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Message no. 1
From: One Ronin <ronin@*******.COM>
Subject: Lasers and Ronin's combat corner......
Date: Tue, 10 Nov 1998 17:23:57 PST
Gather 'round boys and girls......it's time to dicuss Shadowrun combat
stuff. For those of you who don't know me, I'm Ronin. I occasionally
post combat related things to ShadowRN. I have some years experience in
the military (Army Infantry), which gives me a certain view on combat
that not a whole lot of non-military/non-law enforcement people have. I
don't consider myself an expert, just someone who's got a little
experience. Oh, and as you can tell, I'm quite long winded. Anyway, to
the point....

Welcome to Ronin's Combat Corner....part 1.

Today's topic: Laser Weapons.....and why no intelligent Shadowrunner
would use one.

First, I want to say that Lasers are quite powerful weapons. 15M vs 1/2
impact armor will tear through almost anything, plus you don't have to
worry about recoil. Not to mention that their firing trajectory is dead
straight out PAST maximum effective range, and the beam isn't effected
by wind.

That having been said, let's get to the drawbacks. I won't talk about
cost or availability...that is a given. Let's talk about penetration.
High penetration is a double edged sword, especially for lasers. Sure,
that laser beam will shoot clean through the badguy's armored jacket,
but it's also going to go clean through him, the wall behind him, the
wall behind that, the wall behind that, etc.
Think about it....a power of 15 versus 1/2 impact. That means that a
laser fired point blank at a wall with a barrier rating of 28 will punch
clean through and continue on for another several hundred meters before
becoming about as harmless as a flashlight. OUCH! Watch out for the
innocents. Hell, in a crowded city like Seattle, firing this weapon
will almost guarantee a hit on some kid watching the trid, or his mom
washing dishes.

Now, let's say you just don't give a shit about innocents. There's more
drawbacks. Most Shadowrunners do their work at night. This is the
worst absolute time to be packing a laser. First, anytime you fire it,
you're gonna light up the area where you are like a damn beacon.
Perfect to tell the sec-guards right where you are. You won't make much
noise, but everyone for hundreds of meters around you will know exactly
where you are. Bad news in this business. Second problem with lasers
at night......almost anyone operating at night is going to use some kind
of vision aid, be it low light/thermo cybereyes or goggles, or natural
night vision. Low-light amplifies the ambient light in the area to
allow for better night vision. Boy, is that sucker going to flare up
everytime you fire that laser. Many times I've had to fire my M-16 at
night while wearing NVGs, and let me tell ya, boys and girls, just that
little bit of muzzel flash screws up your night vision. Thermo gets
affected just as bad. Imagine how much heat these things produce to
burn through armor like they do. Even if you are going in natural with
no aids or magical assistance, the flash from the laser will screw up
your natural night vision.
Last but not least is target threat evaluation. Check this out: You are
your 5 man security detail are patrolling the grounds for an R&D
intstallation and come across 4 Shadowrunners trying to infiltrate the
place. Weapons are drawn and fire is exchanged. The shadowrunners are
armed with the following, one with a heavy pistol, one with an SMG, one
with a shotgun, and one with a laser. Who's the most immediate threat
to you and your sec-detail in your heavy security armor? Right....shoot
the guy with the laser. Plain and simple. If that doesn't happen, the
GM has just made an insanely idiotic call. Remember, the badguys have
brains too.

Well folks, that concludes my rant about lasers. I never have viewed
them as munchy in the least, but they do become overpowerd when a GM
fails to keep in mind the things that I mentioned above. So, nextime a
PC wants to call in every favor anyone owes him and blow that half a
million nuyen (that he's been saving up his entire career) on a laser,
go ahead, let him have it. Then, watch the fun start every time he
tries to use it.

Thanks for taking the time to read this, which you must have if you got
this far. Next on Ronin's Combat Corner: Silencers, and how they have
bad points too.

Please feel free to e-mail any comments, rants, or flames. I'm no
stranger to criticism...remember, I've been in the Army. Later.

-Ronin.


Mai mentsu konna mai kikyo.

ICQ #:11373195


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Message no. 2
From: Paul Gettle <RunnerPaul@*****.COM>
Subject: Re: Lasers and Ronin's combat corner......
Date: Tue, 10 Nov 1998 23:18:15 -0500
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At 05:23 PM 11/10/98 -0800, Ronin wrote:
>Now, let's say you just don't give a shit about innocents. There's
more
>drawbacks. Most Shadowrunners do their work at night. This is the
>worst absolute time to be packing a laser. First, anytime you fire
it,
>you're gonna light up the area where you are like a damn beacon.

