January 19, 1998 Design News

Technology bulletin

Late developments that shape engineering

by Michael Puttré, Associate Editor

There's life in the old girl yet

NASA's Galileo began the second phase of its Jupiter journey, swooping over the Jovian moon, Europa, at an altitude of only 124 miles. This was the first encounter of the Galileo Europa mission, which began formally on Dec. 8, following the end of Galileo's primary mission. The Galileo Europa mission will study Jupiter's icy satellite in detail in hopes of shedding more light on the intriguing prospect that liquid oceans may lie under Europa's ice crust. The Galileo Europa mission is designed to follow up on these discoveries and will include eight consecutive Europa flybys through February 1999, followed by four Callisto flybys and one or two Iow encounters in late 1999, provided the spacecraft remains healthy. For more information, contact Jane Platt, Jet Propulsion Laboratory, at (818) 354-5011.

Forget Rio, blame it on Jupiter

A better understanding of the Earth's climate requires a better understanding of the interaction between the planet's geophysical processes and the dynamics of the Solar System as a whole. So suggest University of Toronto physicist Jerry Mitrovica and Allessandro Forte of the Institut de Physique du Globe de Paris. The pair reached their conclusion based on numerical simulations that show a connection between Earth's changing shape and the gravitational effects of other bodies in the Solar System, particularly Jupiter and Saturn. "We're showing for the first time that changes in the Earth's shape, when coupled with the gravitational effects from other planets, can produce large changes in the Earth's climate," Mitrovica says, citing numerical simulations to show that these aspects of the Earth's orbit have been affected by the gravitational attraction of Saturn and Jupiter. His figures indicate that at some time during the last 20 million years, the Earth passed through a gravitational resonance associated with the orbits of Jupiter and Saturn, which in turn influenced the way the Earth's axial tilt changed during the same period. This gravitational pull would have had a much greater impact on the Earth millions of years ago when the Earth was shaped differently. For more information, contact Jerry Mitrovica at (416) 978-4946.

Sunspots offer clues about universal gas-flow

Sunspots mark areas on the Sun's surface where the star's magnetic field becomes so intense that a buoyant tube of magnetism literally pops through the Sun's surface. The magnetic field disrupts the outward convection of heat, resulting in dark Earth-sized splotches that are some 2,500 degrees Celsius cooler than the rest of the solar surface. Periods of high sunspot activity also usher in an increase in the number of solar flares--intense bursts of magnetic energy hurling energetic particles out from the Sun. When these flares reach the Earth's magnetic field, they can wreak havoc with electrical lines, communications satellites, and even automatic garage door openers. John H. Thomas, an astrophysicist at the University of Rochester, and Benjamin Montesinos of Madrid's Laboratory for Space Astrophysics and Fundamental Physics have developed what they say is a more realistic version of the siphon-flow model, which predicts how gas flows from sunspots into the solar atmosphere. The work could also offer insights into other astrophysical processes that involve strong magnetic fields and jets of gas, such as when stars form or die--an area that's the focus of much research. For more information, contact John H. Thomas at (716) 275-6717.

Atmospheric sprites have presence

An intense but brief form of lightening known as "red sprites" that occurs high in the atmosphere above large thunderstorms may not be the amorphous blob of light that scientists had first thought. Researchers from Stanford's Very Low Frequency Research Group, who have been studying this phenomenon for several years, now propose that sprites may consist of thousands of fiery streamers, each only a few meters wide. Current observations of sprites, which can be more than 25 miles wide and 25 miles in height, have been made from a considerable distance with high-speed cameras capable of capturing the images of these extremely brief flashes. The best resolution of these images has been several hundred feet, much larger than the size of the streamers that the Stanford model predicts. The group hopes to acquire a special telescope that can capture details in sprites as small as a few feet across. That will allow the scientists to determine if the structure that they have predicted does in fact exist. For more information, contact David F. Salisbury, Stanford News Service, at (650) 725-1944.

