Laser Rifle??? :)

LazyManc · Post by **LazyManc** » Thu Apr 03, 2003 12:15 am

Not as sci-fi as you think

http://www.defensereview.com/modules.ph ... le&sid=304

kipper · Post by **kipper** » Thu Apr 03, 2003 9:33 am

there more worried about the size of the batteries how come no buggers thought of the size of the gas tanks needed (the crappy one in the stock woudnt be enough to pump up a car tyre let alone fire for long) ?

still if you sprayed it a gaudy mixture of yellow/orange/green you could say it was a super soaker and realy supprise someone

kipper · Post by **kipper** » Thu Apr 03, 2003 10:10 am

ok i've read a bit further now, 531 psi in such a small container is quite impressive but they still use a fair bit of gas especially if it is released with every trigger pull

just so you know im not talking out my arse i used to be a CNC laser operator (ask limpmisfit or rebel rider, we worked at the same place - they were both the CAD programmers)

and this is the beastie i used to use, ignore the top photo as it shows a large sheetmetal loader on the arse end of the machine that we never had
http://www.bystronic.ch/english/products/bysprint.asp

or this one (better pic)
http://www.hascotech.com/machines/bystr ... etails.htm

bartender · Post by **bartender** » Thu Apr 03, 2003 1:04 pm

anyone have any clues about how the 'weapon' would be fatal over 1500m. The way I see it it would deliver 665J of energy (excluding any losses from dispersion) with each burst (enough energy to raise the temperature of 1 gram of water by 159 degrees C) which would give you a nasty burn over the 1.3mm if it hit bare skin but certainly wouldn't be fatal.

garlando · Post by **garlando** » Thu Apr 03, 2003 7:26 pm

Just a few questions....
a)

ok i've read a bit further now, 531 psi in such a small container is quite impressive but they still use a fair bit of gas especially if it is released with every trigger pull

Why would they need to release the gas after each trigger pull?
<physics> The way the laser is generated the electrons in the atom are excited by some controlled means to a certain energy level, as there are only set levels they can be raised to this creates a few set wavelengths of light and these can be used to create a single wavelength of light (quantum physics....) and so will cut down on dispertion by refraction (all the same wavelength means all of the rays bend the same amount) any way when the electrons have released that energy as light they return to their rest state and can be used again </physics>, this is how a neon light works but on a much larger and more dangerous scale. So apart from cooling there is no reason that the gas must be vented after each shot.

b)

anyone have any clues about how the 'weapon' would be fatal over 1500m. The way I see it it would deliver 665J of energy (excluding any losses from dispersion) with each burst (enough energy to raise the temperature of 1 gram of water by 159 degrees C) which would give you a nasty burn over the 1.3mm if it hit bare skin but certainly wouldn't be fatal.

The smaller the wavelength of the light in this case (10.9 x10^-6 m) the more energy it has and so the further the quanta penetrate.
Now say as this beam is only 0.65mm in radius the area the amount it is requiered to heat up is very small Feel free to check my maths but:

Say the beam penetrates 10 cm into a water target (as a person is 70 odd% water then it is a model).

The volume of water directly heated would be:
pi x r^2 x distance penetrated
0.00065m^2 x pi x 0.1m = 1.327 x 10^-7 m^3
density of water ~ 1000 kg/m^3
so mass of water heated = 1.327 x10^-7 x 1000
= 1.327 x 10^-4 kg

S.h.c. of water = 4200
Energy in = mass x shc x temp increase
665 = 1.372x10^-4 x 4200 x T
665 = 0.557T
1192.877 = T

So this small amount of energy is enough to raise the temp of the water it touches by over 1000 degrees centigrade.
This is for 10cm penetration of water, as the human body is slightly more dense than water and has a higher shc, the effect would still be disastarous.
And yes a 1.3mm hole in your brain would quite easily kill you, and if in doubt there are still 169 shots left in the next minute alone.

Post by **mid_gen** » Thu Apr 03, 2003 8:01 pm

This is all well and good for civilian killing etc, but doesn't do you a lot of good if the guy is either a) wearing any kind of body armour, or b) is in a tank

LazyManc · Post by **LazyManc** » Thu Apr 03, 2003 9:51 pm

a) = shoot him in the face
b) = get a bigger laser

kipper · Post by **kipper** » Thu Apr 03, 2003 10:06 pm

huh for the gas thing basically if you look at the picture as you read then you will see that the gas is pretty much fired out of its tank into the laser cavity (the red bit) where the energy is generated as per description, now at the shooty end around the secondary mirror (above + below on the pic) actually has a diffuser duct inlet and since there is no fan or other means of suction and the contents of the cavity is preasurized then the gas would escape

kipper · Post by **kipper** » Thu Apr 03, 2003 10:20 pm

and as it states near the bottom of page 4 the gas is expelled

garlando · Post by **garlando** » Thu Apr 03, 2003 10:21 pm

Midway through the barrel, the gas is circulated through a
catalytic converter (as developed by STC Corporation) such that the gas may remain in a closed environment
indefinitely. The gas flow is then returned, via diffusion and a pressure differential provided by an integrated
electrical pump into the gas reservoir for a reinitiation of the gasdynamic laser cycle.

