Good-bye “Beyond the Limits,” Hello “Time and Navigation”

Posted on Tue, August 2, 2011

We have been reminded that the retirement of the space shuttle is not only the end of an era, it is also the beginning of a new phase of human space exploration, with new launch vehicles, destinations, and technology. I don’t wish to make too much of the comparison, but there is a parallel in the Museum, with the closing of one of its most popular galleries in preparation for a new major exhibition, Time and Navigation, now under construction. In May, Beyond the Limits: Flight Enters the Computer Age closed after a successful 22-year run on the second floor of the Museum. I was a member of the exhibition team, and I still have vivid memories of how we planned and carried out that exhibit.  Its premise was that a revolution in computers and microelectronics was transforming aerospace as much as the introduction of the jet engine after World War II transformed aviation. But as everyone knows, advances in computing have been as dramatic since 1989 as they had been in the previous decades, so it is not surprising that this gallery was beginning to look out of date. Before it closed, I took one last look to see whether our initial assumption was correct, and how well the exhibit had held up.


Wind Tunnel Exhibit The analysis of the flow of air over a wing was traditionally done with wind tunnels. It is now primarily done with very fast computers, called supercomputers, which create a mathematical model of the air molecules. Supercomputers also model the flow of gases inside a jet or rocket engine, as shown in these photographs. The technique is called "computational fluid dynamics" (CFD).


Beyond the Limits was designed to look at several areas of aerospace that had been affected by computer technology, with a look at how things had been done, and how the computer was changing those practices. The first was aircraft and spacecraft design, which looked at the emerging technique of Computer-Aided-Design and Computer-Assisted-Manufacturing  (CAD/CAM). At the time of the gallery’s opening, CAD was just beginning to replace drafting boards, blueprints, and hand drawings. Since then CAD has completely prevailed: blueprints are now as rare as manual typewriters. The Boeing 777, introduced a few years after the gallery’s opening, was touted as a “paperless” airplane — designed entirely on computers — and its commercial success helped win over any skeptics.  Likewise, numerically-controlled machine tools were still somewhat controversial in the 1980s, especially concerning its impact on skilled labor, but it, too, has prevailed.  The next section, on the use of supercomputers to replace wind tunnels for aerodynamics research, has also been vindicated. Wind tunnels are still in use, but to a much lesser extent, and many of the largest tunnels in the United States have closed or are dormant.  That was a bold prediction in 1989, but it has come true.


X-29 The unusual design of the Grumman X-29 fighter, with its forward-swept wings and forward stabilizer, makes the airplane exceedingly unstable but tremendously agile. To maintain stability, the pilot must rely on three onboard computers, which assess and adjust the airplane's control surfaces 40 times a second. Two X-29s were built; this one is a full-scale model.


A section on “fly-by-wire”: the use of on-board computers to control aircraft that otherwise would be unflyable by a human pilot, was illustrated by a full-scale model of the X-29 research aircraft. The concept originated with the Apollo landings on the Moon two decades earlier, where the Lunar Module had to have computer control to allow it to land safely. Fly-by-wire is also now common in most new military and commercial aircraft. The X-29’s unusual forward-swept wing configuration, however, seems to have been a dead-end, save for a few recent unmanned-aerial-vehicles. And that leads to what we missed when we did that gallery. The first was stealth. The X-29 was a wonderful aircraft, but it was hardly a stealthy configuration. We failed to see how the use of fly-by-wire, coupled with computer simulations of different designs, could lead to aircraft that were inherently unstable but also had fewer control surfaces that would reflect radar. Stealth technology was well underway by the 1980s, but it was still a well-kept secret. By the time we learned of it, the gallery was already under construction. The second was the Global Positioning System (GPS). Early in the planning stages for Beyond the Limits, I was given a video cassette by an aerospace employee, who asked if I might consider showing it. The tape was called “NAVSTAR Crosses the Atlantic,” and it was about a small jet that flew from the United States to Europe with only satellites to assist with its navigation. At that time, the system was still called by its earlier name “NAVSTAR,” and only a few of the planned 24 satellites were in orbit—just enough to make a transatlantic flight possible. I turned the offer down. I simply did not see what was so significant about satellite positioning. In the spring of 2013, Museum will open a gallery devoted to Time and Navigation, with a major portion devoted to the origins, operation, and effects of GPS.  The other areas of aerospace continue to be affected by the relentless progress in computers and microelectronics, but the rise of satellite navigation, especially when coupled with cell phones and other so-called “smart” devices on the ground, have been startling — and unforeseen, at least by some of us two decades ago. As one of the members of the Time and Navigation team said, fixing a position with a sextant, or using radio devices like LORAN, can tell you where you are with good accuracy, but they cannot tell you where the nearest sushi restaurant is, or whether any of your friends are hanging out there. Beyond the Limits has closed, but the Museum has not abandoned its commitment to keep abreast of new developments in aerospace, wherever they may take us. Paul Ceruzzi is the Chair of the Space History Division at the National Air and Space Museum.

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