Laser Weapons

[Nightcrawler]

As an addendum to the Plasma Weapons thread, let us discuss the more plausible technology of laser weapons.

Now, unlike in hollywood, most lasers will be invisible to the naked eye, unless the beam is directly IN your eye (which is bad for your), or there's something in the atmosphere to ionize it an make it visible (like when you shine a laser pointer into fog or smoke).

Assuming we had a viable battery or power cell to operate such a weapon, what kind of energy levels are we looking at for the weapon to be effective?

That said, if a viable laser rifle could be produced with an appropriate power source, it would have many advantages over current firearms:

-No recoil;
-Little sound, if any (nothing like a gunshot);
-Capacity limited only by the power cell; no extra ammunition to add bulk or weight;
-Laser strikes instantaneously; no need to lead targets at any range, nor any need to adjust for windage or elevation;

Of course, the weapon as I see it would have downsides:

-A laser hot enough to kill someone with one strike will possibly leave a vapor trail in the atmosphere;
-Unless there's some variation on the laser that I'm unaware of, most could be disrupted by smoke, clouds, or dust. I think there's a way round this, though;
-All of this is assuming an appropriate power source. That IS the big catch, isn't it?;
-Could possibly be deflected by mirrors;
-Unless you're careful, firing a laser rifle into the forest could start a big forest fire (bad if your troops are caught in the woods);


Any thoughts? Ideas?

 

[Jamie Young]

Assuming we had a viable battery or power cell to operate such a weapon, what kind of energy levels are we looking at for the weapon to be effective?

I'm wondering how a laser than burns a 22caliber sized hole in you would been any more effective than a regular bullet. You would still need the energy to smack someone instead of just incinerating tissue.

Thats why they came up with "Partical Beams" and hypothetical "Phasers".

 

[Nightcrawler]

Well, the question is in the energy. If your laser can generate 10 kilojoules of energy for each shot, that translates into (according to THIS CONVERSION TABLE) 7,375 foot-pounds of energy! That's equivalent to getting hit with six or seven 5.56mm rounds AT ONCE.

Of course, as I said, this would take an ample power source, and most of the energy would be expended in the form of heat and burn damage. Quite destructive, though.

 

[Kaylee]

I'm wondering how a laser than burns a 22caliber sized hole in you would been any more effective than a regular bullet.

Leave the beam on.
Sweep your target.
Problem solved.




-K

edit...

actually, that does bring up an interesting point.. I can see whole new fields of marksmanship crop up around such a weapon, especially in close quarters. Lots of short "flash-bursts" done with a flicking motion of the wrist, or a little circling movement of the weapon's forearm... kinda like a knife-fight at 20 meters.

...sounds messy.

 

[Nightcrawler]

I'm assuming that in order to conserve power each pull of the trigger would produce a laser burst that lasts about as long as it takes for a digital camera to take a picture. Each shot would translate that energy onto whatever it hit. Operation wouldn't be that much different from a standard firearm.

On the otherhand, let's get really sophisticated and say your laser weapon had a backpack micro-fusion powerplant or something. Then you might see targets being carved up, flash incinerated, you name it.

Unpleasant, anyway you slice it. (No pun intended. Really.)

 

[mnealtx]

Wouldnt some sort of capacitive discharge work for this type of application? It'd be individual pulses rather than a continuous beam, but it seems feasible.

 

[Tamara]

I'm wondering how a laser than burns a 22caliber sized hole in you would been any more effective than a regular bullet. You would still need the energy to smack someone instead of just incinerating tissue.

Because, much like that .22 caliber bullet, it has a lot of side effects caused by the energy it sheds.

In the case of a laser and a human body, remember that tissue is roughly 70% water. Imagine this water flashing very suddenly to steam. Have you ever watched popcorn pop? It'd do nasty things all around the point of impact.

 

[Christopher II]

It would be quite possible to build a laser weapon today. Get a big kilowatt-output CO2 industrial cutting laser and a large backpack full of high-density deep cycle gel cells, and you'd have something that could do some damage at close range. It wouldn't be too portable, but TANSTAAFL...

A laser beam will be disrupted slightly by traveling in atmosphere, to say nothing of rain, smoke, or other particulates. You'd see a considerable reduction in the effective range, although I'm not sure how considerable. I'll ask my boss when I get a chance.

Deflecting a laser with a mirror is a myth. Low-powered lasers, right, it works fine, but even the best 1st-surface mirror is only about 50% efficent (the other 50% is transfered to the mirror in the form of heat.) With a powerful laser, the mirror would fail almost instantly.

