
Military technology: Laser weapons get real - etiam
http://www.nature.com/news/military-technology-laser-weapons-get-real-1.17613
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ChuckMcM
The interesting bit is that folks realized that you can combine lasers without
having them be coherent and still get decent amounts of power on target. That
made a lot of off the shelf lasers much more viable.

The key though is the $10 a shot versus $100,000 a missile. That is what will
change the equation permanently. If the price of operation of a PATRIOT type
missile battery (or Israel's IRON DOME) goes from $1M/day in combat to
$100/day, you will see them deployed a lot more frequently.

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megrimlock
For a reference point on how far this tech has come:
[https://en.wikipedia.org/wiki/Soviet_laser_pistol](https://en.wikipedia.org/wiki/Soviet_laser_pistol)

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stevenrace
While that was designed in 1984, the US DoD had successfully tested laser
weapons over a decade earlier:

'The first was in 1973 when the USAF shot down a winged drone at their Sandia
Optical Range, New Mexico, using a carbon dioxide GDL and a gimballed
telescope. Subsequently, in 1976, the US Army employed an electrically pumped
HEL to destroy a number of winged and helicopter drones at the Redstone
Arsenal in Alabama. The USN, in March 1978, then engaged and destroyed an Army
TOW missile in flight' [1]

The first targets destroyed from an airborne platform (KC-135) were in 1979.

[1] [http://www.ausairpower.net/APA-DEW-HEL-
Analysis.html](http://www.ausairpower.net/APA-DEW-HEL-Analysis.html)

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codewithcheese
Serious question: is there a recorded case of a laser weapon being used in
combat?

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woodman
Yes, a US soldier was blinded by an Iraqi in Desert Strom [0]. The article
doesn't cover it, but as I remember it, the laser was part of a tank laser
range finding system - not a purpose build blinding device (the Chinese were
openly producing such weapons at the time). Another class of weapon would be a
dazzler [1], and those are used frequently.

[0] [http://www.ipsnews.net/1995/09/disarmament-blinding-laser-
we...](http://www.ipsnews.net/1995/09/disarmament-blinding-laser-weapons-must-
be-banned-now-red-cross/)

[1]
[http://en.wikipedia.org/wiki/Dazzler_(weapon)](http://en.wikipedia.org/wiki/Dazzler_\(weapon\))

~~~
codewithcheese
Thanks

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forgotAgain
Another Pentagon budget cycle has begun. Seemingly forever US companies have
put out puff pieces about technology which are then regurgitated by the media.
It's all about getting the public to support the ever increasing US military
budget.

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jessaustin
Looks like Nature is on-board with the effort this time around! Perhaps some
editors are looking forward to posh think-tank appointments?

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Retric
A surprising limitation on these systems is how short range they are. Ships
and Aircraft regularly fire on targets that are over the horizon, but lasers
are pure line of sight.

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ianstallings
True, but the horizon goes _down_ as you go _up_ ;)

Besides those are just weapon delivery systems. Those same systems can be used
to transport a laser weapon system to the area they want to attack (e.g.
missile + laser, aircraft + laser)

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Retric
These systems are huge, so you might get them in a drone but it would be a
large target as in the size of 20 seat business jet to a full 747.

Line of sight is ed: Nm.

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mrec
Probably a silly question, but would it be even remotely feasible to bounce a
ground- or ship-based laser off a drone-mounted mirror?

Pretty sure the obstacles to positioning the drone/mirror precisely enough
(and keeping the mirror clean enough) would be insurmountable, but couldn't
help wondering.

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Retric
Only in the rube Goldberg sense of a ridiculously inefficient system.

Also, if you can build a mirror to bounce the laser you can use that same
mirror to protect the target. But, N beams and N mirrors sidesteps this issue.

PS: An amusing idea is to use a fleet of drones with mirrors to cook the
target using sunlight.

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gliese1337

      Also, if you can build a mirror to bounce the laser you can use that same mirror to protect the target.
    

Not necessarily. The attacker controls the focal distance of the laser. If
they are using a mirror offensively, they can adjust the focal distance to
ensure that flux is not destructively high at the location of the relay
mirror, but is at the target. If you are trying to use the same mirror
defensively, the attacker can simply consider that mirror to be a new armor
target that needs to be destroyed before they can get at you, and adjust their
focus to create unsurvivable flux at the mirror surface.

