Good guys get blue, bad guys get red.

November 19, 2009 12:06 PM

How close are we to handheld laser weapons? I read an article about a laser on a C-130 burning a hole through a car, a 747 that can shoot down an ICBM, and now a truck-mounted laser that can bring down a plane or UAV. What kind of science challenges do we need to meet before these weapons are issued to soldiers, etc.?

I'm sure the power is the biggest challenge, what other ones are there?

posted by uaudio to grab bag (23 comments total)

Well... Oddly enough, after you hit your target with a laser and burn a hole through it, the light continues on to whatever is behind it.
posted by Nanukthedog at 12:14 PM on November 19, 2009

I would think power density would be the top one, followed closely by improvement of efficiencies in gas and chemical lasers. IIRC, the rough efficiency of these lasers is around 10%, and require large amounts of gas or liquids to operate. Remember that SSD lasers (such as the ones you see in your favorite laser pointer, do not have the power output that chemical-based ones do, such as the 747-based ICBM hunter you mention.
posted by SeanMac at 12:17 PM on November 19, 2009

There's the fact that the destruction is not instantaneous, but instead requires the laser to be trained on the target for significantly longer than a conventional gun does in order to be effective. Even if the power and size issue were resolved to the point where it could be hand-held, having to keep aimed and perfectly still at a specific point for even several seconds before the weapon could destroy the target is a serious drawback.
posted by The World Famous at 12:18 PM on November 19, 2009 [1 favorite]

The first two lasers you're talking about are Chemical Oxygen Iodine Lasers. They use a chemical reaction to drive the laser. The chemicals used (chlorine, iodine, hydrogen peroxide, and potassium hydroxide) are all dangerous, reactive substances. What's more, they have to be move around, pressurized, at very high flow rates, which means either using a pump or a high pressure tank. Even if it could be effectively miniaturized, I don't know that one would want a handheld version.

What's more, what is the benefit of a handheld laser? The reason they're being developed for aerospace use is that lasers are, obviously, very fast, which makes targeting and hitting fast moving things much easier than shooting projectiles. At the kinds of ranges small arms are used for, bullets are near enough to instantaneous as makes no differences.
posted by jedicus at 12:22 PM on November 19, 2009 [2 favorites]

A long ways off. The stuff in a 747 and whatnot are chemical lasers. We can't do things nearly as awesome as that with solid-state lasers. And then once we're talking about hand-held — where are you going to get all that energy from?
posted by floam at 12:36 PM on November 19, 2009

My experience with military grade lasers is limited to watching Val Kilmer in Real Genius, so I don't know much. I guess you could have gyroscopic control over the beam in order to keep it lined up for the period of time needed to destroy something.

Interesting to me about the beam continuing past the target. Wouldn't the strength of the energy decay over distance? I don't know how much of a concern it would be; you're shooting at people on a battlefield, there's probably some degree of collateral damage expected.
posted by uaudio at 12:37 PM on November 19, 2009

You've asked about science challenges, but there are also potential legal challenges due to the protocol on blinding laser weapons. This wouldn't necessarily prohibit a laser designed to burn through something (rather than destroy eyesight), but it would be a consideration.
posted by A Thousand Baited Hooks at 12:43 PM on November 19, 2009

What kind of science challenges do we need to meet before these weapons are issued to soldiers, etc.?

Reliability in ground combat, for one thing. Who wants to hump one of these around when fog and rain and, hell, intervening foliage negate it? It would be like carrying a rifle that:

a) has to be aimed at a specific point on a moving target for multiple seconds while firing
b) doesn't work in fog
c) doesn't work in dusty situations

Never mind that making the optics reliable in the field without a technician servicing them is going to be a real challenge. Dirt, mud, and optics alignment while taking lots of bumps, are all serious obstacles, I would imagine.
posted by zippy at 12:46 PM on November 19, 2009

A collimated laser beam doesn't spread out (much) -- that's why the laser pointer's dot is the same size at five feet and at five hundred feet.
posted by phliar at 12:46 PM on November 19, 2009

Lasers can also be trivially defeated through the use of mirrors or clothing the same color as the laser.

