AidSpace Blog

Lippisch DM 1 Reconsidered – Part 2

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In this four-part series, curators Russ Lee and Evelyn Crellin take an in-depth look at the Lippisch DM 1, an experimental German glider. At the conclusion of Part 1, construction of the glider had begun in August 1944 by students of the Flugtechnische Fachgruppe (FFG).

Construction of the experimental glider was derailed dramatically on September 11 and 12, 1944, when Allied bombers struck Darmstadt, including the building that housed the FFG D 33 project. Everything the students could salvage from the rubble was moved to Prien Airport at Chiemsee in Bavaria, where students of FFG Munich had operated a large workshop since 1924. Prien had been the starting point of many famous gliding events from 1918 to 1939 including attempts to cross the Alps in gliders and set altitude records. Now, Prien Airport and the FFG Munich workshop became the new home of the glider, where both FFG groups—Darmstadt and Munich—combined their efforts to continue building the aircraft. This collaborative effort led to a new designation for the glider using the letters ‘D’ for Darmstadt and ‘M’ for Munich to rename the aircraft the DM 1. Increasingly difficult wartime conditions, however, prevented Lippisch from assisting further with design and construction.

Students glued, bolted, nailed, and screwed together the cantilever fuselage and various components made of wood, plywood, and steel tubes. They covered the entire glider with 1.6 mm (1/16-inch), 3-ply birch plywood. To cover the very thick leading edges of the wings and vertical stabilizer, the students had to first heat the plywood with steam. These very thick sections were unsuitable for high-speed flight and suggested that Lippisch designed the DM 1 for experiments at low flying speeds. They gave the pilot a window on the cockpit floor to see ahead of the glider at the high pitch angles that would be necessary during launch and landing. To evaluate how the glider handled in flight with the center of gravity at various locations, the pilot could hand-pump 35 liters (9 gallons) of water between two tanks inside the nose and tail of the aircraft. Armament was not planned for this experimental glider.

Looking aft through the nose toward the tail, the pilot’s control stick is at center and tilted to the right. The pilot worked the lever with the red knob at right to pump water between tanks at the nose and tail to adjust the center of gravity of the DM 1. Photo: Ben Sullivan

The students fashioned the wheeled, three-strut, tricycle undercarriage from steel. Contrary to a recent published account stating that the gear was fitted with shock absorbers that had 60 cm (2 ft) of travel, direct observation of the DM 1 aircraft in the Mary Baker Engen Restoration Hangar at the Steven F. Udvar-Hazy Center in Chantilly, Virginia, confirms that the struts are solid steel with no capacity to absorb shocks. To reduce the stress of landing at the high angles of attack required for delta wing aircraft, the struts are set so close together that the glider appeared ready to tip over. Lippisch may have imagined the test pilot would land on a wooden skid or even on the smooth belly of the aircraft since touching down on the gear legs without shock absorbers would probably have damaged the delicate internal wooden structure. Museum treatment specialist Matt Nazarro likened the structure to the fragile insides of a wooden guitar. The design called for ground technicians to retract the undercarriage after they had mounted the glider piggyback onto a larger powered aircraft, so the gear may only have provided the techicians with a convenient way to move the aircraft around on the ground.

Two main landing gear struts and other structural components viewed from the right side of the aircraft. The control stick is visible at right. Photo: Ben Sullivan

Authorities had planned to carry the experimental glider into the air piggyback atop a twin-engine and propeller-driven Siebel 204 A aircraft. The DM 1 pilot would have released from the carrier aircraft at altitude and descended with additional thrust from two solid-fuel rockets at an estimated speed of around 800 kph (500 mph). A former coworker of Alexander Lippisch, test pilot Hans Zacher from the DFS (Deutsches Forschunginstitut für Segelflug, German Research Institute for Gliding), was designated to perform the DM 1 test flights. However, Zacher joined the project at a late stage, and the war ended before the students could finish building the glider.

