By Patrick Jackson
BBC News
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alt="The heat-ray gun mounted on a Humvee vehicle"
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The heat gun's dish could make a target for an RPG
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The US military revealed a heat-ray gun, the Active Denial
System (ADS), to reporters this week.
The technology brings a new, more disorientating
dimension to crowd control.
Rioters know where they are with a water cannon: they can
see where the cooling is coming from.
Likewise, tear gas smokes before it stings and baton
rounds are meant to bounce before they hit the crowd.
href="http://news.bbc.co.uk/2/hi/americas/6300985.stm#graphic"> How
the heat-ray gun works
A millimetre-wave beam is different: a hot blast which,
at a maximum range the Pentagon says is 10 times greater than that of
other "non-lethal weapons", effectively comes out of nowhere, silently
and invisibly.
Longer, lighter, simpler
"Imagine you're a marine guarding your post and you see
some suspicious-looking people coming towards you at a distance," said
Susan LeVine, principal deputy of the Joint Non-Lethal Weapons (JNLW)
Directorate which tested the system.
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RIOT CONTROL MILESTONES
![]()
alt="The jet from a police water cannon hits a South Korean demonstrator, December 2006"
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1958: British Army use CS tear gas in Cyprus
1960s: Lorry-mounted water cannon used in US
1960s: UK uses baton rounds - wood, rubber,
finally plastic
1980s: Pepper spray - a bear repellent - adopted
by US police forces
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"You will be able to engage them at a point well beyond
small-arms range so that you can give them a clear signal to stop," she
told the BBC News website.
Bill Sweetman, technology and aerospace editor for Jane's
Information Group, believes the primary purpose of the heat-ray gun
will be to disperse a crowd which could be concealing gunmen.
The beam, he says, has advantages over existing
non-lethal weapons other than range:
- it is more economical, as you can keep generating power
pulses in different directions while there is petrol in the generator
- it is less indiscriminate than tear gas and less
cumbersome than water cannon
- it is more accurate as it travels at the speed of light
and is not subject to the effect of wind
'Not to be trusted'
The heat beam may be an advance on the water jet but it
is causing alarm for other reasons.
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src="/cid:part6.00020408."> People hit the
pain waves and don't know which way to run ![]()
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Dr Steve Wright
Leeds Metropolitan University
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"What happens when people are in the first rows of a
dense crowd and cannot flee?" asks Dr Steve Wright, associate director
of Leeds Metropolitan University's Praxis Centre, which studies
conflict resolution technology.
"How do subjects exposed from a distance know where to
flee from the beam?
"People hit the pain waves and don't know which way to
run."
Such a weapon also has the potential to cause panic and
deadly stampedes, Dr Wright says.
He is also concerned that America is developing weapons
of "tuneable lethality" whereby "you can tune in the amount of pain the
weapon provides, from heating to death".
Put to the test
Alan Fischer, media relations manager of Raytheon, which
built the ADS as well as making its own commercial version Silent
Guardian, is concerned that some people have been likening the
technology to a microwave oven.
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![]()
src="/cid:part6.00020408."> It is a bit of a
uni-tasker and my feeling is that uni-taskers of one kind or another
seldom cause military revolutions ![]()
alt="" src="/cid:part7.07000708.">
Bill Sweetman
Jane's Information Group
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Some of the confusion may arise from the fact that
Raytheon built the first microwave oven back in 1947.
The millimetre wave may, like microwaves and radars,
operate in the radio frequency spectrum but it is "only designed to go
a very shallow distance into the skin", Mr Fischer told the BBC News
website.
"This has nothing to do with microwaves or microwave
cooking or anything like that," he says.
Dr Wright asks if Pentagon tests on healthy service
volunteers adequately reflect the potential effect on pregnant women,
children and babies.
Ms LeVine, one of the 600-odd people exposed to the beam
in tests, says that health tests have been rigorous:
"We've looked at the risk of injuries, at the risk of
skin cancer, birth defects, impact on fertility and everything has
proved to be negative."
Chinks in the armour?
But how vulnerable might it be in the field to what the
Pentagon calls "counter-measures"?
Dr Wright suggests that something as simple as household
foil and "a fine metal mesh in front of the eyes" could counteract it.
Attempts to get around the beam would only prove its
value, Ms LeVine argues.
"The point of ADS is to assess intent so if somebody is
coming at you and they have knocked up something that clearly shows
they are going to try and get by this beam, the system has already done
its job," she says.
Bill Sweetman questions whether the Humvee-mounted
version of the ADS - a "pretty obvious target" - would be vulnerable to
a rocket-propelled grenade.
As far as Ms LeVine is concerned, "a lot of vehicles
would be vulnerable to an RPG".
But the Jane's editor is not convinced the heat-ray gun
will prove a decisive weapon.
"It is a bit of a uni-tasker and my feeling is that
uni-taskers of one kind or another seldom cause military revolutions,"
he says.
It may serve its military purpose well enough, Mr
Sweetman adds, but law enforcement is a different story.
"I don't think you would use this unless you thought
there was a risk of the other side escalating it into lethal force," he
says.
"I don't think you would use this against a bunch of
Millwall football fans on the rampage."
HOW HEAT-RAY GUN WORKS
![BBC graphic]()
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1 360-degree operation for maximum effect
Antenna, linked to transmitter unit, can be
mounted on vehicle
Automatic target tracking
2 Antenna sealed against dust and can
withstand bullet fire
3 Invisible beam of millimetre-wave energy can
travel over 500m
4 Heat energy up to 54C (130F) penetrates less
than 0.5mm of skin
Manufacturers say this avoids injury, although
long-term effects are not known
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