The most likely use of lasers in ground-level battle is in blinding (permanently) your opponent while leaving him otherwise uninjured; this is likely to lead to swift expansion of the geneva conventions to outlaw them. The parallels with chemical weapons are pretty clear.
posted by jenkinsEar at 12:50 PM on November 19, 2009

One other challenge: these lasers, while invisible to the naked eye, are visible as infrared. So every time you fire you're painting a bright straight line back to your position. I would imagine an opposing force could develop inexpensive tools to take advantage of this.

Basically, some poor schmo would be carrying a very bright (infrared) strobe light. It would be like being the guy who carries the flamethrower. You just know you're going to be everyone's target.

An enemy force facing this weapon could integrate IR sensors into their targeting systems and have a nice way to direct their return fire.
posted by zippy at 12:52 PM on November 19, 2009 [1 favorite]

Blinding weapons are already banned by international treaty.

Power density is certainly the biggest challenge. But coming close behind that is cooling. If you have a 100 kilowatt laser in your hand, it's going to dissipate 300 or 400 kilowatts of heat into the space near your hand. Ouch! (The Second Law of Thermodynamics really sucks, you know that?)
posted by Chocolate Pickle at 12:54 PM on November 19, 2009

It's all about energy storage. We've already got the technology to generate lasers which can punch holes in sheet metal across disgusting distances in a fraction of a second. They're already in use in factories worldwide. The problem is that this takes a few hundred thousand watts of power. The lasers themselves aren't terribly large compared to the massive infrastructure you need to 1) puch that much power through the device in such a short time, and 2) keep the thing from melting as a result. All of which is kind of hard to store in something you can hold.

This is actually the problem for many of the sci-fi technologies you see in the movies. A partial list of things we could build with existing technologies if we could radically miniaturize power generation technologies:
- Powered armor
- Jet packs
- Flying cars
- Practical interplanetary spacecraft
- Hand-held railguns

It's also worth noting that what counts as a "laser gun" in science-fiction settings are frequently more like energized gas cannons. This is the case in at least the Star Wars universe. This is probably due to the fact that a true laser gun wouldn't be very cinematic. No flashing lights or blaster bolts. Kind of boring to watch. But it's also kind of a nod to the fact that it's going to take a lot more energy to destroy something with a light beam alone than it will to destroy that same thing with a blast of energized matter. Even so, the energy generation/storage problem is largely the same.
posted by valkyryn at 12:56 PM on November 19, 2009 [4 favorites]

Wouldn't the strength of the energy decay over distance?

sure, but that's why you are using a laser, which doesn't spread out like a regular beam of light.
posted by ArgentCorvid at 1:48 PM on November 19, 2009

What's more likely to come: some kind of ionized plasma burst guns that don't require an external power source other than a reactive substance in the magazines or cartridges.
posted by Burhanistan at 2:26 PM on November 19, 2009

They already exist, as A Thousand Baited Hooks referred to. They just don't burn holes in anything except human retinas.
posted by procrastination at 2:48 PM on November 19, 2009

Note that laser dazzlers, as opposed to laser blinding weapons, are already in common use. They're usually just a medium-to-high-powered green DPSS laser pointer with the collimating lens wound out a bit to give a narrow conical spotlight beam, so the operator doesn't have to aim unreasonably carefully to hit the target's face.

At close range, laser dazzlers actually could permanently damage the target's eyes, and there's been some discussion about whether they should therefore be prohibited. (Green lasers are not as much of a blinding risk as you might think, as I discovered when I wrote about a high-powered green pointer a while ago. Broader beam means lower energy per unit area, so dazzlers, at least when they are hand-held and shooting at moving targets, are no more or less dangerous than the standard super-tight beam.)

