Man-portable directed energy weapons possible?
Gil Lau
I know, this should probably be in the FAQ somewhere. If
this thread has been hammered to death, could someone
send me a summary?
The gist of the question is in the subject. Is it possible to
develop man-portable directed energy weapons for use
on a battlefield with foreseeable (i.e. near future, roughly
50 years) technologies? Solving power requirements for
a laser rifle is one thing, but will it be useless in early-
morning fog? Stuff like that. Thanks.
-- Gil
Alan D Kohler
In article <3367e...@news1.ibm.net>, gl...@jmpstart.com says...
I don't claim to be an expert, and most of those who could claim to be an
experts aren't allowed to discuss classified information :-), but from my
understanding, you can build a reasonably powerful man portable laser with
current technology, and it'd be the size of an older video recorder (very
bulky), and nowhere as efficient or weight effective as conventional weapons.
The main limiting factor is battery mass, but it's a big one.
And yes, a laser would be diminished if not totally stopped by a significant
layer of fog.
As for the next 50 years, that would depend on whether or not we have an
unforseable quantum leap in electrical power storage in that time - which
could happen; those who want to make more efficient electrical vehicles are
laboriously looking for just such a technology, which could easily be turned
to other purposes.
--
SPAM FILTER NOTICE - REMOVE "REMOVE2REPLY" to reply by email.
Alan D Kohler hwk...@REMOVE2REPLYpoky.srv.net
"Good, bad - I'm the guy with the gun." Ash, Army of Darkness
Dave Clements
Alan D Kohler wrote:
>
> In article <3367e...@news1.ibm.net>, gl...@jmpstart.com says...
> >
> >I know, this should probably be in the FAQ somewhere. If
> >this thread has been hammered to death, could someone
> >send me a summary?
> >
> >The gist of the question is in the subject. Is it possible to
> >develop man-portable directed energy weapons for use
> >on a battlefield with foreseeable (i.e. near future, roughly
> >50 years) technologies? Solving power requirements for
> >a laser rifle is one thing, but will it be useless in early-
> >morning fog? Stuff like that. Thanks.
>
> I don't claim to be an expert, and most of those who could claim to be an
> experts aren't allowed to discuss classified information :-), but from my
> understanding, you can build a reasonably powerful man portable laser with
> current technology, and it'd be the size of an older video recorder (very
> bulky), and nowhere as efficient or weight effective as conventional weapons.
> The main limiting factor is battery mass, but it's a big one.
In a sense we're already there. The lasers used to paint targets for
smart bombs and missiles etc. are man portable and are already powerful
enough to cause sight problems if you hit a man in the eyes.
> And yes, a laser would be diminished if not totally stopped by a significant
> layer of fog.
Operating at non-optical wavelengths can address this issue. I believe
that tanks use 10 micron imagers to see through smoke, for example.
> As for the next 50 years, that would depend on whether or not we have an
> unforseable quantum leap in electrical power storage in that time - which
> could happen; those who want to make more efficient electrical vehicles are
> laboriously looking for just such a technology, which could easily be turned
> to other purposes.
This is assuming that an electrical power system is used. The most
powerful lasers weight-for-weight developed to date are not in fact
electricallu powered but are chemical lasers. A friend of mine once
discussed this issue with someone who should know (OK, weak referencing
I know), and they came up with a plausible man-portable offensive laser
chemical laser system.
It would look something like a flame thrower, with backpack mounted
tanks for the powering chemicals and for the expended fuel. I'm not sure
how powerful this would be, but I suspect it could work as an
anti-personel weapon and against light armour. You'd need something
heavier to take on, say, an M1.
The system does have some disadvantages though... The main fuel for this
thing is fluorine, one of the most unpleastantly reactive gases known to
man, and the residue or exhaust is hydrogen fluoride or hydrofluoric
acid, if you disolve it in water. This is possibly even more unpleasant
than flourine itself. You would not want to be near anyone with one of
these things on!
The conclusions they came to were that this weapon would be more
dangerous to the side using it then the side it was used on, and you can
get most of the same effects anyway with man-portable missiles and the
like.
Dave
--
====================================================================
Dave Clements Astronomy, Cosmology
IAS, Batiment 121, http://www.ias.fr/~clements/
Universite Paris XI, This space
91405 ORSAY CEDEX for rent
France IAS has no responsibility for me
====================================================================
Paul F. Dietz
On Thu, 01 May 1997 13:31:08 +0200, Dave Clements <clem...@ias.fr>
wrote:
> The most
>powerful lasers weight-for-weight developed to date are not in fact
>electricallu powered but are chemical lasers.
...
>The system does have some disadvantages though... The main fuel for this
>thing is fluorine, one of the most unpleastantly reactive gases known to
>man, and the residue or exhaust is hydrogen fluoride or hydrofluoric
>acid, if you disolve it in water.
One would probably want to use a chemical oxygen-iodine laser (COIL)
instead. The reactants there are hydrogen peroxide and chlorine,
producing excited monatomic oxygen that excites iodine molecules.
Recently a 747-mounted COIL has been seriously proposed as an
antimissile (and ASAT) weapon.
Directed kinetic energy weapons are still a whole lot more effective,
and will become even more effective with the advent of smart bullets.
The advantage of directed energy weapons (shorter time to target) is
only really significant over long distances.
Paul
Bob Dowling
In article <3368883a...@nntp.interaccess.com>,
di...@interaccess.com (Paul F. Dietz) writes:
|> The advantage of directed energy weapons (shorter time to target) is
|> only really significant over long distances.
The other advantage of directed energy weapons over kinetic weapons is for
assassins. DEWs leave no pellet for forensic analysis. Bullets, at least
current ones, carry information about the rifling of the gun that fired them.
Or am I overestimating the amount of information carried by a bullet?
--
Bob Dowling: UNIX Support, University of Cambridge Computing Service,
rj...@cam.ac.uk New Museums Site, Pembroke Street, Cambridge, UK. CB2 3QG.
+44 1223 334728 http://www-uxsup.csx.cam.ac.uk/
-------- Those who do not learn from Dilbert are doomed to repeat it. --------
Dave Clements
Paul F. Dietz wrote:
>
> On Thu, 01 May 1997 13:31:08 +0200, Dave Clements <clem...@ias.fr>
> wrote:
>
> >The system does have some disadvantages though... The main fuel for this
> >thing is fluorine, one of the most unpleastantly reactive gases known to
> >man, and the residue or exhaust is hydrogen fluoride or hydrofluoric
> >acid, if you disolve it in water.
>
> One would probably want to use a chemical oxygen-iodine laser (COIL)
> instead. The reactants there are hydrogen peroxide and chlorine,
> producing excited monatomic oxygen that excites iodine molecules.
Sorry - did you mean hydrogen peroxide and iodine rather than chlorine,
or is the idodien somewhere else?
Much better than flourine, but still unpleasant!
> Recently a 747-mounted COIL has been seriously proposed as an
> antimissile (and ASAT) weapon.
I'd wondered what they were going to pump the laser with. Thanks!
Dave Clements
Bob Dowling wrote:
>
> In article <3368883a...@nntp.interaccess.com>,
> di...@interaccess.com (Paul F. Dietz) writes:
>
> |> The advantage of directed energy weapons (shorter time to target) is
> |> only really significant over long distances.
>
> The other advantage of directed energy weapons over kinetic weapons is for
> assassins. DEWs leave no pellet for forensic analysis. Bullets, at least
> current ones, carry information about the rifling of the gun that fired them.
> Or am I overestimating the amount of information carried by a bullet?
I think it depends on the bullet, and on whether you leave cartridge
cases etc. around. A shotgun won't leave much info. in the pellets, so
you can be pretty anonymous if you take the empty shells with you.
I'd also suspect something like an explosive or dum-dum bullet might
also be harder to do ballistics on. A discarding sabot-type flechette,
as long as you collected the sabots, might also be anonymous and, unlike
a dum-dum or shot gun, might be able to travel long distances...
Dave
Isaac Kuo
In article <5ka54r$i...@lyra.csx.cam.ac.uk>, Bob Dowling <rj...@cam.ac.uk> wrote:
>In article <3368883a...@nntp.interaccess.com>,
> di...@interaccess.com (Paul F. Dietz) writes:
>|> The advantage of directed energy weapons (shorter time to target) is
>|> only really significant over long distances.
>The other advantage of directed energy weapons over kinetic weapons is for
>assassins. DEWs leave no pellet for forensic analysis. Bullets, at least
>current ones, carry information about the rifling of the gun that fired them.
If some assassin used a powerful laser or other beam weapon in the
near future to kill someone, it would say a lot more about the
assassin than a rifle bullet would.
Obviously, this "advantage" is moot unless these weapons are already
in common use (presumably because of other advantages).
>Or am I overestimating the amount of information carried by a bullet?
Well, the information carried by a rifle bullet can't identify an
individual gun if that gun is disposed of.
--
_____ Isaac Kuo (k...@bit.csc.lsu.edu)
__|_>o<_|__
/___________\ "Kinou no ban no koto oboeteimasu?
\=\>-----</=/ ... Ayukawa! Ayukawa-te!" - Hikaru
John Schilling
rj...@cam.ac.uk (Bob Dowling) writes:
>In article <3368883a...@nntp.interaccess.com>,
> di...@interaccess.com (Paul F. Dietz) writes:
>|> The advantage of directed energy weapons (shorter time to target) is
>|> only really significant over long distances.
>The other advantage of directed energy weapons over kinetic weapons is for
>assassins. DEWs leave no pellet for forensic analysis. Bullets, at least
>current ones, carry information about the rifling of the gun that fired them.
>Or am I overestimating the amount of information carried by a bullet?
A bullet carries no *useful* information unless and until a suspect weapon
is in hand to compare it with - you can't send a bullet to some forensics
lab and get make, model, and serial number of the weapon which fired it,
you have to send bullet and gun together, or two bullets, and ask if they
match.
As there are no shortage of firearms suitable for assassination available,
i.e. millions, the obvious strategy is to pick a previously-unused weapon
and destroy it immediately afterwards. The only reason foresic ballistics
is of any use today, is because some criminals are either too stupid to do
this or too poor to afford disposable weapons. Neither of these conditions
is likely to apply to any hypothetical assassin in a position to use laser
or particle-beam weaponry.
Besides, I just remembered that, according to _Battlestar Galactica_, you can
in fact perform a forensic analysis of energy weapons & their targets using a
"Laseronic Ergon Scanner", or some such. I really wish I hadn't remembered
that :-)
--
*John Schilling * "You can have Peace, *
*Member:AIAA,NRA,ACLU,SAS,LP * or you can have Freedom. *
*University of Southern California * Don't ever count on having both *
*Aerospace Engineering Department * at the same time." *
*schi...@spock.usc.edu * - Robert A. Heinlein *
*(213)-740-5311 or 747-2527 * Finger for PGP public key *
Erik Max Francis
Bob Dowling wrote:
> The other advantage of directed energy weapons over kinetic weapons is
> for
> assassins. DEWs leave no pellet for forensic analysis. Bullets, at
> least
> current ones, carry information about the rifling of the gun that fired
> them.
> Or am I overestimating the amount of information carried by a bullet?
The bullet can contain information about which gun it was fired from.
Often medical examiners can even tell what calibre the bullet was from the
injuries (or certainly get it to within a narrow range). Trajectory,
range, and such is revealed by entry angles and whether or not there are
powder burns on the victim, and so this isn't intrinsically determined by
the bullet itself.
So basically with the bullet you can (sometimes; if the bullet ricocheted
or met a lot of resistance, it will be damaged beyond recognition) connect
the bullet with the specific gun it was fired from. Most of the rest of
the information comes from elsewhere.
Right now, obviously, killing someone with a portable beam weapon is going
to be a great deal easier to find. The ME will still be able to determine
entry angle, etc. From the size of the wound and burns they'll probably
even be able to estimate the wattage and beam duration, whether or not it
was moved while firing, etc. From that, it's simply a question of, "This
is not a common weapon. Who could build such a thing?" and move the
investigation on from there.
--
Erik Max Francis, &tSftDotIotE / email / m...@alcyone.com
Alcyone Systems / web / http://www.alcyone.com/max/
San Jose, California, United States / icbm / 37 20 07 N 121 53 38 W
\
"The future / is right there."
/ Bill Moyers
Parish A Mozdzierz
Gil Lau (gl...@jmpstart.com) wrote:
: I know, this should probably be in the FAQ somewhere. If
: this thread has been hammered to death, could someone
: send me a summary?
:
: The gist of the question is in the subject. Is it possible to
: develop man-portable directed energy weapons for use
: on a battlefield with foreseeable (i.e. near future, roughly
: 50 years) technologies? Solving power requirements for
: a laser rifle is one thing, but will it be useless in early-
: morning fog? Stuff like that. Thanks.
: -- Gil
______________________________________________
I seem to recall hearing about some ideas for a 'microwave' gun, that
might fit the bill (probably require bulky backpack for power,etc.).
Don't recall exactly the details, or if it could even really work or not.
Some kind of railgun, which would act like a portable particle
accelerator, might be possible one day.
Why energy guns?
Not sure why there would be a demand for one. IF the energy were visible,
i'm sure snipers and soldiers wouldn't want it. Second, if object is to
devise way to 'set' damage on the weapons, there is probably easier
solutions than energy guns (rubber bullets, sonics, gas, etc...)
P-man
Steve Hix
In article 7...@ias.fr, Dave Clements <clem...@ias.fr> writes:
:Bob Dowling wrote:
:>
:> In article <3368883a...@nntp.interaccess.com>,:> |> The advantage of directed energy weapons (shorter time to target) is
:> |> only really significant over long distances.
:> The other advantage of directed energy weapons over kinetic weapons is for
:> assassins. DEWs leave no pellet for forensic analysis. Bullets, at least
:> current ones, carry information about the rifling of the gun that fired them.
:> Or am I overestimating the amount of information carried by a bullet?
