Laser weapons?

I was reading something about a laser weapon that Boeing is developing to shoot down aircraft.

I’m guessing that within the next decade, we are going to see actual military laser weapons, just like in the movies.

My question is this:

How effective/practical would a laser weapon be?

In terms of range, speed to target, and “balistic” properties(infinite, instant, and straight, for all practical purposes) a laser is obviously superior to a projectile (which have a finite range, take time to reach their arget, and must account for wind and drop).

But couldn’t a laser be deflected by a mirrored surface?

Also, by the time a laser can burn through a heavy armored vehicle like a tank, couldn’t it have just as easily be destroyed by a SABOT round?

The pros and cons of laser weapons were debated at considerable length during the Reagan “Star Wars” program over fifteen years ago. Go back and read the stuff from then (books, magazine articles, etc.) The laws of physics haven’t changed noticeably since then.

The advntage of a laser weapon is that you don’t have to lead your target, as with a projectile weapon. The speed is virtually infinite (at least as ar as the missile is concerned), so it goes where you oint it. The problem is that, with some lasers, you have to leave it there while to do any damage, so you have a “dwell” time, so it’s not necessarly a savings. More problematic in some cases is targetin in th first place – they wanted to shoot at far-away boosters rising through the atmosphere, but if you target on the highly-visible exhaust plume your laser won’t do any good – you have to extrapolate where the booster skin is, and tht’s not trivial.

Then there are ddges like spinning the rocket, putting an ablative coating on the rocket, covering it with a evaporatable liquid skin etc. These would, as critics note, add weight (and therefore, fuel, and therefore, more weight) to the booster. There’s a whole series of measures and countermeasures that can be imagined. Nothing’s ever simple.

A good book from the late eightes is Jeff Hecht’s Beam Weapons.

From what I understand(and we all know that i dont understand much), there would be absolutely NO way to avoid a laser attack. Because a laser travels at the speed of light, no evasional tactics would work. The Millenium Falcon would not be able to dodge the laser shots from the Empire.

Apparently the military is satisfied that it is highly practical. The chemical laser for the ABL itself is proven technology; IIRC, a trailer-borne, ground-based laser anti-missile system also is being developed for Israel.

It appears that the main issue to be addressed for the ABL is ensuring that the target acquisition system works correctly aboard the (moving) 747 that will carry it. In any event, several copies of the the ABL system are being built with the intention of being combat operational by around 2008.

I recall from my reading on the ABL site that the system is limited to about 20 shots per sortie. It would of course be most effective on thin-skinned targets; although the web site is careful to specify that the system is intended to disable ballistic missiles in flight, I see no practical reason why it could not be used on aircraft, light vehicles or personnel, in clear weather at least.

Nonsense. If a soldier can avoid being shot by an assault rifle at fifty yards, then he can avoid being shot by a laser - we’re talking about milliseconds here. It may be more accurate, but that doesn’t mean it’s better aimed.


If you’re referring to the Nautilus system, then IIRC it’s been active for the past few months, although it has yet to be tested in battle.

And it was developed with Israel as a joint project.

Well, it’s about time, dammit. It’s the first year of the twenty-first century, and I haven’t seen one flying car yet, either.

Alessan said:

You cannot avoid it, because by definition the very first information you can get about the laser is the laser beam itself. Since it is travelling at the speed of light, you can literally never know what hit you.

Mind you, it would have to be targeted in some way, so if you could detect whatever it’s using to target the beam you *might be able to avoid it.

Okay, I’m not a laser physicist, but I have read a few articles.

Any errors I mention here are likely flaws of my recollection of said articles. Be warned.

First off, the laser weapon has one huge problem, and that is the fact that a great deal of it’s energy is lost to the air. Even on a clear, calm day, megawatts of the laser’s output is simply heating up the air in it’s path, basically boring a hole in the atmosphere itself.

The heated air roils and throws the laser off target, just as the air will shimmer a little on a hot day. When the range-to-target is measured in miles, even a tiny error caused by the motion of the superheated air can mean a miss.

