Pedro Rustan conceived and launched a small spacecraft on a less than lofty budget in under two years. When his ship, called Clementine, failed in May 1994 before completing its mission, Rustan was despondent. Now he feels vindicated. His concept of a small, cheap, disposable spacecraft has become a model for NASA.
But Rustan, an Air Force colonel and an electrical engineer, hadn’t set out to advance the cause of cheap spaceflight. He was just doing his best on a small budget. In fact, he was working at the time for the Strategic Defense Initiative, the missile defense project popularly known as Star Wars. As mission director for the project, he originally sent Clementine up to chase an asteroid called Geographos--a kind of dry run for the interception of a nuclear warhead. Since the encounter with Geographos was scheduled to last only about 20 seconds, Rustan tacked on a 72-day moon-mapping mission almost as an afterthought. He pushed the project to completion in 22 months because he wanted to launch Clementine before his tour of duty was over.
Engineers at the Naval Research Lab rose to the challenge and brought Clementine in on time and for $55 million--a mere pittance for a space project. They delivered a 500-pound bundle that included such high- tech fare as tiny ring-laser gyros, a nickel-hydrogen battery, gallium- arsenide-on-germanium solar cells, and a suite of fancy sensors. The probe was so simple to operate that Rustan’s mission control center comprised eight engineers working in a warehouse in Alexandria, Virginia. Shortly after launch in January 1994, the ship succeeded in mapping the moon, collecting 1.8 million images of startling clarity in wavelengths from ultraviolet to infrared.
Unfortunately, Clementine’s journey to Geographos was cut short by a software glitch that caused the ship to waste fuel. If I didn’t have that launch deadline, complains Rustan, I would have found the small bug. Nonetheless, now that Clementine’s moon data are filling science journals and copycat designs are giving expensive spacecraft nimble competition, Rustan is feeling much better about the oversight.
Penn State’s Ultrasonic Probe
Innovator: Joseph Rose
After an Aloha Airlines 737 came apart at the seams in midair in 1988, the Federal Aviation Administration required airlines to keep a closer eye on aging airplanes. But the eye alone is not enough to detect cracks or corrosion hidden under several layers of paint.
These signs of wear do not escape a new ultrasonic probe designed by Joseph Rose, an electrical engineer at Penn State. Whereas previous ultrasonic probes covered only one spot on the plane at a time, Rose’s C- shaped probe can inspect a 12-inch swath of a plane’s aluminum sheeting. And because it is flexible, technicians can cram it into every nook and cranny, cutting the time it takes to inspect a plane twentyfold. The probe sends out ultrasound waves in both longitudinal (left-to-right) and transverse (up-and-down) directions. This gridlike pattern lessens the chances that an odd shape on the plane, such as a joint or a corner, will cause interference that obscures signs of wear. And if that doesn’t do the trick, the technician can also fine-tune the probe by changing the frequency of the ultrasound. It’s a guided wave, which enables us to inspect even odd shapes like the nose of a plane, says Rose. Aviation firms Krautkramer Branson of Lewistown, Pennsylvania, and Rosemount Aerospace of Minneapolis plan to market the FAA-tested probe this year.
AlliedSignal’s Predictive Wind-Shear Radar
Innovator: Bill Weist
Pilots generally try to avoid wind shear, that radical shift in wind speed and direction that can arise seemingly from nowhere and suddenly dash an airplane to the ground. Engineer Bill Weist and his team actually went out of their way to find it.
They were testing a new airborne radar they designed to detect wind shear, and they found it consistently gave them at least a ten-second warning before the winds struck--time enough for a pilot to take preventive action such as reconfiguring the wing flaps. Weist, senior staff engineer at AlliedSignal Commercial Avionics Systems in Fort Lauderdale, Florida, had created the first FAA-certified wind-shear radar.
Radar works by sending out radio signals and then listening to their echo as they bounce off objects. Wind shear produces a very faint echo that is easily drowned out by the echoes from buildings and moving cars on the ground--identifying it is like hearing a whisper at a rock concert, Weist says. Moreover, because wind shear is characterized by two sheets of air moving in opposite directions, radar tends to confuse wind shear with highway traffic--both involve movement in opposite directions at similar speeds. To tell one from the other, Weist tuned his radar, which relies on 18 specially designed computer chips, to seek a big, diffuse weather blob rather than a skinny highway.
The result is a radar that produces only one false alarm in 10,000. At $30,000 for each system, the radar adds about a third to the cost of a typical airplane radar. Continental Airlines is currently installing it on its jets. Weist is glad to be finished with the testing. The 200 flights he took around Florida in a turboprop were marked by frequent roller-coaster-type drops. It’s not a sport for the fainthearted, he says.
Eye in the Sky
Westinghouse Norden’s Airport Surface Detection
Innovator: David Nussbaum
How do airports keep planes from colliding with each other on the runway? Usually they rely on pilots peering out cockpit windows and traffic controllers looking down from the tower. Radar does the job in a few airports, but it can’t penetrate a driving rain or a pea-soup fog.
David Nussbaum, a program manager at Westinghouse Norden Systems in Norwalk, Connecticut, devised an airport radar that works in heavy rain, fog, and snow by modifying navy radars that scan the ocean for vessels. His biggest challenge was how to present the data graphically to harried air- traffic controllers who need their information fast and unambiguously. Nussbaum found a way to give controllers multiple windows--of the software variety--and the ability to zoom in on one part of the airport to get greater detail. In addition, his display lets controllers tack tails onto each plane so they can see the path the plane has taken in its approach. Text bubbles, similar to the ones used in comic strips, also give controllers important information about the planes, such as flight numbers and type of aircraft. If two planes appear likely to collide or are violating airport rules, the system emits a warning. Westinghouse Norden has already sold the radar to more than 30 airports.
Nussbaum expects to double the radar’s capacity to about 500 objects by year’s end--enough to track not only airplanes but ground vehicles such as baggage carts and fire trucks. After working on military projects for most of his career, Nussbaum finds civilian work refreshing. You’re helping people every day, he says, rather than hoping your product never has to be used.
Capturing Shock Waves on Film
NASA Langley’s Schlieren Camera
Innovator: Leonard Weinstein
Anybody who’s seen a recent airline commercial on television has witnessed the schlieren effect. As a jet crosses the sun, its otherwise invisible exhaust plume bends the sun’s rays and lights up in brilliant hues of orange.
Engineers have long exploited this phenomenon to photograph the flow of air over airplanes in wind tunnels. Leonard Weinstein, senior research scientist at NASA Langley Research Center, went one better: he figured out a way to take a schlieren photograph, from the ground, of a plane in flight, showing the shock waves that emanate from the front and sides of the plane. When the plane passes through the air, it creates areas of high pressure that bend the sun’s light. The resulting image is too faint to see with the naked eye, but not for Weinstein’s schlieren camera. It has a telescopic lens, and its shutter stays open the entire time the plane is moving across the camera’s view. At the same time, the film moves in such a way that it tracks the motion of the airplane. Weinstein first tested his device in December 1993. He waited patiently behind his tripod- mounted camera on Assateague Island, Maryland, for the weather and the NASA T-138 plane to cooperate. At last the plane flew by at Mach 1.1, its shock waves caught the sun’s rays, and the camera’s film rolled to track it. The result was the first schlieren image of a supersonic boom, showing the shock waves emanating in black and white. Since then engineers have been using these images to study the aerodynamics of airplanes and have made plans to do the same for missiles. Weinstein is now developing a filmless, electronic version of his camera.