Monthly Archives: December 2011

Leaving the Moon, Watching at Home

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Apollo 17

The Apollo 17 ascent stage lifts off from the Moon, marking the last time humans left the Moon on December 14, 1972.

After pressing some buttons to start up the ascent engine of their lunar module Challenger, astronauts Gene Cernan and Harrison Schmitt left the Moon on December 14, 1972. That’s 39 years ago – before many of us were even born. While these men looked out the tiny triangular windows of the lunar module to see the lunar surface getting farther away, viewers around the world watched that same spacecraft leave the Moon, live and in color on their television sets. Departing the Moon for the last time was (not surprisingly, perhaps) far less interesting to most people than Apollo 11’s first landing over three years prior. Some evidence even suggests that NASA had to pay television networks to cover Apollo 17’s mission at all. Despite all their hard work and technological developments, the final liftoff of humans from the Moon came and went with just a brief notice on the nightly news.

That story, however, overlooks the difficulties engineers had in developing the ability to show the lunar module rocketing back into space. Television cameras of the late 1960s and early 1970s were notoriously bulky, usually requiring huge rolling bases or portable stands. For space use, any piece of equipment needed to be light-weight and easily portable. NASA awarded contracts to build television cameras for Apollo alternately to RCA and Westinghouse, and both companies managed to build units for different missions that met NASA standards for weight, materials, and functionality. For the final three Apollo missions, RCA provided small, portable, color television cameras that could show the astronauts stepping off the lunar module and onto the Moon, and then be moved to a stand or the lunar rover for mobile exploration.

The cameras were very successful, capturing images of numerous EVAs that included sample collection, a driver’s eye-view from the mobile rover, and the pitfalls of trying to just stay standing in a space suit in 1/6 gravity. For the lunar liftoff though, engineers had numerous calculations to make prior to the mission to allow for filming. Attached to a pan and tilt unit, the television camera could be controlled directly from Earth via a large high-gain antenna on the rover. Since signals to and from Earth are delayed by a few seconds due to the 240,000 mile distance, mission engineers suggested pre-programming the lunar module liftoffs for Apollo missions 15, 16, and 17. Based on mathematical calculations, the rover would be driven and left some distance from lunar module, and the camera would automatically tilt up to show the ascent when commanded by the operator on Earth.

That was the plan at least.

On Apollo 15, the tilt mechanism malfunctioned and the camera never moved upwards, allowing the lunar module to slip out of sight. And while the attempt on Apollo 16 gave a longer view of the lunar module rising up, the astronauts actually parked the rover too close to it, which threw off the calculations and timing of the tilt upwards so it left view just a few moments into the flight.

Thankfully, for NASA, those watching at home, and anyone reviewing film footage today, the third attempt was the charm. Cernan and Schmitt parked the rover at just the right distance, all of the mechanisms worked flawlessly, and viewers can still see today how that awkwardly-shaped ascent stage keeps going up until it becomes just a bright speck the sky on its way back to the command module.

How we saw and continue to see the Apollo program is due not only to the engineers at RCA for creating this unique ability, but also the NASA camera operator in Houston, Ed Fendell, for getting the timing just right, and NASA itself for recording and preserving these moments for our collective memory of our last departure from the Moon.

How big of a part do you think NASA’s television coverage of Apollo 17 plays in how we think about that time period? Do you think the same is true of the end of the Space Shuttle program in 2011?

 

Apollo 17

A view of the Apollo 17 landing site as seen from the lunar module ascent stage as it left the surface. On the left, you can see the descent stage, the small gold-colored circle, and numerous tracks leading away from it, marking the paths astronauts took on their extra-vehicular activities.

Jennifer Levasseur is a museum specialist in the Space History Division of the National Air and Space Museum, and is responsible curator for the Museum’s collection of space cameras and early human spaceflight astronaut equipment.

The Santa Claus Express, Then and Now

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Santa Claus

NASM 7A45388; Courtesy of the Goodyear Tire & Rubber Company Records, the University of Akron, University Libraries, Archival Services.