The power source, as said before, is the big issue. Lasers aren't too power-efficent, and you only get out a fraction of what you put in.

- Chris

 

[HankB]

Ignoring the use of multi-megawatt class lasers for missle defense and considering only "personal" lasers:

The problem with using a powerful continuous laser as a weapon is that it will vaporize the surface layer of the target first . . . that will create a plume which will partially obscure the target and absorb much of the energy of the laser.

To make an effective weapon, a laser would have to be VERY powerful...which isn't easy. For example, a 50W CO2 laser weighs about 40 pounds (less power supply), will typically draw about 30 amps at 110 volts, and requires water cooling. The beam will heat a spot on firebrick white hot, which is impressive, but at 1 inch per second, it won't cut through a hot dog. So to be effective as a weapon, you'd have to increase power by orders of magnitude.

Other lasers take more - or less - power. Some 20W Argon-Ion lab-grade lasers use a 480V power supply and draw about 65A. A 20W diode laser array will run off house current. (Beam quality is another issue.)

Now, depending on wavelength and power, with a pulsed laser you might get what's called "acoustic damage." A very short, powerful pulse would cause whatever it hit to flash into vapor so fast, you'd effectively get a steam explosion at the surface. If the laser was operating at a short wavelength, you'd break chemical bonds, too. This might be nasty, but you'd have to deposit an awful lot of energy.

And then there's the effect of clothing...

And powerful lasers - those designated as Class IV - will, depending on power and wavelength, often pose a danger to the user by diffuse reflections. In other words, shooting a laser at a close target could pose the same danger to your eyes that shooting a .44 Magnum indoors would pose to your ears.

IMHO we've got a long, LONG way to go before beams will have the stopping power of bullets.

but even the best 1st-surface mirror is only about 50% efficent

Not strictly true. An enhanced aluminum mirror will provide better than 90% reflectivity across most of the visible spectrum. High energy laser mirrors, with multilayer coatings optimized for a particular wavelength, can have reflectivities above 99%.

 

[Hutch]

Tamara beat me to the point. Ever wonder why trees split open or explode from a lightning strike? The water in them flashes to steam and RAPIDLY expands.

Regarding the distortion caused by atmospherics, that's a whole field of study that was investigated during the height of the SDI project. Overcoming the problem requires something, generally referred to as "adaptive optics". Read a bit of the well-researched Clancy novel "Cardinal of the Kremlin" for a good layman's discussion of the issue. Last I read, the state of the art in laser weaponry was to mount a laser in a 747 and get it above a good portion of the atmosphere to engage ICBMs in the most vulnerable boost phase. As described in earlier posts, these weapons "pulse", so the light-saber routine doesn't seem too likely anytime soon.

I'm no expert, but I would GUESS that if conditions allow you to see your target clearly, then conditions are adequate to engage the target with a laser.

 

[Kaylee]

Tamara beat me to the point. Ever wonder why trees split open or explode from a lightning strike? The water in them flashes to steam and RAPIDLY expands.

Hrmm.. good point. Not thought of that.

Not quite the same thing, but in my last emergency med class, they were handing out pictures of lightning wounds. NASTY stuff.. exit holes and everything, just like you'ld see with one of these sci-fi blasters.

Didn't look like much fun.

-K

 

[RikWriter]

As a science fiction afficianado and writer, I have researched this topic quite a bit.
To be practical, hand-held laser weapons would have to fire a pulse rather than a continuous beam and would likely be powered by quick-discharge superconductive capacitors or else small explosive cartridges.
The pulses would NOT be invisible in an atmosphere because they would ionize the atmosphere like a lightning bolt, also causing an evacuated path that would be filled with air in a miniature thunderclap. A contemporary, low-power laser doesn't have the energy to do this, but a weapons grade laser certainly would.
Tamara was correct about the effects on a human body---a weapons grade laser would flash-heat the fluid in human tissue and cause a wound analogous to a bullet wound, with the severity dependant on how powerful the pulse was.

 

[Bog]

As has been kinda mentioned once or twice, power supply is the whole issue here. Our current published abilities to generate and transport electricity frankly suck. We're still using copper plates stuck in lemons - the same kind of batteries found in 5,000 year old pyramids.

If we can get something slightly more useful in terms of power generation or transport, then the sky's the limit with the ol' laser or it's related technologies.

BTW, if anyone's not watched Real Genius, now's a good time. The aircraft-based laser concept's involved, just to make it related, but it's one of the funniest films in existance for people who watch SF and have twisted senses of humour.