On May 3, 1945, American troops occupied Prien Airport and found the incomplete glider. German historian and author Hans-Peter Dabrowski wrote in his article Flying Triangle (Klassiker der Luftfahrt, July 2014, p.61) that when U. S. Army General George S. Patton and other high-ranking officers visited Prien on May 9, 1945, the advanced design features of the aircraft impressed them and Patton ordered the students to resume construction and complete the aircraft. Dabrowski also wrote that Dr. Theodore von Kármén argued vehemently to finish the DM 1, and that Major A. C. Hazen of the Air Technical Intelligence Section, U. S. Army Air Forces in Europe, became the project manager.

Hazen worked closely with test pilot Hans Zacher who remained very involved with work on the DM 1. On one particular day, Zacher was visited by group of Americans who had come to study the glider. At the time, they were unknown to Zacher. During small talk he mentioned that he had studied the work of Walter Stuart Diehl, the famous American pioneer of aerodynamics and author of the authoritative Engineering Aerodynamics (1928), who actively participated in and strongly influenced continuing advances in aerodynamics and hydrodynamics. To Zacher’s surprise, one of his counterparts identified himself as Walter Diehl. From this encounter a lifelong friendship arose between Zacher and Diehl.

The workshop at Prien Airport would also receive a visit from another famous American before construction of the DM 1 was completed. Find out who next week, but feel free to guess in the meantime.

Russ Lee is the Chair of the Aeronautics Department and the Curator of Gliders and Sailplanes, and Evelyn Crellin is the Curator of European Aircraft at the National Air and Space Museum.

Dabrowski, Hans-Peter. “Flying Triangle,” Klassiker der Luftfahrt, July 2014.
Lindbergh, Charles A. The Wartime Journals of Charles A. Lindbergh, (New York, 1970).

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Swimming with the WASPs

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As summer heats up in Washington, DC, swimming pool attendance skyrockets. For Women Air Service Pilots (WASPs) training to fly military aircraft during World War II at Avenger Field in Sweetwater, Texas, a dip in the pool was more than fun and games.

For any pilot, there exists the possibility of an aircraft going down over water. To prepare, WASPs without any swimming abilities were enrolled in a regular swimming class.

Regular swimming class for WASP trainees who did not know how to swim. Town Pool, Sweetwater, Texas. NASM A-4492-F

The reality of a water landing or parachute jump is that a pilot will still be wearing all of her clothes. WASPs trained for that scenario by jumping into the pool fully clothed.

Not the Sweetwater Synchronized Swimming Team! WASPs train for survival in water with their clothes on. NASM A-4492-E

Wet WASPs exit the pool after training for survival in water with their clothes on. NASM A-4564-D 

Training time in the pool was commemorated in a poem in Bernice Falk Haydu’s 318th WASP Yearbook, a rhyming laundry list of common experiences and slang:

Zoot suits
Turbans white
It ain’t right
Flight Line
Mess Time…
Ground School
Swimming pool
Just can’t think
In stinky Link
Hairnets too
Glamour’s few…
Dirt on floor
Sweep some more
Shots and such
Don’t help much

Elizabeth C. Borja is an archivist in the National Air and Space Museum’s Archives Department.

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Lippisch DM 1 Reconsidered – Part 1

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In this four-part series, curators Russ Lee and Evelyn Crellin take an in-depth look at the Lippisch DM 1, an experimental German glider.

Right side view of the Lippisch DM 1 experimental glider on the Prien Airfield outside Chiemsee in the Bavarian region of southern Germany in October 1945. The landing gear is grouped close together to reduce the impact forces on the nose gear during landing at high angles of attack. A Douglas C-47 transport and several Piper L-4 scout and liaison aircraft are visible in the background. Photo: NASM 2003-34023.

The Lippisch DM 1 played a vital role in the development of the first jet-propelled delta wing aircraft to fly, the Convair XF-92A. The extensive flight tests that Convair and the U. S. Air Force conducted with the XF-92A led the company to develop the Convair F-102 Delta Dagger and the F-106 Delta Dart, both delta wing fighters, as well as the B-58 Hustler supersonic delta wing bomber. The United States Air Force and the Air National Guard operated more than 1,400 of these aircraft from 1956 to 1988. For its role in the advancement of delta wing fighters, the Lippisch DM 1 warrants further examination from its early days in war-torn Germany to wind tunnels studies in the U.S.

