early 1944, due to the fuel shortage in Germany at that stage in the war,
Dr. Alexander Lippisch
and his design team though to use other kind of material be the alternative fuel
for the power of his ramjet fighter designs, such as P.13a. They tried "coal"
powder and designed a hexagonal / round shaped chamber which was suitable
for coal combustion, and was refilled
from top center. However, the fuel chamber could not fit into the P.13a fuselage.
It was led to the
follow-on design, the P.13b which was started in November 1944. It also featured a delta wing plan
design as Lippisch's favorite. The cockpit was moved forward for better pilot's
visibility. The double rudders were chosen to provide steady flight. The
main landing gear was the retractable landing skid, and rear rested on the
reinforced wingtips. No actual craft was built as end of the war. It only
stayed in stage of concept sketches.