The problems with using the information include having to obtain
the weapon used to perform the match (sometimes tricky), and being
able to ensure that the weapon in question hasn't been fired much
after the assasin's use. You can even change the pattern of grooves
enough with a single shot to make matching impossible, or very unlikely.
(Fire a round with some grinding compound, for example.)
The problems with ballistic matching are the main stumbling block for
schemes of ballistic registration of legally-owned firearms. (Never mind
the criminals, they don't tend to helpfully bring in their weapons for
registration. Usually.)
Paul F. Dietz
On Thu, 01 May 1997 16:55:29 +0200, Dave Clements <clem...@ias.fr>
wrote:
>> One would probably want to use a chemical oxygen-iodine laser (COIL)
>> instead. The reactants there are hydrogen peroxide and chlorine,
>> producing excited monatomic oxygen that excites iodine molecules.
>
>Sorry - did you mean hydrogen peroxide and iodine rather than chlorine,
>or is the idodien somewhere else?
Hydrogen peroxide and chlorine react to make excited atomic oxygen.
The atomic oxygen is then (quickly) used to excite the iodine.
I believe the 747 mounted laser will recycle the chlorine and iodine.
IIRC, COILs can have efficiencies of 10% (I'm not confident on that).
Paul
bla...@freenet.edmonton.ab.ca
Gil Lau (gl...@jmpstart.com) wrote:
: I know, this should probably be in the FAQ somewhere. If
: this thread has been hammered to death, could someone
: send me a summary?
I am busy revising an article to be included in the FAQ, addressing this
point among others.
: The gist of the question is in the subject. Is it possible to
: develop man-portable directed energy weapons for use
: on a battlefield with foreseeable (i.e. near future, roughly
: 50 years) technologies? Solving power requirements for
: a laser rifle is one thing, but will it be useless in early-
: morning fog? Stuff like that. Thanks.
One problem is that lasers and particle beams are very inefficient, espec-
ially with high power lasers (typical efficiency 1-10%, IIRC). Only a small
fraction of the energy consumed goes into the beam; most becomes waste heat.
However, there have been breakthroughs in semiconductor lasers. In fifty
years there could well be a laser small and powerful enough to be a hand-
held weapon, with about 60% to 80% efficiency.
For a laser handgun to inflict damage comparable to that of a projectile
handgun, the battery must have an energy density comparable to that of
chemical explosives. That is another hurdle for designers to overcome.
Then again, a cable leading to a large battery in backpack or belt would
also help power an energy pistol.
Remember that lasers and other energy weapons are not super-powerful.
They have their limitations (such as reflecting materials, firing through
fog or even air). As anti-personnel weapons, they are generally less
useful than projectiles. Cost is another factor; unless portable energy
weapons can be mass produced cheaply, they will not see much use except
in elite military units (as in _Akira_).
===================== ====================================
BLAINE GORDON MANYLUK email: bla...@freenet.edmonton.ab.ca
EDMONTON, AB
Gil Lau
di...@interaccess.com (Paul F. Dietz) wrote:
>On Thu, 01 May 1997 13:31:08 +0200, Dave Clements <clem...@ias.fr>
>wrote:
>Directed kinetic energy weapons are still a whole lot more effective,
>and will become even more effective with the advent of smart bullets.
>The advantage of directed energy weapons (shorter time to target) is
>only really significant over long distances.
Well, when I first posted this question I also had other factors in
mind: simplicity (once the technology is commonplace) and
logistics. Hook up a DEW to a Mr. Fusion and the future soldier
won't have to worry about running low on bullets. OTOH, that
silent invisible laser's no good if it can't shoot through smoke.
-- Gil
Christian Weisgerber
di...@interaccess.com (Paul F. Dietz) writes:
> Directed kinetic energy weapons are still a whole lot more effective,
> and will become even more effective with the advent of smart bullets.
I don't expect to see smart bullets any time soon. What are you thinking
of?
> The advantage of directed energy weapons (shorter time to target) is
> only really significant over long distances.
Lack of recoil might be considered an advantage. Simpler aiming
certainly is one - just point and shoot, no need to bother with
pesky ballistics.
Even assuming the mentioned quantum leap in energy storage, efficiency
remains a major problem. It takes ludicrous power to do damage with a
laser and at efficiencies of 2% (or even 10%) you are not only wasting
your limited energy but you also have to dispose of even more ludicrous
amounts of the waste heat.
--
Christian 'naddy' Weisgerber na...@mips.rhein-neckar.de
See another pointless homepage at <URL:http://home.pages.de/~naddy/>.
John Schilling
na...@mips.rhein-neckar.de (Christian Weisgerber) writes:
>Even assuming the mentioned quantum leap in energy storage, efficiency
>remains a major problem. It takes ludicrous power to do damage with a
>laser and at efficiencies of 2% (or even 10%) you are not only wasting
>your limited energy but you also have to dispose of even more ludicrous
>amounts of the waste heat.
We *already* know how to make high-power lasers with efficiencies of ~75%,
and yes, that is total system efficiency from wall plug to beam. There are
currently problems with cost and beam quality that make it impractical to
use such lasers as weapons, but that is just a matter of time and engineering
effort; the power supply problem is the only real sticking point.
Bottom line is, "lasers are only 2% efficient and are not practical as
weapons" is a myth, and always has been. Why people spread such myths,
is another matter.
Del Cotter
On Wed, 30 Apr 1997, in rec.arts.sf.science
Gil Lau <gl...@jmpstart.com> wrote
>Is it possible to
>develop man-portable directed energy weapons for use
>on a battlefield with foreseeable (i.e. near future, roughly
>50 years) technologies? Solving power requirements for
>a laser rifle is one thing, but will it be useless in early-
>morning fog? Stuff like that. Thanks.
You might want to take a look at Dave Langford's "War in 2080". A
physicist himself, he examines this and other staples of SF warfare with
a sceptical eye.
--
Del Cotter d...@branta.demon.co.uk
[1] David Langford "War in 2080: The Future of Military Technology" (Sphere
Books, 1981)
Keith Morrison
Paul F. Dietz wrote:
> Directed kinetic energy weapons are still a whole lot more effective,
> and will become even more effective with the advent of smart bullets.
> The advantage of directed energy weapons (shorter time to target) is
> only really significant over long distances.
Line of sight weapon. This makes useful for sniping as well as hitting
moving targets without having to go through the contortions necessary
to calculate deflection and drop.
--
Keith Morrison
lone...@nbnet.nb.ca
Paul F. Dietz
On 2 May 1997 10:05:50 -0700, schi...@spock.usc.edu (John Schilling)
wrote:
> We *already* know how to make high-power lasers with efficiencies of ~75%,
> and yes, that is total system efficiency from wall plug to beam. There are
> currently problems with cost and beam quality that make it impractical to
> use such lasers as weapons, but that is just a matter of time and engineering
> effort; the power supply problem is the only real sticking point.
You're talking about FELs. These things are very large. And getting
rid of their energetic bremsstrahlung (from collisions of parts of the
electron beam with things) would be essential for a hand weapon; you
can't carry the shielding necessary to absorb it.
Smart projectiles are going to be a lot easier -- and a lot more
lethal per joule, even if the laser is 100% efficient. A projectile
can kill you by punching a hole in you, which takes much less energy
than vaporizing a hole in you.
Paul
Paul F. Dietz
On 2 May 1997 15:25:24 +0200, na...@mips.rhein-neckar.de (Christian
Weisgerber) wrote:
>> Directed kinetic energy weapons are still a whole lot more effective,
>> and will become even more effective with the advent of smart bullets.
>
>I don't expect to see smart bullets any time soon. What are you thinking
>of?
I expect to see smart 20 mm air-to-air shells within 10 years and
smart bullets for hand weapons within 20 years. "Smart" in the sense
of being laser guided. They'd use piezoelectric rod actuators to move
the nose of the projectile a fraction of a degree (at a rate high
enough to keep up with the rotation of the projectile). Aerodynamic
tests on this form of projectile have recently been conducted in
supersonic wind tunnels.
Paul
Charlie Stross
Alan D Kohler<hwk...@REMOVE2REPLY.poky.srv.net> wrote (in article <5k990t$i...@mars.hyperk.com>):
>
>As for the next 50 years, that would depend on whether or not we have an
>unforseable quantum leap in electrical power storage in that time - which
>could happen; those who want to make more efficient electrical vehicles are
>laboriously looking for just such a technology, which could easily be turned
>to other purposes.
Power _is_ the issue, but it can be tackled in many different ways.
A couple of weeks ago New Scientist covered a fuel cell being developed
for the US military. It runs off a 5% methanol in water solution and a
gadget about the size of a trade paperback was able to pump out 50 watts
of electricity for several hundred hours with no sign of degradation (as
long as they kept adding fuel) -- it used atmospheric oxygen as an
oxidant, and some kind of _very_ expensive membrane to separate the
electrolytes. Now imagine a backpack containing a gallon of methanol
fuel, a 50-100 watt power supply, some capacitors, and a big pulsed
laser. You _don't_ use something that looks like a gun; instead, you use
an eyeball-tracking head-up display inside the soldier's helmet to
identify targets, and a mirror in a turret sticking up above the helmet
or backpack to angle the beam. Look and kill, look and kill. All the
technology is essentially here today -- it's just a matter of putting
it together.
Another issue is the hybrid rifle -- a projectile weapon which is also
capable of firing laser pulses. Some research was allegedly conducted in
the UK into turning a conventional rifle into a laser. The key was the
cartridge; instead of being a conventional round, it was a cell containing
two reagents, separated by a membrane. On detonation, the membrane ruptures,
allowing the reagents to mix; they lase spontaneously, and the gun barrel
(a long steel tube) acts as a collimator. I don't think it got too far,
but a cartridge-fed chemical laser would certainly side-step most of the
'flame-thrower' laser's problems.
And then there's the blinding laser -- I believe it's now banned under
the Geneva conventions. Simply a continuous-output high power laser (a
couple of watts is more than enough!) that sits under a tumbling prism
that 'paints' the landscape in front of it. If you're eyeballs are part
of the landscape, well: you'd better be wearing some serious shades,
because otherwise you're going to need a new pair of eyeballs. (Three
guesses why this one was banned.)
The real question is 'what use is an infantry-portable laser weapon'? I
can see several things:
* target designation (already in use)
* blinding (banned)
* silent operations (special ops, may not apply to cartridge-fed designs)
* quick reaction weapons, e.g. light anti-aircraft (the eyeball-tracked
backpack design)
The only significant advantage a laser offers over a projectile weapon
seems to me to be that when you increase the calibre (energy load) you
don't have to increase the size of the front-end of the device as
much. Go to a larger calibre gun, you need bigger shock absorbers,
heavier suspension, larger ammo carriers, and so on. Go to a higher
power laser and you may need a more efficient power source and a better
heat sink -- but the optics you use to direct the beam stay pretty much
the same size until you're talking about ABM systems. It's easier to
direct a small mirror at a target than to point a rifle or light cannon
at a target; so conceivably a laser weapon could give you a much shorter
time to bring the weapon to bear.
-- Charlie
John Schilling
di...@interaccess.com (Paul F. Dietz) writes:
>On 2 May 1997 10:05:50 -0700, schi...@spock.usc.edu (John Schilling)
>wrote:
>>We *already* know how to make high-power lasers with efficiencies of ~75%,
>>and yes, that is total system efficiency from wall plug to beam. There are
>>currently problems with cost and beam quality that make it impractical to
>>use such lasers as weapons, but that is just a matter of time and engineering
>>effort; the power supply problem is the only real sticking point.
>You're talking about FELs. These things are very large. And getting
>rid of their energetic bremsstrahlung (from collisions of parts of the
>electron beam with things) would be essential for a hand weapon.
Actually, no. I'm not talking about free electron lasers at all - as far as
I know, none have ever broken 50% efficiency yet.
I'm talking about diode laser arrays, which are compact, powerful, efficient,
and devoid of any ionizing radiation problems. Cost is currently ~$1/watt,
which is a bit high for a weapon, and there is the problem of phase-locking
the individual laser elements, but these are known to be soluble problems.
It is only the power supply we are missing.
Charlie Stross
Christian Weisgerber<na...@mips.rhein-neckar.de> wrote (in article <5kcq05$q...@mips.rhein-neckar.de>):
>> and will become even more effective with the advent of smart bullets.
>
>I don't expect to see smart bullets any time soon. What are you thinking
>of?
Then your expectations are wrong -- go read up on BLAMs (Barrel Launched
Autonomous Munitions, or some such silly acronym), covered in New
Scientist a couple of weeks ago. They're intended to be fired from
rifled barrels, and they steer by using piezoelectric 'tendons' to warp
their nose by a fraction of a degree. The USAF is developing the
technology, initially for 30mm aviation cannon; one shell today costs
$30, and a typical airborn gun fires 50-100 shells in a one second burst
-- replacing a burst with a single guided bullet would be a _lot_
cheaper, even if it cost $1000+ per round. Sidearm-sized guided rounds
are probably 5-15 years away. It's an expensive technology, but as with
all such developments the aerospace industry is already investigating
it. Remember, the USAF is willing to consider $1Bn bombers; a $1000
bullet that always hits the target probably strikes them as cheap at the
price.
-- Charlie
Paul F. Dietz
On 3 May 1997 10:38:14 -0700, schi...@spock.usc.edu (John Schilling)
wrote:
>Actually, no. I'm not talking about free electron lasers at all - as far as
>I know, none have ever broken 50% efficiency yet.
>
>I'm talking about diode laser arrays, which are compact, powerful, efficient,
>and devoid of any ionizing radiation problems. Cost is currently ~$1/watt,
>which is a bit high for a weapon, and there is the problem of phase-locking
>the individual laser elements, but these are known to be soluble problems.
>It is only the power supply we are missing.
And the cooling system for the laser diodes. The heat in projectile
weapons is mostly carried off in the propellant gases; it doesn't have
to conduct out of a chip.
I'd guess we're talking about peak power of at least a megawatt for an
effective hand weapon; is that $1 per CW watt or peak power watt?