Lasers promise improved peening

A powerful laser developed at Lawrence Livermore National Laboratory could improve the manufacturing of some airplane components, hip implants, and other metal products. The Lab and Metal Improvement Co. Inc. have signed a license agreement and cooperative research deal to adapt the laser technology to peen, or surface treat, metal. Historically, metals have been peened by bombarding the material with metal balls as small as salt or pepper grains to induce compressive stress that prevents metal fatigue and reduces corrosion. Metal Improvement has found that while conventional peening reaches a depth of about 1/100 of an inch to instill compressive strength, the laser peening method extends some four times deeper. "Laser peening was developed in the 1980s, but never went into production because of high cost and slow lasers," says Jim Daly, senior vice president for Metal Improvement. Livermore's neodymium-doped glass laser achieves 600 watts of average power and is capable of firing 10 pulses per second, compared with one pulse every two seconds from the best commercial lasers. One of the first industries where Daly sees the new laser having an impact is the aviation industry, for peening jet engine components like rotors, disks, blades and shafts. Aviation industry studies have shown that engine blades, which can cost $30,000 to $40,000 apiece, last three to five times longer when treated with the laser peening process. Another plus of the laser peening technique is that it has the potential to increase the resistance of airplane blades to objects like birds, ice, or stones that can damage the edge of a blade. Another use of laser peening beyond safer aircraft could be in the medical industry, for example, in the treatment of the surface of hip joint implants. Other industrial applications foreseen are: oil tools, such as drill collars and mud pumps; marine engines and shafts; rocket engine parts; and the chemical and power-generation industries. Commercial products manufactured with the laser peening process are expected to be two to four years away from introduction. For more information, contact Stephen Wampler, LLNL, at (510) 423-3107.

Dinosaurs: the soundtrack

Scientists at Sandia National Laboratories and the New Mexico Museum of Natural History and Science have collaborated to recreate the sound a dinosaur made 75 million years ago. The low-frequency sound was produced using computed tomography (CT scans) and powerful computers. The study of dinosaur vocalization began after the discovery in August 1995 of a rare Parasaurolophus skull fossil measuring about 4.5 feet long. The dinosaur had a bony tubular crest that extended back from the top of its head. Many scientists have believed the crest, containing a labyrinth of air cavities and shaped something like a trombone, might have been used to produce distinctive sounds. As expected, based on the structure of the crest, the dinosaur apparently emitted a resonating low-frequency rumbling sound that can change in pitch. The sound is an approximation of the possible tones that the dinosaur crest was capable of producing. The computer-modeling techniques used to create the dinosaur sound are the same ones Sandia uses to create complex, three-dimensional models for conducting computer simulations of problems that cannot be subjected to real-world tests. The same 3-D imaging techniques can be used to analyze and predict the structural integrity of mounting brackets on aging airplanes, the internal structures of aging weapons, and the accurate reconstruction of the forces and mechanical failures associated with the crash of an airplane carrying nuclear weapons. For more information, contact Carl Diegert, Sandia, at (505) 845-7193.

Virtual machining for trial runs

MIT has developed a Machining Variation Analysis system that allows designers to create machine tools on the computer and use those tools to virtually machine parts and predict the exact shape of a part given any error that may exist in the machine tool. "Before the MVA, machine-tool designers could not predict the effects of the dozens of error sources that plague a real process," said MIT Professor Alexander Slocum of the Department of Mechanical Engineering. "Every time a machine was designed to make a new part, the company took a gamble. The MVA takes the risk out of developing new manufacturing equipment." With MVA, the user provides information including the geometry of the part and sources of error in the machine's operation. With these parameters, MVA determines the exact shape of the part including all the consequences of the specified errors in machine operation. Slocum developed the MVA with Professor Kevin Otto of mechanical engineering, Daniel Frey of MIT's System Design and Management Program, and colleagues from the National Institute of Standards and Technology and the Landis Division of Western Atlas, Inc. For more information, e-mail the news office at [email protected] or call (617) 253-2700.

Electronic devices, now in convenient tubes

Scientists with the Ernest Orlando Lawrence Berkeley National Laboratory have confirmed the existence of atom-sized elec