Really? I was always taught that lasers produce a coherant beam of
light with minimal beam spread, and that unless there was a
signifigant amount of suspended particulates matter in the air that
the laser is fired through the beam is practically invisible.

- From what I understand, the only thing that would get lit up like a
damn beacon would be the centimeter-sized spot where the laser
intersects with the target. From the footage I've seen of some of the
lasers tested in the SDI project, the target point gets lit up, but
there is no visible beam.

Any of the list's resident Physics Gurus have practical experience
with high power, extremely short pulse lasers?

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--
-- Paul Gettle, #970 of 1000 (RunnerPaul@*****.com)
PGP Fingerprint, Key ID:0x48F3AACD (RSA 1024, created 98/06/26)
C260 94B3 6722 6A25 63F8 0690 9EA2 3344
Message no. 3
From: Robert Watkins <robert.watkins@******.COM>
Subject: Re: Lasers and Ronin's combat corner......
Date: Wed, 11 Nov 1998 15:37:52 +1100
Paul Gettle writes:
> - From what I understand, the only thing that would get lit up like a
> damn beacon would be the centimeter-sized spot where the laser
> intersects with the target. From the footage I've seen of some of the
> lasers tested in the SDI project, the target point gets lit up, but
> there is no visible beam.
>
> Any of the list's resident Physics Gurus have practical experience
> with high power, extremely short pulse lasers?

Any short duration pulse laser would not produce a visible beam. The pulse
would last about half a second at most, and your brain wouldn't register it
before it had gone, assuming that there was sufficent light scatter from the
beam to register anyway.

And as for the high power and punching holes in stuff that Ronin mentioned,
I'd dispute it, but the Physics Gurus can feel free to correct me. Laser is
light. It's not going to go through something that's not transparent, so you
won't have to worry about the laser light coming out the other side until
there's a clear hole. Now, no matter how powerful the beam, the dispersion
of the target material will take time, and a pulse laser doesn't have that
much time. Odds are the target will eat all the energy of the pulse, save
for what gets reflected away.

All IMNSHO, of course.

--
Duct tape is like the Force: There's a Light side, a Dark side, and it
binds the Universe together.
Robert Watkins -- robert.watkins@******.com
Message no. 4
From: "D. Ghost" <dghost@****.COM>
Subject: Re: Lasers and Ronin's combat corner......
Date: Tue, 10 Nov 1998 22:54:13 -0600
On Tue, 10 Nov 1998 23:18:15 -0500 Paul Gettle <RunnerPaul@*****.COM>
writes:
>-----BEGIN PGP SIGNED MESSAGE-----
>At 05:23 PM 11/10/98 -0800, Ronin wrote:
>>Now, let's say you just don't give a shit about innocents. There's
more
>>drawbacks. Most Shadowrunners do their work at night. This is the
>>worst absolute time to be packing a laser. First, anytime you fireit,
>>you're gonna light up the area where you are like a damn beacon.

>Really? I was always taught that lasers produce a coherant beam of
>light with minimal beam spread, and that unless there was a
>signifigant amount of suspended particulates matter in the air that
>the laser is fired through the beam is practically invisible.
>
>- From what I understand, the only thing that would get lit up like a
>damn beacon would be the centimeter-sized spot where the laser
>intersects with the target. From the footage I've seen of some of the
>lasers tested in the SDI project, the target point gets lit up, but
>there is no visible beam.
>
>Any of the list's resident Physics Gurus have practical experience
>with high power, extremely short pulse lasers?

I'm no Physics Guru (yet ;), but from what I understand, there are always
particles in the air and they will cause some beam dispersion. In most
cases, this effect is negligable. Maybe you can see a faint beam if you
have low-light vision. I don't know about thermo. The only time the
beam will be openly visible is if there are some heavy duty particles in
the path (ie, smoke, dust, mist, etc.). The problem (for the guy with
the laser) here is that this praticly creates an arrow saying "He's over
there!".

If you want to know what shooting a laser would look like, try this: If
you have access to a laser sight or laser pointer, turn out the lights
and point the thing at a wall. What do you see? Well, I happen to have
laser handy and know what? All I see is the projection on a wall.

The reason is exactly what Paul said. All the little photons are
traveling straight towards the target and (ideally) none are travelling
elsewhere. What Ronin might be thinking of is a light bulb (ie, he might
have considered the beam as one big light bulb.). A light bulb projects
photons in all directions (almost all ... some are blocked by the
fixture.). Thus, light bulbs light up rooms very well but lasers don't.


When you have beam scatter, some of the photons are reflected off the
particles intercepting the beam.

In ideal conditions, the "invisibility" of the beam is independent of the
power output (which is just how many photons are being cranked out and
possibly what wavelength.). In practical conditions, the higher output
beams are more visible because there are more photons to be potentially
reflected.

