5 Insane Facts About The Pratt & Whitney J58

The Pratt & Whitney J58 wasn’t just another jet engine—it was a masterpiece of aerospace engineering, built to power some of the fastest aircraft ever created: the Lockheed A-12 and its legendary successor, the SR-71 Blackbird. In a revealing interview with Air Zoo, Arnie Gunderson, a 33-year Pratt & Whitney veteran and J58 Program Manager, shared five mind-blowing facts about this beast of an engine.

1. Built From Space-Age Metals

While most jet engines used high-strength steel, the J58 took it to another level. The majority of the engine was made from Waspaloy, an iron-nickel superalloy built to survive the extreme heat of Mach 3 flight. But up front, it gets even more exotic—the first-stage compressor blades, inlet case, and surrounding components were made of 811 titanium, chosen for its strength-to-weight ratio and high-temperature resistance.

2. Simplicity at Supersonic Speed

At its core, the J58 was a single-spool turbojet—a relatively simple design. It featured a nine-stage compressor, can-annular combustors, a single-stage turbine, and a monster afterburner. Despite this simplicity, it could almost hit Mach 3 under its own power, no fancy bypass systems needed. In Gunderson’s words, it could “muscle its way up there”—much like the Soviet MiG-25.

3. Born for Altitude

Developed in the late 1950s for the U.S. Navy, the J58 was designed for missions that pushed the edge of what was aerodynamically and thermally possible. It was built to sustain speeds above Mach 3 and cruise at altitudes over 80,000 feet—well beyond the reach of enemy interceptors or missiles at the time.

4. A Trailblazer in Afterburner Tech

Most jet engines only use the afterburner in short bursts—but not the J58. This was the first engine designed to run in afterburner for extended periods. Even more impressive? It was the first jet engine certified as flight-qualified at Mach 3 by the U.S. Air Force. That’s a whole new level of “fire and forget.”

5. From Black Ops to NASA

Originally developed to meet the demands of the CIA and U.S. Air Force, the J58 would later be modified for NASA, helping to carry heavier payloads during experimental high-speed flights. It remained one of the most powerful and advanced engines of its time—and arguably, one of the most enduring engineering successes of the Cold War.