Paul
David Given
In article <3369a...@news1.ibm.net>, Gil Lau <gl...@jmpstart.com> wrote:
>di...@interaccess.com (Paul F. Dietz) wrote:
[...]
>Well, when I first posted this question I also had other factors in
>mind: simplicity (once the technology is commonplace) and
>logistics. Hook up a DEW to a Mr. Fusion and the future soldier
>won't have to worry about running low on bullets. OTOH, that
>silent invisible laser's no good if it can't shoot through smoke.
Silent? Invisible? Hahahaha!
Consider: a laser shot sufficient to do considerable damage to a target
in, say, quarter of a second is going to have spew out a *lot* of energy.
This is going to superheat the air it passes through. Each laser shot is
going to produce a thunder-crack of sound, and probably a blue-white trace
as well. Of course, the sound will be produced along the entire line of
the beam; you know someone's firing, but can't necessarily see *where*.
--
------------------- http://www-hons-cs.cs.st-and.ac.uk/~dg --------------------
If you're up against someone more intelligent than you are, do something
totally insane and let him think himself to death. --- Pyanfar Chanur
---------------- Sun-Earther David Daton Given of Lochcarron ------------------
John Schilling
di...@interaccess.com (Paul F. Dietz) writes:
>On 3 May 1997 10:38:14 -0700, schi...@spock.usc.edu (John Schilling)
>wrote:
>>I'm talking about diode laser arrays, which are compact, powerful, efficient,
>>and devoid of any ionizing radiation problems. Cost is currently ~$1/watt,
>>which is a bit high for a weapon, and there is the problem of phase-locking
>>the individual laser elements, but these are known to be soluble problems.
>>It is only the power supply we are missing.
>And the cooling system for the laser diodes. The heat in projectile
>weapons is mostly carried off in the propellant gases; it doesn't have
>to conduct out of a chip.
For every joule of energy carried by a bullet, another joule is deposited
as heat in the barrel - not carried off in the propellant gasses. By
comparison, a 75% efficient laser only has to dispose of 0.33 joules
of waste heat per jouls of beam energy. So, all other things being
equal, the advantage lies with the laser, and the various techniques
already used for cooling guns should be applicable.
And conducting heat out of a chip has never been a problem - chips are
thin, and silicon has a reasonably good thermal conductivity. The
problem with cooling electronics derives from the fact that we insist
on packaging the chips in, and mounting them on, structures made from
thermal insulators. Stick your chips on a copper ground plate, and
there's no reason why you couldn't, and the cooling problem simplifies
dramatically.
>I'd guess we're talking about peak power of at least a megawatt for an
>effective hand weapon; is that $1 per CW watt or peak power watt?
CW. And a megawatt is gross overkill for a point-target antipersonell
weapon; a hundred kilowatts ought to be quite adequate.
Keith Morrison
David Given wrote:
> Silent? Invisible? Hahahaha!
>
> Consider: a laser shot sufficient to do considerable damage to a target
> in, say, quarter of a second is going to have spew out a *lot* of energy.
> This is going to superheat the air it passes through. Each laser shot is
> going to produce a thunder-crack of sound, and probably a blue-white trace
> as well. Of course, the sound will be produced along the entire line of
> the beam; you know someone's firing, but can't necessarily see *where*.
That blue-white trace might be a good clue...
--
Keith Morrison
lone...@nbnet.nb.ca
Johan Forsberg
David Given wrote:
>
> Silent? Invisible? Hahahaha!
>
> Consider: a laser shot sufficient to do considerable damage to a target
> in, say, quarter of a second is going to have spew out a *lot* of energy.
> This is going to superheat the air it passes through. Each laser shot is
> going to produce a thunder-crack of sound, and probably a blue-white trace
> as well. Of course, the sound will be produced along the entire line of
> the beam; you know someone's firing, but can't necessarily see *where*.
Which reminds me of a really great photo I once saw in a book of a
big x-ray (I think) laser being fired through atmosphere...
It looked something like thousands of brilliantly blue soap bubbles
along the beam (bubbles of ionized air).
Can anyone id this book? It was a really good encyclopedia of the
science
behind science fiction, going through subjects like lasers, disruptors,
FTL, time travel, psionics (nice pix from _Scanners_), et very cetera,
and
detailing the current state in science about the subjects.
I read it only once, when I was about 12 years old ('85-ish). I'd really
love to find it again...
--
<--/---\------76-cols-----------------^-----Your-Name-Here----Something---->
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Brian Trosko
Johan Forsberg <REMOVE_TH...@nada.kth.se> wrote:
: Which reminds me of a really great photo I once saw in a book of a
: big x-ray (I think) laser being fired through atmosphere...
I *really* doubt it was an X-ray laser. Last I heard, you had to pump
those with a nuclear explosion.
bla...@freenet.edmonton.ab.ca
Brian Trosko (btr...@primenet.com) wrote:
Or a very large, very powerful conventional (IR to UV) laser.
Ross Smith
Johan Forsberg wrote:
>
> Which reminds me of a really great photo I once saw in a book of a
> big x-ray (I think) laser being fired through atmosphere...
> along the beam (bubbles of ionized air).
>
> Can anyone id this book? It was a really good encyclopedia of the
> science
> behind science fiction, going through subjects like lasers, disruptors,
> FTL, time travel, psionics (nice pix from _Scanners_), et very cetera,
> and
> detailing the current state in science about the subjects.
The photo you describe is in _War in 2080_ by David Langford (1979), but
the rest of your description doesn't quite match it. I'd guess that your
book was probably _The Science in Science Fiction_ by David Langford,
Peter Nicholls, and Brian Stableford (I'm pretty sure I've got those
names right) -- I can't remember whether it had that particular picture,
but it seems likely.
--
Ross Smith (Wellington, New Zealand) <mailto:al...@netlink.co.nz>
<http://www.geocities.com/SiliconValley/Park/3699/>
"Like us, the Muppets imitate human beings. But they do it better."
-- Clive James
Stephan Zielinski
schi...@spock.usc.edu (John Schilling) writes:
> For every joule of energy carried by a bullet, another joule is deposited
> as heat in the barrel - not carried off in the propellant gasses.
Way off. The bulk of the energy ends up in the bullet-- otherwise
firing a shotgun would be a life threatening experience.
This subject came up in alt.folklore.urban, and then again in
rec.games.frp. Hence, for the third time, the math:
The relevant equations are:
(1.1) Momentum = mass * velocity
(1.2) Kinetic energy = .5 * mass * velocity^2
Example: a pistol massing one kilogram fires a ten gram bullet at
three hundred meters per second. Ignoring the energy and momentum
lost to sound and propellent gasses, determine the momentum and energy
of the bullet, and the momentum, energy, and velocity of the pistol.
Momentum of bullet: .01 kg * 300 m / s = 3 kg m / s
Energy of bullet: .5 * .01 kg * (300 m / s)^2
= .5 * .01 kg * 90000 m^2 / s^2 = 450 kg m^2 / s^2
Momentum of pistol: -3 kg m / s.
Velocity of pistol: -3 kg m / s = 1 kg * velocity
Velocity of pistol is thus -3 m / s
Energy of pistol: .5 * 1 kg * (-3 m / s)^2
= .5 * 1 kg * 9 m^2 / s^2
= 4.5 kg m^2 / s^2
Special bonus round: The above bullet strikes a 69.99 kg man and
embeds itself in his spine directly behind his heart. Ignoring the
energy and momentum of the spurt of blood issuing from his severed
aorta, compute his resulting velocity. You may assume he is standing
on a frictionless surface, in a vacuum.
Total mass of man-bullet system: 69.99 kg + .01 kg = 70 kg
Momentum of man-bullet system: 3 kg m / s
From equation 1.1: 3 kg m / s = 70 kg * velocity
.0429 m / s = velocity
Bonus round part two: What is the kinetic energy of the man-bullet system?
From equation 1.2: Kinetic energy = .5 * 70 kg * (.0429 m / s)^2
= .0644 kg m^2 / s^2
Final part of bonus round: If the bullet had an energy of 450 Joules,
but the kinetic energy of the man-bullet system has a kinetic energy
of only .0644 Joules, where did the extra energy go?
Final answer: the energy went into the work of shattering the victim's
bones and rending his flesh, eventually becoming thermal energy.
Small objects moving at high velocity are effective projectiles
because the bulk of the energy of the projectile is available to
damage the target, rather than being wasted on knockback by
accelerating the target away.
For extra credit, compute the energy available to inflict damage on a
70 kg target in the following cases, each with 450 Joules of kinetic
energy: a 1 kg rock traveling at 30 m / s, a ten kg frozen turkey
traveling at 9.49 m / s, a small megalith massing 1000 kg traveling at
.949 m / s, and an asteroid massing 1 000 000 kg traveling at .03 m /
s.
--
Stephan "Can you tell that high school physics is the last hard
science class I actually understood?" Zielinski
Cardinal Fang
gl...@jmpstart.com (Gil Lau) rambled on in the following manner:
>The gist of the question is in the subject. Is it possible to
>develop man-portable directed energy weapons for use
>on a battlefield with foreseeable (i.e. near future, roughly
>50 years) technologies?
I have been reading the posts on this topic and I think there is an
aspect which has been overlooked. Has anyone here ever put aluminum
foil in the microwave? A microwave laser, even one that was not very
powerful, would likely do a good job of trashing an enemy's
electronics. Perhaps it would be used to fry the chips of enemy
helicopters or laser guided missiles. It could also be used to
"sweep" a mine field (in a hazardous fashion).
Just a thought.
_.'__ `.
.--(#)(##)---/#\
.' @ /###\ "People that are really very weird can
: , ##### get into sensitive positions and
`-..__.-' _.-\###/ have a tremendous impact on history."
`;_: `"' - Vice President Dan Quayle
.'"""""`.
/, JOE ,\
// COOL! \\
`-._______.-'
___`. | .'___
jgs (______|______)
Daniel Gentry (SAR)
Sorry for not posting this in my last message about the maser, but
I had to verify something. It turns out that the military has been
experimenting with microwave lasers for years. The major problem with
getting them to work turns out to be keeping them from frying themselves.
This problem has been so far insurmountable.
Nyrath the nearly wise
gl...@jmpstart.com (Gil Lau) rambled on in the following manner:
:
: >The gist of the question is in the subject. Is it possible to
: >develop man-portable directed energy weapons for use
: >on a battlefield with foreseeable (i.e. near future, roughly
: >50 years) technologies?
I'm still not convinced that a man-portable energy weapon
would have much advantage over a more conventional projectile
weapon. The idea is to efficiently inflict enough damage to
your hapless target in order to disable and/or kill it.
Offhand it seems that the only advantage a beam weapon has
is freedom from the arcing trajectory that bullets are heir to.
As far as powering the sucker, well! Here's Han Solo with his
tiny hand-blaster, who's clip contains about two kilowatt-years
worth of energy! Make sure your finger doesn't brush the
two contacts when you change the battery or your vaporous
remains will clog the air conditioner. And if an enemy's
lucky shot happens to shatter the battery, the results
will no doubt be exceedingly unfortunate.
+----------------------------------------------------------------------------+
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| Nyrath the nearly wise nyr...@clark.net |
+---_---+---------------------[ SURREAL SAGE SEZ: ]--------------------------+
| /_\ | "If you've got to ask, you aren't ever going to know" -- Louie |
| <(*)> | Armstrong, when asked to explain something about jazz. |
|/_/|\_\| |
| //|\\ | |
+///|\\\+--------------------------------------------------------------------+
Erik Max Francis
Stephan Zielinski wrote:
> Way off. The bulk of the energy ends up in the bullet-- otherwise
> firing a shotgun would be a life threatening experience.
A considerably amount of energy is released by the igniting powder. Even
if only a fraction of this goes into the kinetic energy of the bullet, the
results can still be pretty devastating for the poor soul in the line of
fire.
> This subject came up in alt.folklore.urban, and then again in
> rec.games.frp. Hence, for the third time, the math:
The original poster was talking about _heat_, not kinetic energy (which is
what you post about below). Basically the original poster is talking
about efficiency -- the ratio of the energy released by the igniting
charge to the amount that goes into the kinetic energy of the bullet. The
rest is released as sound, heat, light, and the kinetic energy of the
recoiling gun.
As for the amount of heat dissipated, it's not trivial -- anyone who's
fired a gun knows that the barrel gets _hot_. Nothing is perfect, and in
fact most human inventions have comparatively low efficiencies. For the
exact numbers, one should probably check out rec.guns.
--
Erik Max Francis, &tSftDotIotE / email / m...@alcyone.com
Alcyone Systems / web / http://www.alcyone.com/max/
San Jose, California, United States / icbm / 37 20 07 N 121 53 38 W
\
"The future / is right there."
/ Bill Moyers
John Schilling
Stephan Zielinski <szie...@well.com> writes:
>schi...@spock.usc.edu (John Schilling) writes:
>> For every joule of energy carried by a bullet, another joule is deposited
>> as heat in the barrel - not carried off in the propellant gasses.
>Way off. The bulk of the energy ends up in the bullet-- otherwise
>firing a shotgun would be a life threatening experience.
>This subject came up in alt.folklore.urban, and then again in
>rec.games.frp. Hence, for the third time, the math:
Then the folks in afu and rgf are wrong - it wouldn't be the first time.
>The relevant equations are:
>
>(1.1) Momentum = mass * velocity
>
>(1.2) Kinetic energy = .5 * mass * velocity^2
Actually, these are not the relevant equations. As we are talking about
waste heat, you should have been suspicious when neither of your "relevant
equations" included terms for temperature or heat energy. This is not a
conservation-of-momentum problem, it is a thermodynamic efficiency problem.
>Example: a pistol massing one kilogram fires a ten gram bullet at
>three hundred meters per second. Ignoring the energy and momentum
>lost to sound and propellent gasses, determine the momentum and energy
*No*.
This is the whole *point*. *Most* of the energy is lost, to sound, to
propellant gasses, to heat, etc. You can't "Ignore the energy lost..."
and then claim that guns are remarkably efficient.