 

In 1925, Mr. S. Claus was looking for a modern alternative to his old-fashioned reindeer-powered sleigh. Having once shown an interest in lighter-than-air flight in the form of hot-air balloons, Santa was favorably inclined when Goodyear came up with a solution — toy delivery via airship, in this case, Pilgrim I, renamed the Santa Claus Express for the occasion. In the photograph shown here, Pilgrim’s pilot Carl Wollam holds the gondola door for Santa (as portrayed by Goodyear employee Jack Yolton). Curiously, they seem to be unconcerned about the effect of drag from the presents festooning the gondola, but as Pilgrim’s top speed was only about 40 MPH, it probably didn’t make much of a difference. Here are some more photographs of Goodyear’s Santa Claus Express, 1925-1927, from the University of Akron’s library. By the way, the Pilgrim gondola is on display at the Museum’s Udvar-Hazy Center in Chantilly, Virginia — we might consider loaning it out to qualified Jolly Old Elves around this time of year…

 

santa

Photograph by Edward E. Ogden. Courtesy of the Goodyear Tire & Rubber Company

The Santa Claus Express was re-instituted by Goodyear last year to support the Marine Corps Reserve’s Toys for Tots program. Santa, portrayed in the photo shown above by Spirit of Goodyear mechanic Ron Heaps, and Spirit pilot Gerald Hissem re-enact the original Santa Claus Express photograph.

The staff and volunteers of the National Air and Space Museum hope that all of our readers, visitors and friends have a fine holiday season; and that whatever method of aerial transport Santa chooses, that you’ll get a visit from him on Christmas Eve.

 

Allan Janus is a museum specialist in the National Air and Space Museum’s Archives Division

 

 

The Rutan Voyager

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Twenty-five years ago, the staff of the National Air and Space Museum held its collective breath for nine days as a seemingly fragile, flying fuel tank made its way across oceans and continents in an attempt to become the first aircraft to fly around the world non-stop and unrefueled. The odd-looking bird had departed Edwards Air Force Base, California, on the morning of December 14, 1986, and the rest of the world was following as continuous sightings and updates flowed to the media, the Museum, and to the flight’s headquarters in Mojave, California. Everyone wondered if you really could fly around the world on one tank of gas?

 

Voyager

"Voyager" departing the coast of California on Dec. 14, 1986, soon to leave behind Burt Rutan in the Duchess chase plane.

As it turned out, you needed 17 tanks of fuel all in one vehicle from start to finish.  Voyager, the ultimate homebuilt, was the brainchild of unconventional designer Burt Rutan and two record-setting pilots, his brother Dick Rutan and Jeana Yeager.  Six years from initial conception on a napkin, as the story goes, to completion of the flight two days before Christmas in 1986, this trio successfully proved that lots of hard work and a little bit of luck could still make dreams come true.  Of course they didn’t do it alone.  A dedicated team of volunteers supported every aspect of the endeavor, but it was Dick Rutan and Yeager who beat the bushes for donations from the general public and corporate sponsors (they never did get a big-time sponsor) and built and tested the aircraft themselves. In the end, their dramatic quest created a public following that rivaled the flight-tracking of Santa Claus on Christmas Eve.

All of a sudden Museum curators were being asked who else had flown around the world, how and when were the flights accomplished, and was this really the last aviation milestone?  We knew the answers to the first two questions: in 1924, Army Air Corps crews flew two Douglas World Cruisers biplanes on the first round the world flight, a six-month marathon around oceans and through the arctic snow and tropical jungles — one of the airplanes, the Chicago, is in the Museum’s Barron Hilton Pioneers of Flight Gallery.  Then in 1957, three USAF B-52B bomber crews made the first non-stop flights around the world aided by aerial refueling.  No one seriously considered it possible to accomplish the flight without some sort of refueling, until Burt Rutan did.

The sheer audacity of assuming it could be done had to wait for dramatic changes in aircraft construction material and an out-of-the-box thinker. Weight, the ever-present penalty for aircraft, was the ultimate problem to be conquered.  How could you squeeze in enough fuel to fly nearly 25,000 miles and yet keep the aircraft light enough to even take off? Carbon fiber was the answer, making the aircraft half the weight of conventional aluminum construction, but as strong as steel.  Burt Rutan’s design certainly turned heads with its forward canard and graceful wings connecting two out-rigger booms, all of which contained 7011.5 pounds of fuel.  Every effort was made to keep the aircraft light, and thankfully Yeager weighed only 95 pounds. The two pilots were crammed into a phone booth-sized barebones cockpit and they would be there for nine days.  That alone earns gasps when people first see the aircraft but add the fact that, unbeknownst to the public, the pilots had not been getting along very well and you have a truly incredible feat.

