The Lippisch P.13

Lippisch P-13a

Professor Alexander Lippisch,(see biography below) one of the most dedicated promoters of the flying wing, also tried to create an inexpensive but deadly fighter aircraft that was designed for quick and easy mass production. Apart from his early rocket-propelled tailless designs, Lippisch also developed three advanced flying wings under the designations Li P 12, P 13, and P 13a.

The Li P 12 (below) was an unusual tailless design with an internally positioned athodyd liquid fuel propulsion unit. The air intake was in the nose and the pilot was seated above the combustion chamber. The undercarriage consisted of a single central wheel and outrigger skids on the wing tips. The wing area was about 210 sq ft. In August 1944, it was suggested to air-launch the aircraft using a Fw 58 Weihe (Harrier) as a carrier for the first evaluation stage, the Li P 12 being mounted piggy-back on top of the Fw 58.

In order to test the properties of the advanced flying-wing configuration, about fifteen tests of flying scale models were carried out near Vienna commencing on November 28, 1944. Previous wind tunnel tests had confirmed the soundness of the Lippisch configuration, and additional successful tests were carried out in the Spitzerberg hills near Hamburg, Austria.

A few weeks later around Christmas 1944, a full-scale piloted prototype, known as the DM 1 (DM - Darmstadt München Entwurf 1, the first project and the location of its development), was under construction at Prien on Lake Chiemsee in Bavaria. For actual flight testing, the DM 1 was to be mounted on top of a Siebel 204A carrier aircraft.

At a later stage the DM- 1 was to be flown at a speed of 497 mph under the power of a rocket motor. At the other end of the speed range, the aerodynamic characteristics of this little single-seat aircraft were such that a landing speed of only 44 mph was expected.

When Allied tanks appeared on the air field at Prien on May 3, 1945, the aircraft was nearly complete. Ninety days after the end of the war in Europe, August 6, 1945, the Americans proposed finishing the project and test-flying the prototype atop a Douglas DC-3. However, by the time the DM 1 was completed a few weeks later, the group was ordered to transfer the experimental aircraft to the United States for proper evaluation. In January 1950, the DM 1 became the property of the National Air and Space Museum (NASM) and was transferred to their storage facility outside Washington, DC.

The projected Li P 13 was originally designed as a two-seater, but later appeared in modified form as the single seat Li P 13a. The leading-edge sweep back had been increased to 60 degrees. The span was 19.7 ft, the wing area was approximately 215 sq ft, and the aspect ratio was calculated at 1.8 !!

The pilot was seated in the narrow leading edge of the large dorsal fin. The solid fuel, in the form of small pellets of lignite (brown coal), was to be carried in a wire-mesh container mounted at a slight angle in the duct that was at an angle to the air stream. The airflow in the lower duct was therefore obstructed, and it was intended to start a progressive reaction with oxygen passing through the fuel. After ignition carbon monoxide was produced by the burning fuel, which combined with the oxygen in the air passing through the upper unobstructed duct section and formed carbon dioxide. This highly innovative system failed to function effectively in disappointing tests, and it was abandoned.

An improved solid-fuel design, the Li P 13b, utilized a circular basket of oval cross section suspended in the duct and rotating on its vertical axis at about 60 rpm. The combustion was started by a gas burner with liquid fuel used to facilitate starting. An alternate, more easily combustible fuel in the form of coal dust pellets was proposed, with an oxygen carrying material spread over the outer surface of the charge.

The P-13a consisted basically solely of engine and fuel tank with some room provided for the pilot. The pulse engine from Schmidt-Argus, similar to the ramjet, was certainly not a new concept, and the Fieseler Fi 103 flying bomb (right)- better known as the V1 - flew in massive numbers against England with this type of engine.