"Ignoring the energy lost...", the worst gas-guzzler Detroit ever made
suddenly becomes a marvel of efficiency.
>of the bullet, and the momentum, energy, and velocity of the pistol.
>Momentum of bullet: .01 kg * 300 m / s = 3 kg m / s
>Energy of bullet: .5 * .01 kg * (300 m / s)^2
> = .5 * .01 kg * 90000 m^2 / s^2 = 450 kg m^2 / s^2
>
>Momentum of pistol: -3 kg m / s.
>Velocity of pistol: -3 kg m / s = 1 kg * velocity
> Velocity of pistol is thus -3 m / s
>Energy of pistol: .5 * 1 kg * (-3 m / s)^2
> = .5 * 1 kg * 9 m^2 / s^2
> = 4.5 kg m^2 / s^2
Correct. In this example, the kinetic energy of the bullet is 450 Joules
and the kinetic energy of the gun is about 5 Joules.
However, the propellant charge uesd to fire the bullet, probably contained
at least 1,000 Joules of chemical energy.
And after firing, the gun is probably about 1 degree (centigrade) hotter
on average than it was before.
Strangely, the ammount of heat energy associated with raising the temperature
of one kilogram of steel by one degree centigrade, is about 500 Joules.
[stupid extra credit problems deleted]
>Stephan "Can you tell that high school physics is the last hard
>science class I actually understood?" Zielinski
No. It may have been the last class you thought you understood, but you
were wrong.
That there are many different forms of energy, of which kinetic energy is
only one, is basic high school physics. And you seem to have forgotten it.
John Schilling
nyr...@clark.net (Nyrath the nearly wise) writes:
>gl...@jmpstart.com (Gil Lau) rambled on in the following manner:
>:
>: >The gist of the question is in the subject. Is it possible to
>: >develop man-portable directed energy weapons for use
>: >on a battlefield with foreseeable (i.e. near future, roughly
>: >50 years) technologies?
>I'm still not convinced that a man-portable energy weapon
>would have much advantage over a more conventional projectile
>weapon. The idea is to efficiently inflict enough damage to
>your hapless target in order to disable and/or kill it.
>Offhand it seems that the only advantage a beam weapon has
>is freedom from the arcing trajectory that bullets are heir to.
Lack of recoil would be a much bigger advantage, allowing truly effective
automatic fire from a hand weapon. Even if fired in a single-shot mode,
rapid aimed fire based on feedback from previous shots would be much more
effective than is the case with current weapons. At present, a shooter
who misses the target may well be able to see exactly where the shot went,
and so where the gun was aligned and what correction he should have made,
but courtesy of recoil the gun is no longer aligned in that direction to
begin with and he has to start over essentially from scratch.
Eliminating the projectile also potentially increases the "ammunition"
capacity of the weapon - with firearms, less than one-tenth of the
weight of a cartridge is devoted to the energy source; most is consumed
by the inert mass of the projectile.
And depending on what sort of "energy" you are talking about, and how
much of it, you might get better penetration and/or stopping power than
with projectile weapons. The idea is indeed to "inflict enough damage
on your target to disable and/or kill it", and modern hand weapons are
only marginally effective at doing this. We tend to accept them as
being "good enough" only because we don't know how to make anything
better, but I'll trade my 9mm for one of David Drake's 1cm "powerguns"
any day of the week.
>As far as powering the sucker, well! Here's Han Solo with his
>tiny hand-blaster, who's clip contains about two kilowatt-years
>worth of energy! Make sure your finger doesn't brush the
>two contacts when you change the battery or your vaporous
>remains will clog the air conditioner. And if an enemy's
>lucky shot happens to shatter the battery, the results
>will no doubt be exceedingly unfortunate
The battery under the hood of your car contains energy equivilant to
rooughly a pound of TNT, but this does not mean it causes an explosion
of similar force if shorted across, or even physically ruptured.
Energy is not the same as explosive force - to get an explosion, you
need to release energy at a very high *rate*, which is well beyond the
ability of any battery to provide. And well beyond what is necessary
to cause the localized damage one would expect from a hand weapon.
Yeah, you could probably kill yourself if you insisted on french-kissing
the battery of your laser pistol, but you'd have to work at it. And
all you'd accomplish is your own electrocution; the folks standing next
to you would get a nice laugh out of it, but they wouldn't be hurt.
Nyrath the nearly wise
In article <5m4vkq$198$1...@spock.usc.edu> John wrote:
: nyr...@clark.net (Nyrath the nearly wise) writes:
: >I'm still not convinced that a man-portable energy weapon
: >would have much advantage over a more conventional projectile
: >weapon.
:
: Lack of recoil would be a much bigger advantage, allowing truly effective
: automatic fire from a hand weapon.
<rest of thoughtful analysis snipped>
Excellent! I've saved your post to go over in more detail later.
I'm glad to be proven shortsighted, as I have the standard
SF fan's bias towards ray-guns.
: better, but I'll trade my 9mm for one of David Drake's 1cm "powerguns"
: any day of the week.
Me too. Drake has neatly side-stepped the problem by postulating
an as-yet undiscovered law of physics. His mention of the
discovery as the result of studying anomalous deaths during
an ancient volcanic eruption was a masterful example of
hand-waving that is gentle on one's willing suspension of disbelief.
: >As far as powering the sucker, well! Here's Han Solo with his
: >tiny hand-blaster, who's clip contains about two kilowatt-years
: >worth of energy!
:
: The battery under the hood of your car contains energy equivilant to
: rooughly a pound of TNT, but this does not mean it causes an explosion
: of similar force if shorted across, or even physically ruptured.
Yes, true. What annoys me is how many SF authors do not
think about the implications of having so much energy in
the clips of their laser guns. Have you ever seen somebody
in an SF novel jump-start their car with the battery
of their blaster? Heck, they could probably energize the
all the lights in a skyscraper for a few minutes.
Though I have a vague memory of a passing line in RINGWORLD,
something about Louis remembering how to rig a flashlight-laser
battery to explode like a grenade.
+----------------------------------------------------------------------------+
| WINCHELL CHUNG http://www.clark.net/pub/nyrath/home.html |
| Nyrath the nearly wise nyr...@clark.net |
+---_---+---------------------[ SURREAL SAGE SEZ: ]--------------------------+
| /_\ | Never say never; say 'highly unlikely' instead. |
| <(*)> | |
bla...@freenet.edmonton.ab.ca
Nyrath the nearly wise (nyr...@clark.net) wrote:
: In article <5m4vkq$198$1...@spock.usc.edu> John wrote:
: : nyr...@clark.net (Nyrath the nearly wise) writes:
: : >As far as powering the sucker, well! Here's Han Solo with his
: : >tiny hand-blaster, who's clip contains about two kilowatt-years
: : >worth of energy!
: :
: : The battery under the hood of your car contains energy equivilant to
: : rooughly a pound of TNT, but this does not mean it causes an explosion
: : of similar force if shorted across, or even physically ruptured.
: Yes, true. What annoys me is how many SF authors do not
: think about the implications of having so much energy in
: the clips of their laser guns. Have you ever seen somebody
: in an SF novel jump-start their car with the battery
: of their blaster? Heck, they could probably energize the
: all the lights in a skyscraper for a few minutes.
The main factor is energy density. A car battery may contain the chemical
potential energy of a pound of TNT, but its own mass is sure more than one
pound! The FAQ article I am working on for this group mentions battery
energy density as an engineering obstacle to practical ebergy weapons.
For a laser/particle handgun to inflict the same damage as an existing
projectile handgun, its battery would need to have energy density about
the same as the bullets in the projectile gun.
: Though I have a vague memory of a passing line in RINGWORLD,
: something about Louis remembering how to rig a flashlight-laser
: battery to explode like a grenade.
In _Star Trek_, phasers can be set to overload, resulting in a powerful
bomb that can be thrown like a grenade. Phaser overloading happened
three times on ST Classic, but in none of these cases was it used
deliberately as a grenade.
A Type I phaser overload just disintegrates a nearby object ("City on the
Edge of Forever"). A Type II phaser explosion is more powerful, with an
effective radius slightly more than throwing range ("That Which Survives").
It seems like neither of these make good grenades. Since the phaser
explodes 30 seconds after overloading, it makes a better time bomb or
demolition charge (as used in "Conscience of the King").
David Given
In article <5m734p$gec$1...@news.sas.ab.ca>,
<bla...@freenet.edmonton.ab.ca> wrote:
[...]
>The main factor is energy density. A car battery may contain the chemical
>potential energy of a pound of TNT, but its own mass is sure more than one
>pound! The FAQ article I am working on for this group mentions battery
>energy density as an engineering obstacle to practical ebergy weapons.
>
>For a laser/particle handgun to inflict the same damage as an existing
>projectile handgun, its battery would need to have energy density about
>the same as the bullets in the projectile gun.
One of my current enthusiasms is superconducting storage rings.
You can store *hideous* amounts of energy in a SSR, particularly with the
new superconductors that don't quench (anyone got any more info on this? I
know the stuff about Couper pairs and why they aren't susceptible to
magnetic fields, but does anyone have physical details?). I can imagine,
say, charging up a hand-sized ring at a nuclear power plant for a couple
of days and then running your car off it for weeks. It may even by
economic to ship energy down from orbit, using massive banks of solar
panels to charge a ring and then flying it down on a shuttle.
Unfortunately, they're also a little on the dangerous side.
Take the shuttle: something goes wrong. It doesn't crash, but ditches in
the sea. Since shuttles aren't air-tight, it'll sink. Water will get into
the cargo hold. Water will penetrate the SSR. Eventually, it won't be
superconducting any more. All that energy, enough to make it worthwhile
actually bringing the ring down by shuttle, is suddenly not going to be
content with zipping happily round the ring but is going to want to get
out more. We're talking lots of heat here. Unfortunately, I don't know the
exact numbers but a guesstimate is on the lines of small nuke scale. We're
at sea, remember? Tidal waves.
Even the car-sized ones are pretty nasty. People expect cars to blow up
when they crash even when they don't, due to seeing it happen all the time
in films. If they were powered with SSR's... they *would* blow up. And you
certainly wouldn't recover the body.
[...]
--
------------------- http://www-hons-cs.cs.st-and.ac.uk/~dg --------------------
*** IMPORTANT! *** My email address is changing soon, and I won't have access
to my current one. Please address all correspondence to:
--------------------------- d...@freeyellow.com ---------------------------------
Paul F. Dietz
On 25 May 1997 00:56:38 GMT, d...@dufftown.cc.ukans.edu (David Given)
wrote:
>You can store *hideous* amounts of energy in a SSR, particularly with the
>new superconductors that don't quench (anyone got any more info on this? I
>know the stuff about Couper pairs and why they aren't susceptible to
>magnetic fields, but does anyone have physical details?). I can imagine,
>say, charging up a hand-sized ring at a nuclear power plant for a couple
>of days and then running your car off it for weeks
Unfortunately, this doesn't work. Any superconducting magnetic energy
storage device experiences net outward J x B forces. Strength of
materials limits how much energy you can store in the device, to at
most on the order of the volume integral of the tensile strength of
the support structure. See "virial theorem".
Paul
rupert smith
>One of my current enthusiasms is superconducting storage rings.
>
>You can store *hideous* amounts of energy in a SSR, particularly with the
>new superconductors that don't quench (anyone got any more info on this? I
>know the stuff about Couper pairs and why they aren't susceptible to
>magnetic fields, but does anyone have physical details?).
there was an article about it in new scientist a few weeks ago. IIRC in a
standard superconductor the elctron pair up spin antialigned. when they move
through a magnetic field the magnetic moments of the electrons tear the cooper
pair apart. in this new superconductor the electrons pair up with spins
aligned, making a spin 1 cooper pair which can survive magnetic fields.
whether this would still lead to magnetic vortices in these new
superconductors, i don't know.
>It may even by
>economic to ship energy down from orbit, using massive banks of solar
>panels to charge a ring and then flying it down on a shuttle.
only, i suspect, if you had made the SSR in orbit. the energy costs (in
expensive and non-renewable hydrocarbons) would make dragging the SSR into
orbit uneconomical.
>Unfortunately, they're also a little on the dangerous side.
current superconducting magnets have this problem; if they exceed their
threshold current they suddenly become normal conductors, with hideously high
currents. the coil heats up viciously, and the liquid helium used to cool it
boils... and you get a rather large explosion.
that's one problem with SSRs: huge magnetic fields.
------------------------------------------------------------------------------
rupert smith linc...@sable.ox.ac.uk http://info.ox.ac.uk/~linc0015
this statement is false.
John Schilling
di...@interaccess.com (Paul F. Dietz) writes:
>On 25 May 1997 00:56:38 GMT, d...@dufftown.cc.ukans.edu (David Given)
>wrote:
>>You can store *hideous* amounts of energy in a SSR, particularly with the
>>new superconductors that don't quench (anyone got any more info on this? I
>>know the stuff about Couper pairs and why they aren't susceptible to
>>magnetic fields, but does anyone have physical details?). I can imagine,
>>say, charging up a hand-sized ring at a nuclear power plant for a couple
>>of days and then running your car off it for weeks
>Unfortunately, this doesn't work. Any superconducting magnetic energy
>storage device experiences net outward J x B forces. Strength of
>materials limits how much energy you can store in the device, to at
>most on the order of the volume integral of the tensile strength of
>the support structure. See "virial theorem".
However, the tensile strength of graphite or silicon-carbide whiskers is
on the order of 20 Gigapascals, so a composite material of whiskers in
a superconducting matrix were developed one could see energy densities
of 10 kilojoules per cubic centimeter.
By comparison, the magazine of my Glock 17 pistol holds seventeen cartridges,
each capable of propelling a single bullet with kinetic energy of roughly
600 Joules, or about 10 kJ for the entire magazine. Yet the volume of said
magazine is approximately one hundred cubic centimeters.
So there's room for about two orders of magnitude improvement over current
state of the art, if we can shift to superconducting-loop energy storage
efficiently coupled to a directed-energy weapon of some sort.
