Lasers as weapons

On television and in the movies, lasers are used as weapons. Yet, in real life, they’re used for surgery, or pointers, or targeting, or, as far as I know, anything but weapons. Well, does the “Star wars defense system” use lasers? If so, that’s about the only example I can think of.

But what about using lasers as weapons against people? For example, with the existing technology, could a laser gun, make that a fully functional and working laser gun, actually for those of you who might play semantics games and go “Well what do you mean by working?” I’ll define that as a gun that can shoot a laser through your body, thus, being able to do as least as much damage as a hand gun would.

Again, with existing technology, could such a gun be made? How practical would it be? Would it have to be battery powered or recharged every so often, or…?


The “star wars defense system” does not use lasers because no star wars defense system actually exists right now.

There are various research projects on using lasers as weapons underway, the most advanced of which is the airborne laser. This will be a 747 with a frickin’ huge laser stuck in it. The aircraft has not even flown yet, because there are a great many technical hurdles to conquer: how to generate enough energy within the restricted confines of an aircraft to power a very large laser, how to stabilize the laser so that turbulence doesn’t throw it off target, and how to deliver enough energy over enough distance to make it worth while.

Note that the purpose of this laser isn’t to vaporize incoming warheads. It’s pretty much just to make a very small hole in a missile that is just lifting off, allowing the hot exhaust gasses to escape and throw the missile off, destroying it in the process. Think of the Space Shuttle Challenger and how a small defect in the rocket blew the whole thing up; that’s pretty much what the ABL would aim to do.

This weapon will not be fielded for many years to come.

We had a few high power lasers in the Physics lab where I went to college. They could have produced a nasty burn but not cut through your body. Even these, however, were large, occupying 10 feet or more of lab table space and weighing 100lbs or more. Basically, it’s very difficult to sync enough energy into a laser fast enough to do any great damage and the power sources are ultimately electrical, which means carrying bulky batteries or at least fuel cells around. Ballistic firearms work by converting chemical explosive energy very efficiently and directly into kinetic energy in a projectile. A laser, to do equivalent damage to even a handgun, would need to be huge.

OK, I was thinking that it probably wasn’t possible, at least yet.

One more question, if I can phrase it right. Does anybody know how much energy is required to fire a laser beam that can do some damage? For example, the harmless laser pointers (I assume they’re real lasers, right?) work on AA or AAA batteries, but what would you need for something more powerful? For example, how much power is used for lasers used in eye surgery? Thanks.

Welcome to the Airborne Laser Home Page

Tactical High Energy Laser (THEL) Program

Mobil Tactical High Energy Laser (MTHEL)

I read a little discussion on this a while back and one point brought up is that while a pistol round takes somewhere between a few hundred and a thousand Joules to kill somebody by punching a hole into a vital organ, a laser would take around 20,000J to do the same thing by vaporizing a hole the same size.

A cartridge is just a very efficient way of hauling that energy around and as David Drake pointed out in one of his science-fiction books, “A machinegun is just as effective (once) with a single bullet as it is with a thousand. A man-killing laser requires a 100kg fusion plant to drive it.” We don’t have 100kg fusion power plants just yet but you see the problem.

Out of curiosity I wanted to check the math in that first paragraph so I assumed that for a laser to knock the same size hole in a person as a bullet you’d have to vaporize a hole 1cm across 10cm deep into the target. Also assumed that body tissue is just water in terms of heating it up and vaporizing it.

The energy to heat that much water from body temp to boiling and then turn it into vapor works out to…

21,000 Joules! Wow, that article I read was right on the nose (or at least made the same assumptions)

To figure out how much power you’ve actually got to pump into your laser you’d need to know how long it takes to do this damage, and how much the beam attenuates going through the air (especially the dusty, smoky air of a battlefield). I dunno this stuff at all but suppose you want to burn that hole in 0.1 seconds, you’re looking at delivering 210kw of power to the target itself and that seems like a lot.

Frankly there’s a lot of wiggle room in these numbers but any way you slice it you are talking about needing many kilowatts to drive your laser. If that requires a big power plant then it doesn’t look like it makes a lot of sense to work on lasers that would replace an M-16. The military antipersonnel lasers I’ve heard of were intended to blind soldiers, not kill them. I think they’ve been banned, I do remember seeing a Chinese example at some international defense exhibit on TV.

Ah, they’re…

Nope. Not going to do it.

I’ve thought about this a bit. I think the reason why lasers are desirable in missle defense is that the beam can go to the target at the speed of light. Further, bringing down a nuke would be worth whatever power is required, certainly.

For rifles and whatnot, it’s hard to see the value, as other posters have indicated. Unless you have some really serious power behind the shot, the beam could easily be blocked with armor, etc.