To sum up, in most cases laser beams are "invisible", while the point the
strike isn't.

If you want to look to Hollywood for laser effects, don't look at space
flicks. Look at the spy and cat burglar movies where an assassin's laser
sight is spotted by the little red dot on the chest or where the thief
sprays something in the air to spot the laser sights.

I'm sure Mr. Wizar--err--Adam (or someone else) will correct me if I got
any of that wrong.

--
D. Ghost
(aka Pixel, Tantrum, RuPixel)
"Coffee without caffeine is like sex without the spanking." -- Cupid
re-cur-sion (ri-kur'-zhen) noun. 1. See recursion.

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Message no. 5
From: Paul Gettle <RunnerPaul@*****.COM>
Subject: Re: Lasers and Ronin's combat corner......
Date: Wed, 11 Nov 1998 00:11:13 -0500
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At 03:37 PM 11/11/98 +1100, Robert wrote:
>Any short duration pulse laser would not produce a visible beam. The
pulse
>would last about half a second at most, and your brain wouldn't
register it
>before it had gone, assuming that there was sufficent light scatter
from the
>beam to register anyway.

Are you sure that the brain wouldn't register a short duration burst
of bright light? When was the last time someone took a flash
photograph in your general vicinity? Weapons grade lasers would
probably have a pulse significantly shorter than a camera flash
though; from what I remember hearing about the theory of weapons
lasers, they have very brief pulses, to minimize the effects of target
movement.

However, I'm still skeptical that there would be enough beam scatter
to begin with.

>And as for the high power and punching holes in stuff that Ronin
mentioned,
>I'd dispute it, but the Physics Gurus can feel free to correct me.
Laser is
>light. It's not going to go through something that's not transparent,
so you
>won't have to worry about the laser light coming out the other side
until
>there's a clear hole. Now, no matter how powerful the beam, the
dispersion
>of the target material will take time, and a pulse laser doesn't have
that
>much time. Odds are the target will eat all the energy of the pulse,
save
>for what gets reflected away.

The bits above about lasers being stopped by non-transparent material
is certainly true, but then again, bullets are usually stopped by
solid objects. Shadowrun does have rules for Firing Through Barriers,
which works reasonably well for bullets being able to punch through a
solid mass, but the interaction between lasers and barriers has never
been sufficiently fleshed out. Ronin's interpertaion has the lasers
treating barriers the same way as they do impact armor. I think I'd
use a full barrier rating, if I were making the call.

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--
-- Paul Gettle, #970 of 1000 (RunnerPaul@*****.com)
PGP Fingerprint, Key ID:0x48F3AACD (RSA 1024, created 98/06/26)
C260 94B3 6722 6A25 63F8 0690 9EA2 3344
Message no. 6
From: Paul Gettle <RunnerPaul@*****.COM>
Subject: Re: Lasers and Ronin's combat corner......
Date: Wed, 11 Nov 1998 00:23:12 -0500
-----BEGIN PGP SIGNED MESSAGE-----

At 10:54 PM 11/10/98 -0600, D.Ghost wrote:
<<I've changed the order of a few of D.Ghost's paragraphs. --Ed.>>
>When you have beam scatter, some of the photons are reflected off the
>particles intercepting the beam.
>
>In ideal conditions, the "invisibility" of the beam is independent of
the
>power output (which is just how many photons are being cranked out
and
>possibly what wavelength.). In practical conditions, the higher
output
>beams are more visible because there are more photons to be
potentially
>reflected.

Another thing to consider, something in Ronin's favor, is the fact
that since this is such a high power laser, any particles that would
be in the beam's path would not just scatter the beam, but would
perhaps even become incandescant as the laser vaporizes them.

>The problem (for the guy with the laser) here is that this praticly
>creates an arrow saying "He's over there!".

However, weapons lasers typically have very short pulses, to make sure
that the target doesn't have much time to move about while the beam is
striking. This ensures that the bulk of the laser's energy lands on a
small point of the target, concentrating the energy into a single spot
of damage.

If there were a visible beam, would it be of enough duration to point
back to the shooter, or would it just be enough to flash dazzle
everyone?

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--
-- Paul Gettle, #970 of 1000 (RunnerPaul@*****.com)
PGP Fingerprint, Key ID:0x48F3AACD (RSA 1024, created 98/06/26)
C260 94B3 6722 6A25 63F8 0690 9EA2 3344
Message no. 7
From: "D. Ghost" <dghost@****.COM>
Subject: Re: Lasers and Ronin's combat corner......
Date: Wed, 11 Nov 1998 00:17:11 -0600
On Wed, 11 Nov 1998 00:23:12 -0500 Paul Gettle <RunnerPaul@*****.COM>
writes:
>-----BEGIN PGP SIGNED MESSAGE-----
<SNIP>
>>The problem (for the guy with the laser) here is that this praticly
>>creates an arrow saying "He's over there!".