Paul F. Dietz
On 25 May 1997 12:55:33 -0700, schi...@spock.usc.edu (John Schilling)
wrote:
>di...@interaccess.com (Paul F. Dietz) writes:
>
>>On 25 May 1997 00:56:38 GMT, d...@dufftown.cc.ukans.edu (David Given)
>>wrote:
>
>>>You can store *hideous* amounts of energy in a SSR, particularly with the
>>>new superconductors that don't quench (anyone got any more info on this? I
>>>know the stuff about Couper pairs and why they aren't susceptible to
>>>magnetic fields, but does anyone have physical details?). I can imagine,
>>>say, charging up a hand-sized ring at a nuclear power plant for a couple
>>>of days and then running your car off it for weeks
>
>>Unfortunately, this doesn't work. Any superconducting magnetic energy
>>storage device experiences net outward J x B forces. Strength of
>>materials limits how much energy you can store in the device, to at
>>most on the order of the volume integral of the tensile strength of
>>the support structure. See "virial theorem".
>
>
>However, the tensile strength of graphite or silicon-carbide whiskers is
>on the order of 20 Gigapascals, so a composite material of whiskers in
>a superconducting matrix were developed one could see energy densities
>of 10 kilojoules per cubic centimeter.
Sure, but that's not sufficient for a "hand-sized ring [to run] your
car [...] for weeks." It's also on the rough order of the energy
density of high explosives, and less than the combustion energy
density of gasoline.
> By comparison, the magazine of my Glock 17 pistol holds seventeen
> cartridges, each capable of propelling a single bullet with kinetic
> energy of roughly 600 Joules, or about 10 kJ for the entire magazine.
> Yet the volume of said magazine is approximately one hundred cubic
> centimeters.
But 600 joules in a CW laser weapon will not, I think, be useful for
much of anything, beyond causing nuisance skin burns and blindness (if
the eyes are hit). That much energy will boil about a quarter of a
gram of water.
I suppose if you made the target stand right next to you and hold
still, and you focused the beam down to a fraction of a millimeter,
you might punch a thin, deep hole.
Paul
Leonard Erickson
d...@freeyellow.com writes:
> One of my current enthusiasms is superconducting storage rings.
>
> You can store *hideous* amounts of energy in a SSR, particularly with the
> new superconductors that don't quench (anyone got any more info on this? I
> know the stuff about Couper pairs and why they aren't susceptible to
> magnetic fields, but does anyone have physical details?). I can imagine,
> say, charging up a hand-sized ring at a nuclear power plant for a couple
> of days and then running your car off it for weeks. It may even by
> economic to ship energy down from orbit, using massive banks of solar
> panels to charge a ring and then flying it down on a shuttle.
There's a drwaback that you have overlooked. It's why they aren't used
in situations where the cryogenics are already available now.
The magnetic field density acts just like *pressure*. Thus the higher
the energy density, the greater the stress on the ring as this pressure
tries to *stretch* it. Once it hits the tensile strength of the
superconductor, the ring fails.
Likewise, if you try to reinforce the ring by encasing it in something
to support it against the pressure, you'll get failure when the outward
(radial) component of the pressure exceeds the compressive strength of
the superconductor. It'll crack, and bad things happen as it vaporizes
explosively once the resistance exceeds zero.
> Unfortunately, they're also a little on the dangerous side.
See above. If cracked, you get an arc which has *real*, non-zero
resistance. The resulting heat results in explosive release of energy
from positive feedback type effects of heat and resistance interactions.
(heat increases resistance which leads to more heat which... *BOOM*)
--
Leonard Erickson (aka Shadow)
sha...@krypton.rain.com <--preferred
leo...@qiclab.scn.rain.com <--last resort
Johnny TwoBit
In article <rnqhgg0...@decay.pbi.net>, Stephan Zielinski
<szie...@well.com> wrote:
> Special bonus round: The above bullet strikes a 69.99 kg man and
> embeds itself in his spine directly behind his heart. Ignoring the
> energy and momentum of the spurt of blood issuing from his severed
> aorta, compute his resulting velocity. You may assume he is standing
> on a frictionless surface, in a vacuum.
>
> Total mass of man-bullet system: 69.99 kg + .01 kg = 70 kg
> Momentum of man-bullet system: 3 kg m / s
> From equation 1.1: 3 kg m / s = 70 kg * velocity
> .0429 m / s = velocity
>
This _exactly_ what every Hollywood director refuses to see. The fact that
an ordinary passive bullet fired from a gun that just gives me a bit of a
jolt in the arm somehow manages to throw the victim ten feet backwards has
always amazed me. There must be some magic that increases bullet momentum
by the factor of camera angle coolness ;)
-- Johnny
- j...@freeyellow.com
Isaac Kuo
In article <jpl-ya02408000R...@nntpserver.swip.net>,
Johnny TwoBit <j...@freeyellow.com> wrote:
[about the amount of momentum in a bullet]
>This _exactly_ what every Hollywood director refuses to see. The fact that
>an ordinary passive bullet fired from a gun that just gives me a bit of a
>jolt in the arm somehow manages to throw the victim ten feet backwards has
>always amazed me. There must be some magic that increases bullet momentum
>by the factor of camera angle coolness ;)
Well, bullets in a John Wu movie don't blow back victims much
individually, but that's only so the other 37 bullets apparently
needed to kill a person can hit.
--
_____ Isaac Kuo (k...@bit.csc.lsu.edu)
__|_>o<_|__
/___________\ "Kinou no ban no koto oboeteimasu?
\=\>-----</=/ ... Ayukawa! Ayukawa-te!" - Hikaru
Keith Morrison
Paul F. Dietz wrote:
> > By comparison, the magazine of my Glock 17 pistol holds seventeen
> > cartridges, each capable of propelling a single bullet with kinetic
> > energy of roughly 600 Joules, or about 10 kJ for the entire magazine.
> > Yet the volume of said magazine is approximately one hundred cubic
> > centimeters.
>
> But 600 joules in a CW laser weapon will not, I think, be useful for
> much of anything, beyond causing nuisance skin burns and blindness (if
> the eyes are hit). That much energy will boil about a quarter of a
> gram of water.
That brings up an interesting question. What level of energy, delivered
in the form of a laser, would actually be as useful as a bullet?
I have a suspicion it would have to be an ungodly amount to get massive
disruption from the sudden vaporization of tissue, otherwise you would
get a neat hole that the enemy has also kindly cauterized so you do
not bleed to death.
--
Keith Morrison
lone...@nbnet.nb.ca
John Schilling
di...@interaccess.com (Paul F. Dietz) writes:
>On 25 May 1997 12:55:33 -0700, schi...@spock.usc.edu (John Schilling)
>wrote:
>>di...@interaccess.com (Paul F. Dietz) writes:
[superconducting-loop energy storage]
>>>Unfortunately, this doesn't work. Any superconducting magnetic energy
>>>storage device experiences net outward J x B forces. Strength of
>>>materials limits how much energy you can store in the device, to at
>>>most on the order of the volume integral of the tensile strength of
>>However, the tensile strength of graphite or silicon-carbide whiskers is
>>on the order of 20 Gigapascals, so a composite material of whiskers in
>>a superconducting matrix were developed one could see energy densities
>>of 10 kilojoules per cubic centimeter.
>Sure, but that's not sufficient for a "hand-sized ring [to run] your
>car [...] for weeks." It's also on the rough order of the energy
>density of high explosives, and less than the combustion energy
>density of gasoline.
I never said it *was* enough to run a car for weeks. That was someone
else's argument. I merely asserted that it would be enough to power
a hand-held energy weapon, which is another matter entirely.
>> By comparison, the magazine of my Glock 17 pistol holds seventeen
>> cartridges, each capable of propelling a single bullet with kinetic
>> energy of roughly 600 Joules, or about 10 kJ for the entire magazine.
>> Yet the volume of said magazine is approximately one hundred cubic
>> centimeters.
>But 600 joules in a CW laser weapon will not, I think, be useful for
>much of anything, beyond causing nuisance skin burns and blindness (if
>the eyes are hit). That much energy will boil about a quarter of a
>gram of water.
We were talking about hand-held directed energy weapons, not CW laser
weapons. "CW laser weapon" is almost an oxymoron; if you want to hurt
someone or damage something with a laser, you pulse it. Or you go with
charged-particle beams, or plasma discharges, etc.
Whatever mechanism you use, though, if you can boil a quarter of a gram
of water in an arbitrarily short period of time, while it is still inside
the target's body, you'll get far more than a "nuisance skin burn". Think
in terms of nasty little steam explosions gouging out chunks of the target's
flesh. And, contrary to the standard SF cliche, the wound won't be neatly
cauterized.
>I suppose if you made the target stand right next to you and hold
>still, and you focused the beam down to a fraction of a millimeter,
>you might punch a thin, deep hole.
Why do you need to do either? A "laser pistol" ought to be able to focus
its beam to sub-millimeter spot sizes at typical combat ranges, and if you
rapidly pulse the laser you can punch the hole in under a millisecond.
For the 600-Joule case, go with 30 pulses each of 20 Joules, at intervals
of ten microseconds. Each would suffice to vaporize about one cubic
millimeter of soft tissue, and ten microseconds allows enough time for
the debris to clear the beam path for the next pulse. 300 microseconds
later, you've drilled a hole a foot deep into the target.
And while the hole may only be a millimeter in diameter to start, it will
also be filled with steam at about 20,000 psi, which should open things
up a bit.
Or you could get the same effect with a single pulse from a 500 MeV electron
gun, which would deposit its energy along a track roughly thirty centimeters
long and one beam diameter wide.
It is easy to "prove" that hand-held directed energy weapons are impossible
if one is allowed to assume that such weapons must be CW lasers, and that
the target can be damaged only by purely thermal effects. But if that were
the case, an awful lot of the medical and industrial applications of laser
and particle-beam technology, which actually seem to work in the real world,
would be equally impossible.
Stephan Zielinski
schi...@spock.usc.edu (John Schilling) writes:
> However, the propellant charge uesd to fire the bullet, probably contained
> at least 1,000 Joules of chemical energy.
I don't believe this is the case. However, it's easy enough to figure
out; when I get to my reference books, I'll look up the chemical
energy figures for nitrocelluose (for single base powders) and
nitroglycerine (for double base powders,) and compare it to the muzzle
velocity data from my reloader's manual.
I'm tempted to bet you a beer on the outcome, but it'd take half a
dozen messages before we agreed on what kind of powder, what kind of
round, what kind of barrel, etcetera. My intuition is that efficiency
figures are over 75% for a "reasonable" pistol or rifle, though.
[The reason I went through the momentum-dance before, rather than
going straight to calculating the efficiency, was (A) it showed that
by accelerating a small bullet to high velocity, most of the energy
ended up in the bullet, demonstrating the potential for high
efficiencies, and (B) I had the figures lying around from a previous
post and I lazily recycled them. Oh, well. Never take a short-cut on
Usenet.]
--
Stephan "Damn. Homework." Zielinski
Dave Clements
Keith Morrison wrote:
>
> Paul F. Dietz wrote:
>
> > But 600 joules in a CW laser weapon will not, I think, be useful for
> > much of anything, beyond causing nuisance skin burns and blindness (if
> > the eyes are hit). That much energy will boil about a quarter of a
> > gram of water.
>
> That brings up an interesting question. What level of energy, delivered
> in the form of a laser, would actually be as useful as a bullet?
> I have a suspicion it would have to be an ungodly amount to get massive
> disruption from the sudden vaporization of tissue, otherwise you would
> get a neat hole that the enemy has also kindly cauterized so you do
> not bleed to death.
This is the problem with optical and near-IR lasers as weapons. You may
be able to boil off a small amount of tissue, or heat a larger volume to
a high temperature, but on the surface that will do noting except annoy
your enemy (or blind them if you're very accurate).
This is why I think that masers are a much better form of DEW to look
into.
Consider a maser tuned to one of the excitation modes of water. You get
heating *within* the body, which can cause some really horrible effects.
Consider - very unpleasant effects occur if the body's temperature rises
above 107 F. Just heating the brain with a maser to above this
temperature would be enough to kill. That would take about 20kJ
according to my handy envelope. This ignores any fatal effcts you might
get with localised heating as well.
Masers can be pretty efficient, and we know how to build CW microwave
trnasmitters pretty easily.
For a man-portable maser weapon, you might just need a petrol-powered
generator on your back, rather than some nifty chemical or
superconduting power source for a laser.
Dave
--
====================================================================
Dave Clements Astronomy, Cosmology
IAS, Batiment 121, http://www.ias.fr/~clements/
Universite Paris XI, This space
91405 ORSAY CEDEX for rent
France IAS has no responsibility for me
====================================================================
Doug Lampert
In article <338C14...@ias.fr>, Dave Clements <clem...@ias.fr> wrote:
>Keith Morrison wrote:
>Masers can be pretty efficient, and we know how to build CW microwave
>trnasmitters pretty easily.
>For a man-portable maser weapon, you might just need a petrol-powered
>generator on your back, rather than some nifty chemical or
>superconduting power source for a laser.
Diffraction Scattering. A hand held microwave beam generator will generate
a beam which spreads far too quickly. Beam spread is approximated (IIRC) by
range * wavelength * a constant which is close to one / emitters diameter.
Thus a 2 cm microwave from a 155 mm microwave cannon (the size of a good
sized artillery pieces bore) will spread to around a 12 meter radius beam
within the first hundred or so meters.
Note I am doing this without my references so some of the numbers will
not be exact. Note also that all of these 'beams' are actually interference
patterns, and that the beam width is simply the approximate area of highest
intensity.
DougL
Isaac Kuo
>> in the form of a laser, would actually be as useful as a bullet?
>> I have a suspicion it would have to be an ungodly amount to get massive
>This is the problem with optical and near-IR lasers as weapons. You may
>be able to boil off a small amount of tissue, or heat a larger volume to
>a high temperature, but on the surface that will do noting except annoy
>your enemy (or blind them if you're very accurate).