 

Dick and Jeanna

Dick Rutan and Jeana Yeager in Voyager’s cramped cockpit

The Rutans and Yeager made it clear they expected success and they wanted to see the aircraft hanging at the Smithsonian.  The Museum adopted a wait and see attitude; given the long delays in the program and the dangers and pitfalls of the proposed flight, would this ever really happen?

Ultimately, determination and perseverance prevailed as Voyager and its crew endured the loss of its winglets on and just after  takeoff, a typhoon, thunderstorms that flipped the craft to a 90-degree bank, fuel starvation in one engine, and severe physiological and psychological stress.

The Museum followed the nine-day trip in the Air Transportation gallery but there were still questions — was it really one of the last great records of aviation?  By the time Rutan and Yeager landed back at Edwards AFB at 8:05am PST on December 23, 1986, it was clear that history had been made.  Not only were they the first to fly non-stop non-refueled around the world, they also set eight absolute or world class records.  Winning aviation’s prestigious Collier Trophy settled the discussion. While the press lavished praise couched in holiday cheer, the Museum began planning for a new addition to its collection.

In the summer of 1987, Voyager was dismantled for its trip by trailer from California to the Paul E. Garber Preservation, Restoration and Storage Facility in Suitland, Maryland.  While Voyager received accolades at the Experimental Aircraft Association Convention in Oshkosh, Wisconsin, structural engineer and curator Howard Wolko calculated how to get this huge aircraft into the building.  After a midnight wide-load ride from the Garber Facility to the west terrace of the Museum in Washington, DC, our team of specialists moved the center section onto dollies.

Then the carefully laid plans came to a halt. Just inside the west doors a replica aircraft carrier deck which held our Grumman Hellcat protruded a little too far, and it was clear that Voyager would not pass.  In the wee hours of the morning, a solution was found: elevate and tilt the center section with a hydraulic lift, inching it over and past the offending carrier deck.  After barely sliding by the Air Transportation gallery, the center section was rolled into the South Lobby at dawn.  Thankfully the assembly of the wings, empennage, and engines was routine and our able but tired staff suspended Voyager using scissor lifts and winches in time for our 10:00 a.m. opening.  The near catastrophic loss of the winglets on takeoff proved fortunate for us by reducing the wingspan by two feet and allowing the aircraft to fit snugly into the South Lobby. On the first anniversary of the flight, Burt and Dick Rutan and Jeana Yeager reached their final goal of seeing Voyager suspended in the south lobby of the National Air and Space Museum.

Dorothy Cochrane is a curator in the Aeronautics Division of the National Air and Space Museum

The Meaning Behind Folding an American Flag

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The American flag is one of the most important symbols of the United States.  For many, it symbolizes respect, honor, and freedom.  For others, the flag represents reflection, courage and sorrow.  The National Air and Space Museum cares for a number of American flags in the Smithsonian Institution’s national collection, many of which represent significant events in the history of space exploration or aeronautics. One belonged to Amelia Earhart.  One was flown aboard Gemini 4 by NASA astronauts James McDivitt and Edward H. White in 1965.  And the Museum has several replicas of the flag that was left on the Moon during the Apollo 11 lunar landing in 1969.  Although each flag has a story that is worth telling, the care and preservation of these unique objects is also noteworthy.

Even though Museum staff are trained to handle cultural objects, sometimes an object requires special attention. With the upcoming installation of new displays in the Moving Beyond Earth gallery highlighting the history of the space shuttle program, a very special flag was chosen for display.  This particular flag was flown over the U.S. Capitol on February 1, 2003 as a tribute to the crew of STS-107, who died when the space shuttle Columbia was lost during re-entry at the end of its mission.  It was donated to the Museum by Dennis Hastert, then Speaker of the House of Representatives, to honor the astronauts.

 

flag

This flag was presented to the National Air and Space Museum by Dennis Hastert, then Speaker of the House of Representatives (Photograph by Gregory K.H. Bryant)

flag

Flag prior to folding on table in conservation laboratory (Photograph by Marcy Borger)

When it was decided to display the flag in the new gallery, the conservation staff unfolded the flag from its original box so that it could be examined, photographed, and cleaned. The curatorial team agreed that the flag should be folded in the traditional, triangular pattern before putting it on display. Because the flag represents an American tragedy of significant proportion and out of respect for the proper treatment of the artifact, the Museum invited a member of the military to assist with folding the flag.  Army Major Warren R. Stump, who recently returned from Afghanistan, assisted the conservation staff.

