AidSpace Blog

Casting Shadows on the Moon

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Much of the Moon is blanketed by a thick layer of dust, built up from the rocky surface over billions of years by the impacts of small meteorites. Hidden beneath the dust is evidence of ancient geologic activity – great volcanic eruptions, tectonic shifts in the crust, and vast deposits of once-molten material hurled outward during the formation of the giant impact basins.

Smithsonian scientists, using the world’s two largest radio telescopes, bounce radar signals off the Moon to map these geologic features below the surface. Radio signals have a much longer wavelength than visible light, so they penetrate far into the dry lunar dust and reflect back from boulders and rugged surfaces beneath. The radar maps are created by measuring with great precision the round-trip time of the echoes and the shifts in frequency created by the slow spin of the Moon.

A radar image of the Moon collected using the Arecibo Observatory and Green Bank Telescope in 2015. The dark ring is caused by the shape of the radar beam. The north pole of the Moon is at the bottom center of this image. Younger craters with rugged floors and rims are very bright. Bruce Campbell, Smithsonian Institution

Radar images look like photographs, but the illumination is provided entirely by the transmitted signal so the position of the Sun (the phase of the Moon) does not matter. Sometimes the lighting provided by the radar, especially when it falls on terrain near the visible edge of the Moon, can lead to long shadows behind mountains and ridges.

A radar view of Bel’kovich-A crater (58 km/36 miles in diameter) near Mare Humboldtianum on the Moon. The radar shadows cast by the mountainous crater rim can be seen clearly on the crater floor. Bruce Campbell, Smithsonian Institution

Radar can also “see” into craters near the Moon’s poles that are never lit by the Sun, which are of great interest as traps for icy material delivered to the surface by comets. For these polar mapping observations, the slow wobble (or libration) of the Moon becomes important, as it alternately brings the two poles into better view from Earth. Radar images collected at different times during this cycle can look very much like photos taken at different times of day, but with the shadows aligned with the direction of the incident radar signal rather than with the Sun.

Radar views of an area near the Moon’s north pole collected on different days. In the left image, the Moon’s wobble has brought more of the polar region into view, so the shadows of the large mountain at center are shorter. Bruce Campbell, Smithsonian Institution

 

A more detailed explanation of the radar mapping and image products may be found on the Museum’s website.

Bruce Campbell is a Senior Scientist and Chair of the Center for Earth and Planetary Studies at the National Air and Space Museum.

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Lippisch DM 1 Reconsidered – Part 4

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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 3, the glider was tested in the National Advisory Committee for Aeronautics (NACA) Full-Scale Wind Tunnel. In this final post, Russ and Evelyn connect those early tests with the world’s first delta wing aircraft. 

We have found no written confirmation that Convair incorporated the NACA data from the DM 1 directly into their groundbreaking work to design and build the first jet-propelled delta wing aircraft. Yet it must be so. When the Convair XF-92A became the world’s first delta wing aircraft to fly on September 18, 1948, it marked the triumphant culmination to a project that started in September 1946. Convair’s goal was to develop and evaluate the aerodynamic characteristics of the delta wing configuration by flight-testing an experimental prototype aircraft called the Model 7002. The Air Force renamed this aircraft the XF-92A in May 1949. Recall that NACA tested the DM 1 in the wind tunnel in April, June, August, and November of 1946. Interest in the DM 1 probably led to the visit that Convair Chief of Aerodynamics Ralph H. Shick made to DM 1 designer Alexander Lippisch in July 1946. In October, Lippisch and two other German scientists moved for a few weeks to Convair’s home airfield in San Diego. Convair had plenty of time to study the DM 1 wind tunnel data, consult with Lippisch and his colleagues, and then incorporate the results during design and construction of the Model 7002.