>However, weapons lasers typically have very short pulses, to make sure
>that the target doesn't have much time to move about while the beam is
>striking. This ensures that the bulk of the laser's energy lands on a
>small point of the target, concentrating the energy into a single spot
>of damage.

True.

>If there were a visible beam, would it be of enough duration to point
>back to the shooter, or would it just be enough to flash dazzle
>everyone?

Well, if the beam was visible, it'd still be relatively faint. With
enough scatter, you could see it well but it still wouldn't dazzle anyone
(except maybe the target ;). Remember, even with some hefty scatter,
most of the beam is going towards the target, and of the percentage
that's not going towards the target, most is NOT going towards you. In
answer to the rest of your question, it depends on how short the duration
is and I don't really know about that.

--
D. Ghost
(aka Pixel, Tantrum, RuPixel)
"Coffee without caffeine is like sex without the spanking." -- Cupid
re-cur-sion (ri-kur'-zhen) noun. 1. See recursion.

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Message no. 8
From: Rune Fostervoll <runefo@***.UIO.NO>
Subject: Re: Lasers and Ronin's combat corner......
Date: Wed, 11 Nov 1998 10:58:20 GMT
*SNIP laser fire can be traced*

Yes and no.

A laser gives off light by definition, but it might as well be infrared or
ultraviolet as light in the visible spectrum. (Ultraviolet light is harder
to manufacture, though, IIRC). So using ifrared, it will not be directly
visible light. Even if the light was visible, it would not be visible
unless it was reflected off something - fog, smoke or rain, for instance,
which also reduces the effect of the weapon. It would reflect off
sparse dust particles, which would flash burn, in almost any enviornment.
These flashes would be visible at night, less so at day. It would also
leave a trail of heated air visible with thermographic.

Thus, the firer can be detected, and it leaves a trail towards the firer
for those that know how to look. On the other hand it is extremely quiet, has
good range, no recoil (so it can be fired from any position) and good killing
power... at short range.

It's an okay weapon, IMO, but know thy foe and know thy terrain before deciding
to use it. In an ideal situation it's a bloody good weapon, in the wrong
situation it's a bloody nuisance. (But then, aren't everything?)

Regards,
Fade

--

ADVICE, n. The smallest current coin.
-Ambrose Bierce
Message no. 9
From: Gurth <gurth@******.NL>
Subject: Re: Lasers and Ronin's combat corner......
Date: Wed, 11 Nov 1998 13:08:37 +0100
According to One Ronin, at 17:23 on 10 Nov 98, the word on the street was...

> Now, let's say you just don't give a shit about innocents. There's more
> drawbacks. Most Shadowrunners do their work at night. This is the
> worst absolute time to be packing a laser. First, anytime you fire it,
> you're gonna light up the area where you are like a damn beacon.
> Perfect to tell the sec-guards right where you are. You won't make much
> noise, but everyone for hundreds of meters around you will know exactly
> where you are. Bad news in this business.

Only if there is enough dust or vapor in the air to scatter the beam
enough to make it visible. Also, if the laser does not work in the visible
spectrum, most people won't be able to see it; only dwarfs and trolls, and
of course anyone with thermographic modifications, can spot it.

> Many times I've had to fire my M-16 at night while wearing NVGs, and let
> me tell ya, boys and girls, just that little bit of muzzel flash screws
> up your night vision.

There's a reason tank fire control systems close the gunner's optics when
the main gun is fired... Hmm, idea for smartlink cyberware: link it to
cybereyes and artificially make them blink (i.e. shut off the link to the
brain) every time the gun fires. This might be impractical at full-auto,
but it could help with single shots.

--
Gurth@******.nl - http://www.xs4all.nl/~gurth/index.html
He likes to sleep. Sometimes he has good dreams.
-> NERPS Project Leader * ShadowRN GridSec * Unofficial Shadowrun Guru <-
-> The Plastic Warriors Page: http://www.xs4all.nl/~gurth/plastic.html <-
-> The New Character Mortuary: http://www.electricferret.com/mortuary/ <-

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Incubated into the First Church of the Sqooshy Ball, 21-05-1998
Message no. 10
From: "D. Ghost" <dghost@****.COM>
Subject: Re: Lasers and Ronin's combat corner......
Date: Wed, 11 Nov 1998 06:42:40 -0600
On Wed, 11 Nov 1998 10:58:20 GMT Rune Fostervoll <runefo@***.UIO.NO>
writes:
>*SNIP laser fire can be traced*
>
>Yes and no.
>
<SNIP>
>It would also
>leave a trail of heated air visible with thermographic.
>
>Thus, the firer can be detected, and it leaves a trail towards the firer
>for those that know how to look.
<SNIP>

And how long will this trail linger?

