A jet engine burns only part of the oxygen in the air it swallows. An afterburner uses the rest: behind the turbine, it sprays extra fuel straight into the hot exhaust and burns it. The exhaust comes out hotter and faster, and the nozzle opens wider to let it out. On the F-15E’s Pratt & Whitney F100 engines that’s about 60% more thrust, for roughly four to five times the fuel.
The bright knots in the flame are shock diamonds (or Mach diamonds). The exhaust leaves faster than sound and at a different pressure from the air around it, so a chain of shock waves forms in it; each one squeezes and heats the gas so it glows brighter. Rockets make them too.
The engine is running in a hush house, an engine test building at RAF Lakenheath in England, where engines are tested after maintenance before they go back into a jet.
#afterburner #jetengine #f15 #shockdiamonds #aviation #engineering #shorts
Sources:
– NASA Glenn Research Center, Beginner’s Guide to Aeronautics: “Afterburning Turbojet” and “Nozzles”
– NASA TM-81656 (1981), afterburning F100 engine tests (fuel-air ratio, nozzle area)
– National Museum of the US Air Force, “Pratt & Whitney F100-PW-220”; Pratt & Whitney F100 page; Purdue AAE engine table (dry thrust)
– MIT 16.50 lecture notes (combustion and excess air)
– Aerospaceweb and NASA reports on shock diamonds
– US Air Force / 48th Fighter Wing captions on DVIDS (hush house, engine tests)
Footage: “RAF Lakenheath Hush House”, U.S. Air Force video by Airman 1st Class Renee Nicole S.N. Finona, 48th Fighter Wing (2023); “F-15 Test Cell B-Roll”, U.S. Air Force video by Airman 1st Class Anthony Clingerman (2020); F-15E takeoff, U.S. Air Force video (DVIDS 913916). All public domain (DVIDS). The test-cell shots are rotated 90° so the flame rises. Diagram: from US patent application 2007/0220893 (General Electric), public domain, reference numbers removed.
Animation: illustrative. Sound effects: CC0 and our own; engine sound from the footage. Music: original, made with Lyria.
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