[TABING]

Scientific American Aprill 1999

Weaponry

TAKING BALLISTICS BY STORM

An electronic gun with
no mechanical parts fires a million
rounds per minute


by Dan Drollette in Canberra, Australia

"When you first hear of a gun without any moving mechanical parts, you
tend to laugh. I know I had to withhold my giggles," recalls physicist
Adam Drobot of Science Applications International Corporation (SAIC), a
company based in San Diego that evaluates new technologies. "But once
you see the videotape of this test-firing, the giggle factor goes away."

The gun in question is something that even its inventor says comes out of
left field. Termed Metal Storm, the weapon has no hammer, no trigger,
no breechblock and no shell casings to eject. Equally unusual, a single
barrel fires at a rate equivalent to one million rounds per minute. In
comparison, the fastest conventional firearms (Gatling guns) fire only
6,000 rounds per minute.

Metal Storm's origins are unorthodox as well. It was invented by former
grocery wholesaler Mike O'Dwyer, a lone Australian tinkerer with no
formal education in ballistics or engineering. His previous patents are for
devices such as air-cooled sneakers. ("They pump air through as you
jog," he explains.) Yet after 15 years of trial and error in his tropical
Queensland home, O'Dwyer came up with a gun prototype that recently
fired 180 rounds of nine-millimeter bullets in 0.01 second during a
demonstration before military officials in Adelaide. Metal Storm's bullets
leave its barrel so quickly that they are only microseconds apart--when
one bullet is flying through the air, the next is just 10 centimeters (four
inches) behind. For current machine guns, the gap between bullets is 30
meters.

"It could replace our existing technology on the battlefield," says Maj.
David Goyne, a weapons specialist at Australian Defense Headquarters.
The gun is ideal for close-in situations, such as defending ships against
incoming missiles. Goyne comments that it could also eliminate land
mines in open areas such as Kuwait's deserts: a helicopter using the gun
could hover above the sands and clear a minefield by spraying it from a
distance, exploding mines harmlessly.

The gun works through a combination of specially designed bullets and an
electronic firing mechanism, which O'Dwyer describes as "a barrel tube
with an electrical wire attached." Jacketless bullets are lined up inside,
nose to tail, and are separated from one another by a layer of propellant.
When an electric current makes its way down the strip, the bullets are set
off one by one. To stop them from going off simultaneously--a problem
previously encountered when putting many bullets in a single
barrel--O'Dwyer designed the bullets to work together. The high pressure
caused by the firing of the first projectile makes the nose of the next one
in line swell against the walls, temporarily sealing off the rest of the barrel.
(In ballistics terms, the nose of the second bullet effectively acts as a
breechblock to prevent an uncontrolled sympathetic ignition.) After the
first bullet exits, the pressure drops, and the nose of the second one
loosens up, enabling the bullet to be fired. This process continues for each
successive bullet.

Other than the projectiles themselves, there are no moving parts. To get
even more firepower, several loaded barrels can be set up side by side.
Once a barrel is used up, it can be discarded or sent back to the factory
for reloading.

Variations of electrically fired weapons have been tried before. For
instance, Sandia National Laboratories developed an electromagnetic coil
gun designed to hurl 100-kilogram (220-pound) satellites into orbit. But a
number of differences separate the two approaches, observes Vinod Puri,
senior research scientist with the Australian Defense Science and
Technology Organization: "The electromagnetic coil gun demands lots of
energy, achieves high velocities and sends large objects great distances. In
contrast, Metal Storm requires less energy, works at lower velocities, uses
normal gun propellant and sends out more, smaller projectiles per minute
for shorter distances."

O'Dwyer points out another feature of guns like Metal Storm: because
electronics are such an integral part of their makeup, they offer a good
opportunity for built-in electronic safeguards, such as security keypads. If
an unauthorized user tried to bypass the gun's security system by
disabling the electronics, the gun simply couldn't fire. The device has
many nonmilitary uses, too, Drobot notes. A slower version could replace
the nail guns used by carpenters and roofers and may find a use in
riveting and other industrial applications.

Goyne remarks that the technology still needs fine-tuning--it fires
relatively small caliber bullets, for example. But physicists such as Puri
say its basic design is "very solid." The Australian Trade Commission is
promoting the weapon, which has attracted attention in Australia and
Britain.

In the U.S., General Dynamics has tested it, and SAIC has been
contracted to help develop it further. A. Fenner Milton, previously in
charge of weapons acquisition for the U.S. Army and now running the
army's night-vision lab, attended a test-firing of a Metal Storm prototype
in Australia last year. "In my opinion, Metal Storm represents a truly
innovative approach to lethality, that if further developed has great
potential for defensive weapon systems that can take advantage of its
extraordinarily high burst rate of fire," an impressed Milton says.

What seems to surprise most experts about the technology is its source.
"It sometimes takes someone who isn't very conventional to come up
with new ideas," Drobot observes. "My amazement is at the
process--O'Dwyer didn't blow up a barrel or kill himself while making it."


The Author

DAN DROLLETTE described how wallabies could replace the lab rat in
the Octo