The NACA stored the DM 1 in a shed at Langley Field in January 1948 and then offered it to the Smithsonian in November 1949. Unaware of the significance of the DM 1, Paul Garber declined the offer so NACA transferred the glider to the Air Force Museum at Wright-Patterson Air Force Base in Ohio. As a decade passed, the U.S. Air Force placed into service hundreds of delta-wing fighters and flight tested the supersonic delta-wing Convair B-58 Hustler. These developments helped to convince the Smithsonian to acquire the DM 1 when the Air Force Museum offered it in 1959. The glider was too large to ship in one piece so craftspersons removed the wing tips and vertical fin before the aircraft arrived at the Smithsonian. Collections staff moved the DM 1 from the Paul E. Garber Facility to the Mary Baker Engen Restoration Hangar at the Steven F. Udvar-Hazy Center, in Chantilly, Virginia, in 2011.

Joe Chambers summed up the DM 1 legacy this way: “The DM 1 activity was one of the first at Langley to exploit control of vortex flows for high-angle-of-attack performance, and led to an ongoing program of increasing interest with industry and [the Department of Defense] over several decades that ultimately led to the use of structural airframe devices called wing leading-edge extensions.” Today, leading edge extensions are fitted to many domestic and foreign military aircraft and they function just as the Lippisch DM 1 did in the Full-Scale Tunnel at Langley after NACA engineers added the thin metal leading edges in 1946.

Visitors study the DM 1 as it dangles from a chain hoist attached to an A-frame during the Open House at the Steven F. Udvar-Hazy Center in January 2014. In this photograph, the outboard pair of eleven control surfaces is stored elsewhere but the inboard elevons are visible along with the original left wing tip on the shop floor. The Air Force Museum had to remove both wing tips to ship the glider to the Smithsonian in 1959. The original fin covered the gap visible in the middle of the wing. Photo: John Bretschneider

Lippisch designed a cutout section of the nose and covered it with clear plastic to allow the pilot to see the ground when the glider was flying at high pitch angles. This view shows the clear plastic removed from the cutout. Photo: Scott Willey

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.

Sources:
Bradley, Robert E. “The Birth of the Delta Wing,” American Aviation Historical Society, Winter 2003.
Chambers to Lee email, 3/29/15.
Lippisch DM 1 Curatorial files, National Air and Space Museum.


Previous Posts in the Series: Part 1, Part 2, and Part 3.

Did you enjoy this series? Would you like to see more? Let us know what you think in the comments. 

 

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Obscure Objects: Buck Rogers Spaceship Toy

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“Buck…Rogers…in the twenty-fifth CEN-TURYYY!” This enthusiastic refrain from a deep-voiced announcer is how the popular 1930s radio show featuring space hero Buck Rogers began. It was followed by the roar of a spaceship blasting off, simulated by the sound of an air conditioning vent.

Many of you have probably never heard of Buck Rogers, but he was a household name in the 1930s and ‘40s. Rogers was the very first science fiction comic strip hero.

The character, at first named Anthony Rogers, was introduced in the first science fiction magazine, Amazing Stories, in August 1928. In a story titled, Armageddon 2419 A.D., written by Philip Nowlan, Rogers was a 29-year-old World War I veteran who took a job inspecting mines for radioactive gases. One day, the mine caved in, trapping Rogers and surrounding him with mysterious gases that caused him to pass out. When he awoke, 500 years had passed, and the first person he saw was the beautiful, spunky Wilma Deering, a lieutenant in the Space Corps, who informs him the world has been taken over by evil Mongolians. This reflected the biases at the time against Asians embodied in such Asian supervillains.

You can imagine the adventures that ensued for Rogers and Deering in this futuristic society, with a host of amazing gizmos at their disposal. It’s a classic tale of good versus evil in a fictional world of the future.

The story led to the creation of a comic strip debuting in January 1929, with Anthony renamed “Buck,” which sounded more heroic and capitalized on the popularity of Westerns at that time. This was followed by a radio show, which began in 1932. Both the comic strip and radio show were wildly popular and soon Buck Rogers merchandise was everywhere. According to Toy Collector magazine, “Over the next decade, rockets, ray guns, figures, books, cards, premiums, spacesuits, helmets, printing sets, puzzles, pencil cases, sneakers, skates, buttons, watches, rings, and other products bearing Buck’s image or name flooded the marketplace.”