This engine (called the "Lorin" engine after its inventor) with the wings of the Li P12/13, which could be controlled by flaps in the exhaust flow and ultimately was a flying wing, was called a "Triebflugel" (powered wing) by Lippisch. This was not to be confused with the ramjet-powered (Lorin) "Triebflugel" project of Focke-Wulf. This was a separate helicopter-like vertical takeoff aircraft with everything else operating as with a flying wing. The ramjet operated by itself only after a certain speed had been reached. This process involved ram air entering in through an opening in the front, being mixed with fuel, compressed, ignited and forced out the back.

The P13a (a supersonic fighter) was made of wood, plywood and steel tubing. One-piece wing of open rib design, cantilever, vertical and horizontal stabilizer surfaces were hinged, with trim tabs in the interior portion. There was no fuselage in the normal sense, the cockpit was located in part within the forward portion of the vertical stabilizer, in part just behind the forward leading edge between the two main spars.

A window in the lower forward floor provided better view at high angles of attack (during landing at roughly 35 degrees). The triangular vertical stabilizer had a similar profile as the wing. Trimming was accomplished by a manually operated water transfer pump 9 gallons from a rear tank to a nose tank and back. The tricycle landing gear, which could only be retracted on the ground, had a 23 inch travel stroke. No type of armament was planned for this test version; overall, the DM-1 was kept to simple, spartan standards.

There were no complicated, moving parts and this little terror was to be quick and cheap to build. The P-13a fighter being proposed by Lippisch would be powered in part by coal as fuel.

The Flying Coal Oven:

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. 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. A jet of flame from tanks of bottled gas would fire into the basket once the P.13a had reached operating speed (above 199 mph), whether by using a RATO unit or being towed.

The air passing through the ramjet would take the fumes from the burning coal towards the rear where they would mix under high pressure with clean air taken from a separate intake. The resulting mixture of gas would then be directed out through a rear nozzle to provide thrust. A burner and drum were built and tested successfully in Vienna by the design team before the end of the war.

It is not known what armament would have been carried by the P.13a; the MK 103 cannon would have been too heavy and large for such a small aircraft and it is possible that one or two large-caliber machine guns would have been used. The MX 108 (30 mm caliber ), then common to all jet and rocket fighters, would have been utilized.

On 11/12 September 1944 the FFG Darmstadt was destroyed in a bombing attack and everything pertaining to aircraft and materials which could be saved was sent elsewhere.

At the end of the war not even the prototype DM-1 test glider had not been finished when it was captured by US forces. It was ordered to be completed by Lippisch's team and was then shipped to the USA where it was test-flown. Reportedly the results were very positive and lessons learned were incorporated into NASA's research aircraft of the 1950s and on.

The Americans shipped the prototype back to the USA for completion and flight testing, and the resulting data were incorporated into the design of the many US delta-wing aircraft which appeared in subsequent years.

BIBLIOGRAPHY:

Alexander Lippisch was born Nov. 2, 1894 into a highly cultured family. His father was a creative artist and Alexander apparently took after his father in art as well as music. During his early youth he became interested in flying after observing the flights of the Wright bothers in 1909. He was drafted by the by the military in early 1915 and in the fall became ill with pneumonia. After recovering he got a job in aerial surveying with the army. In 1918 he was discharged from the army and got a job in the Zeppelin factory where he was appointed to work under Mr. Claude Dornier. Here he studied the new science of aerodynamics and worked there until the armistices was signed in 1918.

After the war, Lippisch was out of a job and returned home until 1921 when he worked on sailplanes. During the 1920's he was involved in the design and construction of many sailplanes and gliders. Included were many unusual designs and swept wing configurations. These designs led to the tailless aircraft and the delta wing configuration which Lippisch felt was the configuration of the future.

Although he never went to college he learned engineering from his work at the Zeppelin factory under the Claude Dornier. He also conferred with Professor Ludwig Prandtl one of the foremost aerodynamics of his time. Based on the work with the delta wing and tailless airplanes he wrote his Doctor Dissertation to earn his degree.

