3.2 for hours. As Johnson himself recalled, “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.”

Engineering challenges were enormous. It needed new kinds of wire for its avionics that could withstand temperature fluctuations, and hydraulic fluids with special formulation. The structure, 93% consisting of titanium was bought secretly from the Soviet Union through a series of shell companies the CIA set up. Even the windshield had to be in solid quartz to withstand such heat of sustained Mach 3 flight.

Its stealth combined with speed made the SR-71 a very elusive target: having no more than 22 square inches of radar cross-section. By the time an SA-2 missile would be launched, the Blackbird would well be out of range.

Also emerging in 1970 as its contender, the MiG-25 was developed in response to U.S. supersonic bombers. Capable of reaching speeds between Mach 2.5 and 2.83, the MiG-25 reportedly reached Mach 3.2+ in short sprints. These sprints came at a great cost, however, since doing so would typically render its engines irreparable. The SR-71 had no such problem, reaching Mach 3.2 with ease thanks to its Pratt & Whitney J58 turbojet engines.

Soviet MiG-25 pilot Lt. Viktor Belenko, who defected westward in 1976, said the Foxbat climbed too slowly to catch the SR-71 and that its missiles lacked sufficient thrust to close the gap. Even head-to-head, the SR-71’s closure rate was beyond the Foxbat’s guidance system’s ability to cope. “They taunted and toyed with the MiG-25s sent up to intercept them,” Belenko related.

Years later, Soviet pilot Captain Mikhail Myagkiy reported that he had locked onto an SR-71 flying in his territory in his MiG-31 but did not fire because the aircraft had not violated Soviet airspace. This has not been confirmed by the American side.

The only foreign fighter ever to lock onto the SR-71 was the Swedish Air Force’s JA-37 Viggen. These pilots, with very good planning and skill, were able to intercept the Blackbird. One incident involved Viggens escorting an SR-71 with a malfunctioning engine back to friendly airspace, and were awarded U.S. Air Force Air Medals for their effort.

Yet, the SR-71 Blackbird still stands as testimony to the prowess of American engineering-a symbolic notion of speed and stealth that continues to impress aerospace fancies across the world.

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