Which brings us to our obscure object: a 1934 toy Buck Rogers Rocket Police Patrol spaceship.

Buck Rogers spaceship toy. Photo by Eric Long NASM2014-04377

The green and red spaceship measures 31.8 x 10.2 x 12.7 centimeters (12 1/2 x 4 x 5 inches) and is made of tin. It was manufactured by Louis Marx & Co., which advertised it as a “flashing roaring speeding sky police patrol rocket ship” that “shoots out harmless sparks as it darts across the floor.” You can see it in the Barron Hilton Pioneers of Flight Gallery in the Museum in Washington, DC.

Collector Michael O’Harro, a successful businessman and restaurateur, donated the spaceship to the Museum in 1993, along with his entire 2,200-piece science fiction collection. Frank Winter was the popular culture curator at the time of the donation.

“I was astounded,” recalled Winter in a May 2002 article in Air & Space magazine. “It was like walking into Tut’s Tomb!” The article goes on to say, “Over the years, O’Harro had collected many rare items, including original comic strips, a Buck Rogers watch, tin spaceships, lead figures, games, trading cards, and a prototype ray gun that was used to create a production toy. Although most centered on Buck Rogers, there were also items based on Flash Gordon and even Captain Video. O’Harro’s collection spanned the entire history of space toys, from Buck Rogers in the 1920s to Star Wars in the 1980s.”

Other items from O’Harro’s collection, such as ray gun toys, are on display in the James S. McDonnell Space Hangar at the Udvar-Hazy Center and in the Barron Hilton Pioneers of Flight Gallery.

Why would a museum that possesses the most iconic artifacts from aviation and space history collect such “silly” items as science fiction toys? According to the current popular culture curator, Margaret Weitekamp, “Science fiction toys show us how people have imagined spaceflight. Some of those visions inspired real discoveries—and real engineers. The Buck Rogers toys demonstrate Americans’ excitement about spaceflight even decades before the first humans launched into space.”

For more on Buck Rogers and the O’Harro collection, listen to Buck Rogers radio shows on the Old Time Radio Lover website, learn about ray gun toys in this blog post by Margaret Weitekamp, and read the above-mentioned Air & Space article. Also, you can view a large array of Buck Rogers comic strips by googling that phrase.

Kathleen Hanser is a writer-editor in the Office of Communications at the National Air and Space Museum.

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The NACA/NASA Full Scale Wind Tunnel

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The Scene: A new wind tunnel, the NACA Full Scale Tunnel at the NACA Langley Memorial Aeronautical Laboratory, Hampton, Virginia

The Time: May 27, 1931

The Action: A Navy Vought O3U-1 “Corsair II” –the whole airplane—is mounted in the wind tunnel. The airplane engine is turned on, and shortly the airplane is “flying” at 120 miles per hour. But, in reality, this airplane is standing still, and the air in the wind tunnel is blowing over it at 120 miles per hour.

The significance: This is the first test carried out in the new National Advisory Committee for Aeronautics  (NACA), the precursor to NASA, Full Scale Tunnel (FST), not on a model of the airplane, but on the airplane itself. Here is the advantage of the FST–a whole airplane could be mounted in the cavernous test section, which is 9 meters (30 feet) high and 18 meters (60 feet) wide, thus eliminating the uncertainty associated with testing small models in small wind tunnels due to so-called “scale effects.”

Vought O3U-1 “Corsair,” the first airplane tested in the Full Scale Tunnel.

For the next 10 years, the Langley FST would be the largest wind tunnel in the world. It was a major factor in enhancing the world-wide presence of the United States in aeronautics. Moreover, for the next 78 years, virtually every American fighter airplane through the Lockheed Martin F-22 was tested in the FST. Of particular importance was the major series of tests called the “drag cleanup tests,” conducted during the period from 1938 to 1945. For these tests, a given airplane in its full operational configuration would be systematically stripped one-by-one of its external appendages, and rough contours smoothed over with putty, until just the smooth basic shape remained. The aerodynamic drag was measured at each stage, identifying the drag due to each item. In this fashion, those items causing the most drag were identified and modified so as to lower the overall drag of the airplane. These drag cleanup tests contributed to the increased speed of many U.S. airplanes during World War II.