Front view of the DM 1. The clear plastic canopy that covered the single-seat cockpit at the base of the vertical fin has been removed. The tube projecting from the nose at lower right was a boom to mount the pitot tube or angle of attack sensor. Photo: NASM A-4404-C

Alexander M. Lippisch, a German aircraft designer, devoted much of his career to understanding and developing advanced, unconventional aircraft. Between 1921 and 1945, he embarked on more than 100 projects that led to the construction and successful flight of about 60 different aircraft including the Messerschmitt Me 163 Komet rocket fighter, currently on display at the Steven F. Udvar Hazy Center in Chantilly, Virginia. The Komet was the world’s first operational fighter aircraft powered by a liquid-fueled rocket engine becoming operational in May 1944.

Alexander Lippisch designed the Messerschmitt Me 163 B-1a on display at the Steven F. Udvar-Hazy Center. Photo: Dane Penland

By the late 1930s, aircraft designers and engineers began to understand that traditional straight wings and relatively thick airfoils were not ideal for flight at the speed of sound or beyond. Sound travels at different speeds primarily due to variations in air temperature. At sea level and under normal atmospheric conditions it travels at 1,220 km/h (760 mph). To reduce the drag of the air that quadruples when airspeed doubles, and to solve other problems that arise at transonic speeds, Lippisch proposed a delta wing configuration so named because it resembles the fourth letter ‘Delta’ of the ancient Greek alphabet whose uppercase form looks like this: ‘Δ’. This shape has several advantages for high-speed flight. It combines sharply swept leading edges to minimize drag at high speeds with a large surface area needed to make lift at low speeds. The delta had favorable structural characteristics, too. It allowed engineers to build thin wings making less drag without losing the strength needed to withstand the powerful air loads encountered at transonic speeds.

In spring 1943, Lippisch took charge of the Luftfahrt-Forschungsanstalt Wien (Aeronautical Research Establishment Vienna, or LFW). He began working on several projects. One of them was the project “P 13 a,” the idea for a semi-tailless supersonic fighter aircraft. At the time, Allied bombing operations were increasing in scope and intensity. To counter the bombers, Germany needed new fighter aircraft with performance superior to Allied aircraft. The new designs also had to be quick to build using inexpensive materials that were easily obtained. To boost high-speed performance, Lippisch envisioned powering the P 13 a with a ram-jet engine that consisted of just a few moving parts and operated by burning a mixture of coal dust and heavy oil or gasoline.

The Reichsluftfahrtministerium, or German Air Ministry (RLM), became interested in this project, perhaps because several firms were already developing unusual forms of semi-tailless or all-wing designs for fighter aircraft powered by either jet turbine or rocket engines. In addition to the Me 163 B-1a already mentioned, another notable example is the all-wing Horten Ho 229 V3 (‘aich-oh two-two-nine vee-three’) currently on display in the Mary Baker Engen Restoration Hangar at the Steven F. Udvar-Hazy Center.  Lippisch designed the P 13 a to be built of aluminum and he hoped it could attain supersonic speeds. The wing would be a cantilever structure, a smooth outer surface without external supports such as struts or wires. It would also have a 60° nose angle and a profile thickness of 15%—the thickness of the wing as a percentage of the width of the wing from leading to trailing edge.