 

[Brett Bellmore]

I can't see man portable lasers becoming practical weapons general purpose use; At moderate range projectile weapons are more efficient in delivering energy to the target. Recoil a problem? Barret, I believe, (Or was it Maahdi Griffin?) built an experimental .50 cal BMG pistol, whose muzzle brake was so effective it actually jerked you forward after each shot!

The real advantage of the laser is range. Secondarilly, lack of recoil, allowing you to get off rapid second shots. I see it as a weapon for snipers, perhaps.

 

[Nightcrawler]

pressure and power

Effective manportable laser weapons, essentially, require two things: better batteries and better optics. These things seem far off and outlandish now, but think.

If you could go back to 1873, and tell Col. Sam Colt that someday, revovler design essentailly like his would be firing cartriges with the chamber pressures of .454 Casull he would've thought you crazy. He would've thought you even more crazy if you would've told him they could make compact self loading handguns that can fire ten or more times without realoading and have more power at the muzzle than his .45 Colt round.

All it took is better metallurgy. All we need for weapons grade lasers is better batteries and better optics. These things will come.

What kind of power levels do you think are necessary for a weapons-grade laser? I think 10kJ would be fine for a long arm, perhaps 2 or 3kJ for a pistol. You can go to the conversion table I linked to and see how many foot pounds of energy a 3kJ laser strike translates into.

RikWriter, I'm curious about the use of weapons grade lasers in an atmosphere. If the laser ionized the air, does that mean you'd be able to see a colored beam like in the movies? I think there'd be a vapor trail, too, depending on humidity.

 

[Mark D]

Just a random thought...

If lasers fight against creating so much heat/vapor/ionization, could they be used as a form of detonation or propulsion for a projectile? Kind of an exothermically powered railgun?

A thirty or forty grain tungsten projectile doing ten-thousand FPS would be interesting.

 

[Brett Bellmore]

For an effective man portable laser weapon, I think we'd have to get away from the whole idea of using something which looks like a gun, only with a lens on the end. I think in the end you'll be looking at some kind of solid state phased array of laser diodes; The emitter area would be anywhere up to a foot in diameter, and all the aiming and focusing could be accomplished using phase control, just like in some radars.

You might have a gun shaped target designator, but even that makes little sense in this context; The big advantage of lasers is range, and you just can't point a gun accurately enough to exploit the range of lasers.

Instead, I think the weapon would be built into a helmet. The helmet would provide a stablized, magnified image of the target, use eye tracking to control where the beam is directed, and use the area of the helmet as the emitting surface. By starting the beam out wide at your end, you avoid the very high energy density which would cause the air to ionize immediately in front of your weapon, which can seriously damage optics. You want the beam concentrated at the target! Not at the weapon.

You'd probably want the emitter to be demountable, though, so that it could be stuck out from behind cover, while you still use the helmet display to control it.

Further, a phased array emiter could take localized damage, and degrade it's performance gracefully, by simply shutting off the emitters in the damaged area. Regular high energy optics tend to fail catastrophicly, as a flaw heats up and the damage spreads rapidly across the lens or mirror.

Finally, since the battlefield of the future is probably going to involve the use of very small autonomous projectiles, which loiter over the field looking for targets, then swoop in and blow up, the helmet would also provide you with automatic point defense.

 

[Nightcrawler]

Particle Beams

Okay, I've done a little research on particle beam technology. A particle beam rifle would seem to be a more useful replacement for a firearm than a simple laser, as the particle is fires, moving at near-light speed, would have substantial penetration capabilities.

Question that begs to be asked: Would a particle beam be visible to the naked eye in a vacuum? What about in the atmosphere?

 

[RikWriter]

RikWriter, I'm curious about the use of weapons grade lasers in an atmosphere. If the laser ionized the air, does that mean you'd be able to see a colored beam like in the movies? I think there'd be a vapor trail, too, depending on humidity.

It wouldn't be a colored beam like in the movies unless it was going through particulate clouds of smoke, but it would cause a flash and possible sparks.

 

[Gewehr98]

I'm not only curious...

I managed to get myself assigned as one of the aircrew on this beast, with a reporting date later this fall. Firing a chemical oxygen-iodine laser, it ruptures the skin of a rogue missile in boost phase, allowing the missile's internal pressure to complete the destruction.

http://www.airbornelaser.com/

Here she is, being modified to accept the laser and all the systems needed to support it as a weapon: