November 6, 1997

NC State Engineers' Research Aims at Power and Safety of Weaponry

Safety, accuracy and distance--if you are on a Navy gunship or in an Army tank, these are important factors that could save your life. Research conducted in the College of Engineering at North Carolina State University is aimed at maximizing these factors.

Dr. Mohamed Bourham, professor of nuclear engineering, and Dr. John Gilligan, professor of nuclear engineering and associate dean for research and graduate education, are working to develop weapons that use electrothermal (ET) plasma in the ignition of large guns, such as those on ships and tanks. What they have found is that by using ET plasma to ignite a chemical propellant, the mortar or shell can be propelled much farther using far less of the volatile chemical propellant (gunpowder).

Bourham and Gilligan have been working with the U.S. Department of Defense to create safer, stronger and more accurate weaponry for the past 10 years. Their ET guns are part of that research.

"Our ET gun uses electrical energy to create high pressures to shoot a projectile," says Gilligan. "We can use the plasma as the ignition for the propellant or use the plasma as the propellant. It is the gun of the future--superior to the present guns that use chemical energy."

At present, the guns used on ships and tanks require large amounts of chemical propellant to project mortar shells from the large guns. This means that in storing propellant, the ship or tank itself is vulnerable to explosion. By reducing or eliminating the need for propellant in the guns, Bourham and Gilligan hope to increase the safety of ships and tanks.

So far the two researchers have developed two types of guns and have created models that they and the Department of Defense use in research. Currently, their 50 millimeter gun is on loan to the Defense Nuclear Agency in San Diego, California. NC State is the only university in the nation to own these types of guns and conduct ET gun research.

The guns use electrothermal plasma--a burst of extreme energy generated from a plasma source--to ignite propellant and project mortar shells in a range of 50 kilometers--an increase in distance over the conventional guns. The ET technology also makes the weapon more powerful. The plasma ignition creates a velocity of several kilometers per second for the projectile, greatly exceeding the velocity achieved by conventional ignition and increasing the projectile's ability to penetrate the target.

Bourham and Gilligan hope to develop a method that will enable a retrofit of existing big guns to avoid the need to replace the large guns on ships and tanks. So far, the heat of the ET plasma creates warping in the barrels of the guns--an indication of the extreme power unleashed in the fraction-of-a-second ignition.

As part of the ET gun research, Bourham and Gilligan are working on research projects that look at the interaction of the surface, or barrier, layer of material and how it reacts with the plasma to solve the problem of the warping of the gun barrels. The researchers are using the information learned in the ET gun research to help in an international research project--one that may someday supply the world with safe, reliable and efficient energy source--to develop a nuclear fusion reactor. The International Thermonuclear Experimental Reactor (ITER) team of researchers from the U.S., Europe, Japan and Russia is working to build a TOKAMAK fusion reactor that could become an alternative energy producer. Unlike the current fission reactors, nuclear fusion reactors would not produce waste products that are harmful to the environment.

"What we learn from the weapons research carries over to daily life," says Bourham, "because what we discover about improving the safety of weapons will also work in other applications, such as nuclear fusion reactions."

The barrier layer research can help researchers understand the reaction of high energy plasmas, which can occur in fusion reactors, with the material containing the reactor. The warping that occurs in the ET gun could occur in the fusion reactor, creating a weakness in the reactor container that could compromise safety.

"Understanding the interaction of the plasma energy and the barrier layer of the container is key to creating a safe fusion reactor," says Bourham.

Bourham and Gilligan predict that the safer, more powerful ET guns will be in place on ships and tanks within the next five to seven years.

"It is our hope that we can save lives with our research," says Gilligan. "By adding distance to the projectile and eliminating or reducing the propellant, we are increasing the safety factor for our soldiers."

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