Tapping on bombs is often thought of as a good way to get oneself blown up. But engineers at Purdue University in West Lafayette, Ind., have discovered that to find damage in missile casings, it's best to give them a solid thwack.

Modern military missiles have skins made of carbon fiber or Kevlar rather than metal. In spite of their many advantages in weight and cost, these composites often hide damage until it's too late.

As helicopters land in desert environments, such as in Iraq, the wash from their rotors can kick up potentially damaging rocks. A new monitoring system will tell pilots if their missiles have been damaged.

The Purdue researchers, led by mechanical engineering professor Douglas Adams, put a triaxial accelerometer attached to a seven-inch-wide missile casing, the long cylinder that connects the rocket motor to the warhead. Striking the tube with a hammer, the engineers were able to gather data to create a mathematical model of what a healthy casing should "sound" like. Then they struck the tube with a large steel rod dropped from a height. The sound of the impact, combined with the model of the casing, enabled the researchers to determine with just one piece of data not only where on the tube the impact took place, but whether the casing was damaged. The system worked 98 percent of the time in a laboratory setting.

Placing similar sensors on missiles used in combat could be essential. The weapons can be damaged by rocks and other debris kicked up by helicopter rotors or through casual mishandling. The data may also help weapons designers create missiles that distribute the stress of impacts better, enabling them to hold up in hostile environments.

If you have a string that's too long, there's no secret about what you do: You grab a pair of scissors and cut. But what happens if the string is the chain of amino acids that make up a protein? In March, Japanese researchers demonstrated a pair of scissors that is just three nanometers long, designed to work on molecules.

Like the scissors used by coupon clippers, the nanoscissors have handles and two blades attached by a pivot. The pivot in this case is two carbon plates on either side of a spherical iron atom. The handles are bound to photo-reactive azobenzene atoms; the azobenzene contracts when exposed to ultraviolet light and expands when visible light is shined on it. Alternating UV and visible light causes the handles to open and close, much like real scissor handles.

The blades, however, are not able to slice through the protein molecules. Instead, they grab the molecules and twist them back and forth. The way proteins are folded affects their function, so it's thought that this might one day be able to disable or reprogram disease-causing proteins.

What's more, since some forms of light can penetrate deeply within human tissue, doctors may be able to control these sorts of light-activated nanomachines at work inside the body of a patient.

With oil and natural gas fetching premium prices, finding new supplies quickly and cheaply has become a priority. The traditional method for finding those sources, seismic surveys, is unfortunately both expensive and cumbersome. But a California company announced in April that it might have found a quicker and easier way—conducting reconnaissance surveys for natural gas from the air.

In a report at the Panhandle Producers and Royalty Owners Association convention in Amarillo, Texas, workers from eField Exploration LLC, a start-up based in Yorba Linda, Calif., said they had mapped a known gas reservoir from an airplane flying some 1,000 feet above the surface.

Seismic surveys involve setting off explosive charges on the surface and, using strategically placed seismographs, recording the way the pressure waves reflect off various strata of the underlying rock. By looking for seams in the rock, geologists can infer the location of possible oil and gas deposits.

The eField technology is based on an entirely different premise and takes advantage of electric currents that flow through the earth as a consequence of cosmic ray bombardment and lightning strikes. The way these currents flow around oil and gas deposits or through saline aquifers can be detected from a distance using sensitive electric field sensors.

The company's technology combines two existing electromagnetic methods: measuring the resistivity of the earth's crust and detecting electric charges that build up on beads of oil or gas suspended in water. And while these methods have been used by applying an artificial current to the survey site, eField relies only on natural electric currents.

In the tests announced in April, the gas field detected lay some 8,000 feet below the surface. The company claims that deposits as deep as 20,000 feet can be found using its technology.

If this technology proves out, it could speed further oil and gas exploration. The company claims to be able to cover up to 100 miles a day with a single plane at a cost less than a tenth that of a seismic survey.

home | features | breaking news | marketplace | departments | about ME back issues | ASME | site search

© 2007 by The American Society of Mechanical Engineers