--
D. Ghost
(aka Pixel, Tantrum, RuPixel)
"Coffee without caffeine is like sex without the spanking." -- Cupid
re-cur-sion (ri-kur'-zhen) noun. 1. See recursion.

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Message no. 11
From: Sean McCrohan <mccrohan@*****.OIT.GATECH.EDU>
Subject: Re: Lasers and Ronin's combat corner......
Date: Wed, 11 Nov 1998 08:25:39 -0500
Quoting D. Ghost (dghost@****.COM):
> <SNIP>
> >It would also
> >leave a trail of heated air visible with thermographic.
> >
> >Thus, the firer can be detected, and it leaves a trail towards the firer
> >for those that know how to look.
> <SNIP>
> And how long will this trail linger?

Ought to depend on ambient temperature, amount of air circulation,
etc.

--Sean
--
Sean McCrohan (mccrohan@**.gatech.edu) | "He uses his folly as a stalking
Grad Student, Human-Computer Interaction | horse, and under the presentation
Georgia Institute of Technology | of that he shoots his wit."
http://www.lcc.gatech.edu/~smccrohan | _As You Like It_, Act 5 Sc 4
Message no. 12
From: Hatchetman <hatchet@*********.BC.CA>
Subject: Re: Lasers and Ronin's combat corner......
Date: Wed, 11 Nov 1998 05:35:55 -0800
> If you want to know what shooting a laser would look like, try this: If
> you have access to a laser sight or laser pointer, turn out the lights
> and point the thing at a wall. What do you see? Well, I happen to have
> laser handy and know what? All I see is the projection on a wall.
>
> The reason is exactly what Paul said. All the little photons are
> traveling straight towards the target and (ideally) none are travelling
> elsewhere. What Ronin might be thinking of is a light bulb (ie, he might
> have considered the beam as one big light bulb.). A light bulb projects
> photons in all directions (almost all ... some are blocked by the
> fixture.). Thus, light bulbs light up rooms very well but lasers don't.

Correct me if I'm wrong, but I thought that a laser powerful enough to do
damage to walls, people, and such ionized the air along it's path similar
to what lightning does, and that's the flare you see. I've got laser
pointers too, but they're too weak to be a good example.
Message no. 13
From: David Buehrer <dbuehrer@******.CARL.ORG>
Subject: Re: Lasers and Ronin's combat corner......
Date: Wed, 11 Nov 1998 08:01:19 -0700
For the mere cost of a Thaum, Gurth wrote:
/
/ > me tell ya, boys and girls, just that little bit of muzzel flash screws
/ > up your night vision.
/
/ There's a reason tank fire control systems close the gunner's optics when
/ the main gun is fired... Hmm, idea for smartlink cyberware: link it to
/ cybereyes and artificially make them blink (i.e. shut off the link to the
/ brain) every time the gun fires. This might be impractical at full-auto,
/ but it could help with single shots.

Or, you could just get Flare Compensation for your cybereyes. Or would
that be to easy? ;)

-David B.
--
"Earn what you have been given."
--
email: dbuehrer@******.carl.org
http://www.geocities.com/TimesSquare/1068/homepage.htm
Message no. 14
From: K in the Shadows <Ereskanti@***.COM>
Subject: Re: Lasers and Ronin's combat corner......
Date: Wed, 11 Nov 1998 13:14:27 EST
In a message dated 11/11/1998 8:26:29 AM US Eastern Standard Time,
mccrohan@*****.OIT.GATECH.EDU writes:

> > >Thus, the firer can be detected, and it leaves a trail towards the firer
> > >for those that know how to look.
> > <SNIP>
> > And how long will this trail linger?
>
> Ought to depend on ambient temperature, amount of air circulation,
> etc.
>
> --Sean
Here's a consideration all. Anyone seen those really cool thermal images of
lightning bolts? Anyone seen the movie-like versions, that show what the
trail of thermality is like after the strike? For something that lasts only a
relatively short amount of time, it's thermal trail is nearly as short.
Inrushing air fans out the thermal plumage fairly quickly.

Granted, this is a LOT more power than a laser, but the thermal plumage left
by an MP3 would be equally reduced, and therefore, IMO, not nearly as
traceable as one might be led to believe/hope for.

-K
Message no. 15
From: Gurth <gurth@******.NL>
Subject: Re: Lasers and Ronin's combat corner......
Date: Wed, 11 Nov 1998 19:40:37 +0100
According to David Buehrer, at 8:01 on 11 Nov 98, the word on the street was...