Beginning in May 1944, experts evaluated the design at Spitzerberg Mountain near Vienna using a scale-model of the P 13 a. In August 1944, the aerodynamic characteristics of a P 13 a wind tunnel model were tested in the supersonic wind tunnel at Aerodynamische Versuchsanstalt, the Aerodynamic Research Institute (AVA) in Göttingen. Following these tests, Lippisch pushed to build a full-size version without an engine. A powered aircraft would tow aloft the experimental glider manned by a test pilot who would study the takeoff, landing, and handling qualities of the design in flight. A young man assisting Lippisch at the LFW was Wolfgang Heinemann, persuaded the designer that he and his fellow students of the Flugtechnische Fachgruppe (aeronautical expert groups, FFG) at Darmstadt Technical College could build the experimental glider according to Lippisch’s specifications. Heinemann was one of many German students majoring in engineering and aeronautics who joined such academic flying groups where they obtained their pilots’ licenses, tried to solve various aeronautical problems, and were not afraid to tackle challenges at the limits of the aeronautical sciences. The students began their work in August 1944. Since FFG Darmstadt numbered their designs sequentially, the new aircraft became the D 33. Lippisch later said the designation should have been “P 13 a V1” (Project 13 a, prototype 1).

Construction of the aircraft, however, was abruptly halted when Allied bombers struck Darmstadt, including the building that housed the FFG experimental glider project. Next week in Part 2, we will see what impact this had on the completion of the D 33.

Russ Lee is the chair of the Aeronautics Department and the curator of gliders and sailplanes, and Evelyn Crellin is the curator of European aircraft at the National Air and Space Museum.

Chambers, Joseph R. Cave of Winds: The Remarkable History of the Langley Full-Scale Wind Tunnel, (NASA SP-2014-614), 2014.
Dabrowski, Hans-Peter, Überschalljäger Lippisch P 13 and Versuchsgleiter DM-1 (Supersonic Flighter P 13 abd Experimental Glider DM-1), Podzun-Pallas Verlag Stutgart 1986
Dabrowski, Hans-Peter. “Fliegendes Dreieck (Flying Triangle),” Klassiker der Luftfahrt, July 2014.
Lippisch, Alexander M. The Delta Wing-History and Development, Gertrude Lippisch translator, (Ames, Iowa, 1981).

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Star Trek “Considered Harmful”

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Star Trek starship Enterprise studio model – “Considered Harmful” by the author

When the Boeing Milestones of Flight Hall opens in the summer of 2016, one of its central artifacts will be the Star Trek starship Enterprise studio model, used to film the original television series. As a member of the curatorial team that has been working on this exciting revision of the Milestones Hall, I have been immersed in the culture and lore of that artifact, as I have sought to place it in the context of the Lunar Module, Spirit of St Louis, Bell X-1, and other iconic artifacts that will populate the space. What follows are some observations.

On September 12, 1962, at Rice University in Houston, Texas, President John F. Kennedy gave a speech that stated the country’s commitment to landing human beings on the Moon and returning them safely by the end of that decade. In the speech’s most memorable passage, he said:

“We choose to go to the moon. We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win…”

That statement echoed one that was given over six decades earlier in 1900. At the second International Congress of Mathematicians in Paris, Professor David Hilbert listed a set of mathematical problems that he suggested his colleagues ought to be able to work on for the coming century. Like President Kennedy, Hilbert was remarkably prescient. His list of 23 problems served to define mathematics for the following century and beyond. In choosing such problems, Hilbert acknowledged that he could not foresee the future with any clarity, but he was guided by this criterion:

“…a mathematical problem should be difficult in order to entice us, yet not completely inaccessible, lest it mock our efforts.”

Professor David Hilbert

Professor David Hilbert

Though a much shorter passage than Kennedy’s, it stated the same thing. Progress in science and technology requires defining and attacking problems that are just within the realm of possibility, but not so far advanced that they doom us to frustration and endless disappointment. Before committing the nation to a Moon landing, the President conferred with advisers who told him that the United States, at the time behind the Soviet Union, could with a strenuous effort beat the Soviets to the Moon by the end of the decade. Like Hilbert before him, President Kennedy made the right call, although it was close.

How are we to know which current problems meet that criterion? The answer brings us to the current U.S. space program, and to the television series Star Trek, which aired for three seasons on network television beginning in the fall of 1966. There is no need to enumerate the many scientific theories and technical advances in that show; these have been documented and explained in the excellent book by professor Lawrence M. Krauss, The Physics of Star Trek (Revised Edition, Basic Books, 2007).