 

stump

Flag being folded by Major Warren R. Stump. Moving Beyond Earth contractor Stephanie Spence is assisting (Photograph by Marcy Borger)

Major Stump, with assistance from Stephanie Spence and Dawn Planas (conservation contractors for the Moving Beyond Earth gallery) folded the flag, while I (Lisa Young) read an explanation of the meaning behind each of the thirteen folds in a properly-folded American flag.  The flag is folded to represent the original thirteen colonies of the United States.  Each fold also carries its own meaning.  According to the description, some folds symbolize freedom, life, or pay tribute to mothers, fathers, and those who serve in the Armed Forces.  When the flag is completely folded and tucked in, it takes on the appearance of a cocked hat, representing the soldiers who served under George Washington, the sailors and marines who served under John Paul Jones, and the many who have followed in their footsteps.

 

stump

Major Stump folding the flag (Photograph by Marcy Borger)

Now folded into the traditional triangle shape, the STS-107 Capitol-flown flag will be displayed in the Moving Beyond Earth gallery. The flag will serve as a reminder of the heroes who flew aboard the Space Shuttle Columbia, and who paved the way for further space exploration.  It will also serve as a reminder to Museum staff about how special objects take on new meaning as they are interpreted for public display.  We are grateful to Major Stump for helping the Museum to pay full respect to this significant artifact.

 

group

Presenting the flag to the Moving Beyond Earth Curator, Margaret Weitekamp and conservation team members John Holman, Lisa Young, Dawn Planas and Stephanie Spence. (Photograph by Marcy Borger)

Lisa A. Young is a conservator in the Collections Division and Margaret Weitekamp is a curator in the Space History Division of the National Air and Space Museum.

WINGS: From the Wright Brothers to the Present

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Airplane designers will tell you that the wing is the heart of an airplane. For conventional airplanes, it provides most of the lift generated by the airplane; the fuselage and tail contribute only a few percent of the overall lift of the airplane.

1900 Wright Glider

A reproduction of the 1900 Wright glider on display in The Wright Brothers & The Invention of the Aerial Age gallery at the National Air and Space Museum in Washington, DC.

The Wright brothers recognized this from the very start of their work on flying machines.  The wings of their first gliders in 1900 and 1901 were designed on the basis of the aeronautical data reported by the German aeronautical pioneer, Otto Lilienthal. When, however, they measured the aerodynamic lift on their gliders, they found that the measured lift was only one-third of their calculated lift based on Lilienthal’s data. (We know today that the problem was not with Lilienthal’s data, but rather with the Wright’s misinterpretation of his data, based on lack of information about the wing  geometry of Lilienthal’s test model.) Nevertheless, the Wright’s proceeded to carry out their own tests, using a rudimentary wind tunnel of their own design. They learned from their wind tunnel tests the important effect of wing aspect ratio on the lift and drag. (For their rectangular wings, the aspect ratio is equal to the wing span divided by the chord. A large aspect ratio wing is like a slat from a Venetian blind; a low aspect ratio wing is short and stubby.) Their 1900 and 1901 gliders had low aspect ratio wings, aspect ratios of 3.4 and 3.3 respectively. (Lilienthal’s model aspect ratio was 6.48, and is the main reason why the measured  lift of the 1900 and 1901 gliders did not agree with the Wrights’ calculations based on the Lilienthal’s data.)From their wind tunnel data, the Wrights found that a high aspect wing produced more lift and less drag than a low aspect ratio wing. The aspect ratio for their next glider in 1902 was 6.7, and this glider flew beautifully.  The Wright Flyer had an aspect ratio of 6.4. We note that many conventional airplanes today have very similar aspect ratios.

Otto Lilienthal

Otto Lilienthal in flight (1894 – 1896)

The wings of the Wright’s flying machines had another important feature. The wing tips could be warped in opposite directions, setting up an unbalanced lift force on the two wings, and hence providing a control mechanism to roll the airplane. The Wrights pioneered the concept of lateral (roll) control – one of their most important technical contributions to the airplane. After a few years, ailerons were employed for roll control in lieu of wing warping, but the Wrights’ contribution was seminal.