Having re-read the white paper, the gas is pumped back into the resivoir.

garlando · Post by **garlando** » Thu Apr 03, 2003 10:24 pm

mid_gen wrote:This is all well and good for civilian killing etc, but doesn't do you a lot of good if the guy is either a) wearing any kind of body armour, or b) is in a tank

a) cotton has a far lower shc than water ie u need less energy to get it hotter
b) thats what rockets are for

or as lazymanc stated, if at first u dont suceed, get a bigger gun

bartender · Post by **bartender** » Thu Apr 03, 2003 10:39 pm

Why would they need to release the gas after each trigger pull?

Well laser action works by a population inversion of the populated energy levels within each atom, this inversion can occur through many different mechanisms but in the case of this 'gun' the inversion occurs through the release of gas through a supersonic expansion nozzle at which point the inversion is achieved and the excited electrons fall back down to their ground state releasing a photon with the corresponding amount of energy thus producing the laser action. In the lab the population inversion is produced using an electrical discharge but the power supply needed wouldn't make for a very mobile weapon and so they have opted for the vibrational pumping method.

The smaller the wavelength of the light in this case (10.9 x10^-6 m) the more energy it has and so the further the quanta penetrate.

Not strictly true as 10micrometers is infrared the penetration into the skin (as we have things that absorb infrared in our skin i.e. are tan) would be limited to a few millimeters at best into the skin.

Now say as this beam is only 0.65mm in radius

So thats 1.3mm diameter which isn't that uncommon in the hospital so it would be like having a red hot needle pushed into you. I agree it's not going to be pleasent but certainly not fatal.

I think neither of us has all the right facts to be doing these calculations as yours seem to over estimate and mine under (all though 1gram of water does seem large)the only sure way of telling would be to shoot a volunteer……anyone want to take a giant step for mankind?

Post by **Kulgan** » Thu Apr 03, 2003 11:30 pm

bartender wrote:the only sure way of telling would be to shoot a volunteer……anyone want to take a giant step for mankind?

No thanks, I believe that's what lab animals are for.
Hmmm. Political correctness appears to have deserted me there. Never mind eh?

K

kipper · Post by **kipper** » Fri Apr 04, 2003 1:30 am

isnt there some small furry rodent called dav around here, i hear he has lab tattoo'ed on his forehead already anyway

garlando · Post by **garlando** » Fri Apr 04, 2003 7:05 am

Quote:
The smaller the wavelength of the light in this case (10.9 x10^-6 m) the more energy it has and so the further the quanta penetrate.

Not strictly true as 10micrometers is infrared the penetration into the skin (as we have things that absorb infrared in our skin i.e. are tan) would be limited to a few millimeters at best into the skin.

Sorry i was making two points at the same time. first, yes the beam would only penetrate a few mm into the skin but it would very quickly burn/boil away that piece of flesh and then move deeper in and my calcualtions are if the energy of the beam were spread over a 10cm penetration, the maths for how far it would actually penetrate are a) unknown to me b) far too complicated for this forum

uatec · Post by **uatec** » Mon Apr 07, 2003 4:00 pm

suffice to say, it would be effing painful, and not immediatly lethal. I certainly don't want THIS particular weapon to be used against me.

garlando · Post by **garlando** » Mon Apr 07, 2003 6:45 pm

uatec wrote:suffice to say, it would be effing painful, and not immediatly lethal. I certainly don't want THIS particular weapon to be used against me.

Ohh it would be immediatly lethal. That sort of temp would cause the flesh it touches to flash boil causing the person to explode from the inside out. Not very nice at all

Post by **mid_gen** » Mon Apr 07, 2003 7:55 pm

Is there a way to explode from the outside in? If there is, I'm not sure I'd want to see it

kipper · Post by **kipper** » Mon Apr 07, 2003 9:17 pm

you mean implosion as opposed to explosion? normally you only do that under extreme preasure

garlando · Post by **garlando** » Mon Apr 07, 2003 9:41 pm

ouch, that would hurt quite a lot