> Or, you could just get Flare Compensation for your cybereyes. Or would
> that be to easy? ;)

The way it's written in SR, no. But SR's flare compensation is just about
perfect anyway, in that it removes _all_ glare modifiers instantly (except
for really bright, fast strobe lights like those of flash paks). Rules-
wise, I have to agree with you that getting flare comp would negate any
penalty you might get from muzzle flash, but it doesn't make much sense
IRL if you ask me.

--
Gurth@******.nl - http://www.xs4all.nl/~gurth/index.html
He likes to sleep. Sometimes he has good dreams.
-> NERPS Project Leader * ShadowRN GridSec * Unofficial Shadowrun Guru <-
-> The Plastic Warriors Page: http://www.xs4all.nl/~gurth/plastic.html <-
-> The New Character Mortuary: http://www.electricferret.com/mortuary/ <-

GC3.1: GAT/! d-(dpu) s:- !a>? C+(++)@ U P L E? W(++) N o? K- w+ O V? PS+
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Incubated into the First Church of the Sqooshy Ball, 21-05-1998
Message no. 16
From: jpmumme <Grimlakin@**********.COM>
Subject: Re: Lasers and Ronin's combat corner......
Date: Wed, 11 Nov 1998 13:43:44 -0500
One Ronin wrote:

> Now, let's say you just don't give a shit about innocents. There's more
> drawbacks. Most Shadowrunners do their work at night. This is the
> worst absolute time to be packing a laser. First, anytime you fire it,
> you're gonna light up the area where you are like a damn beacon.
> Perfect to tell the sec-guards right where you are.

Just one problem that I see here Ronin. Lasers do not have to be visible.
if you extend your hand do you see the light reflecting off of the surface?
No. But it is their. Again lasers do NOT have to be visible things. You
could have a laser that fires into a spectrum that we can not see with the
naked eye. Now infrared or thermal I have no argument that they will be
able to see that blazeing trail.

> -Ronin.
>

Grimlakin
Message no. 17
From: Paul Gettle <RunnerPaul@*****.COM>
Subject: Re: Lasers and Ronin's combat corner......
Date: Wed, 11 Nov 1998 20:52:27 -0500
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At 10:58 AM 11/11/98 +0000, Fade wrote:
>It would also
>leave a trail of heated air visible with thermographic.

Wouldn't natural convection currents in the air disperse and obscure
such a trail? That heated air is going to start rising, after all; in
the few seconds after firing, wouldn't such a trail only be good for
determining the general direction the shot came from?

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--
-- Paul Gettle, #970 of 1000 (RunnerPaul@*****.com)
PGP Fingerprint, Key ID:0x48F3AACD (RSA 1024, created 98/06/26)
C260 94B3 6722 6A25 63F8 0690 9EA2 3344
Message no. 18
From: Hatchetman <hatchet@*********.BC.CA>
Subject: Re: Lasers and Ronin's combat corner......
Date: Wed, 11 Nov 1998 19:21:05 -0800
> Wouldn't natural convection currents in the air disperse and obscure
> such a trail? That heated air is going to start rising, after all; in
> the few seconds after firing, wouldn't such a trail only be good for
> determining the general direction the shot came from?

Close is good enough when you're looking. Gives you the general area.
Message no. 19
From: Robert Watkins <robert.watkins@******.COM>
Subject: Re: Lasers and Ronin's combat corner......
Date: Thu, 12 Nov 1998 13:30:58 +1000
About the laser "punching through" the target...

I'd say no, and here's why. All of this is based on my admittedly limited
understanding of how laser weapons work, and I invite those who know more to
correct me.

When a bullet hits a target, it causes damage by transfering its kinetic
energy to the target. That transfer of energy takes time, during which the
bullet is still moving, through the target. Under certain circumstances, the
bullet can shoot through. This is more likely to happen with high-power
bullets, as they move faster.

With a laser, it causes damage by transferring the light energy. Light is
either absorbed or reflected, or a bit of both, by the target. If the energy
is absorbed, it causes the temperature of the target area to rise. The
object of a laser weapon is to cause the temperature to rise sufficently to
cause a plasma to form, literally vaporising the target area. It is this
plasma that causes damage outside the area directly under the laser beam,
usually by explosively expanding. While this could explode through the
target, it's not going to go very far... someone a couple of meters behind
the victim isn't going to be affected too much by it. The laser beam itself
won't make it through the hole it is creating, because the plasma itself is
going to absorb the beam, and won't have cleared by the time the last of the
short pulse reaches the target. This is desired, because this means all the
energy of the beam (except for what is reflected) is absorbed by the victim.
(NOTE: This is for PULSE lasers only. Long duration lasers may very well be
able to shoot through, as the plasma will clear sooner or later)

So, shooting through barriers just don't work with lasers, unless the
barrier is extremely thin (like a Japanese paper wall thingy). Any barrier
that's actually got a rating will probably stop a laser beam, but anything
nearby would be affected still. In other words, if the barrier is being used
as extra armour, you'll still be hurt. If the barrier is a distance away,
you won't be.