Before talking about the tissue, shouldn't we first consider the
target's clothing? Even civilians tend to wear quite a bit in
the winter.
>This is why I think that masers are a much better form of DEW to look
>into.
>Consider a maser tuned to one of the excitation modes of water. You get
>heating *within* the body, which can cause some really horrible effects.
I honestly wonder, does this actually occur? It sounds like the
common myth that microwaves heat from the inside out. Anyone
who's tried to cook any meat in a microwave thicker than a
hamburger patty knows those microwaves don't penetrate more
than half an inch (if that much). Since microwave microwaves
are tuned to be absorbed by water, it's common sense that they
won't penetrate much water.
Of course, those microwaves certainly don't penetrate aluminum
foil.
Paul F. Dietz
On 26 May 1997 14:15:43 -0700, schi...@spock.usc.edu (John Schilling)
wrote:
>>But 600 joules in a CW laser weapon will not, I think, be useful for
>>much of anything, beyond causing nuisance skin burns and blindness (if
>>the eyes are hit). That much energy will boil about a quarter of a
>>gram of water.
>
>We were talking about hand-held directed energy weapons, not CW laser
>weapons. "CW laser weapon" is almost an oxymoron; if you want to hurt
>someone or damage something with a laser, you pulse it. Or you go with
>charged-particle beams, or plasma discharges, etc.
I thought you were advocating laser diodes, which (correct me if
I'm wrong) are more high CW or quasi-CW power devices.
>>I suppose if you made the target stand right next to you and hold
>>still, and you focused the beam down to a fraction of a millimeter,
>>you might punch a thin, deep hole.
>
>
>Why do you need to do either? A "laser pistol" ought to be able to focus
>its beam to sub-millimeter spot sizes at typical combat ranges, and if you
>rapidly pulse the laser you can punch the hole in under a millisecond.
Let's see. Assume a spot size of .5 mm, and a wavelength of .5
microns. To focus at 100 meters requires the laster pistol have an
aperture of on the order of 10 centimeters. Hmm... not obviously
impossible, but kind of bulky. You'd need some way to control the
focus as a function of the range to the target; presumably you make
the pistol smart enough to do its own laser ranging.
>For the 600-Joule case, go with 30 pulses each of 20 Joules, at intervals
>of ten microseconds. Each would suffice to vaporize about one cubic
>millimeter of soft tissue, and ten microseconds allows enough time for
>the debris to clear the beam path for the next pulse. 300 microseconds
>later, you've drilled a hole a foot deep into the target.
Whoa. Not clear that the debris is going to get out of the beam's
path once the hole is deep enough. You'll get a hole with a cloud of
cooked tissue debris.
>Or you could get the same effect with a single pulse from a 500 MeV electron
>gun, which would deposit its energy along a track roughly thirty centimeters
>long and one beam diameter wide.
That beam is going to (1) give the person firing it a nasty case
of backscattered bremmstrahlung, and (2) have a short range in air
(a few meters). To get it to propagate at all, you need to preionize
a channel and displace almost all of its air, so the electrons
will not lose energy. An intense electron beam will likely also
suffer from plasma instabilities as it travels through the low
density plasma of the channel.
> But if [weapons were CW] were
>the case, an awful lot of the medical and industrial applications of laser
>and particle-beam technology, which actually seem to work in the real world,
>would be equally impossible.
Industrial applications of particle and intense laser beams typically
put the final optics close to the target.
Paul
Paul F. Dietz
>>Or you could get the same effect with a single pulse from a 500 MeV electron
>>gun, which would deposit its energy along a track roughly thirty centimeters
>>long and one beam diameter wide.
>
>That beam is going to (1) give the person firing it a nasty case
>of backscattered bremmstrahlung, and (2) have a short range in air
>(a few meters).
Oops. I screwed up on the last point (dropped a decimal point).
The radiation length for high energy electrons in air is about 300
meters.
If you did use electron beams, depending on thermal effects, or even
mechanical effects from local pulsed energy deposition, isn't too
sensible. The lethal whole body dose of ionizing radiation is only a
few hundred joules.
Paul
Andrew Plotkin
Yeah, but how long does that dose take to kill you? The last thing you want
is a hand weapon that turns a healthy enemy soldier into an apparently
healthy enemy soldier who knows he's got twelve hours to live and also
knows it's *your fault*.
--Z
--
"And Aholibamah bare Jeush, and Jaalam, and Korah: these were the
borogoves..."
Keith Morrison
Andrew Plotkin wrote:
> > If you did use electron beams, depending on thermal effects, or even
> > mechanical effects from local pulsed energy deposition, isn't too
> > sensible. The lethal whole body dose of ionizing radiation is only a
> > few hundred joules.
>
> Yeah, but how long does that dose take to kill you? The last thing you want
> is a hand weapon that turns a healthy enemy soldier into an apparently
> healthy enemy soldier who knows he's got twelve hours to live and also
> knows it's *your fault*.
That's one argument against the use of "clean" nuclear weapons like
neutron bombs. Armies of walking dead who know they are going to
probably die painfully of incurable cancer so they really don't
care if they die, know surrender is pointless and really, really
want your ass on a plate.
--
Keith Morrison
lone...@nbnet.nb.ca
Erik Max Francis
Paul F. Dietz wrote:
> If you did use electron beams, depending on thermal effects, or even
> mechanical effects from local pulsed energy deposition, isn't too
> sensible. The lethal whole body dose of ionizing radiation is only a
> few hundred joules.
I get a few thousand joules.
Short, LD50 dose is about 4000 rem, or 40 Sv. Assuming radiation with a
quality factor of 1 (x-rays, gammas, electrons, muons), this corresponds
to an absorbed dose of (duh) 40 Gy, which is 40 J/kg. Given an average
human with a mass of 70 kg (~= 150 lbs), that corresponds to 2800 J of
ionizing radiation.
--
Erik Max Francis, &tSftDotIotE / email / m...@alcyone.com
Alcyone Systems / web / http://www.alcyone.com/max/
San Jose, California, United States / icbm / 37 20 07 N 121 53 38 W
\
"Covenants without the sword / are but words."
/ Camden
Paul F. Dietz
On Thu, 29 May 1997 15:35:12 GMT, erky...@netcom.com (Andrew Plotkin)
wrote:
>> If you did use electron beams, depending on thermal effects, or even
>> mechanical effects from local pulsed energy deposition, isn't too
>> sensible. The lethal whole body dose of ionizing radiation is only a
>> few hundred joules.
>
>Yeah, but how long does that dose take to kill you? The last thing you want
>is a hand weapon that turns a healthy enemy soldier into an apparently
>healthy enemy soldier who knows he's got twelve hours to live and also
>knows it's *your fault*.
Just-lethal doses can take two to six weeks to kill. However, the
lethal dose varies from person to person, and there's no way for the
enemy to know if (say) 300 rads will kill them, or just make them
very sick. Since radiation damage over short times is cumulative, a
sublethally exposed soldier will likely be more, not less, cautious.
If you want prompt incapacitation I think the energy required is
in the kilojoules (about 5000 rads). This causes death in about a
week.
Paul
Geoffrey A. Landis
>>One of my current enthusiasms is superconducting storage rings.
Referred to in the energy business as "superconducting magnetic storage
systems" (SMES), by the way (since the energy is actually stored in the
form of magnetic fields)
In article <5m9ek8$a...@news.ox.ac.uk> rupert smith,
linc...@sable.ox.ac.uk writes:
>>It may even by
>>economic to ship energy down from orbit, using massive banks of solar
>>panels to charge a [superconducting] ring and then flying it down on a shuttle.
No.
Not by several orders of magnitude.
______________________
Geoffrey A. Landis
Physicist and part-time Science Fiction writer
Ohio Aerospace Institute at NASA Lewis Research Center
http://www.sff.net/people/Geoffrey.Landis
Erik Max Francis
Paul F. Dietz wrote:
> The LD50 for death within one month is 400 to 500 rem. 4000 rem is
> 100% lethal -- even 1000 rem is 100% lethal. (All this for doses
> received over a period of < 1 week.)
>
> Perhaps you are thinking of the immediately incapacitating dose, which
> is close to that (see my followup).
Well, I did it again. I just remembered the figure wrong. "A short dose
of 1000 rem [10 Sv] is nearly always fatal. A 400-rem [4-Sv] dose in a
short period of time is fatal in 50 percent of the cases. However, the
body possesses remarkable repair processes so that a 400-rem [4-Sv] dose
spread over several weeks is usually not fatal. It will, nonetheless,
cause considerable damage to the body" (_Physics 2nd ed._, Giancoli, p.
740).
I just added an order of magnitude somewhere. 4 Sv delivered over a short
time is indeed LD50. That corresponds to 280 J for a 70 kg human, or a
few hundred joules, just like you said. Thanks for catching that goof.
rupert smith
a long time ago, in a land far far away Geoffrey A. Landis <Geoffrey...@lerc.nasa.gov> wrote:
>>>One of my current enthusiasms is superconducting storage rings.
>
>Referred to in the energy business as "superconducting magnetic storage
>systems" (SMES), by the way (since the energy is actually stored in the
>form of magnetic fields)
well, /yes/, that business with poynting vectors and suchlike, but it's a bit
pedantic..
>In article <5m9ek8$a...@news.ox.ac.uk> rupert smith,
>linc...@sable.ox.ac.uk writes:
>>>It may even by
>>>economic to ship energy down from orbit, using massive banks of solar
>>>panels to charge a [superconducting] ring and then flying it down on a
> shuttle.
>
>No.
i agree, but i didn't actually say that. be careful with your attributions.
------------------------------------------------------------------------------
rupert smith linc0015(at)sable.ox.ac.uk http://users.ox.ac.uk/~linc0015
lazing on a sunny afternoon..
Paul F. Dietz
On Thu, 29 May 1997 15:35:21 -0700, Erik Max Francis <m...@alcyone.com>
wrote:
>Paul F. Dietz wrote:
>
>> If you did use electron beams, depending on thermal effects, or even
>> mechanical effects from local pulsed energy deposition, isn't too
>> sensible. The lethal whole body dose of ionizing radiation is only a
>> few hundred joules.
>
>I get a few thousand joules.
>
>Short, LD50 dose is about 4000 rem, or 40 Sv.
The LD50 for death within one month is 400 to 500 rem. 4000 rem is
100% lethal -- even 1000 rem is 100% lethal. (All this for doses
received over a period of < 1 week.)
Perhaps you are thinking of the immediately incapacitating dose, which
is close to that (see my followup).
Paul
John F. Eldredge
di...@interaccess.com (Paul F. Dietz) wrote:
>On Thu, 29 May 1997 15:35:12 GMT, erky...@netcom.com (Andrew Plotkin)
>wrote:
>
>
>>> If you did use electron beams, depending on thermal effects, or even
>>> mechanical effects from local pulsed energy deposition, isn't too
>>> sensible. The lethal whole body dose of ionizing radiation is only a
>>> few hundred joules.
>>
>>Yeah, but how long does that dose take to kill you? The last thing you want
>>is a hand weapon that turns a healthy enemy soldier into an apparently
>>healthy enemy soldier who knows he's got twelve hours to live and also
>>knows it's *your fault*.
>
>Just-lethal doses can take two to six weeks to kill. However, the
>lethal dose varies from person to person, and there's no way for the
>enemy to know if (say) 300 rads will kill them, or just make them
>very sick. Since radiation damage over short times is cumulative, a
>sublethally exposed soldier will likely be more, not less, cautious.
>
>If you want prompt incapacitation I think the energy required is
>in the kilojoules (about 5000 rads). This causes death in about a
>week.
>
> Paul
Here, in Nashville, Tennessee, USA, there was a case a few years ago
of a teenage girl who wanted to get a suntan overnight. She went to a
succession of tanning salons, getting the maximum exposure time
allowed at each. She died as a result of the severe sunburn that
resulted (sunburn is a form of radiation poisoning). I don't remember
the details about the total amount of exposure, but will try to look
them up.
--
John F. Eldredge -- eldr...@poboxes.com
PGP key available from http://www.netforward.com/poboxes/?eldredge/
--
"There must be, not a balance of power, but a community of power;
not organized rivalries, but an organized common peace." - Woodrow Wilson
Andrew Plotkin
John F. Eldredge (eldr...@poboxes.com) wrote:
> Here, in Nashville, Tennessee, USA, there was a case a few years ago
> of a teenage girl who wanted to get a suntan overnight. She went to a
> succession of tanning salons, getting the maximum exposure time
> allowed at each. She died as a result of the severe sunburn that
> resulted (sunburn is a form of radiation poisoning). I don't remember
> the details about the total amount of exposure, but will try to look
> them up.
Well, I've heard that as an urban legend (in a considerably less
plausible form, however.) Hm. (Footnote: Not saying it didn't happen.)
Sunburn is a form of radiation poisoning, but of the skin only. I'd
exposure to UV to behave differently from exposure to higher-energy
ionizing radiation, which damages internal organs. Different forms of
death. I wouldn't try comparing the LD50 dosages of the two.
John Schilling
di...@interaccess.com (Paul F. Dietz) writes:
>On 26 May 1997 14:15:43 -0700, schi...@spock.usc.edu (John Schilling)
>wrote:
>>>But 600 joules in a CW laser weapon will not, I think, be useful for
>>>much of anything, beyond causing nuisance skin burns and blindness (if
>>>the eyes are hit). That much energy will boil about a quarter of a
>>>gram of water.
>>We were talking about hand-held directed energy weapons, not CW laser
>>weapons. "CW laser weapon" is almost an oxymoron; if you want to hurt
>>someone or damage something with a laser, you pulse it. Or you go with
>>charged-particle beams, or plasma discharges, etc.
>I thought you were advocating laser diodes, which (correct me if
>I'm wrong) are more high CW or quasi-CW power devices.
I used laser diodes as an existence proof of the proposition that lasers
can be very efficient, which is not the same as advocating them as the
One True Way of making a laser weapon. However, there is no fundamental
reason why a laser diode cannot be operated in a pulsed mode. There is
at present no need for such, and it complicates the power supply design
quite a bit, so it isn't done. But it almost certainly could be.