On March 6, 1943, a unique two-day test commenced in the tunnel; it was the most secret test ever conducted in the Full Scale Tunnel, and it has come to light only recently. The story began on June 4, 1942 when Japanese warplanes attacked the American military base at Dutch Harbor in the Aleutians. During this attack, a Japanese Mitsubishi Zero fighter had its oil line severed by ground fire, and the pilot had to make an emergency landing in what seemed to be a field of grass. The grass, however, concealed a bog covered with water and mud. The landing gear of the airplane dug in, the plane flipped over on its back, and the pilot was killed. The crashed airplane was spotted a month later by a U. S. Navy patrol airplane, and an inspection showed it to be salvageable. It was the first flyable Japanese Zero to fall into U.S. hands–a warplane of great value.

The airplane was tested by the U.S. Navy at San Diego and at Anascostia in Washington, D.C. Then it was flown to the NACA Langley Memorial Laboratory for the installation of special instrumentation. It arrived at Langley about 3:00 pm on Friday, March 5, 1943 and was parked in plain sight on the Langley flight line. That night, under the cover of darkness, the Zero was secretly mounted in the Full Scale Tunnel, and for two days was tested under wraps. A special wind tunnel crew was sworn to absolute secrecy. When light dawned on Monday morning, the airplane was back at its original location on the flight line, as if nothing had happened. Existence of these secret tests came to light 67 years later when Joe Chambers, a previous director of the Full Scale Tunnel, interviewed some  of the retired Langley personnel who participated in these secret tests. No photographs of the Zero in the wind tunnel exist, and Chambers was unable to find the test results anywhere, so intense was the secrecy. But these tests underscored the value of the Full Scale Tunnel–nowhere else could a whole enemy airplane be flown into Langley Air Field on its way to Wright Field, rolled off the runway, spirited into the wind tunnel, tested in such an impromptu manner under the veil of the strictest secrecy, and have almost nobody know about for 67 years.

Captured Japanese Zero on the flight line at the NACA Langley Memorial Aeronautical Laboratory. Photo: NASA

Captured Japanese Zero on the flight line at the NACA Langley Memorial Aeronautical Laboratory. Photo: NASA

The post-war years at the NACA focused on high-speed aircraft in the flight range towards Mach 1. However, these aircraft had to take off and land at low speeds, and the Full Scale Tunnel was an ideal facility for such low-speed tests. Also, helicopter testing became more frequent in the Tunnel as well.

In 1958 the NACA morphed into NASA, and the national space program went into full-tilt. Although space vehicles in low earth orbit travel at about 7,925 meters (26,000 feet) per second, and those intended to go the Moon and back enter the Earth’s atmosphere at 10,973 meters (36,000 feet) per second, these extreme hypersonic vehicles still have to land at low speeds, and once again the (now) NASA Langley Full Scale Tunnel became a workhorse for low-speed testing of the Air Force Dyna-Soar reentry glider, the Mercury Space Capsule, and the HL-10 lifting body. Also, during this period, free-flight testing of models commenced in the FST; this involved “flying” the models in the tunnel airstream by remote control. The large size of the Full Scale Tunnel test section facilitated such free-flight testing, which continued through the remainder of the FST days before demolition started. (Indeed, the National Air and Space Museum has in it collection a free-flight model of the futuristic Boeing X-48 blended wing body that was flown in the wind tunnel. It is currently on display in the How Things Fly gallery in the Museum in Washington, DC.) These free-flight tests were pioneering because they freed the model from any structural attachment to the tunnel such as being mounted on a force balance, and allowed the stability and control characteristics of the model to be tested and observed, unhindered by any fixed attachment. In the 1960s and ’70s, there was  a great deal of interest in the aerodynamic characteristics of aircraft at very high angles of attack, and once again models were flown remotely in the Full Scale Tunnel at angles of attack of near 90 degrees in order to study such aerodynamic behavior.

