How much energy would a usable laser small-arm require?

[His Divine Shadow]

Anyone have any ideas what would be required for one to be effective?

I'm thinking ofcourse of a pulse rifle here, not a beam type, that would fire a very very quick laser pulse.

Just guesstimating I say maybe a 10Kj pulse fired in 1/100th of a second might be effective.

[Enforcer Talen]

. . .lots.

[Slartibartfast]

1.21 jigowatts.

[Zoink]

You could base it on how much material you want to vaporize per second. Perhaps 1kg/iron per second. Multiply that by a factor to take into account effeciency of the laser mechanism and transmission.

4 MW at 100% effeciency (pulled this from DW site, did it quickly, may want to double check).

or about 4 AAA batteries ( jk )

For human killing, you could probably reduce the figure by a factor of 10 at least, taking a human to be essentially water.

[Ted C]

A bullet can kill you with just a few thousand joules, so there's no reason a laser weapon would require a great deal more. A laser capable of delivering a few kilowatts should be sufficient.

Other major factors in feasibility would be the capacity and weight of the power supply: you'd want to have at least as many shots per unit of mass as a modern assault rifle, and you'd want a reasonably short recharge time, as well.

[GrandMasterTerwynn]

Anyone have any ideas what would be required for one to be effective?

I'm thinking ofcourse of a pulse rifle here, not a beam type, that would fire a very very quick laser pulse.

Just guesstimating I say maybe a 10Kj pulse fired in 1/100th of a second might be effective.

To guesstimate how much destructive energy must go into your laser pulse, one should consider that the human body is a sack of water with some hydrocarbon glue holding it together. So, one tunes the energy delivered by the laser pulse to be sufficient to boil or vaporize some small mass of water. The difference in volume between some mass of liquid water, and an identical mass of water vapor is very substantial. The expansion as the water is vaporized will do the bulk of the damage to your target.

Now, that only provides a basic estimate if you were firing your laser weapon against naked human targets. It says nothing about penetrating any armor they might be wearing.

[Kuroneko]

I'm thinking ofcourse of a pulse rifle here, not a beam type, that would fire a very very quick laser pulse... Just guesstimating I say maybe a 10Kj pulse fired in 1/100th of a second might be effective.

A quick pulse would be terribly inefficient, although if you can afford to dump 10KJ into an unarmored person over 10ms in a concentrated spot, you'd have a kill anyway.

To get penetration, what would be better is having many smaller pulses over that 10ms period to decrease the lateral spread of energy. A small pulse will vaporize the target to some depth, followed by another pulse after the vapor clears. Unfortunately, to get a proper timing analysis (how many pulses in what amount of time, etc.) you need to know the penetration depth of the laser, which is dependent on both the wavelength of the laser and the material which it hits, as well as the thermal diffusivity of the material.

Fortunately, it is still possible to roughly estimate a minimal energy requirement. Under the fairly crude assumption of flesh being essentially water, the laser having a 2mm spot size (nominal area A = 3.142 mm^2), and the requirement to vaporize a 100mm column of flesh (in reality, the laser pulses will be vaporizing it bit-by-bit.) The volume of the column is V = 3.142e-7 m^3, it has a mass M = 3.142e-4 kg, and heat of vaporization 2.296e6*M ~ 720 J. To bring it to this point from 310K (98.6F) to 373K (212F), it takes about 100 J, or 810J in total.

But we don't want to just vaporize it merely to the point that the vapor pressure is little higher than one atmosphere, with negligible overpressure. That wouldn't do much damage and take too long. It would be much better if the overpressure was in the dozens of ksi range, in which case the vapor will expand explosively almost as if the surrounding tissue wasn't even there, doing massive damage to it. However, since I don't have the relevant information on me right now, and I don't feel like doing research for this, I'll simply guesstimate it to be 1600J in total (which is actually very close to the muzzle energy of a .50AE round from a Desert Eagle).

The lethality is probably comparable to a Desert Eagle, too, assuming you get a body or head shot. There are capacitors that have energy densities of about 14kJ/kg (the aptly named 'supercapacitors' wouldn't handle the sheer power requirement, though, but let's ignore that), so with a 1.8kg capacitor (mass of an unloaded Desert Eagle), you get four shots at the most at 25% laser efficiency. And that ignores the mass of the laser itself (which, at current tech level, would be more than you could carry around anyway). Stick with the Desert Eagle.

[Admiral Valdemar]

1.9kW for taking out medium armoured infantry at 1500m in 10.6 micrometre wavelength for .35 seconds.

[Kuroneko]

1.9kW for taking out medium armoured infantry at 1500m in 10.6 micrometre wavelength for .35 seconds.

CW or pulsed?

[Admiral Valdemar]

1.9kW for taking out medium armoured infantry at 1500m in 10.6 micrometre wavelength for .35 seconds.