How does that sound to the physics gurus out there?
--
.sig deleted to conserve electrons. robert.watkins@******.com
Message no. 20
From: Fade <runefo@***.UIO.NO>
Subject: Re: Lasers and Ronin's combat corner......
Date: Thu, 12 Nov 1998 04:32:14 +0000
Sean assumed:
> > >It would also
> > >leave a trail of heated air visible with thermographic.
> > >
> > >Thus, the firer can be detected, and it leaves a trail towards the firer
> > >for those that know how to look.
> > <SNIP>
> > And how long will this trail linger?
>
> Ought to depend on ambient temperature, amount of air circulation,
> etc.

That sounds reasonable, but doesn't give an idea of the time
involved.

I'd say one or perhaps two seconds, max. This is barely even an
educated guess, though, so your guess is as good as mine.

Perhaps very advanced tracking gear could trace it for longer, but
probably not more than 5-10 seconds.

Regards,
--
Fade

And the Prince of Lies said:
"To reign is worth ambition, though in Hell:
Better to reign in hell than to serve in heaven."
-John Milton, Paradise Lost
Message no. 21
From: Adam Getchell <acgetchell@*******.EDU>
Subject: Re: Lasers and Ronin's combat corner......
Date: Thu, 12 Nov 1998 11:51:30 -0800
>Any of the list's resident Physics Gurus have practical experience
>with high power, extremely short pulse lasers?

Lasers in the laboratory are generally classified by types: Class 1, Class
2, Class 3A, Class 3B, and Class 4.

A Class 1 laser is totally enclosed, small output laser that cannot exceed
the Maximum Permitted Exposure Level (MPEL) under any conditions.

Class 2 and 3A lasers are low and medium power, visible range (400-700
nanometers), and will only cause damage if a person stares into the beam
for a long time or uses optical aids such as telescopes or binoculars. The
natural aversion response generally keeps exposure to under MPEL.

Class 3B lasers have output over 1 milliwatt and irradiance over 25 W-m^2.
Direct beam or specular reflection will cause damage to the retina.

A Class 4 laser can cause eye damage by diffuse or specular reflection.
This means that even if the beam reflects off something not-shiny (your
shirt, for example) it has enough intensity to cause retinal damage.

That being said, military lasers are Class 4.

The Hague convention prohibits the use of blinding lasers, but it is
certainly much easier to construct a laser to do this than a weapons grade
laser.

Military lasers, in general, use wavelengths that are most "transparent" in
the atmosphere. That includes visible light, the 2500 nanometer IR band,
UV, etc. The state of the free-electron laser technology is such that we
just about have a portable desktop free-electron X-ray laser.

(Pardon me, I'm amused by the above because the venerable Traveller game
predicts such things at TL13, and we are TL8 right now).

Lasers, by their nature, are phase-locked monochromatic beams, and are
scarcely visible in use unless significant dust or fog is available to
backscatter radiation in the direction of an observer. Target impact is
typically seen in the flash of the explosion, rather than backscattered
laser photons.

I do not think the retina would be able to register a nanosecond or
femtosecond pulse.

For military purposes, it requires 2 megajoules of energy per square
centimeter to be deposited on steel in order to vaporize it. Due to this
power requirement (and the realities of dispersion, attenuation, and
angular divergence) pulse lasers are most efficient, typically in the
nanosecond range (although femtosecond pulses are possible).

However, the problem arises that incoming laser light, as correctly noted
by Robert, converts the target surface into plasma, and the rest of the
pulse energy is dumped into this plasma rather than the target. This causes
"steam explosion" in organic targets, but reduces penetration of armor.

This problem is overcome in beam lasers through the use of a focussing or
pathway beam (typically IR) which provides information on target distance
and placement fed into the adaptive optics of the weapons laser, allowing
the beam to focus beyond the plasma. I've seen an impressive demonstration
of an Army air defense laser melting its way rather quickly through a 30cm
block of plastic.

A laser can burn its way through substances quickly under the proper
circumstances: enough energy deposition in a short amount of time focussed
on the same area. This is why simple SDI countermeasures included spinning
missiles and the use of reflective coatings.

A military X-ray laser, of course, would have enormous penetration. With
the use of the above adaptive optics, one could arrange for the energy dump
to peak at a particular location inside the target. It also negates the
strategies mentioned above. Unfortunate victims of such a weapon would
probably develop cancers or other radiation-exposure illnesses, assuming
they lived that long.