In 1985, The U.S. Department of the Interior designated the Langley Full Scale Tunnel as a National Historic Landmark. However, being such a landmark did not guarantee that the facility would be exempt from eventual demolition. In the early 1990s the pressure on NASA to reduce its wind tunnel inventory became overwhelming, and the director of Langley at that time, Paul Holloway, looked for a non-traditional way of preserving the Full Scale Tunnel. He found the answer in the form of nearby Old Dominion University. He approached Jim Cross, dean of Old Dominion’s College of Engineering, and encouraged him to submit a proposal to Langley for the college to take over the operation of the Full Scale Tunnel. Cross saw the opportunity to use the facility for some non-traditional aerodynamic testing. On August 19, 1997, Old Dominion University took over the operation of the Full Scale Tunnel. The tunnel became the largest university-operated tunnel in the world. Old Dominion University operated the tunnel from 1996 to 2009. During that time such non-traditional models including a reproduction of  the 1903 Wright Flyer by the Wright Experience  and NASCAR  racers  were tested.

Replica of the 1903 Wright Flyer in the Full Scale Tunnel. Photo: NASA

Boeing X-48, the final test conducted in the Full Scale Tunnel. Photo: NASA

However, On September 4, 2009, the last test was run in the FST; the configuration tested was a Boeing X-48  blended wing body. Demolition started, and was completed by May 18, 2011, almost 80 years to the day after the facility was dedicated in 1931. Virtually the only artifact that remains from this historic tunnel is one of the two drive fans, acquired by the National Air and Space Museum.

This fan assembly was installed in the Museum’s Boeing Milestones of Flight Hall in February 2015.

The Wind Tunnel fan in its original configuration at the NACA Full Scale Tunnel. Photo: NASA

NACA Wind Tunnel fan in the Boeing Milestones of Flight Hall in the Museum in Washington, DC.

John D. Anderson, Jr., is a curator of Aerodynamics in the Aeronautics Department.

Reference: The definitive history of the FST is detailed in Cave of the Winds, by Joseph R. Chambers, NASA SP-2014-614, 2014. Joe Chambers was the Director of the FST from 1974 to 1981.

 

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Lippisch DM 1 Reconsidered – Part 3

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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 2, U.S. Army General George S. Patton ordered the students to resume construction of the glider at the Prien Airport. A number of American visitors arrived to witness the construction of the DM 1, including the famous American pioneer of aerodynamics Walter Stuart Diehl.

Another famous visitor to Prien airfield was Charles A. Lindbergh. According to German historian and author Hans-Peter Dabrowski, Lindbergh inspected the DM 1. We know that Lindbergh crisscrossed Germany with the U. S. Naval Technical Mission investigating the newest developments in aircraft and missiles made by German scientists and engineers. In June 1945, he arrived at Prien airfield and talked at some length to Dr. Felix Kracht about a supersonic, swept-wing rocket glider and a ramjet engine that used coal for fuel, but in his book, The Wartime Journals of Charles A. Lindbergh, Lindbergh does not say he personally inspected the DM 1.

What is certain is that construction work on the glider resumed during the summer of 1945 and ended a few months later. The finished aircraft spanned 6 m (19 ft 8 in), the tip of the vertical tail reached  3.2 m (10 ft. 7 in.), and empty it weighed 374 kg (825 lb). Joe Chambers wrote in his book, Cave of Winds: The Remarkable History of the Langley Full-Scale Wind Tunnel, that in August, American officials considered testing the DM 1 in Germany by launching it from atop a twin-engine Douglas C-47 transport, but they also may have considered towing it aloft on a cable behind the C-47. Whatever their initial intent, the Americans soon abandoned the idea of flying the glider and set about moving it to the U.S. for further evaluation. American personnel placed the aircraft into a large wooden crate designed and built specifically to protect it in one piece. Men in a truck hauled the crate away on November 9 and dropped it off in Mannheim, Germany, where workers loaded it aboard a ship that sailed to Rotterdam. The DM 1 moved from Rotterdam to Boston and arrived there on January 19, 1946. Two days later, the Army Air Forces Material Command asked the National Advisory Committee for Aeronautics (NACA) to evaluate the DM 1 using the Full-Scale Tunnel (FST) at the Langley Memorial Aeronautical Laboratory at Langley Field, Virginia. Another ship carried the glider down the East Coast to Norfolk where a truck moved the aircraft to Langley Field.