CW or pulsed?

Pulsed, naturally. 170 shots per minute if need be, power cell is Polonium-210 with a life of 60 days before severe reduced range. Beam diameter is 1.3mm, gas lasing medium is a 10, 89, 1% mix of CO2, N and He.

[Kuroneko]

Pulsed, naturally. 170 shots per minute if need be, ....

No, I mean whether it is continuous over the 0.35s shot or is pulsed within it.

[Admiral Valdemar]

Pulsed, naturally. 170 shots per minute if need be, ....

No, I mean whether it is continuous over the 0.35s shot or is pulsed within it.

I assumed pulsed as stated, it's the most efficient method for a potential laser rifle.

[Kuroneko]

I assumed pulsed as stated, it's the most efficient method for a potential laser rifle.

It would be nice to know how much energy it actually puts out per shot. If it's continuous over the 0.35s, it's straightforward: 1.9e3/0.35 = 5430 J. If it's pulsed, the time interval between the pulses needs to be known.

[Admiral Valdemar]

I assumed pulsed as stated, it's the most efficient method for a potential laser rifle.

It would be nice to know how much energy it actually puts out per shot. If it's continuous over the 0.35s, it's straightforward: 1.9e3/0.35 = 5430 J. If it's pulsed, the time interval between the pulses needs to be known.

I'll look through the specs again, this is a proposal for the TIS-1 infantry carried laser rifle being created by Stavatti Inc. for the US Army, so a lot of it is theory but fairly straight forward.

[Kuroneko]

I'll look through the specs again, this is a proposal for the TIS-1 infantry carried laser rifle being created by Stavatti Inc. for the US Army, so a lot of it is theory but fairly straight forward.

Are the specs available online?

[Admiral Valdemar]

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

[Beowulf]

Dude! It's a fucking april's fools joke! Don' believe me? http://www.stavatti.com/diversified/firearms.html

Stavatti builds space fighters. We know what threats are out there. A 9mm just won’t cut it when you are facing 30 ft tall insectoids, or the reptile alien overlords from Rigel.

[Admiral Valdemar]

Dude! It's a fucking april's fools joke! Don' believe me? http://www.stavatti.com/diversified/firearms.html

Stavatti builds space fighters. We know what threats are out there. A 9mm just won’t cut it when you are facing 30 ft tall insectoids, or the reptile alien overlords from Rigel.

Aw, you bloody ruined it.

I'll be honest, lasers really aren't the best rifle for modern soldiers, they don't have anywhere near the power for defeating high thermal tolerant materials, while a .50 BMG round will do it nicely.

Basically, smokeless powder is going to be the driving force of our guns for a long time yet*.

*Until high density power cells or RTGs are shrunk and made more suitable to power railguns.

[Beowulf]

Aw, you bloody ruined it.

Sorry, too many people believe that it actually exists... When if you just look up the company on google, you'd see that it was an obvious hoax... lot's of pretty CG aircraft though...

[Kuroneko]

...

Well, the whole site seems to be one big joke.

[Admiral Valdemar]

Aw, you bloody ruined it.

Sorry, too many people believe that it actually exists... When if you just look up the company on google, you'd see that it was an obvious hoax... lot's of pretty CG aircraft though...

Yeah, a lot of the planes look like AV Pro models that were made for the MoD to review for the RAF in the next 50 years (one looks like a YF-19 from Macross Plus).

[Captain Jack]

Aw, you bloody ruined it.

Sorry, too many people believe that it actually exists... When if you just look up the company on google, you'd see that it was an obvious hoax... lot's of pretty CG aircraft though...

Yeah, a lot of the planes look like AV Pro models that were made for the MoD to review for the RAF in the next 50 years (one looks like a YF-19 from Macross Plus).

GODDAMMIT!!
I believed you.

[Admiral Valdemar]

Sorry, too many people believe that it actually exists... When if you just look up the company on google, you'd see that it was an obvious hoax... lot's of pretty CG aircraft though...

Yeah, a lot of the planes look like AV Pro models that were made for the MoD to review for the RAF in the next 50 years (one looks like a YF-19 from Macross Plus).

GODDAMMIT!!
I believed you.

I believed it at first and even posted it on another board before seeing the main site.

It's a well thought out hoax though, many people will believe it just as people believe HAARP is a mind control ray and the RAF have alien stealth fighters.

[Kuroneko]

It's a well thought out hoax though, many people will believe it just as people believe HAARP is a mind control ray and the RAF have alien stealth fighters.

Not until they see the actual 'white paper'.

[Captain Jack]

I believed it at first and even posted it on another board before seeing the main site.

It's a well thought out hoax though, many people will believe it just as people believe HAARP is a mind control ray and the RAF have alien stealth fighters.

Well it is an easy mistake to make.