The dirty secret of lasers is that they are shockingly inefficient in converting your electric energy (or chemical, or what have you) into that beam of light. Lasers almost invariably have a built-in inefficiency in the way theuy generate a population inversion – some energy has to be dumped just to create the lasting condition. The highest efficiencies I’ve seen were for some defenct lasers that were optically pumped and had something like 80% efficiency between energy in and energy out. More typical are efficiencies of 20% or less. The really big high power lasers often have overall efficiencies of 5% or less. The rest of the energy ends up as heat that has to be dissipated, which is why you need big fans or (preferably) liquid circulating systems. One of the old weapons laserrs built into a tank had a huge cooling system built in. I think it required another vehicle.

(There are ways around this, like chemical laser systems that create excited state systems by mixing chemicals. But that then requires huge tanks of gas, since you have to mix a fresh batch for each shot. There’s no free lunch). A handheld laser putting out appreciable amounts of power is pretty impractical, then. Even a hand-held Argon-Ion laser producing a few watts would weigh down the wearer with the fans and batteries for everything. (Just look at the elaborate battery packs worn on belts that TV news crews carry – a laser would require a lot more). And that’s before we get to the awesome powers required to boil the body’s water, as noted above. Easier to hit 'em with a rock.

We’ve got a couple interesting (and dangerous) lasers here. One we use for, among other things, looking at rotational diffusion. This is a green laser (I want to say 526 nm, but that’s probably wrong and I don’t remember exactly what type it is) and will blind you basically instantly if you look at it. We’ve got another one that is part of the LIBS and is used to make a plasma ball. Interesting idea but I’m not sure the proof of concept is really there yet.

Some laser weapon applications have been considered, & they are chilling.

Notably, as a booby trap.

A laser, spraying light around a given area, can leave hundreds, even thousands of soldiers stone blind.

For life.

In an instant.
Not funny anymore, is it?

BTW–all laser wounds must automatically be considered septic. They are burns, after all.

Oh, I dunno. You can still get a good chuckle out of it, I suppose! Regardless, such weapons are the stuff of drawing boards, or potentially terrorists, I suppose. There are not going to be many situations where the enemy neatly lines up and lets you zotz ‘thousands’ of them in the eyes. Line of sight (heh) and energy-intensive weapons that they are, their use as some sort of ‘terror of the Civil War battlefield’ would be severely limited.

Of course, most American (and all Western armies, I imagine) optics, from binoculars to general-use field goggles, are coated to protect against laser ‘dazzling’, more from stray targeting lasers and whatnot, rather than against Dr.Evil and his Blind-o-tron.

That’s right. NATO, and especially not the USA, would never use lasers as a blinding weapon. Especially not fitted for aircraft-aircraft combat. We’d NEVER do that. Because it would be wrong…and I think it would involve some part of the Geneva Convention we haven’t discarded yet. (that last bit was mean-spirited, sarcastic and not at all constructive.)

I can’t say for certain that our binoculars (bitchin’ though they were) had any kind of coating, but 99% of the time we had no eye protection other than the Ray-Bans we brought with us. Any such coating is not useful unless you’ve got it on ALL THE TIME.

Unless the coating is completely opaque at the wavelength of the laser it will not protect you if the laser is coming at you from within the field of view of the binoculars/goggles. Since most lasers operate in the visible range this is unlikely unless the coating designers are willing to sacrifice some part of the spectrum. Varying the frequency of the laser would allow the enemy to defeat even this tactic though. Binoculars, also, amplify what light they collect.

1920’s-style DEATH RAYS!!!


Nitpick: Binoculars actually spread out light. They don’t create more light, so they don’t amplify it. They take light coming in and spread it out so that something small looks like it’s coming from a larger area, and so looks bigger.

The other problem with using lasers is that they have to hit the same spot on the moving target for more than a fraction of a second so they burn through. This is in stark contrast to something like a missle that can blow up anywhere in a given radius and and have a pretty good chance of putting lots of shrapnel into the target.

Missles and bullets also aren’t line-of-sight and aren’t scattered by clouds or other atmospheric changes.

Cardinal, your post is wrong on every single point.

Every last point!
[li]Binoculars use convex lenses to gather & concentrate light. If they disperesed light, the image would become dim when you used them. Look here. LINK [/li][li]A high energy laser pulse can vaporize the immediate surface of an object in less than a second. You don’t need to burn through.[/li][li]Hi Opal! Can I borrow your laser? Or your 1920’s Style Death Ray?[/li][li]Bullets aren’t line of sight? Since when?[/li][/ul]

HUMPH! Binoculars are small folded telescopes. They gather light.


Here’s a listing of the magnitude limits for many popular binocular configurations.

It’s not every single point. You conveniently skipped all the ones I was right about.

Bullets in a sense aren’t line of sight in this very small way: the target doesn’t have to be visible to the human eye.

You just admitted that lasers burn through things. What is the difference supposed to be that they “vaporise” things? You also admitted that they do have to be held on target for what could be considered an appreciable amount of time, especially when talking about hitting an ICBM in full flight on a path with a significant angle to the laser.

I also wasn’t wrong that binoculars don’t amplify light.

Seriously, if you’re going to go to the trouble of emphasing how I was wrong on every last point, the least you could do is be right about it.