Joe Chambers noted that aerodynamicists tested the DM 1 in three phases in April, June, and November 1946. American companies such as Convair had developed an independent interest in delta-wing aircraft and they tested small models in wind tunnels to determine the high-lift characteristics of these designs. When initial NACA tests of the DM 1 failed to produce the amount of lift at angles of attack that U.S. companies had expected, the work turned to modifying the German glider until its performance matched that revealed by the small models. During this process, the NACA researchers began to appreciate the importance of the rather blunt leading edges of the DM 1 wings. Technicians added sharp leading edges similar to classical stall strips to the wings, they reshaped the vertical fin and removed it for some tests, and they modified the control surfaces. Aerodynamicists and engineers conducted extensive flow visualization tests using small strands of wool attached to the upper surfaces of the wings. Wind tunnel tests continued and the modified wings exhibited strong swirling vortex airflows over the top surface of the wings at low speeds and high angles of attack.

Each metal strip that technicians attached to the leading edges of the DM 1 wings was 130 inches long. Herbert A. Wilson, Jr., and J. Calvin Lovell, “Full-Scale Investigation of the Maximum Lift and Flow Characteristics of an Airplane Having Approximately Triangular Plan Form,” NACA Research Memorandum No. L6K20, 12 February 1947, Langley Memorial Aeronautical Laboratory, Langley Field, VA

Each metal strip that technicians attached to the leading edges of the DM 1 wings was 330 cm (130 in.) long. Illustration Source: Herbert A. Wilson, Jr., and J. Calvin Lovell, “Full-Scale Investigation of the Maximum Lift and Flow Characteristics of an Airplane Having Approximately Triangular Plan Form,” NACA Research Memorandum No. L6K20, February 12, 1947, Langley Memorial Aeronautical Laboratory, Langley Field, VA

Figs. (a) and (b) show that without the thin metal leading edges, no vortex formed above the DM 1 wings in the wind tunnel at high angles of attack and low speeds. With the metal edges attached, Figs. (c) and (d), powerful vortices formed at the leading edges and extended back beyond the trailing edge, resulting in increased lift at low speeds. Herbert A. Wilson, Jr., and J. Calvin Lovell, “Full-Scale Investigation of the Maximum Lift and Flow Characteristics of an Airplane Having Approximately Triangular Plan Form,” NACA Research Memorandum No. L6K20, 12 February 1947, Langley Memorial Aeronautical Laboratory, Langley Field, VA

Figs. (a) and (b) show that without the thin metal leading edges, no vortex formed above the DM 1 wings in the wind tunnel at high angles of attack and low speeds. With the metal edges attached, Figs. (c) and (d), powerful vortices formed at the leading edges and extended back beyond the trailing edge, resulting in increased lift at low speeds. Illustration Source: Herbert A. Wilson, Jr., and J. Calvin Lovell, “Full-Scale Investigation of the Maximum Lift and Flow Characteristics of an Airplane Having Approximately Triangular Plan Form,” NACA Research Memorandum No. L6K20, 12 February 1947, Langley Memorial Aeronautical Laboratory, Langley Field, VA

This video shows the DM 1 inside the FST at Langley during a test on August 1, 1946. Smoke makes the airflow visible. At video time 1:22, a metal strip attached to the right wing leading edge can be seen causing a powerful vortex to stream over the wing. This vortex was critical to preventing the wing from stalling when flown at the high angles of attack required to slow down the delta for landing. The vortices also helped the pilot maintain directional control about the yaw axis using the rudder.