As I understand it, the real problem is less mere raw power, it’s getting that power to the target. The “cure”, so to speak, is massive computer power linked to super-accurate radars, which in turn run “adaptive” optics- meaning a deformable aiming mirror, which does the actual aiming of the beam.

The heating problem, even with the advanced optics, becomes even more of a problem when the target is travelling at a high rate of speed. The laser then has to keep cutting a new path through the air as it tracks.

As for defenses, a high-power laser weapon will have little or no “dwell” time- the incoming beam literally strikes like a cannon shell, producing something more like an impact effect rather than a “burning” or “melting” effect.

A polished surface may actually attenuate the effects to a tiny fraction of a degree, but by no means will a potential target be astronomical-mirror-quality polished. And in any case, from what I’ve read, the surface finish is more or less irrelevant, since, as I mentioned, the high-energy photos strike with something like an impact force, not a “heat” effect.

The same goes for ablative armor or “liquid” shielding- which I haven’t heard of. For something like a ballistic missile, even the near-explosive destruction of a layer of ablative armor will very likely damage the missile itself.
And as mentioned, the weight of the armor itself might cut the range of the missile down by a significant margin.

As for targeting, in an infantry situation- say a laser-tank 200 yards away, the “beam” cannot be “dodged”. But then, the same can be said for a bullet too. The bullet may take milliseconds, while the beam may take fractions of a microsecond, but in either case, it travels about three orders of magnitude faster than human reflexes.

However, targets move, it takes time for weapons to function, and it takes even more time for an operator to actually fire it.

For example, it might take several milliseconds for the gunner to recognize the target, possibly most of a full second to align the sights- if he’s fast- and a few more milliseconds to tell his trigger finger to pull the trigger.
Then in a mechanical gun, there’s a few more milliseconds for the firing mechanism to ignite the primer, and depending on the range to target, a sizeable fraction of a second (or even several whole seconds) for the projectile to actually traverse the distance.

With a laser weapon- which we’ll assume near-instantaneous discharge when fired- the speed of the “projectile” may well be faster, but the human reaction times (to fire the thing) and the time needed to actually aim the bloody thing, will not be all that much different.

And when one considers a ground-based (or even airborne) laser many miles from the target, which is travelling at what, several thousand miles an hour? Then even the fractions of a microsecond it takes for the beam to traverse the distance can still mean a miss.

Anyway, to answer the original post, it’s my opinion that laser and “particle beam” weapons (lasers are, after all, simply beams of concentrated, energized pparticles called photons) when properly developed and aimed, will definitely be part of future weaponry.

The effectiveness will depend on how portable a powerful laser can be made, how accurate the aiming system- whether it’s a dot-sight for a trooper or a radar array for an ABM system- and how fragile it all will be.

Simply due to the fact that even with ultra-miniaturization of the circuitry, and advanced developments on electronic efficiency, I doubt the individual soldier will ever have a laser-rifle to replace the M-16. But for something like an Aegis cruiser anti-missile defense, or a replacement for the CWIS/Phalanx anti-missile system, very possible indeed. Given a compact enough bank of capacitors, even tanks and Bradleys could have effective lasers… eventually.

Well, I’m not a Rocket Scientist and I don’t sh*t Jet Fuel, but that “beam of projectile” thing has me stumped. I’m not saying isn’t possible, but I would like someone to explain it to me.

I was a crewman in an M1A1 Abrams Main Battle Tank from 4-96/ 9-2000. I don’t think we will ever see engagement ranges measured in miles, even with laser weapons. There are just too many problems down on the deck. The first is terrain. Too many things to obscure the target. The next is optics. The The M1A1 uses a 3x sight to aquire tagets and then the gunner switches to 10x to get a better sight picture. I have heard talk of bumping it up to 12x, but I can’t imagine much more power. The problem is that everything between the gunner and target is magnified, including mirage (a.k.a. Heat Shimmer). This can visually obscure the target at ranges less than 1,000 meters. Wind can actually “move” the target in mirage conditions.