The delta wing and tailless designs led the aircraft using the Walter liquid-fueled rocket engine. Lippisch was in charge of the airframe design and Walter was in charge of the engine. The airplane was designated the Me 163. According to German records 364 Me 163 were built. The airplane was far ahead of its time and was aerodynamic clean and was very fast achieving a Mach number of approximately 0.8 in level flight. Due to personality difficulties Lippisch left Messerschmitt and went to another German research institute at in 1943 Vienna. Austria. Here he worked on designs of advance aircraft including configurations for operation at Mach numbers above 1.0.

At the end of the war he left Germany and came to the USA under operation paper clip along with other German engineers and scientists. Here he worked for the Navy and finally for Collins Radio. Here his work was supported by the Office of Naval Research and included design work on various wingless and other aircraft including ground effect machines.

In reviewing the work and life of Alexander Lippisch it became apparent that his work was very creative and much ahead of its time. He apparently was not bothered by theoretical considerations but was more interested in the overall picture. Like the Wright brothers whom he admired; much or his work was cut and try based on an the overall need. As Lippisch was a product of a different time period his life and work can not be compared with those of the present time. For this reason he can not be judged based on present day standards but must be judged based on his accomplishment of the time.

Reference: Al, The Cedar Rapids Gazette: August 1 to 8 1978. "Alexander Lippisch Man of the Future".

Specifications
	Length: 22 ft Wingspan: 19 ft 9 in Height: 10 ft 8 in Wing area: 215 ft² Loaded weight: 5,060 lb Powerplant: 1× Kronach Lorin coal-burning ramjet Performance Maximum speed: 1,025 mph Range: 621 miles Wing loading: 24 lb/ft²

Dr. Alexander Lippisch designed this ramjet powered interceptor in late 1944, much of the research coming from his work on the DM-1 test glider (see below). The wings were sharply swept back at 60 degrees, and there was a single large fin and rudder in which the cockpit was located. The ramjet was fed by a circular intake that protruded from the nose, and exhausted beneath the vertical fin at the rear. Research in the DVL high-speed wind-tunnel indicated that the P.13a had outstanding stability up to the maximum tested speed of Mach 2.6, and no unfavorable characteristics in the subsonic range. A liquid fueled rocket motor was planned for takeoff and to get the aircraft to ramjet operating speed. Since fuel was in short supply by this stage in the war, powdered coal was to be used in the ramjet.

Click on Picture to enlarge

P 13 sketch	Concept sketch of the P 13a

Detail sketch of the P-13a	Control schematic

Layout designs leading to the DM-1	Detail of propulsion system	Artist's drawing of P 13 in flight

Larger version of the P 13 with two vertical tails.		Note similarities between Lippisch P.11 Delta V and the final P.13B

Usage	Ramjet/rocket fighter	Developed by Hubert, the first version of the P 13 was a tailless high-speed bomber, with fore-and-aft tandem propellers and two piston engines. A completely different plane, designed by Lippisch, also was called the P 13 (actually P 13a). The P 13a was designed to make use of an unusual fuel source for an airplane: coal. Liquid fuel was getting scarce, and a plane which could burn coal products would have been very desirable. Wind tunnel tests of the P 12 and P 13a and tests of free flight models were very successful, and did not reveal any problems. Another version of the P 13 had a much wider wing, and used a cylindrical combustion area. Still yet another version of the P 13 became the DM-1 full scale flight test model
Status	Design
Powerplant	One Lippisch coal-burning ramjet plus auxiliary rocket motor
Span	5.92 m
Length	6.70 m
Wing Area	20.0 m²
Aspect Ratio	1.75
Maximum Weight	2,295 kg
Wing loading	114.75 kg/m²
Maximum speed	1,650 km/hr at high altitude
Endurance	45 minutes with 800 kg coal
Maximum speed	1,200 km/h @ 5,900 m
Cruising speed	850 km/h
Armament	Two MK 103 30 mm cannon

Specifications