
Frickin’ Laser Beams: Fact vs Fiction - J3L2404
http://martianchronicles.wordpress.com/2010/02/08/frickin-laser-beams-fact-vs-fiction/
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rflrob
>But really, the most likely place for lasers as a viable weapon is space.
Without air, the difficulties with plasma creation and turbulence are removed.
The issue of power and optics remain, but I could plausibly see a satellite or
space station with the stability and power to use a laser as a weapon.

The hard part of almost any space-based power consumption is the difficulty of
later dissipating the wasted heat energy. Conduction and convection don't work
when there's no surrounding medium. Without lots of clever technology, then,
your space-based laser is a double-edged sword.

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electromagnetic
> The hard part of almost any space-based power consumption is the difficulty
> of later dissipating the wasted heat energy. ... Without lots of clever
> technology, then, your space-based laser is a double-edged sword.

Not if you design it like a mine or a one-shot munition. Cheap high-powered
lasers and targeting systems will pave the way for laser-mines in space.
Without air, there is little need to pulse your lasers. Your weapon might as
well expend itself ASAP to do maximum damage without prolonged tracking and
risk of retaliatory fire. If you can only sustain pulsed fire at say 6 shots
per minute, that gives your enemy a lot of time to triangulate and return
fire, potentially with more lasers than you have. However, you could simply
expend your munition by firing it continuously for a minute until your mine
overheats and its systems fail.

If you're lucky your mine might survive the battle through a bad retaliatory
shot, or by destroying the target. If your mine survives, it could well live
to fight another day. It will eventually cool down, and assuming you'd provide
it with solar panels it could well charge itself up to repeat the process next
time you're attacked. It's also nice to point out that smaller objects
dissipate their heat faster, so attaching your weapons inside your ship may
only serve to hamper your efforts to fight effectively.

If you're actually defending _something_ , like say a asteroid mine then
you're likely to have enough spare material to afford heat sinks, or you could
use several meter wide asteroids to mount your lasers. Drill tubes and heat-
sink into the asteroid (it doesn't matter what it's made of, but a metallic
asteroid would be ideal) with copper-rods and you could fire for even longer
periods. On top of this, you could use the asteroid as a heat-sink for the
enemy fire. If you know a ship-mounted laser only fires once every 10 seconds,
you could simply realign so that there's a high probability that your enemy
will be hitting rock and not a vital system.

I doubt we'll be using them any time soon, but I think what people fail to
understand is the incredible vastness of space, but also the potentially
endless resources we will find there (at least from our present perspective
where we can't strip-mine our planet because of all that inconvenient molten-
gooiness that is containing precious materials).

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IgorPartola
One myth left: can I just use a mirror to reflect the high power laser at the
gun that fired it to destroy it?

~~~
mechanical_fish
Mirrors are not 100% efficient. That fraction of one percent will kill you if
the incident power density is high enough. Once one little portion of the
mirror is absorbing more energy than it can dissipate, that portion will heat
up and up. When it gets hot enough it tends to become less reflective - it
oxidizes or maybe just evaporates - and then you've got even higher absorption
at that spot, which makes it fail even faster and helps heat up adjacent
spots...

When this happens with a pulsed laser you can sometimes hear it. That tiny
snap-snap-snap is the sound of your three-hundred-dollar optic heading for the
trash. You'll look at it and see the telltale little spots. If you're cheap
you'll try just sliding it sideways to a non-spotted bit of surface, but
sometimes there isn't enough mirror for that...

That's with a high-tech custom-designed laser mirror, not a random surface of
some random object. And we're generally not _trying_ to destroy it. And yet
they often get destroyed, when you screw around with high-intensity lasers.

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eof
> The air poses another problem: it absorbs light. In fact, a high enough
> powered laser can cause the air itself to break down into a ragged line of
> plasma. I’ve seen this in the lab and it is awesome.

Badass.

edit: <http://www.youtube.com/watch?v=ZeqIZyUMDP4>

~~~
quanticle
_I mentioned lightning earlier and that’s relevant here. There is a way to
make use of the “plasma issue”, because plasmas conduct electricity. So in
theory it would be possible to use a laser as a long-distance taser! The laser
would first create a conduit of plasma out of the air, and then with a high
enough voltage, an electric shock could be send down the plasma to the target.
This would not be a subtle weapon: at this point the lightning analogy is not
really an analogy anymore. It would basically be a lightning gun, and would
make a noise to match. I thought I was being really clever when I thought of
this, but it turns out I’m not the first: the US military has experimented
with them._

So we don't get lasers but we do get plasma cannon/particle beams/PPCs? I'm
okay with that.

~~~
nolite
Hmmm... so controlled dielectric breakdown with lasers... Use E-fields from
lightning to produce gamma rays via

[http://www.wired.com/wiredscience/2011/01/lightning-
antimatt...](http://www.wired.com/wiredscience/2011/01/lightning-antimatter-
physics/)

collect positrons with a magnetic bottle. Finish with big jars of antimatter.
I wonder...