The cross-section of a wing taken in the flight direction is called an airfoil. The shape of an airfoil is an important design feature of a wing. For example, it affects the lift and drag of the wing, and has a major effect on the stalling angle of attack (the angle of attack of the wing beyond which the lift dramatically drops off and the drag suddenly increases).The airfoils used by the Wrights were very thin because their wind tunnel test indicated that very thin shapes resulted in lower drag than thick airfoils. Most airplanes through World War I followed suit and used thin airfoils. The early wind tunnel results were misleading, however, because the wind tunnel models were small and the airflow speeds of the air in the wind tunnels were low.  We know today that the much larger size and airspeeds associated with full scale flight resulted in the opposite effect. Thin airfoils experienced “thin airfoil stall” at angles of attack much lower than normal stalling angles of attack. This was due to the separation of the flow over the top surface of the thin airfoil, hence creating much higher drag and a loss of lift. In contrast, under the same operating conditions, thicker airfoils did not encounter flow separation until much higher angles of attack, hence producing more lift and less drag at higher angles of attack. This was discovered by German engineers, and thick airfoils were employed on the Fokker Triplane and the Fokker D-7 toward the end of World War I. These airplanes were able to climb faster and maneuver more sharply than airplanes using thin airfoils, and resulted in the Fokker D-7 being one of the most effective fighters of the War.

airfoil

Airfoil is the name for the special shape of airplane wings. A wing’s airfoil shape—like a teardrop on its side—is always designed to create lift. An airplane wing is designed so air flows faster over the wing than it does beneath the wing.

In the 1920s airplane designers moved towards the use of thick airfoils. By the 1930s, efficient wing designs exhibited large aspect ratios and thick airfoils. The famous Douglas DC-3 is an excellent example, with its aesthetically beautiful high wing  aspect ratio of 9.14 and streamlined 15 percent thick airfoil. Thick airfoils had structural as well as aerodynamic advantages. A thicker wing allowed storage space for fuel tanks and retractable landing gear. A thicker wing also allowed a larger and stronger structural spar along the inside of the wing, which in turn allowed the wing to be cantilevered from the fuselage without any external support wires and struts. This helped to encourage the use of the modern single wing (monoplane) instead of the older two-wing (biplane) configuration.

With the advent of jet airplanes in the 1950s pushing speeds close to and beyond the speed of sound, airfoil and wing shapes made another dramatic change. Thinner airfoils allowed subsonic airplanes to fly closer to the speed of sound before encountering adverse shock waves over the wing, shock waves which greatly increased the drag and reduced the lift. For supersonic airplanes, the driving design feature was to reduce the strength of shock waves on the wings, and hence to reduce the supersonic wave drag.  The thinner the airfoils, the weaker the shocks, and the lower the wave drag. The Lockheed F-104, the first airplane to be designed for sustained speeds at Mach 2, is a perfect example. The airfoil shape on the F-104 is very thin, about 3.5 percent thick, and the leading edge is razor thin, all to reduce the strength of the shock waves from the leading edge of the wing. At the National Air and Space Museum in Washington, DC, you can get within a few feet of the F-104 wing, and see the dramatically thin airfoil. It is almost like making a full circle in airfoil thickness,  returning to that of the Wright brothers, but for completely different flight conditions. Also, many  high speed subsonic and supersonic airplanes have swept wings rather than straight wings, also to reduce the strength of shock waves and to obtain a lower wave drag.

See if you can find the best lift-to-drag ratio for the F-104 airfoil, and learn more about how wings work, in this fun online activity.

F-104

Lockheed F-104A Starfighter on display at the National Air and Space Museum in Washington, DC.  The National Aeronautics and Space Administration (NASA) flew this F-104A for 19 years as a flying test bed and a chase plane.

Wing and airfoil shapes are still evolving today, driven by new and challenging flight conditions. The drive for more and more fuel economy in flight is driving new and better wing configurations and airfoil shapes to obtain higher lift-to-drag ratios. Also, future hypersonic flight vehicles flying at Mach 5 and higher will require innovative new wing and airfoil shapes. So the evolution marches on.

John Anderson is a curator in the Aeronautics Division of the National Air and Space Museum.