same variations of form as the P.12, being presented in a brochure with the large fin and integral raised cockpit, and with an articulated, double-hinged landing skid. The wing trailing edge is angled slightly forwards and the downturned tip surfaces have been discarded. The outer wing sections could be folded upwards for transportation by rail. A variant with a rectangular canard foreplane was wind-tunnel tested. This was not really consistent with ramming and there are other indications that conventional gun armament was being considered. As conventional fuels were in extremely short supply by late 1944, Lippisch proposed that the P.13a be powered by coal. Lippisch soon came to conclude that this might even be more effective than liquid fuel, as the location of combustion was more precisely controllable. Initially, it was proposed to employ a wire-mesh basket holding even-sized granules of brown coal, placed in the lower region of the internal airflow. The burning coal gave off carbon monoxide (CO) gas which was mixed and combusted with the upper air flow downstream. The arrangement proved inefficient. To replace it a spinning circular basket was developed, revolving on a vertical axis at 60 rpm. The hot exhaust would be mixed with cooler bypass air to improve thermodynamic efficiency, before being expelled through the rear nozzle. Other fuels considered promising, due to their ability to generate flammable vapours, included bituminous coal, or pine wood heat-soaked in oil or paraffin. A burner and drum were built and tested successfully in Vienna. Glider studies and the DM-1 A scale model of the P12/13 configuration was successfully tested at Spitzerberg Airfield, near Vienna in Austria, in 1944. The P.13a had reached a stage where full-scale aerodynamic trials would be possible. A glider with the same general design and wingspan, but with the intake and exhaust faired in, was built as the DM-1. Lippisch however took little interest; having moved on from the design, he set up the glider project only to keep students of Darmstadt and Munich Universities from being drafted into a by-then hopeless war. The DM-1 had not been finished when it was captured by American forces. The Americans ordered Lippisch's team to complete the glider, and it was then shipped to the United States where it was test-flown. According to the National Advisory Committee for Aeronautics the results were positive and lessons learned were incorporated into NASA's research aircraft of the 1950s