Letter: Letters : Coal in the sky

From Mark Hayward

Great Wakering, Essex

I thought that you might be interested in the German proposals at the end
of the Second World War to use coal as a fuel in high performance aircraft,
which, while experimental were certainly scientific fact, not fiction (Letters,
3 February, p 56, 2 March, p 50, and 23 March, p 64). The proposals must have
stemmed from the oil shortage of the latter years of the war, which as your
correspondent Richard Courtney points out, affected German defence capabilities
to an enormous degree.

Information on the plane can be found in standard reference works on
Luftwaffe jets and experimentals, but the best source is German Jet
Genesis by David Masters published by Janes in 1982.

Coal was to be used to fuel a ramjet engine for a supersonic fighter plane
called the Lippisch DM P13a designed by the noted engineer and scientist
Professor Lippisch who also designed the engine fuelled by brown coal
(presumably lignite?). I am unsure as to how far the engine design progressed,
but the tiny delta winged aircraft had a triangular tail fin into which the
pilots cockpit was built. He sat above the ramjet and also had a rocket engine
for take off and to achieve the required ignition speed of the ramjet. Wind
tunnel work was well advanced and a smaller unpowered glider of the same
planform was almost complete. This was captured by the US Army at the end of the
war.

From what I can gather from Masters’s book, the coal particles would have
been suspended in the airflow and rotated, then ignited by a gas flame. The
resulting heated gas would produce thrust to propel the plane at supersonic
speeds. Other planes were also to be powered by the ramjet.