The Leduc ramjet | Hacker News Reader

The Leduc ramjet

scottlocklin.wordpress.com

53 pointsLordFrith8 comments

More about that coal-powered supersonic plane (that didn't fly): https://en.wikipedia.org/wiki/Lippisch_P.13a "Initially, it was proposed that a wire-mesh basket holding coal be mounted behind a nose air intake, protruding slightly into the airflow and ignited by a gas burner ... The coal was to take the form of small granules instead of irregular lumps, to produce a controlled and even burn, and the basket was altered to a mesh drum revolving on a vertical axis at 60 rpm."

Ramjets do live on to an extent, in NASA technological demonstrators but also more interestingly in the SR-71's legendary J58 engines, which switch to from mostly turbojet at low speeds to mostly ramjet at high speeds: the compressor is almost entirely bypassed then[0] and the vast majority of thrust comes from the "afterburner", hence the engine's maximum efficiency being around Mach 3.2.

[0] https://en.wikipedia.org/wiki/Pratt_%26_Whitney_J58#/media/F...

A good fraction of these in service or development missiles still use them: https://en.wikipedia.org/wiki/Ramjet#Missiles_using_ramjets

And the no longer in service Sea Dart was really put to the test in the Falkland Islands war, preformed pretty well and made a material difference. And the somewhat related earlier RIM-8 Talos got 4 MIGs in 3 firings, including "the first downing of a hostile aircraft by a missile fired from a ship" (https://en.wikipedia.org/wiki/RIM-8_Talos).

Momentarily confused between a ramjet[1] and a valveless pulsejet[2] -- the latter are played with by many amateurs( e.g.[3]) producing amusing videos of their cherry-red glow and eardrum-piercing noise.

[1] https://en.wikipedia.org/wiki/Ramjet

[2] https://en.wikipedia.org/wiki/Valveless_pulsejet

[3] https://www.youtube.com/watch?v=8cR6bD57AKw

Ram jets burn (like a turbojet); pulse jets bang (like an internal combustion engine).

I love the hardware the old aircraft and rocket designers came up with(!), and built(!), and flew! For example the ultra heavy lift rocket designs the Air Force solicited in the 50's and 60's, to put military outposts on the moon. The Sea Dragon is a favorite of mine [1]. Not built nor flown, but really interesting.

[1] https://en.wikipedia.org/wiki/Sea_Dragon_(rocket)

Not sure whether the TIE fighter-like sound on the second movie clip [0] is edited in or that a nazi aircraft really did sound like an Empire spacecraft

[0] https://youtu.be/MvtxjSrImHw?t=41s

Edited in; that's a gliding test, so there wouldn't be any engine noise even assuming the original film had an audio track, and given it's a ramjet, even a full-up production aircraft would be gliding at that point in its flight profile.

In any case, the TIE fighter sound was created from whole cloth (actually "an elephant call and car tires on wet pavement", apparently) for the first Star Wars film.

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