Noise Gun: More Bang for SDI Buck

A GUN powered by sound waves? It's not the fantasy of some hostile rock star. It's a concept under study by the Pentagon's ``star wars'' program. Noise cannons won't soon stock America's arsenals. They exist mainly in one inventor's mind. But he says sound can shoot bullets at high velocity. He talks of store-bought, as well as military, sound weapons.

``This could replace all the BB guns in the world,'' says John Cory, owner of Cory Labs in Escondido, Calif.

The Strategic Defense Initiative, or ``star wars,'' is paying Dr. Cory $50,000 to lay out his theory on paper. The money comes from a slice of the SDI budget set aside to fund cutting-edge research at small companies.

Tiny stereos mounted on rifle barrels are not involved. At the heart of Cory's concept is an exotic metal named Nitinol, an alloy of nickel and titanium devised by the Navy Ordnance Laboratory.

Nitinol is known as the metal with a memory. A bent piece, if straightened, will return to its bent shape when heated. By complicated processes involving electrical stimulation, Nitinol may be made to vibrate and produce a powerful pressure wave. Amplified, the resulting sound-wave motion ``could be used to accelerate a hypervelocity projectile to sonic speed and above,'' according to an SDI contract summary.

Cory's money was awarded in 1987, though he did not get funds until last year. If SDI officials approve of his studies, a follow-on contract with money for hardware construction may follow.

To fit in with SDI plans, sonic-wave weapons would have to be in essence space-age antiaircraft guns, capable of shooting down ballistic-missile warheads in flight. But Cory says his theory could have other application besides weaponry. Nitinol-powered ``heat engines'' show promise for space propulsion, he says.

The sonic-wave gun is far from the only novel idea that SDI is funding. Concepts studied under the small business research program include solar-powered lasers and something called a ``laser mass driver.'' The latter project is apparently a sort of high-tech machine gun that would fire balloons through space, at high speed, using a pulsing laser.

``Hypervelocity projectiles for ion-beam coalescence'' sounds like a phrase from a ``Star Trek'' script; in fact it's the title of another SDI study. The scientist who proposed this idea, Paul Kydd of Partnerships Ltd. in Lawrenceville, N.J., says it would be in effect a gun that makes its own bullets. The theory involves a laser-like beam, made of ions, that is neutralized after being created. A close analogy might be a fire hose spouting water that freezes in midstream.

But SDI didn't fund him beyond initial studies. ``The whole thing has lapsed now,'' he says.