Apparently troops in Iraq, in particular, love that they can just shine green lasers on cars approaching a checkpoint or something to strongly indicate that they want that car to stop right now and dazzle the driver so he pretty much HAS to stop, without having to fire shots or try to get the driver to hear a megaphone or something. So green lasers are, like silly string, a product that already has surprising military utility.
posted by dansdata at 3:27 PM on November 19, 2009

Those little green lasers are causing a lot of problems for pilots. Idiots like to sit in their yards and point them at low-flying aircraft. They can and do blind pilots, and the FAA and FBI are taking reports very, very seriously.
posted by Thistledown at 7:47 PM on November 19, 2009

IAmAn Optical Engineer; worked for a company that helped build the Airborne Laser (ABL).

As mentioned above, the major drawbacks for a man-carried laser weapon are:
* High minimal power requirements
* Poor energy efficiency (not the same)
* Toxic lasing medium (glass vials filled with corrosive gases in the midst of your own platoon?)
* Steady & prolonged aiming requirements
* Fragility
* Threat to friendlies (a laser beam is much harder to control than a bullet, since it travels farther)


BTW, phliar:
A collimated laser beam doesn't spread out (much) -- that's why the laser pointer's dot is the same size at five feet and at five hundred feet.

That's not true - the beam will very noticeably spread out over 100x path, probably to larger than plate-sized - but your point is still valid, since even broadened high-power beams can be eye threats.


Conversely, given simple math, Thistledown's claim:
Those little green lasers are causing a lot of problems for pilots. Idiots like to sit in their yards and point them at low-flying aircraft. They can and do blind pilots, and the FAA and FBI are taking reports very, very seriously.
... is just plain techonophobia. Those pointers are eyesafe at 10', 1', and 0' (duh, or they wouldn't be allowed on the market). They're bloody well eyesafe at 1,000'+, where they've expanded considerably (i.e., gotten dimmer).

They have never, ever, ever blinded pilots. No laser pointer blinds people. I've had a laser 5x brighter than a laser pointer in my retina, and later retinal exams (insurance records for a new lab job) showed no damage.
posted by IAmBroom at 10:42 PM on November 19, 2009 [2 favorites]

IAmBroom,

I think be meant temporarily blind (like, during landing), not permanently.
posted by atrazine at 11:24 PM on November 19, 2009

Those little green lasers are causing a lot of problems for pilots. Idiots like to sit in their yards and point them at low-flying aircraft. They can and do blind pilots, and the FAA and FBI are taking reports very, very seriously.

They don't blind at all. The reports are investigated because of the possibility that the lasers are being used as sights for weapons, not because the lasers themselves pose any harm to the pilots.
posted by Burhanistan at 7:27 AM on November 20, 2009

I think be meant temporarily blind (like, during landing), not permanently.

atrazine: Then he's still wrong. It won't termporarily blind anyone at those distances.
posted by IAmBroom at 6:39 PM on November 27, 2009

Late addition:

I looked into the dazzling/retina-damage thing in detail when I wrote this old review of a high-powered green pointer.

Executive summary: No, you can't blind anybody with even a very powerful portable green laser at anything remotely approaching ground-to-aircraft distances. Indoor distances? Yes. Even from chance reflections. Wear your safety glasses. Outdoor distances? Numbers rapidly become ridiculous.

You can dazzle someone enough with such a pointer to make it hard for them to see cockpit instruments and, quite possibly, cause a plane to go-around for another landing attempt. But your average drunken dickhead will have a lot of difficulty doing this if he doesn't move himself dangerously (for him) close to the airport.

Nonetheless, most laser pointers have now been made very illegal here in Australia. I ramble on about this very sensible technique to protect us from the terrifying threat of domestic laser-pointer terrorism here.
posted by dansdata at 5:42 AM on December 10, 2009