~~~
Retric
To be clear, I did not mean that as a total defense. Still mirrors can be
useful in combination with other things.

For example the target can use a high deflection angle to disperse the beam.
AKA you beam's intensity is sin X and as it covers 1 / (sin X) area. So full
intensity = 90 degrees, and at 10 degrees your down to 17.4% intensity. For
something like a Mortar rotation can also be a significant benefit.

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ghostberry
I can't help thinking that in the anti-mortar role, there are very simple
countermeasures that would severely reduce the laser's effectiveness.

Reflective paint, ablative coatings, internal vacuum layer, heat insulation,
thermally insensitive explosive and detonators, etc.

~~~
gliese1337
Reflective paint is surprisingly ineffective. In order to work at all, it
needs to be tuned to the frequency of the attacking laser, and _not get dirty_
, or scratched up, or otherwise gain significant imperfection in the finish,
which is rather difficult to achieve when firing out a cannon and flying
through the air.

Even if those conditions are met, however, mirrors still make for surprisingly
bad defense against weaponized lasers, simply because no mirror is 100%
efficient. The 0.1-ish% of a well focused, high-powered weapons laser that
_doesn 't_ get reflected by a ridiculously high quality mirror on initial
contact will still damage and deform the mirror, thus allowing more and more
of the laser's power to be deposited in the target with increasing dwell time.

Laser weapons avoid destroying their own optics by, first, using optics tuned
exactly to the specific frequencies the weapon is designed to fire, and
second, by using relatively large focusing mirrors / lenses which keep the
power/area on the weapon optics below dangerous levels. Even so, real laser
weapons have ridiculous cooling requirements to keep from destroying
themselves with waste heat, which keeps their efficiency rather low.

There are other countermeasures that can be used against lasers, to be sure;
mirrors just ain't one of them.

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ghostberry
You took "reflective" too literally. I just meant more reflective to IR than
dark green paint that most military stuff gets painted with. I never meant a
mirror surface. Just the IR equivalent of white paint.

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gliese1337
White paint (or IR-colored paint, in this case) is _worse_ than a mirror
surface; it starts out at a disadvantage already. By assuming a mirror
surface, I'm giving you the benefit of the doubt- anything else would be _even
more useless_.

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SomeStupidPoint
I actually don't understand your point.

Are you saying that picking a coating with low absorption in the part of the
spectrum that the laser is in doesn't matter?

I'm not sure I agree with you, since it makes other strategies (such as
rolling the projectile in flight or using ablative materials) more effective
if the projectile is slower to absorb energy from the laser.

The whole name of the game is to collect as little energy as possible,
disperse it as evenly as possible (in non-important areas), and avoid deep
penetration.

It doesn't magically stop the laser to paint it the right color, but choosing
the right paint is an important part to penetrating laser based defenses.

~~~
gliese1337
For a sufficiently powerful laser weapon, yes, low absorption doesn't matter.

If the attacker is just trying to heat up the bulk of the target until it
melts, or is otherwise disabled, then a low-absorption coating would indeed
slow them down. Such weapons have been proposed, but they're not especially
effective anyway, and that's not how modern experimental military lasers are
designed to work.

Weapons lasers are designed to focus as much power as possible into as small
an area as possible in order to cause physical damage at the point of impact-
blasting a hole in the thing, setting it on fire, etc. Heating the bulk of the
target is a mere side-effect.

In that regime, anything less than 100% reflectivity is essentially pointless.
Sure, it'll delay penetration, but not by any significant amount. Within a
very tiny fraction of a second, the part of the laser energy that you do
absorb in the target spot will be enough to destroy the reflective coating,
and bring the full beam energy to bear. Unless your projectiles are expected
to have flight times measured in milliseconds, the delay provided by a special
low-absorption coating is utterly useless.

