Sci-Fi Cloaking Device Could Protect Soldiers from Shock Waves
Sci-Fi Cloaking Device Could Protect Soldiers from Shock Waves
A researcher at the defence company
Boeing has filed a patent for a sci-fi-esque cloaking device that would protect
soldiers from intense shock waves generated by explosions.
Brian J. Tillotson, a senior research
fellow at Boeing, said the idea occurred to him after noticing the kinds of
injuries suffered by soldiers who served in Iraq and Afghanistan. "We were
doing a much better job of stopping shrapnel," Tillotson told Live
Science. "But they were coming home with
brain injuries."
Though the armor
plating on a military vehicle might stop the debris from a roadside bomb from
injuring a soldier, it can't shield against theshock waves generated by such explosions. The blast wave goes right
through a human body and causes massive trauma. (This is why the action-movie
scenes where the hero runs ahead of an explosion and escapes harm are pure
fiction.)
Tillotson's invention is a device that would heat the air in
front of the spot where the bomb goes off. In one version, a detector
"sees" an explosion before the shock wave hits. The detector is
connected to an arc generator, basically two ends of a circuit connected to a
large power source. When the system generates enough current, an arc of
electricity jumps between the two ends of the circuit, like a bolt of lightning.
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That arc heats and ionizes, or charges,
particles of air. The heated air would work as a shield by changing the speed
at which shock waves travel, and therefore bending them around a protected
soldier, Tillotson said.
Sound waves (and
other wave types) propagate faster in hot air, Tillotson said. For that reason,
the shock wave would speed up when it hits the heated air around the electrical
discharge. As the shock wave speeds up, it would change direction slightly, or
refract, away from the person or object behind the arc. That bending occurs
because of the change in speed of the wave, and the shape of the area of hot
air the shock wave hits determines the exact direction.
The process resembles the way lenses
bend light, Tillotson said.
"With a convex lens you focus the
light," he said. "A concave lens spreads it out." Light waves
move slower in glass, so when light hits a glass surface it bends. The
lens must be concave to spread out that light. Because shock waves move faster
in hotter air, a spherical or cylindrical area of hot air will cause the shock
wave to bend, this time spreading out just like the light through a concave
lens, becoming weaker. In doing so that hot-air shield could deflect shock
waves.
Arc generators aren't the only way to
ionize air. Lasers would also work, Tillotson said. A laser fired across the
path of an explosion would ionize and heat the air around the beam, creating
the lensing effect.
In another method, a strip of some metal
could be placed on the side of a truck, for example. "Put a couple of
kilo-amps [thousands of amperes] through a strip of metal, and it will
vaporize," he said. The vaporized metal once again heats the surrounding
air.
One issue for all of these methods of
damping shock waves is the amount of power required. But Tillotson noted a lot
of research in this area shows promise in decreasing that power suck. In
addition, even a high-powered laser doesn't have to be on for long,
perhaps a fraction of a second, to heat the air sufficiently. "It's
basically a solved problem," he said of the power supply.
This isn't the only technology patent
for Tillotson; he has at least a half-dozen others in areas such as
aerodynamics and beamed power sources, and even other methods of damping shock
waves. Whether this particular technology becomes a reality will depend, as
many do, on future interest (and funding) from government and the private
sector.
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