And if that doesn't work, you can definitely use a diode laser to pump
a Q-switched, pulsed crystal laser. With the pump source tuned for
resonant absorbtion, neodymium-YAG lasers have already demonstrated
efficiencies of 40%, and getting to 80+% is only a matter of engineering.
So using only what we already know, we can get compact, high-power, pulsed
lasers with good beam quality, having total system efficiencies of at least
60%. Which, as pointed out earlier, is better than any contemporary firearm.
It would take a lot of work, and a lot of money, to put all the pieces
together, but no fundamental breakthroughs are required. The power supply
is the real sticking point.
>>>I suppose if you made the target stand right next to you and hold
>>>still, and you focused the beam down to a fraction of a millimeter,
>>>you might punch a thin, deep hole.
>>Why do you need to do either? A "laser pistol" ought to be able to focus
>>its beam to sub-millimeter spot sizes at typical combat ranges, and if you
>>rapidly pulse the laser you can punch the hole in under a millisecond.
>Let's see. Assume a spot size of .5 mm, and a wavelength of .5
>microns. To focus at 100 meters requires the laster pistol have an
>aperture of on the order of 10 centimeters. Hmm... not obviously
>impossible, but kind of bulky. You'd need some way to control the
>focus as a function of the range to the target; presumably you make
>the pistol smart enough to do its own laser ranging.
A hundred meters is not a typical combat range for a handgun. Ten meters
or less is typical, but I'd like to see at least 25 meters for a personal
defense weapon and 50 for a heavy police/military sidearm, which should
be possible. Laser ranging and adaptive optics for focussing are a must,
of course. And it would be desirable to allow the weapon to adjust its
pulse rate and energy with range - it should be possible to retain at
least some effect out to a hundred meters even with the 25-meter design.
>>For the 600-Joule case, go with 30 pulses each of 20 Joules, at intervals
>>of ten microseconds. Each would suffice to vaporize about one cubic
>>millimeter of soft tissue, and ten microseconds allows enough time for
>>the debris to clear the beam path for the next pulse. 300 microseconds
>>later, you've drilled a hole a foot deep into the target.
>Whoa. Not clear that the debris is going to get out of the beam's
>path once the hole is deep enough.
Sideways, no matter how deep the hole is. We are talking about energy
densities of several kilojoules per square centimeter, and peak pressures
in excess of a hundred megapascals. The fact that the volume surrounding
the beam path is occupied by some bags of water and dissolved protein,
isn't going to make much difference.
>You'll get a hole with a cloud of cooked tissue debris.
Dimensional analysis suggests that the one-millimeter beam will produce a
hole about four centimeters wide, filled with water vapor and about 0.25%
particulates. Absorbtion from the particulates would set a maximum on
beam penetration, of about 0.8 meters.
The hole will tend to contract once the pressure is off, but I don't have
the figures on tissue elasticity I would need to calculate the effect.
WAG based on projectile terminal ballistics gives one to two centimeters
as the final cavity diameter.
>>Or you could get the same effect with a single pulse from a 500 MeV electron
>>gun, which would deposit its energy along a track roughly thirty centimeters
>>long and one beam diameter wide.
>That beam is going to (1) give the person firing it a nasty case
>of backscattered bremmstrahlung,
A few tens of microrems per shot, possibly. At 500 MeV, just about everything
gets scattered or emitted in a narrow, forward cone.
>and (2) have a short range in air (a few meters). To get it to propagate
>at all, you need to preionize a channel and displace almost all of its air,
>so the electrons will not lose energy.
Two hundred fifty meters with no pre-ionization, actually. At high currents
the beam produces its own ionization channel with little loss, and tends to
magnetically and electrostatically self-focus. Large-angle scattering is
the dominant attenuation mechanism, and at 500 MeV, there isn't much of
that.
>An intense electron beam will likely also suffer from plasma instabilities
>as it travels through the low density plasma of the channel.
Instabilities in relativistic beams tend to be almost entirely longitudinal,
which won't change much from the target's perspective.
>> But if [weapons were CW] were
>>the case, an awful lot of the medical and industrial applications of laser
>>and particle-beam technology, which actually seem to work in the real world,
>>would be equally impossible.
>Industrial applications of particle and intense laser beams typically
>put the final optics close to the target.
Because it is convenient, not because it is necessary. And in this case
irrelevant, because the issue under debate was the ability to punch deep
holes with less energy than would be required using purely thermal effects.
If you want to change the subject to that of achieving high concentrations
on distant targets, a different set of examples become relevant.
Generating beams of directed energy with high efficiency is demonstrably
possible, because it is being done today.
Concentrating beams of directed energy onto small areas of distant targets
is also demonstrably possible, because it is also being done today.
Making deep holes in targets with relatively small ammounts of energy, via
thermomechanical coupling, is also demonstrably possible, because it is
also being done today.
Aside from the power supply, every ingredient one would need for an SF
"laser pistol" is already in existence. Nobody has yet had reason to
put them all in the same package, so if you want you can shift subjects
indefinitely by pointing out that any example put forth doesn't meet
every requirement at once, but that's a prety weak argument.
John D. Gwinner
John:
John Schilling <schi...@spock.usc.edu> wrote in article
<5mpm7j$jek$1...@spock.usc.edu>...
> A hundred meters is not a typical combat range for a handgun. Ten meters
> or less is typical, but I'd like to see at least 25 meters for a personal
> defense weapon and 50 for a heavy police/military sidearm, which should
> be possible.
Depends on what you mean by handgun. If you mean a single handed 'pistol'
type of thing, then 50m is laughable. By that I mean that nobody could hit
the broadside of a barn at 50m. Most people of good marksmanship
(experienced with firearms) are lucking to hit a paper target 4 feet by 2
feet (very roughly) at 7m in a 'rapid fire' type exercise. 25m is about
the best range you can slowly squeeze off a round and hit a reasonable
target (dinner plate size), most (not all) of the time.
However, after having said that, if it truly was a CW laser, 50m might be
very reasonable. Why? Assuming no recoil, you could just 'paint' the
target.
If you miss with a CW weapon, your going to screw up a lot of the real
estate.
I can see it now: "COP BEHEADS 100 PEOPLE AT PRESIDENTIAL ASSASSINATION
ATTEMPT. Assassin slain, but 100 bystanders were sliced in half as the
secret service attempted to hit the assassin". he he
> Laser ranging and adaptive optics for focussing are a must,
> of course. And it would be desirable to allow the weapon to adjust its
> pulse rate and energy with range - it should be possible to retain at
> least some effect out to a hundred meters even with the 25-meter design.
That's something I find a lot of people misunderstand; focal length, and
lens size does make a difference with lasers.
> Two hundred fifty meters with no pre-ionization, actually. At high
currents
> the beam produces its own ionization channel with little loss, and tends
to
> magnetically and electrostatically self-focus. Large-angle scattering is
> the dominant attenuation mechanism, and at 500 MeV, there isn't much of
> that.
Interesting. Professional military might consider 250m to be pretty close
range; I wouldn't use this as my main weapon in an assault, but it might be
good for city use. Most Marines today are trained to be lethal at least
80% of the time at 500m.
> Aside from the power supply, every ingredient one would need for an SF
> "laser pistol" is already in existence. Nobody has yet had reason to
> put them all in the same package, so if you want you can shift subjects
> indefinitely by pointing out that any example put forth doesn't meet
> every requirement at once, but that's a prety weak argument.
Very interesting discussion. What kind of power supply is required? Would
one of these 'photon lances' <G> require a back pack type power supply with
current technology, or are we talking about something bigger?
== John ==
Bill Woods
John D. Gwinner wrote:
>
> John:
>
> John Schilling <schi...@spock.usc.edu> wrote in article
> <5mpm7j$jek$1...@spock.usc.edu>...
>
> > or less is typical, but I'd like to see at least 25 meters for a personal
> > defense weapon and 50 for a heavy police/military sidearm, which should
> > be possible.
>
> type of thing, then 50m is laughable. By that I mean that nobody could hit
> the broadside of a barn at 50m. Most people of good marksmanship
> (experienced with firearms) are lucking to hit a paper target 4 feet by 2
> feet (very roughly) at 7m in a 'rapid fire' type exercise. 25m is about
> the best range you can slowly squeeze off a round and hit a reasonable
> target (dinner plate size), most (not all) of the time.
>
> However, after having said that, if it truly was a CW laser, 50m might be
> very reasonable. Why? Assuming no recoil, you could just 'paint' the
> target.
>
> If you miss with a CW weapon, your going to screw up a lot of the real
> estate.
Paint the target with the laser rangefinder; when you're on target, pull
the trigger all the way back to fire for effect.
> I can see it now: "COP BEHEADS 100 PEOPLE AT PRESIDENTIAL ASSASSINATION
> ATTEMPT. Assassin slain, but 100 bystanders were sliced in half as the
> secret service attempted to hit the assassin". he he
>
> > Laser ranging and adaptive optics for focussing are a must,
> > of course. And it would be desirable to allow the weapon to adjust its
> > pulse rate and energy with range - it should be possible to retain at
> > least some effect out to a hundred meters even with the 25-meter design.
>
> That's something I find a lot of people misunderstand; focal length, and
> lens size does make a difference with lasers.
>
> > Two hundred fifty meters with no pre-ionization, actually. At high
> currents
> > the beam produces its own ionization channel with little loss, and tends
> to
> > magnetically and electrostatically self-focus. Large-angle scattering is
> > the dominant attenuation mechanism, and at 500 MeV, there isn't much of
> > that.
>
> Interesting. Professional military might consider 250m to be pretty close
> range; I wouldn't use this as my main weapon in an assault, but it might be
> good for city use. Most Marines today are trained to be lethal at least
> 80% of the time at 500m.
>
> > Aside from the power supply, every ingredient one would need for an SF
> > "laser pistol" is already in existence. Nobody has yet had reason to
> > put them all in the same package, so if you want you can shift subjects
> > indefinitely by pointing out that any example put forth doesn't meet
> > every requirement at once, but that's a prety weak argument.
>
> Very interesting discussion. What kind of power supply is required? Would
> one of these 'photon lances' <G> require a back pack type power supply with
> current technology, or are we talking about something bigger?
>
> == John ==
How practical would a larger, vehicle-mounted weapon be?
--
Bill Woods
"Whenever I see an adult on a bicycle, I do not despair
for the future of the human race."
--H.G.Wells
Brian Trosko
John D. Gwinner <gwi...@northnet.org> wrote:
: Interesting. Professional military might consider 250m to be pretty close
: range; I wouldn't use this as my main weapon in an assault, but it might be
: good for city use. Most Marines today are trained to be lethal at least
: 80% of the time at 500m.
They're trained to hit a target at 500m, but when was the last time any
unit actually engaged, with small arms fire, an enemy unit at 500m? Most
combat takes place at what would seem like frighteningly close ranges.
John F. Eldredge
"John D. Gwinner" <gwi...@northnet.org> wrote:
>Very interesting discussion. What kind of power supply is required? Would
>one of these 'photon lances' <G> require a back pack type power supply with
>current technology, or are we talking about something bigger?
Given current efficiency ratings, I think a truck-mounted weapon would
be the minimum. A man-portable system with enough output power to be
an effective weapon would use up its power pack too soon to be an
effective battlefield weapon. I suspect the first truly high-powered
beam weapons will be ship-mounted, and used for point defense (against
incoming projectiles).
Nyrath the nearly wise
John Schilling (schi...@spock.usc.edu) wrote:
: The power supply is the real sticking point.
Amen. From laser handguns to Ion drive spaceships to
electric cars, the entire world is waiting for
somebody to invent the Antimatter Eveready!
Brian Trosko
John F. Eldredge <eldr...@poboxes.com> wrote:
: effective battlefield weapon. I suspect the first truly high-powered
: beam weapons will be ship-mounted, and used for point defense (against
: incoming projectiles).
There's a laser weapon under development that already seems quite
promising, and is due to be procured within the next few years. It's an
airborne chemical system carried by a converted 727, and it supposed to be
capable of downing IRBMs from in-theater. The idea is that it'll cruise a
few hundred miles behind the front, and if the Bad Guy flips any Scuds or
FROGs at you, this'll drop'em.
In recent tests, it successfully shot down a Sidewinder missile in flight.
If it can destroy IRBMs during their reentry phase, how much harder would
it be to drill through enemy aircraft?
Erik Max Francis
Nyrath the nearly wise wrote:
> Amen. From laser handguns to Ion drive spaceships to
> electric cars, the entire world is waiting for
> somebody to invent the Antimatter Eveready!
I'm not putting one of the damn things in a CDman.
Phil Hunt
In article <5msh6o$7...@nntp02.primenet.com>
btr...@primenet.com "Brian Trosko" writes:
> There's a laser weapon under development that already seems quite
> promising, and is due to be procured within the next few years. It's an
> airborne chemical system carried by a converted 727, and it supposed to be
> capable of downing IRBMs from in-theater. The idea is that it'll cruise a
> few hundred miles behind the front, and if the Bad Guy flips any Scuds or
> FROGs at you, this'll drop'em.
>
> In recent tests, it successfully shot down a Sidewinder missile in flight.
>
> If it can destroy IRBMs during their reentry phase, how much harder would
> it be to drill through enemy aircraft?
What if the enemy aircraft has lots of little mirrors, in groups of three
at right angles to each other, to send the beam back where it came from?
--
***** Phil Hunt == ph...@vision25.demon.co.uk *****
<http://www.vision25.demon.co.uk/index.htm> for info on:
Eurolang, politics, voting systems, basic income.
Stephan Zielinski
Stephan Zielinski <szie...@well.com> writes:
> schi...@spock.usc.edu (John Schilling) writes:
> > However, the propellant charge uesd to fire the bullet, probably contained
> > at least 1,000 Joules of chemical energy.
>
> I don't believe this is the case.
