Postal Service Unveils X-Planes Stamps
By: Chris Rink

some dude stands in front of two blown-up copies of the x-planes stamps at their unveiling ceremony on mar. 17 in the virginia air and space center. photo by jeff caplan. It may have been St. Patrick's Day, but the predominant color was - blue. There was a little bit of red, some orange, a touch of yellow, and (appropriately) shades of green.

Image Left: Jim Penland, a Distinguished Research Associate at Langley Research Center, stands in front of the U.S. Postal Service's new X-Planes Priority and Express Stamps at an unveiling ceremony at the Virginia Air and Space Center. Photo by Jeff Caplan.

They are the colors of speed; physics made visible; and now available at your local U.S. Post Office.

At an unveiling ceremony in the main gallery of the Virginia Air & Space Center, officials from the U.S. Postal Service and NASA Langley celebrated the March 17th first day of issue of the new X-Planes Priority and Express Stamps. Both feature computer-generated images of the X-15; images that were created by researchers at Langley's Geometry Laboratory.

Langley's work in Computational Fluid Dynamics, or CFD research, essentially started in the '80s; the X-15 CFD images were created in the early '90s; and the two new postage stamps are part of the U.S. Postal Service's 2006 definitive stamp program. So how do two of the fastest stamps on the planet come to be since the last flight of the X-15, the world's first manned hypersonic research aircraft, was in 1968? How? Because it is the X-15.

Three rocket-powered X-15s flew a total of 199 times between 1959 and 1968 with speeds up to Mach 6.7 and an altitude record of 354,200 feet (67 miles). The first, truly successful piloted rocket planes contributed to the development of the Mercury, Gemini, Apollo, and Space Shuttle programs and were part of a joint research program by NASA, the U.S. Air Force, the U.S. Navy, and North American Aviation, Inc. All the X-15 test flights were conducted at the NASA High-Speed Flight Station - now NASA Dryden Flight Research Center - in Edwards, Calif.

Or is the better question, "why"? The best answer is because the X-15 had data; lots and lots of data - flight data and wind tunnel data. And data sets can create computer simulations. When additional wind tunnel or flight-testing is impractical, "flying" on the computer helps researchers safely and efficiently explore flight conditions not achievable by conventional means.

Jim Penland worked for NASA Langley and its predecessor - the National Advisory Committee for Aeronautics or NACA - for a total of 37 years. A self-described wind-tunnel jockey, Penland was an aeronautical engineer on the original NACA X-15 research team. Since his retirement in 1980, he has been a distinguished research associate at NASA Langley.

"These X-15 images were created for the specific purpose of making calculations of mach 6.9 from the tunnel data and the flight data," said Penland. "The reason X-15 was selected because it was the only manned X-15 to fly near Mach 7 at level flight conditions."

a sheet of the new x-planes stamp issued by the u.s. postal service on mar. 17 at the virginia air and space center. photo by jeff caplan. Image Right: A sheet of new X-Plane Express stamps is ready for distribution at the Virginia Air and Space Center. Along with the new X-Plane Priority Stamp, the two new postage stamps were unveiled at a first day of issue ceremony. Photo by Jeff Caplan.

Penland and another NASA Langley retiree, Sharon Stack placed the original request that resulted in these images with Langley's Geo Lab. At the time, Stack was the assistant manager of the numerical applications office of the Hypersonic Technology Office. Most recently and just before her retirement, she was the assistant technology manager of the Hyper-X program for the first Mach 7 flight of another history-making aircraft, the X-43.

A computer simulation program measured a 12-inch wind tunnel model of the X-15 using a laser-digitizing scanner. These measurements were then used to reconstruct a computer model for the simulation software. This was the first real application of a laser digitizer by Langley researchers and showed the practical use of this technology to support computer simulations of aircraft.

Their use of the data sets and the work of Richard Hawkins, the aerodynamicist who ran the code, resulted in a number of simulations and images of the X-15.

And don't forget the computers.

William Jones, a Computer Engineer, at NASA Geometry Laboratory describes the CFD simulations as a complex system of equations, which mathematically model the motion of particles in a continuous medium - such as air.

"These sophisticated computer programs are able to compute properties of the medium at fixed points in a defined space," Jones said. "The points are organized into a network that specifies the connection of a given point with its neighbors. We call this network a grid or mesh."

As the capability has grown, so has the complexity of the problems addressed by computer simulation.

"At the time these X-15 calculations were generated, in the early 1990’s, a million mesh points was considered a complex problem," Jones added. "Today it is common to solve problems requiring 10s of millions of mesh points, and 100s of millions of mesh points are contemplated. Much of this advancement is due to distributed computing, numerical algorithm development, and cutting edge computer science techniques." Some could call it painting by numbers.

The colors in the stamps images show various scales of pressures and temperatures as a result of the calculation simulating the flow of air at supersonic speeds around the X-15 model - blue is the lowest and red is the highest. The Priority Mail stamp shows the X-15 rotated upward to reveal the most surface area. The Express Mail stamp shows the colors against a meshed grid indicating how air is forced over the plane.

Some see the practical application.

"It has always been my interest to find out what has been the improvement in our ability to predict flight conditions from our wind tunnel testing," Penland added.

So the product of an aeronautic research tool, Langley's X-15 CFD images joins panoramas from the nation's National Park system, American scientists who developed polio vaccines, the common Buckeye Butterfly and other stamps in 2006 definitive stamp program.

It may be numerical geometry to some, but today it's collectible art - the U.S. Postal Service says so.

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By Chris Rink
The Researcher News
Langley Research Center
Managing Editor and Responsible NASA Official: H. Keith Henry
Editor and Curator: Patrick Lorentz