I’m getting involved in long-range target shooting (1,000yard Benchrest). The 100 yard guys often use fixed power 36x scopes. These are sometimes modified to 45x or more. The 1,000 yard guys most often use variable power scopes. I have 2, a 6-24x40 and 6-24x50 . Some guys use more power, but not many. Variables are used so that mirage can be “dialed out” by reducing the power. There’s just too much mirage between the target and shooter at that range.

I’m getting away from the main topic of this thread, but if you want to see something really fascinating, go watch the path of a bullet through some type of magnifying optics (rifle scope, binoculars, spotting scope). Sit directly behind the shooter. You will see the path of the bullet as a tiny trail of heat shimmer. It looks like jet exhaust.

*Originally posted by Long D. *

Well, I’m not a Rocket Scientist and I don’t sh*t Jet Fuel, but that “beam of projectile” thing has me stumped. I’m not saying isn’t possible, but I would like someone to explain it to me.

From what I saw in an experiment on TLC, a laser can actually be used to propel a small object. It delivers so much heat energy to the target so quickly that it creates a small explosion (an explosion is just heat energy being converted to kinetic energy). Apparently, it doesn’t cut its target apart like a blowtorch or industrial cutting laser.

kgriffey79 - People avoid being hit by bullets by not being where the bullet is aimed at. Not by dodging it like Keanu Reeves in The Matrix.

Well, the problem I see is not necessarily velocity or strength but range. The thing about a missile is that it fires in an arcing path so you could hit something on the other side of the Earth regardless of the curvature of the planet. With a laser, I would assume its pretty much line of sight (or at least unobstructed path). You can only fire so far before the curvature of the Earth interferes w/ your laser. I guess thats why you put them on planes.

Also, in reference the the proper aiming of targets at long distance, I think that problem is limited only by the computer setup you use to target in the first place. I read somewhere that Navy SEAL snipers can accurately fire their rifles from miles away. Granted it takes two guys and they spend days compensating for the distortion of air and wind, but a computer of sufficient processing power should be able to do it.

IIRC, the original reason that laser weapons were impractical was because even a small amount of atmospheric distortion… clouds, rain, smoke from bombs on a battlefield, etc. would diffuse the beam. However, advances in optics technology have produced compound mirrors and lenses which can be adjusted by computer to match the atmospheric distortion, allowing the laser to cut through.


Here ya go, Zarathustra. Don’t say I never did anything for ya. :wink:

Long D.- Your’re right, battlefield ranges will be probably little more than current artillery at best. And even then, artillery can fire over hills and mountains to strike objects the gunners can’t even see.

Thus the laser on the infantry/tank battlefield will likely be tank-to-tank or even in an anti-aircraft role.

I suppose I wasn’t clear in my earlier post, since I was describing both infantry and tank use, AND anti-ballistic-missile uses of lasers.

And you’re right again, the curvature of the earth limits even the most powerful weapons. The three ways around that that I can recall from my reading, is A) Space-based (satellite) lasers, B) Ground-based lasers with space-based mirrors (put it this way, the 48 GPS satellites cover 100% of the Earth’s surface) and C) airborne lasers.

From what I can tell, the ground-based laser with space-based reflectors is the best option anyone’s come up with. The ground-based laser can be sited in a huge installation, where massive generators and capacitor banks can be brought on-line, and where space and weight is not at a premium, meaning one can simply rack together tens or even hundreds of individual lasers to get the required output.

Site that sucker with a small nuclear reactor or other generating plant, a huge array of small, easy-to-repair and easy-to-cool (and cheap) lasers, and a series of mirrors that can take the power, and a multi-gigawatt laser is not impossible.

