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The Pratt & Whitney J58 was a jet engine that powered the Lockheed A-12, and subsequently the YF-12 and the SR-71 aircraft

The photo below was of Last SR-71 Blackbird engine test in full afterburner at Edwards Air Force Base took place on Sept. 12, 2002

To experience a J58 in full burner close up and personal is hard to describe. Picture a gigantic blow torch, 40 inches in diameter, putting out a blue-yellow-orange flame over 50 feet long.

Imagine standing 30 feet from this, feeling the vibration and heat. You wear both foam plugs and earmuffs. Your ears still ring afterwards, because the sound is conducted through your body.

The back half of the engine transforms from dull gray to bright orange, seemingly transparent. The flame has little three-dimensional diamond shaped shock patterns about every two feet.

I lost count at 13. It is both frightening and beautiful, an amazing demonstration of perfectly controlled power. And to think – this was done with 1950s technology.”

Here is an old Video of J-58 SR 71 Engine test that took place at Beale AFB SR-71 Test Cell in 1986. The engine run was performed by MSgt John Wilson.

Pratt & Whitney J58 was an afterburning turbojet with a unique compressor bleed to the afterburner which gave increased thrust at high speeds.

Because of the wide speed range of the aircraft the engine needed two modes of operation to take it from stationary on the ground to 2,000 mph (3,200 km/h) at altitude.

It was a conventional afterburning turbojet for take-off and acceleration to Mach 2 and then used permanent compressor bleed to the afterburner above Mach 2. The way the engine worked at cruise led it to be described as “acting like a turboramjet”.

It has also been described as a turboramjet based on incorrect statements describing the turbomachinery as being completely bypassed

The propulsion system consisted of the intake, engine, nacelle or secondary airflow and ejector nozzle. The propulsive thrust distribution between these components changed with flight speed: