Begin forwarded message:
Subject: Fighting with photons, from The Economist
Fighting with photons
Oct 30th 2008
From The Economist print edition
http://www.economist.com/science/displaystory.cfm?story_id=12502799
The most famous weapon of science fiction is rapidly becoming fact
LIKE so much else in science fiction, the ray gun was invented by H.G.
Wells. In the tentacles of Wells’s Martians it was a weapon as
unanswerable by earthlings as the Maxim gun in the hands of British
troops was unanswerable by Africans. Science fiction, though, it has
remained. Neither hand-held pistols nor giant, orbiting anti-missile
versions of the weapon have worked. But that is about to change. The
first serious battlefield ray gun is now being deployed. And the next
generation, now in the laboratory, is coming soon.
The deployed ray gun (or “directed-energy weapon”, in the tedious
jargon that military men seem compelled to use to describe technology)
is known as Zeus. It is not designed to kill. Rather, its purpose is
to allow you to remain at a safe distance when you detonate unexploded
ordnance, such as the homemade roadside bombs that plague foreign
troops in Iraq.
This task now calls for explosives. In practice, that often means
using a rocket-propelled grenade, so as not to expose troops to
snipers. But rockets are expensive, and sometimes miss their targets.
Zeus is effective at a distance of 300 metres, and a laser beam,
unlike a rocket, always goes exactly where you point it.
At the moment, there is only one Zeus in the field. It is sitting in
the back of a Humvee in an undisclosed theatre of war. But if it
proves successful it will, according to Scott McPheeters of the
American army’s Cruise Missile Defence Systems Project Office for
Directed Energy Applications, be joined by a dozen more within a year.
You fight with light?
If Zeus works, it will make soldiers’ lives noticeably safer. But what
would really make a difference would be the ability to destroy
incoming artillery rounds. The Laser Area Defence System, LADS, being
developed by Raytheon, is intended to do just that—blowing incoming
shells and small rockets apart with laser beams. The targets are
tracked by radar and (if they are rockets) by infrared sensors. When
they come within range, they are zapped.
If it works, LADS will be a disruptive technology in more senses than
one. It will probably supersede Raytheon’s Phalanx system, which uses
mortars to do the same thing. Phalanx and its competitors require lots
of ammunition, and can be overwhelmed by heavy barrages. By contrast,
Mike Booen, vice-president of Advanced Missile Defence and Directed
Energy Weapons at Raytheon, observes, as long as LADS is supplied with
electricity it has “an infinite magazine”.
And LADS is merely the most advanced of a group of anti-artillery
lasers under development. Though Raytheon is convinced it is on to a
winner and is paying for most of the development costs out of its own
pocket, it has received some money from the Directed Energy Weapons
Programme Office of the American navy. In August, inter-service
rivalry reared its head, when the army handed Boeing a $36m contract
to develop a similar weapon, known at the moment as the High Energy
Laser Technology Demonstrator.
The army’s Space and Missile Defence Command is also in the game. Its
Joint High Power Solid State Laser, a prototype of which should be
ready next summer, is meant to destroy rockets the size of the
Katyushas used by insurgents in Afghanistan and Iraq, and by Hizbullah
in Lebanon.
The most ambitious laser project of all, though, is the Airborne
Laser, or ABL, being developed by the American Missile Defence Agency
and Boeing, Lockheed Martin and Northrop Grumman. The beam is
generated by mixing chemicals in a reactor known as a COIL (chemical
oxygen iodine laser) and packs a far bigger punch than the
electrically generated beams emitted by systems such as LADS. When
mounted in the nose-cone of a specially converted Boeing 747, an ABL
should be capable of disabling a missile from a distance of several
hundred kilometres.
The aim is to hit large ballistic missiles, including ICBMs, just
after they are launched—in the boost phase. The ABL is therefore a son
of Ronald Reagan’s Star Wars scheme, although in that programme, which
dates back to the 1980s, the lasers would have operated from space.
There are many advantages to attacking a missile during its boost
phase. First, it is still travelling slowly, so it is easier to hit.
Second, it is easy to detect because of its exhaust plume (once the
boost phase is over, the engine switches off and the missile follows
Newton’s law of gravity to its target). Third, if it has boosters that
are designed to be jettisoned, it will be a larger target when it is
launched. Fourth, any debris will fall on those who launched it,
rather than those at whom it was aimed.
Getting the system to work in practice will be hard, though. A missile
launch is observed using an infrared detector. Then the missile must
be tracked. When the beam fires, the control system must compensate
both for aircraft jitter and for distortions in the beam’s path caused
by atmospheric conditions. And ABL-carrying planes must be in the
right place at the right time in the first place. Even so, a number of
tests have been carried out, and according to Colonel Robert McMurry,
the head of the Airborne Laser Programme Office at Kirtland Air Force
Base in New Mexico, there will be a full-scale attempt to shoot down a
boost-phase missile off the coast of California next summer.
All of which is good news, at least for countries able to deploy the
new hardware. But wars are not won by defence alone. What people in
the business are more coy about discussing is the offensive use of
lasers. At least one such system is under development, though. The
aeroplane-mounted Advanced Tactical Laser, or ATL, another chemical
laser being put together by Boeing and the American air force, is
designed to “neutralise” targets on the ground from a distance of
several kilometres. Targeting data will be provided by telescopic
cameras on the aircraft, by pictures from satellites and unmanned
aerial drones, and by human target-spotters on the ground. The
question is: what targets?
The ATL’s supporters discuss such possibilities as disabling vehicles
by destroying their wheels and disrupting enemy communications by
severing telephone lines. Killing troops is rarely mentioned. However,
John Pike, the director of GlobalSecurity.org, a military think-tank
in Alexandria, Virginia, who is an expert on ATL, says its main goal
is, indeed, to kill enemy combatants.
Surely this is forbidden?
Boeing is unwilling to discuss the matter and John Wachs, the head of
the Space and Missile Defence Command’s Directed Energy Division,
observes that it is “politically sensitive”. The public may have
misgivings about a silent and invisible weapon that would boil the
body’s fluids before tearing it apart in a burst of vapour.
That seems oddly squeamish, though. War is not a pleasant business. It
is doubtful that being burst by a laser is worse than being hit by a
burst from a machine gun. As the Sudanese found out at the Battle of
Omdurman in 1898, the year that “The War of the Worlds” was published,
that is pretty nasty too.