The Pentagon Is Using the SR-71's Legendary Engine for ... Something (2024)

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• Pratt & Whitney has quietly been working on reusable engines capable of powering an aircraft at hypersonic or near-hypersonic speeds.
• The engine maker is reportedly going back to its work developing the engines on the SR-71 Blackbird.
• Studies indicate the Blackbird’s J58 engine could be developed to provide even more power, making aircraft faster.

The company behind the SR-71 Blackbird’s engine is reportedly working on a hypersonic engine design that draws on that jet’s legendary power plant.

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Pratt & Whitney, which developed the J58 engine that powered the Blackbird, is now scheming up a reusable, low-cost hypersonic engine called the Metacomet. The effort leads to the question of what, exactly, the Pentagon has in mind for the engine.

Pratt & Whitney started working on the Metacomet two years ago, according to Aviation Week & Space Technology. The company’s Gatorworks division is dusting off its work on the J58, which allowed the SR-71 to reach a record-breaking Mach 3.2, with the hopes of using it to help create a new engine capable of propelling a new vehicle even faster.

The J58 was a one-of-a-kind engine. Its unique trick involved the ability to transition from turbojet engine to turbo-ramjet engine in flight, sucking in vast amounts of oxygen-rich air and burning it to drastically increase engine output. Each J58 could generate up to 32,000 pounds of thrust in afterburner mode, a spectacular feat for an engine designed in the 1950s.

The J58 made the SR-71 the fastest air-breathing plane ever. In March 1990, the SR-71 flew from Los Angeles to Washington, D.C. in just over an hour, traveling at an average speed of 2,144 miles per hour.

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For all of its power, however, the J58 engine is more than 60 years old. A new J58, updated with modern materials and advanced cooling systems, could generate even more power, Aviation Week says. Sources say the Metacomet is likely aiming for a speed somewhere between Mach 4 and Mach 5.

But where does the new engine belong? The most likely candidate is in an unmanned, high-speed strategic reconnaissance aircraft. In November 2013, Lockheed Martin proposed the “SR-72,” a follow-up to the SR-71, and observers allegedly spotted a sub-scale flight demonstrator in 2017. That’s the last time we heard anything about the SR-72.

Meanwhile, the engine might be meant for the Air Force Research Lab’s Mayhem demonstrator, which the Air Force describes as a “larger-scale expendable air-breathing hypersonic multi-mission flight demonstrator.” Mayhem will be capable of “carrying larger payloads over distances further than current hypersonic capabilities allow.”

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