This book is owned by many Trek enthusiasts—among them Stephen Hawking, who wrote the forward to the second edition. Hawking makes the important point that, “There is a two-way trade between science fiction and science. Science fiction suggests ideas that scientists incorporate into their theories, but sometimes science turns up notions that are stranger than any science fiction.”

Why then the title of this blog post, which the reader may interpret as having a somewhat pessimistic attitude toward the show? Star Trek assumes a speed of travel that essentially places the entire galaxy within the range of a normal adult human lifetime. That concept does not pass David Hilbert’s test. Faster-than-light travel is worthy of study by physicists, and Hawking and his colleague Kip Thorne (whose ideas formed the basis of the recent movie Interstellar) have suggested avenues of research that may lead to it. But without an extreme form of warp drive, the entire premise of the television series collapses. Meanwhile, the popular press complains that the U.S. space program is moribund because we aren’t planting colonies on the Moon, sending humans to Mars, or building ships to take humans to Saturn, Jupiter, and their moons. All of this noise obscures the tremendous advances right in front of us. Among them are, to name a few:

  • Advances in launch vehicle technology, led by companies such as SpaceX
  • The development of ion propulsion, predicted decades ago but only now becoming a practical reality for spacecraft
  • Deep space guidance and navigation, as demonstrated by the pinpoint landing of Curiosity on Mars in the fall of 2012
  • The almost daily discovery of exoplanets in our galaxy, including some that are in the habitable “Goldilocks” zone
  • Advances in robotics, from companies such as Boston Dynamics
The LS3 developed by Boston Dynamics.

The LS3, a rough-terrain robot, developed by Boston Dynamics. Image Courtesy: Boston Dynamics

  • The development of computer-based imaging, giving us new tools to analyze telescope data and spectacular images from the Hubble Space Telescope
  • Advances in artificial intelligence (AI), a dream of computer scientists where progress had been agonizingly slow, but is now accelerating at a fast pace
  • The further understanding of the elementary particles that make up our universe, as a result of the operation of the Large Hadron Collider
Large Hadron Collider - Credit & Copyright: Maximilien Brice, CERN

Large Hadron Collider – Credit & Copyright: Maximilien Brice, CERN

  • The increased accessibility of general and scientific knowledge that has been enabled by the Internet

Some of these were hinted at in Star Trek episodes, but for me, the sum of these goes far beyond the world envisioned by Gene Roddenberry 50 years ago.

We will restore the Enterprise, and it will be a fantastic addition to the Milestones Hall. But as I have said elsewhere, space exploration does  not always follow the trajectories we want it to. As for visiting other intelligent civilizations in our galaxy?  An attempt to develop warp drive would “mock our efforts,” as Hilbert warned. I suggest an avenue of research that is “difficult enough to entice us, yet not completely inaccessible.” That would be the development of AI to a point where we can download our consciousness onto swarms of robotic spacecraft and send them out into the galaxy. I predict that a first step along these lines will become a reality within my lifetime.

Among the problems that David Hilbert proposed in 1900 was #10: whether it could be “decided” that a certain mathematical function was solvable or not.  A variant of that problem was eventually solved, in the negative, by the Cambridge mathematician Alan Turing. Hilbert had hoped for a positive answer to the “Decision Problem,” but Turing’s 1936 paper laid the theoretical foundations for the digital computer—a device that is only present in a rudimentary form in Star Trek, by the way. Hilbert was on to something after all.

To the skeptics who wonder why the Utopia of space travel implied by the Apollo landings of 1969-1972 has not come to pass, I would only say that we are living in an age of discovery that has no parallel in human history.  Let’s embrace it.

Paul Ceruzzi is a curator in the Space History Department at the National Air and Space Museum.

