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After more than half a decade of research, Florida Tech associate professor of mechanical and aerospace engineering Hector Gutierrez’s work on electromagnetic launch systems has reached a crossroads.
“We could go in the direction in which most research is currently going (railgun technology) and try to address one or more aspects of it, or we could try an entirely different path and see how far that takes us.”
Electromagnetic (EM) launch technology has two attractive potential applications. First, it may provide a cost-effective, more agile, greener way to deploy micro satellites to low-Earth orbit solely from electrical power. Considering the large costs and preparation time associated with conventional satellite launching, the potential impact of rapid, inexpensive launching to LEO from electric power is
very large.
Second, EM launching would open the way to a new generation of long-range kinetic-kill weapons that would have various potential military applications and interesting advantages over conventional weapons based on chemical propulsion and pressure blast.
“Electromagnetic launching has been pursued for nearly three decades. Up to 20 different EM launch concepts have been identified by the Army ARDEC classification, which includes 12 different categories,” he said. “Although some EM guns have been successfully tested, none has yet been deployed. All previously described technologies have been bogged down by one or more unresolved
bottlenecks.”
By the early ’90s, two competing technologies, coilguns and railguns, emerged as leading contenders as the EM launch technology to eventually become a reality. What happened next walked the thin line between technology, defense policy, long-term planning of defense projects, the laws of physics and the difficulty to foresee long-term problems that can be inherent to research.
“In 1995, Prof. E. R. Laithwaite from the Imperial College, London, published a paper in which the practical limitations in coilguns due to inductive heating of the projectile were estimated. He provided an analysis to estimate the maximum speeds that could be achieved before a coilgun projectile with copper windings melted by inductive heating,” said Gutierrez. “His results were discouraging—practical military applications required higher speeds and shorter barrel lengths. It seemed a turning point in coilgun research—over the next few years, most coilgun projects in both the UK and the USA were abandoned, and nearly all the funding and resources for EM launching moved to railgun technology.”
Railguns are impressive weapons, and a great deal of R&D effort has been invested in them—they are very attractive in their apparent simplicity and performance. Railgun technology, however, has been haunted by three main limitations.
“First, the resistive heat generated by firing the gun needs to be extracted as fast as possible before the gun can be fired again. This creates a substantial limitation in rate of fire, a deal breaker for several military applications. Second, metal-to-metal contact at very high speeds generates plasma—a fourth state of the matter in which individual atoms lose their typical electronic configuration. Plasma at high temperatures is highly corrosive, damaging the insulation layers inside of the gun’s bore—which obviously creates a serious reliability and maintenance problem,” said Gutierrez. “Finally, EM guns that circumvent the metal-to-metal contact problem by using AC induction are limited by inductive heating of the projectile—it can only go so fast before it melts.”
Stretching the envelope of railgun performance clearly bumps into the laws of physics. Gutierrez and his collaborators, research scientist Rainer Meinke from Advanced Magnet Lab Inc. (AML) and fellow associate professor in mechanical and aerospace engineering Daniel Kirk, are currently building a prototype that addresses these critical issues—heat and contact.
The proposed concept has the potential of becoming an interesting breakthrough in EM launching—it’s based on an entirely different operating principle than railguns or coilguns, and addresses some of the most critical bottlenecks of previously described technologies: metal-to-metal contact, heating of the projectile, development of muzzle arc, and heating and wear of the gun bore. During the next two years, Gutierrez, Meinke and Kirk will finish developing the concept and will build the first operational prototype.
“We’ve got an exciting two years ahead of us.”
Jay Wilson |
