The Lippisch DM-1 was a single-seat research glider that was designed and built in Germany from 1944.

Development

During World War II, Dr. Alexander Lippisch proposed a ramjet propelled point defence fighter, the Lippisch P.12/13a. It was a sharply-swept delta

flying wing A flying wing is a tailless fixed-wing aircraft that has no definite fuselage, with its crew, payload, fuel, and equipment housed inside the main wing structure. A flying wing may have various small protuberances such as pods, nacelles, blis ...

with the engine buried in a thick, blunt-nosed wing. The pilot was accommodated in the forward section of the tail fin, which was as thick as the wings and almost as large. A scale model of the P.12/13a was successfully flown at Spitzerberg, near Vienna.Dan Sharp; ''Luftwaffe: Secret Jets of the Third Reich'', Mortons, 2015, p.119. Lippisch himself lost interest in the design and began work on the P.13b with a different wing, but he was approached by students of

Akaflieg Darmstadt Akaflieg Darmstadt is one of approximately twenty aviation groups attached to German universities. Akaflieg is an abbreviation for '' Akademische Fliegergruppe'', an academic group of students and faculty from a German University. Akaflieg histo ...

and

Akaflieg München Akaflieg is an abbreviation for ''Akademische Fliegergruppe'', groups of aeronautical engineering students from individual German Technical Universities, pre and postwar, who design aircraft, often gliders. History Otto Lilienthal published his bo ...

, who asked for vital war work so that they would not be drafted. By this time in 1944 Lippisch realised that the war was hopeless and was happy to oblige, arranging for them to build a full-scale aerodynamic test glider for the P.12/13a project. Construction was begun at the workshop of the

, as the Darmstadt D-33. The workshop was bombed in September 1944, so the part-built airframe was moved to the

workshops at Prien am Chiemsee, where it was redesignated the DM-1 (for Darmstadt-München 1). At Prien,

Wolfgang Heinemann Wolfgang is a German male given name traditionally popular in Germany, Austria and Switzerland. The name is a combination of the Old High German words '' wolf'', meaning "wolf", and '' gang'', meaning "path", "journey", "travel". Besides the reg ...

and Hans Zacher from Darmstadt, with Klaus Metzner and Hermann Nenninger from Munich, continued the work. The DM-1 was a single-seat glider made from steel tubing, plywood and bakelite impregnated plywood. The cockpit canopy was integrated into the fin leading edge. Launching the DM-1 was to be by piggy-back or aero-tow. After occupation by U.S. Troops in May 1945, work continued at the DM-1 on behalf of the U.S. military government, with General Patton and Charles Lindbergh visiting Prien to see the project. Completed in early November 1945, the DM-1 was shipped in a wooden box to Langley Field in Virginia where the flow behaviour of the DM-1 was examined in the NACA (National Advisory Committee for Aeronautics, forerunner of today's NASA) full-size wind tunnel.

US modification

Vortex lift

When tested at Langley, the DM-1 was found to perform poorly. It generated significantly less lift at low speeds than small-scale models had suggested. The cause proved to be vortex lift generated by the models which, due to its much higher

Reynolds number In fluid mechanics, the Reynolds number () is a dimensionless quantity that helps predict fluid flow patterns in different situations by measuring the ratio between inertial and viscous forces. At low Reynolds numbers, flows tend to be domi ...

, the full-size aircraft did not produce.Hallion (1979) As a consequence it underwent a programme of modifications. Like all Lippisch deltas it had a thick wing with a blunt leading edge. A strip was fixed along the leading edge to simulate a sharp profile. This created the vortices seen on the model and greatly increased the lift. The origin of modern vortex lift theory (as seen most famously on Concorde) may thus be traced to the NACA study and the modified DM-1.

Drag reduction

The large and even thicker vertical stabilizer was removed and replaced with one of much smaller size, along with a cockpit canopy from a Lockheed P-80 Shooting Star in a more conventional position. Together with improvements to the elevon hinges, this significantly reduced overall drag.

Preservation and restoration

After completion of testing the DM-1 was retired to the

National Air and Space Museum The National Air and Space Museum of the Smithsonian Institution, also called the Air and Space Museum, is a museum in Washington, D.C., in the United States. Established in 1946 as the National Air Museum, it opened its main building on the Nat ...

, Smithsonian Institution in Washington, D.C. for storage at the Paul E. Garber Preservation, Restoration, and Storage Facility.

Controversy over its influence

It has been suggested that the DM-1 influenced design of the Convair delta-wing jets, beginning with the

XF-92A The Convair XF-92 (re-designated from XP-92 in 1948) was an American, delta wing, first-generation jet prototype. Originally conceived as a point-defence interceptor, the design was later used purely for experimental purposes and only one was ...

. Convair engineers are known to have examined the DM-1 and interviewed Lippisch. This has led historians to assume his technical influence, however there is no direct evidence to support this assumption.Crellin and Lee, Part 4. On the contrary, Convair had independently discovered the thin delta wing, while the DM-1 had a thick wing and its aerodynamic behaviour is very different. They knew of Lippisch and at least one engineer met him, but his contribution was more in the nature of "moral support" than anything technical.

Variants

Besides the NASA modifications, the Akafliege Darmstadt and München defined some powered designs for a development programme derived from the DM-1. :DM-1 (Lippisch). Glider as originally built but never flown, with thick wings and large tail. ::(NACA). Glider as modified with leading-edge strip, small thin fin, conventional cockpit and sealed elevon hinges. :DM-2. Larger, supersonic test plane with span, length and prone pilot. Powered by a Walther liquid-fuelled rocket. All-up weight . :DM-3. Developed version of the DM-3 with pressure cabin and more powerful Walther C engine. :DM-4. Engine flight testbed, initially fitted with a Walther C. Airframe weight (without engine)

Specifications (DM-1)

References

Notes

Bibliography

*Crellin, E. and Lee, R,; "Lippisch DM 1 Reconsidered", Parts 1–4, Smithsonian National Air and Space Museum, 2015. (Retrieved 26 September 2020). Parts
1234
*Richard P. Hallion; "Lippisch, Gluhareff, and Jones: The Emergence of the Delta Planform and Origins of the Sweptwing in the United States", ''Aerospace Historian'', Vol.26, No.1, Spring/March 1979. pp. 1–10
JSTOR copy

External links

Akaflieg Darmstadt websiteLippisch DM 1 Reconsidered, Smithsonian NASM"Declassified UFO recovery Nov 3, 1945 Germany Operation Paperclip - Lippisch"
(YouTube video)
"Investigation of the DM-1 Glider"
NACA Langley, 1 August 1946 (YouTube video) {{DEFAULTSORT:Lippisch DM-1 1940s German sailplanes 1940s German experimental aircraft Tailless delta-wing aircraft DM-1 Lippisch aircraft Akaflieg Darmstadt aircraft