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Walking in Space: Our Favorite Facts about the First U.S. Spacewalk

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The first spacewalk by an American, which took place 50 years ago today, marked a new chapter in human exploration of space. Images of Edward White II floating in space with the backdrop of a beautiful blue and white Earth spread a sense of wonder around the world – humans could actually go to this place and it was amazing. While the spacewalk (or EVA, which stands for extra-vehicular activity) lasted less than 20 minutes, its significance for the future of human spaceflight in the American context cannot be underestimated. This was the start of how we understood human activity in the setting of space, and like a child, these first tentative and careful steps led to decades of new capabilities. Working in the vacuum of space, however, took years to make efficient and was dependent on the creation of tools like handholds, better gloves, and specially adapted equipment that would make building and maintaining vehicles possible.

During the five-month long exhibition Outside the Spacecraft: 50 Years of Extra-Vehicular Activity, I have awaited this last week of activity as (sadly) the end of a very successful exhibition, but also the moment we get to mark the anniversary of White’s spacewalk during the Gemini IV mission. Visitors to the Museum in DC now have a rare opportunity to see the capsule uncovered (without Plexiglass) while we renovate the Boeing Milestones of Flight Hall. For our visitors online, I wanted to share a few interesting facts about Gemini IV, its crew, and that game-changing spacewalk.

1. Commander James McDivitt and Ed White became fast friends during their time in the Aeronautical Engineering program at the University of Michigan, which they both graduated from in 1959. They both moved on after graduation to the test pilot school at Edwards Air Force Base, frequently flying together. This made them uniquely compatible for the second Gemini mission.

2. McDivitt and White were members of the “New Nine” class of astronauts, the second ever selected, and were both rookies. Their backup crew consisted of fellow “New Nine” classmates, and future Gemini VII crew members, Frank Borman and James Lovell.

3. McDivitt discovered a potential problem with the spacecraft hatch during a vacuum chamber test when a spring failed to compress correctly. Having studied the mechanism, he was well prepared with a work-around during the flight when the spring caused trouble during the opening and closing of the hatch for the spacewalk.

4. Communication circuits between the astronauts and the ground malfunctioned during the EVA, leading to the need for McDivitt to relay all ground communications to White. This was particularly complicated when mission control wanted White to return to the spacecraft and the faulty circuits, and two exuberant astronauts, delayed the end of the spacewalk.

White against the backdrop of the Earth.

5. For reasons I can only speculate about, the camera attached to the top of White’s maneuvering unit, a Zeiss Contarex, is owned by the National Museum of the U.S. Air Force, but the lens is in the Museum’s collection. My suspicion is that because the “zip gun,” as the maneuvering unit was called, was a contract through the Air Force, they likely supplied the camera as well. It was later transferred to their own museum, while the lens, presumably supplied by NASA, passed to the National Air and Space Museum with other Gemini IV equipment.

Zeiss Contarex camera and lens used by White.

6. The thermal gloves seen covering White’s hands in photographs were important to keeping his hands warm, but one snuck out of the hatch before the astronauts got it closed.

White’s glove can be seen at the top of this film clip. See it escape at minute 1:34 in the video above.

7. The spacesuit’s pressure gloves, underneath the thermal gloves during EVA, were designed with the clever feature of fingertip lights, which White could activate with a small button in order to see cabin controls better during the 45 minutes of dark on each orbit.

Ed White’s mission gloves.

Despite the accomplishments and lessons learned during Gemini IV, the success became somewhat bittersweet at NASA. White would lose his life just 18 months later when a fire started in the command module during a launch pad test for the first Apollo mission. McDivitt went on to command Apollo 9, the first test of the lunar module. The accomplishments and experiences of McDivitt and White during their Gemini IV mission, however, are more than just the story of a spaceflight. They illuminate for us the earliest moments of how we think about human work in space, the quick thinking it takes to overcome obstacles in low and zero gravity environments, and the teamwork needed to make space exploration a success.

Jennifer Levasseur is a museum specialist in the Space History Department of the National Air and Space Museum and is the curator of  Outside the Spacecraft: 50 Years of Extra-Vehicular Activity which will close on June 8, 2015. 

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