Of course, the firer of a poorly designed X-ray laser would contract the
same illnesses if the optics were poorly designed to permit significant
sidelobe scatter. Even so, such a weapon would be the province of a heavily
armored crew, rather than a man-portable device.

> -- Paul Gettle, #970 of 1000 (RunnerPaul@*****.com)
>PGP Fingerprint, Key ID:0x48F3AACD (RSA 1024, created 98/06/26)
>C260 94B3 6722 6A25 63F8 0690 9EA2 3344

--Adam

acgetchell@*******.edu
"Invincibility is in oneself, vulnerability in the opponent." --Sun Tzu
Message no. 22
From: The Bookworm <Thomas.M.Price@*******.EDU>
Subject: Re: Lasers and Ronin's combat corner......
Date: Thu, 12 Nov 1998 16:36:11 -0600
On Thu, 12 Nov 1998, Adam Getchell wrote:

> Military lasers, in general, use wavelengths that are most "transparent" in
> the atmosphere. That includes visible light, the 2500 nanometer IR band,
> UV, etc. The state of the free-electron laser technology is such that we
> just about have a portable desktop free-electron X-ray laser.
> (Pardon me, I'm amused by the above because the venerable Traveller game
> predicts such things at TL13, and we are TL8 right now).

Well it also messured computer memory in Kilobytes and diskspace in
Megabytes IIRC. Git a break, it was written in the early 80's. the SDI
research was still a black project at the time. Cool game though:)

> I do not think the retina would be able to register a nanosecond or
> femtosecond pulse.

.000000001 secounds and .000000000001 secounds respectivly If i rember my
Physics courses. Pulsed lasers are REALLY short. Human reactions are on
the order of .1 secounds at TVs refresh their screens at around .03
secounds to give you some idea of the time scale we have here.

Thomas Price
aka The Bookworm
thomas.m.price@*******.edu
Message no. 23
From: Zixx <t_berghoff@*********.NETSURF.DE>
Subject: Re: Lasers and Ronin's combat corner......
Date: Sun, 15 Nov 1998 23:50:03 +0100
On 11 Nov 98, at 15:37, Robert Watkins wrote:

> Any short duration pulse laser would not produce a visible beam. The
pulse
> would last about half a second at most, and your brain wouldn't register it
> before it had gone, assuming that there was sufficent light scatter from the
> beam to register anyway.
>
> And as for the high power and punching holes in stuff that Ronin mentioned,
> I'd dispute it, but the Physics Gurus can feel free to correct me. Laser is
> light. It's not going to go through something that's not transparent, so you
> won't have to worry about the laser light coming out the other side until
> there's a clear hole. Now, no matter how powerful the beam, the dispersion
> of the target material will take time, and a pulse laser doesn't have that
> much time. Odds are the target will eat all the energy of the pulse, save
> for what gets reflected away.

100 out of 100 points. :)

If the laser wanted to get through the target, it would have to varporize the
matter in its way and then wait until the smoke left the hole (if it doesn't,
there won't be much of a laser left (see Huygens)). Then, repeat the
procedure with the next barrier.


Tobias Berghoff a.k.a Zixx
ICQ: 9293066

A society without religion is like a crazed psychopath without a loaded .45

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Message no. 24
From: Zixx <t_berghoff@*********.NETSURF.DE>
Subject: Re: Lasers and Ronin's combat corner......
Date: Sun, 15 Nov 1998 23:50:03 +0100
On 10 Nov 98, at 23:18, Paul Gettle wrote:

> Really? I was always taught that lasers produce a coherant beam of
> light with minimal beam spread, and that unless there was a
> signifigant amount of suspended particulates matter in the air that
> the laser is fired through the beam is practically invisible.
>
> - From what I understand, the only thing that would get lit up like a
> damn beacon would be the centimeter-sized spot where the laser
> intersects with the target. From the footage I've seen of some of the
> lasers tested in the SDI project, the target point gets lit up, but
> there is no visible beam.
>
> Any of the list's resident Physics Gurus have practical experience
> with high power, extremely short pulse lasers?

I simply consider myself as a part of the group, as a founding memeber
of the (never really established) ShadowRN.physics.comitee. :)

Well, of course you are right. Even a VERY high powered laser is not
going to illuminate anything except the targetspot. Of course, if someone
threw a smokegenade, that's another matter :)

(I've seen a couple of cutting-lasers, and none where visible).

Oh yeah, depending on the frequency of the laser and the target material,
you might not even see the target area.


Tobias Berghoff a.k.a Zixx
ICQ: 9293066

A society without religion is like a crazed psychopath without a loaded .45

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