The Lippisch P.13a never made it past the drawing board, but testing of wind-tunnel models in the DVL high-speed wind tunnel showed that the design had extraordinary stability into the Mach 2.6 range.
The Lippisch P.13a was an experimental ramjet-powered delta wing interceptor aircraft designed in late 1944 by Dr. Alexander Lippisch for Nazi Germany. The aircraft never made it past the drawing board, but testing of wind-tunnel models in the DVL high-speed wind tunnel showed that the design had extraordinary stability into the Mach 2.6 range.
The Lippisch P.13a perhaps is one of the weirdest aircraft ever designed for a few reasons, as explained by Nikolas Pullen, an aviation expert, on Quora:
1. Look at its shape. It looks like some sort of sinister alien fish monster you’d find in an 80’s B-grade-sci-fi-horror film.
2. The actual design:
The pilot sits on top of a ramjet that runs on coal dust stored in the basket in the middle. This ramjet only would start generating sufficient thrust to sustain flight at speeds of around 320 km/h, however, so the aircraft had to be towed or use rocket assisted takeoff pods to even achieve flight at all.
3. Did I mention it runs on coal? Not gasoline, not jet fuel, not even synthetic oil (oil made from coal), straight up ground up coal.
As conventional fuels were in extremely short supply by late 1944, Lippisch proposed that the P.13a be powered by coal. 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. Following wind-tunnel testing of the ramjet and the coal basket, modifications were incorporated to provide more efficient combustion.
Photo credit: FlightSim.com