If you can prevent the enemy from dwelling on a particular spot, then things
look much better. If you can screw up their targeting quickly enough, maybe
you can actually prevent damage to the reflective coating after all. Even if
you can't, maybe you can keep the laser occupied with constantly eating
through fresh areas of reflective armor, never absorbing the beam's full
power. But at that point, it's not the low-absorption coating that's saving
you- it's your ability to screw up their targeting.

~~~
SomeStupidPoint
Again, I don't think reflective coatings are a lone solution, but I do think
that they enhance other tactics, and as such, are a key aspect of defense in
depth. However, those contributions are key to those other systems working at
all.

For example, the typical bullet rotates at ~200,000RPM. This is about 3,000
revolutions a second, or about 300 microseconds a revolution. Figuring a
larger projectile could only rotate about a tenth of the rate, we get about 3
milliseconds per rotation on a shell.

At 3 seconds per revolution, I suspect that we're inside of the timing windows
that talking about the efficiency of energy absorption and dissipation in the
coating that the laser is striking is relevant, and we can begin to talk about
the laser energy being dissipated over more than a single fixed point.

However, I suspect that such tactics (as high velocity spinning) can only
mitigate the effects of the lasers and not stop them in isolation. It needs to
be tied together with a coherent plan to dissipate the energy that areas do
absorb and scatter the beam's focus using ablated coating.

In terms of energy absorption rates, energy dissipation rates, and ablative
properties, picking the right coating for your mortars trying to pierce laser
defenses is essential.

tl;dr: It's a synergy thing, since the low-absorption coating reduces the
demands on screwing up their targeting, and screwing up their targeting
reduces the demand on a protective coating.

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antmaper
Just paint the missiles with reflective paint.

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pingou
From the article:

"MBDA's tests have also helped to debunk the science-fiction idea that
reflective armour would defend against laser weapons. They found that any dust
on the mirrored surface would get burned in, and lead to the destruction of
the target even faster than with a non-reflective surface."

gliese1337 also explained it more in details in this thread.

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antmaper
I need to learn to read before comment lol

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oldpond
_pew_ _pew_ :) Couldn't resist.

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Jun8
Ah, the sound of lasers in space! I find the way laser rays are depicted in
movies interesting (other than the silly "bad guys use red beams" thing). They
are generally shown as a "bolt" with a clear beginning and end that travels
through space at a low speed (good compilation from Star Wars here:
[https://www.youtube.com/watch?v=QRJ9Evjm5Xs](https://www.youtube.com/watch?v=QRJ9Evjm5Xs)).
This, I believe, is why spaceships have to at such close proximity to each
other in battles, you have to see the laser beam bolt thingie go from ship to
the other at that low speed. This also opens up the possibility of dodging
laser beams. Now, it could be that these are not really laser beams but
particle beams
([http://en.wikipedia.org/wiki/Physics_and_Star_Wars](http://en.wikipedia.org/wiki/Physics_and_Star_Wars)).

BTW, I recently found that sound _can_ travel in space, albeit very very
inefficiently: [http://physics.stackexchange.com/questions/162184/what-is-
th...](http://physics.stackexchange.com/questions/162184/what-is-the-speed-of-
sound-in-space)

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oldpond
I like the way they did it in Eve Online with the mining animations. The
"bolt" animation should be plasma weapons, and "pew pew" seems a bit too cute
and cuddly for that.

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baldfat
The question is will it pop popcorn inside a house? A really large amount of
popcorn?

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baldfat
Here the link I am referring to before I get 4 down votes. This "joke"
actually is referring to something special. A 1980s movie about technology,
military and academia.

[https://www.youtube.com/watch?v=rthHSISkM7A](https://www.youtube.com/watch?v=rthHSISkM7A)

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skj
jokes are never funny if you have to explain them. just let the reference sit,
and make those who get it feel special :)

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baldfat
That was 100% my plan but than I was at -3 votes. Figured if I got one more no
one else would see it.

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resonation
Seriously, this community can be a cruel mistress sometimes.