Looks bad for the home team. I did the math and came up with an
efficiency of about 20%. The only thing that can possibly save me now
is if the powder I checked uses inert ingedients in with the
nitrocellulose, or if the figure I have for the energy content of
nitrocellulose is the heat released in full oxidation, not just
detonation. I'll call the manufacturer this week & try to get their
official reckoning of how much oomph a gram of their powder has.
--
Stephan "When calculating muzzle energies from reloading manuals, a
useful intermediate unit is the grain foot squared per second squared,
which I have named the `gisspiss'" Zielinski
Paul F. Dietz
On Sun, 01 Jun 97 22:16:50 GMT, ph...@vision25.demon.co.uk (Phil Hunt)
wrote:
>What if the enemy aircraft has lots of little mirrors, in groups of three
>at right angles to each other, to send the beam back where it came from?
Well, those little mirrors will diffract the heck out of the beam, so
it's no threat to the laser. This *would* make the plane a dandy
target for self-laser-guided missles, though.
Paul
Dave Clements
John F. Eldredge wrote:
>
> Given current efficiency ratings, I think a truck-mounted weapon would
> be the minimum. A man-portable system with enough output power to be
> an effective weapon would use up its power pack too soon to be an
> beam weapons will be ship-mounted, and used for point defense (against
> incoming projectiles).
The first is going to be airplane mounted, in a 747-400, and will be
used for anti-missile defense (and, to some extent, anti-aircraft
self-defense).
Its the prototype airbourne laser (ABL) project currently underway in
the US.
--
====================================================================
Dave Clements Astronomy, Cosmology
IAS, Batiment 121, http://www.ias.fr/~clements/
Universite Paris XI, This space
91405 ORSAY CEDEX for rent
France IAS has no responsibility for me
====================================================================
Brian Trosko
Phil Hunt <ph...@vision25.demon.co.uk> wrote:
: What if the enemy aircraft has lots of little mirrors, in groups of three
: at right angles to each other, to send the beam back where it came from?
Reflecting a high-energy laser isn't as simple as putting up a mirror.
That's a lot of energy hitting that mirror, and unless it's highly
reflective indeed, it'll just vaporize.
High-energy mirrors are very expensive, and sticking them all over the
flight surfaces of your aircraft probably wouldn't be good for their
ability to stay in the air.
And, once your high-energy mirror has been flown around on the wings of a
plane for a few minutes, it's not going to be highly reflective any more.
Dead bugs, exhaust, and a whole bunch of other crud will do that.
Phil Hunt
In article <33921692...@nntp.interaccess.com>
di...@interaccess.com "Paul F. Dietz" writes:
> On Sun, 01 Jun 97 22:16:50 GMT, ph...@vision25.demon.co.uk (Phil Hunt)
> >What if the enemy aircraft has lots of little mirrors, in groups of three
> >at right angles to each other, to send the beam back where it came from?
>
I don't think so. I was thinking of mirrors about 1cm big, which ought
to be big enough to stop too much diffraction.
> so
> it's no threat to the laser. This *would* make the plane a dandy
> target for self-laser-guided missles, though.
That's true. Perhaps it would be better to have a non-reflective plane
and have it shooting out reflective chaff when it is under fire.
B. Vermo
In article <rnqbu5p...@decay.pbi.net>,
Stephan Zielinski <szie...@well.com> wrote:
|
|Looks bad for the home team. I did the math and came up with an
|efficiency of about 20%. The only thing that can possibly save me now
|is if the powder I checked uses inert ingedients in with the
|nitrocellulose
One thought occurred to me - how small must the caliber be for the
effect to look like a beam weapon with the on-target power of a 9mm?
Given our best material technology, what kind of muzzle velocity
could we acheive with a 1mg slug in a 10cm barrel?
Keith Morrison
Phil Hunt wrote:
> I don't think so. I was thinking of mirrors about 1cm big, which ought
> to be big enough to stop too much diffraction.
Of course airflow goes all to hell. And who goes outside to wash
off the accumulated dirt?
> That's true. Perhaps it would be better to have a non-reflective plane
> and have it shooting out reflective chaff when it is under fire.
Limited utility. Chaff, because of the way it works, is only good
directly behind the aircraft for a laser weapon. And you would have
no warning that it might be a good idea to dump chaff unless you
count your wingman suddenly ejecting. And by then you're probably
toast.
Like David Drake said, once you get near speed-of-light line-of-sight
weapons battlefields become the last place you want to be driving an
airplane.
--
Keith Morrison
lone...@nbnet.nb.ca
John Schilling
"John D. Gwinner" <gwi...@northnet.org> writes:
>John Schilling <schi...@spock.usc.edu> wrote in article
><5mpm7j$jek$1...@spock.usc.edu>...
>> A hundred meters is not a typical combat range for a handgun. Ten meters
>> or less is typical, but I'd like to see at least 25 meters for a personal
>> defense weapon and 50 for a heavy police/military sidearm, which should
>> be possible.
>Depends on what you mean by handgun. If you mean a single handed 'pistol'
>type of thing, then 50m is laughable. By that I mean that nobody could hit
>the broadside of a barn at 50m. Most people of good marksmanship
>(experienced with firearms) are lucking to hit a paper target 4 feet by 2
>feet (very roughly) at 7m in a 'rapid fire' type exercise. 25m is about
>the best range you can slowly squeeze off a round and hit a reasonable
>target (dinner plate size), most (not all) of the time.
>However, after having said that, if it truly was a CW laser, 50m might be
>very reasonable. Why? Assuming no recoil, you could just 'paint' the
>target.
Unfortunately, the energy requirements for an effective CW laser weapon are
prohibitive even with the sort of storage systems we are talking about here.
Taking the pulsed laser handgun discussed earlier as a baseline, and insisting
on being able to sweep at 5 degrees/second while still cutting at least 5cm
deep in flesh, results in a power requirement of over half a megawatt. Or
maybe a single second's worth of continuous fire from the powerpack.
I'll stick with rapid pulsing - 20, 1000J shots per second should give the
rough equivilant of an Ingram M-11 machine pistol but with zero recoil and
almost thirty seconds of fire without reloading. Or if we get stuck with
energy storage an order of magnitude less than the ~10 kJ/cm^3 materials
limit, 10 pulses per second for 5 seconds. A 50 meter effective range
seems reasonable either way.
[charged-particle beam effective to 250m at 500 MeV]
>Interesting. Professional military might consider 250m to be pretty close
>range; I wouldn't use this as my main weapon in an assault, but it might be
>good for city use. Most Marines today are trained to be lethal at least
>80% of the time at 500m.
Keep in mind, these are sidearms we are talking about here. For a rifle
equivilant you could jump the energy up to a few GeV with proportionate
increase in range - plasma-wave accelerators are already capable of
producing GeV/meter particle energies, so power and current are the only
real limits. If you've got an order of magnitude more energy storage in
a rifle "magazine" than a pistol, you can get an order of magnitude more
range and penetration, all other things being equal.
That gives an effective range of ~2500 meters in air, and penetration of
25 cm in steel.
>> Aside from the power supply, every ingredient one would need for an SF
>> "laser pistol" is already in existence.
>Very interesting discussion. What kind of power supply is required? Would
>one of these 'photon lances' <G> require a back pack type power supply with
>current technology, or are we talking about something bigger?
We were talking about superconducting magnetic energy storage using high-temp
superconductors reinforced with graphite or SiC whiskers. This is not exactly
known technology, but it is forseeable. With this technology, you get truly
self-contained weapons - I pulled the magazine on my Glock 17 to measure a
baseline volume for pistol energy storage units.
The best current batteries are about an order of magnitude worse, and not a
all suited for the sort of high-rate discharges that would be required. Throw
in every laboratory demonstration at its proponents' claimed performance, and
you might get something reasonable, like the low-option (50 shot x 1000J)
pistol I described, in a package the size of one of the larger current pistols.
Or you could stick the battery on the belt, asjacent to the holster, to keep
the "gun" itself reasonably compact.
Chad Irby
eldr...@poboxes.com (John F. Eldredge) wrote:
> Given current efficiency ratings, I think a truck-mounted weapon would
> be the minimum. A man-portable system with enough output power to be
> an effective weapon would use up its power pack too soon to be an
> effective battlefield weapon. I suspect the first truly high-powered
> beam weapons will be ship-mounted, and used for point defense (against
> incoming projectiles).
There was a "tank-mounted" laser weapon a few years ago- it was a
tank+tracked trailer rig with a single laser weapon in a small turret, and
was supposed to be used to engage aircraft. It wasn't practical, though.
Some of the new "small" lasers are getting into the size/consumables range
to make them useful for antimissile and antiaircraft weapons in medium
sized vehicles.
--
cirby
Chad Irby
Erik Max Francis <m...@alcyone.com> wrote:
> Nyrath the nearly wise wrote:
> > Amen. From laser handguns to Ion drive spaceships to
> > electric cars, the entire world is waiting for
> > somebody to invent the Antimatter Eveready!
>
> I'm not putting one of the damn things in a CDman.
Well, if something goes wrong with the battery/containment, it would be
nice and loud.
Once.
--
cirby
Nyrath the nearly wise
: > the entire world is waiting for
: > somebody to invent the Antimatter Eveready!
:
: I'm not putting one of the damn things in a CDman.
Hmmph! Another Luddite! They're perfectly safe.
Just. Don't. DROP. Them.
<grin>
Keith Morrison
Chad Irby wrote:
> > > Amen. From laser handguns to Ion drive spaceships to
> > > electric cars, the entire world is waiting for
> > > somebody to invent the Antimatter Eveready!
> >
> > I'm not putting one of the damn things in a CDman.
>
> Well, if something goes wrong with the battery/containment, it would be
> nice and loud.
>
> Once.
One can see the Energizer commercials already:
"Sure, use the competition's batteries. They keep blowing
and blowing and blowing and..."
--
Keith Morrison
lone...@nbnet.nb.ca
Isaac Kuo
In article <3394D3...@nbnet.nb.ca>,
Keith Morrison <lone...@nbnet.nb.ca> wrote:
>Like David Drake said, once you get near speed-of-light line-of-sight
>weapons battlefields become the last place you want to be driving an
>airplane.
It depends upon how much range and power they have, doesn't it?
We've had the ability to "blast" a concentrated beam of EM radiation
at a flying airplane with pinpoint accuracy from a hundred miles
away since WWII. All we'd need to do is scale up the power a bit,
right? Yeah, right.
--
_____ Isaac Kuo (k...@bit.csc.lsu.edu)
__|_>o<_|__
/___________\ "Kinou no ban no koto oboeteimasu?
\=\>-----</=/ ... Ayukawa! Ayukawa-te!" - Hikaru
Keith Morrison
Isaac Kuo wrote:
> >Like David Drake said, once you get near speed-of-light line-of-sight
> >weapons battlefields become the last place you want to be driving an
> >airplane.
>
> It depends upon how much range and power they have, doesn't it?
> We've had the ability to "blast" a concentrated beam of EM radiation
> at a flying airplane with pinpoint accuracy from a hundred miles
> away since WWII. All we'd need to do is scale up the power a bit,
> right? Yeah, right.
W-E-A-P-O-N, not R-A-D-A-R.
--
Keith Morrison
lone...@nbnet.nb.ca
Chad Irby
lone...@nbnet.nb.ca wrote:
> Isaac Kuo wrote:
> >
> > It depends upon how much range and power they have, doesn't it?
> > We've had the ability to "blast" a concentrated beam of EM radiation
> > at a flying airplane with pinpoint accuracy from a hundred miles
> > away since WWII. All we'd need to do is scale up the power a bit,
> > right? Yeah, right.
>
> W-E-A-P-O-N, not R-A-D-A-R.
As someone who has accidentally stood in front of a running aircraft radar
(and gotten heated up a bit for his pains), I can vouch for the "scale the
power up a bit" school of thought.
A radar with enough power behind it (and a bit more concentration in the
beam) becomes a pretty effective weapon. For references, stick a whole
uncooked egg in your microwave oven and set the timer for five minutes or
so...
--
cirby
Paul F. Dietz
On Mon, 02 Jun 97 21:00:00 GMT, ph...@vision25.demon.co.uk (Phil Hunt)
wrote:
>In article <33921692...@nntp.interaccess.com>
> di...@interaccess.com "Paul F. Dietz" writes:
>> On Sun, 01 Jun 97 22:16:50 GMT, ph...@vision25.demon.co.uk (Phil Hunt)
>> wrote:
>> >What if the enemy aircraft has lots of little mirrors, in groups of three
>> >at right angles to each other, to send the beam back where it came from?
>>
>> Well, those little mirrors will diffract the heck out of the beam,
>
>I don't think so. I was thinking of mirrors about 1cm big, which ought
>to be big enough to stop too much diffraction.
We were talking about this big airliner mounted chemical
laser (near IR) that would operate at a distance of perhaps 100 km
(for shooting down Scuds and such).
A 1 cm diameter aperture with 1 micron radiation at 100 km gives a
diffraction limited spot with a diameter of ~40 meters. Too big.
Paul
Paul F. Dietz
On 4 Jun 1997 17:09:22 -0700, schi...@spock.usc.edu (John Schilling)
wrote:
>Keep in mind, these are sidearms we are talking about here. For a rifle
>equivilant you could jump the energy up to a few GeV with proportionate
>increase in range - plasma-wave accelerators are already capable of
>producing GeV/meter particle energies, so power and current are the only
>real limits. If you've got an order of magnitude more energy storage in
>a rifle "magazine" than a pistol, you can get an order of magnitude more
>range and penetration, all other things being equal.
Wait: the range of very high energy electrons is roughly independent
of their energy. They lose energy to bremsstrahlung, with the
fraction of energy reduced to 1/e of the original beam energy within
a distance of ~300 meters in air at STP.
The bremmstrahlung photons do produce electron/positron pairs, which
produce more bremsstrahlung, etc., produced an exponentially growing
shower of particles, but this shower penetrates to a distance that
grows only logarithmically in the energy of the initial electron.
Paul