These findings were important. They gave the designers of delta-wing aircraft confidence to proceed with building and flight testing an experimental piloted delta-wing aircraft equipped with a thin wing required for transonic flight because they knew the delta would be stable and controllable at the low speeds needed for takeoff and landing, thanks to the strong vortex flow generated by the sharp leading edge at high angles of attack. Designers had known for years that flight at transonic speeds required a thin and low-aspect ratio form to minimize drag. What no one understood before NACA’s work with the DM 1 was how to stabilize and control these configurations at low airspeeds so that pilots could land using a conventional aircraft landing gear. After all, there was no point in taking off and flying fast enough to break the sound barrier if landing was impossible. The Langley Laboratory team that studied and modified the DM 1 deserves mention: Sam Katzoff, J. Calvin Lovell, and Herbert A. Wilson, Jr. (Chambers, Cave of Winds, 190-226).

NACA’s work was critical to transforming the delta wing concept into a practical application, but the basic idea about sharp leading edges that generate vortex flow dates to the inter-war period. In a paper describing the DM 1 tests at Langley, NACA aerodynamicists Herbert Wilson and J. Lovell cited the work of German aerodynamist H. Winter who observed votices form over rectangular plates that were thin and flat. Winter published his observations in 1936 (see below, Sources).

Lippisch DM 1 in original configuration mounted in the 9 m x 18 m (30 ft x 60 ft) test section of the Langley Full-Scale Tunnel at the Langley Memorial Aeronautical Laboratory at Langley Field, Virginia. At left inside the large oval-shaped duct are the two 10.5 m (35-ft) tunnel propellers, each powered by a 4,000-horsepower electric motor, which moved air through the tunnel at speeds between 40-190 km/h (25-118 mph). NASM displays one of these enormous fans in the Boeing Milestones of Flight Gallery on the Mall in Washington, D. C. Photo: NASA Langley Research Center, LMAL 47684

Lippisch DM 1 in original configuration mounted in the 9 m x 18 m (30 ft. x 60 ft.) test section of the Langley Full-Scale Tunnel at the Langley Memorial Aeronautical Laboratory at Langley Field, Virginia. At left inside the large oval-shaped duct are the two 10.5 m (35 ft.) tunnel propellers, each powered by a 4,000-horsepower electric motor, which moved air through the tunnel at speeds between 40-190 km/h (25-118 mph). The Museum displays one of these enormous fans in the Boeing Milestones of Flight Gallery in Washington, D. C. Photo: NASA Langley Research Center, LMAL 47684

 

During the evaluation program, the Langley Laboratory team modified the Lippisch DM 1 with a new and smaller vertical fin, bubble canopy, and thin metal leading edges. Technicians attached strips of wool called tufts to the top surface to reveal the airflow and painted the surface white to make the tufts stand out in black-and-white photographs. Photo: NASA Langley Research Center, LMAL 49146

During the evaluation program, the Langley Laboratory team modified the Lippisch DM 1 with a new and smaller vertical fin, bubble canopy, and thin metal leading edges. Technicians attached strips of wool called tufts to the top surface to reveal the airflow and painted the surface white to make the tufts stand out in black and white photographs. Photo: NASA Langley Research Center, LMAL 49146

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.

Sources:
Bradley, Robert E. “The Birth of the Delta Wing,” American Aviation Historical Society, Winter 2003.
Chambers, Joseph R. Cave of Winds: The Remarkable History of the Langley Full-Scale Wind Tunnel, (NASA SP-2014-614), 2014.
Chambers to Lee email, 4/20/15.
Wilson, Herbert A., and Lovell, J. Calvin. “Full-Scale Investigation of the Maximum Lift and Flow Characteristics of an Airplane Having Approximately Triangular Plan Form,” NACA Research Memorandum RM No. L6K20, 12 February 1947, Langley Memorial Aeronautical Laboratory, Langley Field, VA.
Winter, H. “Strömungsvorgange an Platten und Profilierten Körpern bei kleinen Spannweiten [Flow Phenomena on Plates and Airfoils of Short Span],” VDI-Special Issue (Aviation), 1936, translated by S. Reiss and published in NACA Technical Memorandum No. 798, July 1936, Washington, D. C.

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