In fact, I believe only the mirrors are the weak point- the more megawatts you fire at it, the more precisely one must polish the mirror, plus mirror cooling (but without temperature-induced distortions) becomes terribly important.
(Since the same energy that can blast an ICBM out of the sky at 1,200 miles, can sure as heck blow up a mirror only fifty feet away. :smiley:

Another thing from a PopSci article on anti-ICBM stuff… the possibility of “dummy” or decoy warheads seems to be a current worry in anti-missle missile technology… But what if the laser can fire, say, every two seconds, with a theoretical 90% hit ratio? An ICBM flight takes ten to twenty minutes to warhead seperation…

You know, all this Death-Ray talk had me thinking about the movie Real Genius. Am I the only one that noticed a dialouge based blooper in the ever-famed scene where Val, after asking the question about his dream where there are women throwing little pickels at him, is cutting off Quarter sized discs of frozen nitrogen for the vending machine. Then the geeky kid asks, “Hey! Is that LIQUID nitrogen?!” to which, I believe Val mutters in agreement. Duh! It was a SOLID rod of frozen nitrogen. Gets me every time.

I now return you to your regularly scheduled thread…

I would guess that lasers would never be used as artillery, unless they were mounted in space. The advantage of artillery (specifically mortars) is that the bomb fires in a high arc that can drop into fortifications from above and explode. A laser is a direct fire weapon (like a rifle or tank cannon) so you are probably correct about them being used or anti aircraft weapons.

I’m not sure how effective they would be as an anti tank weapon. Blasting apart a relatively thin airframe is one thing. Burning through 12" of armor plating is a different story. A conventional cannon or some kind of “rail gun” would probably be more effective. All that armor plating is useless if the force of the projectile sends the vehicle spining 100 yards down range.

I think you misunderstood that scene. The way I interpreted that, was that the cylinder of clear substance was something else which had been suspended in liquid nitrogen. i.e. the liquid nitrogen was still in the container.

After all, you try finding a regular kitchen freezer that will keep SOLID nitrogen solid.

Hmmmm. I hadn’t thought of that. But why would he need liquid nitrogen to freeze water, anyway (not that it was water)? Why wouldn’t he just use Dry Ice for the chips, and keep that insulated in the freezer. It just doesn’t make sence to matter what way you look at it!

I believe the concussive effect is due to heating the surface of the target very quickly. It’s like setting off a hand grenade right next to the skin of the vehicle. Ballistic missiles have enough fragile parts that that amount of energy is sufficient for a high likelyhood of success. It’s also enough energy to do a pretty good number on most aircraft.

OTOH, that’s nowhere near enough energy to do much damage to even a fairly lightly armored ground vehicle. I read an article one time that described how the armor on near-future vehicles could get to the point where the likelyhood of punching through it with anything that could be carried on a tank would be very low. But, that future rail gun projectiles might be able to put enough energy on the target to rip the turret off without ever actually piercing the armor.

You may have been misled. That has been done before, but only once (that we know of). A couple of long-range gurus in Colorado have made shots at 3,120 and 3,600 yards. I don’t have info on the 3,600 yard shot, other than it was done by Kreg Slack with a custom rifle chambered in .338 Lapua. I have an article about the 3,120 yard shot. It’s in the September 2000 issue of Precision Shooting. Bruce Artus used a rifle with a Winchester Model 70 action, Obermeyer barrel chambered in .308 Improved. The scope bases are custom made. For this shot, the front of the scope was tilted down 7.5 degrees. In order to be able to see over the muzzle, the rear base is about 4 inches tall. The scope is a Leupold modified by Premier Reticles. The power was bumped from 8.5-25x up to 20-50x. It has a custom fine crosshair as well. This crosshair subtends 1/8th MOA. In plain english, this means that at 100yards, it blocks out a 1/8" dot on the target. At 3,000 yards, the crosshair alone obscures 4 inches of the target. Because of mirage, there is only about a 30 minute window of opportunity to make a shot like this even on the best day. Scope power is set at around 40x; any more and mirage will obscure the target.

All of this equipment is custom built for shots at these distances. It is much too delicate to survive as an issue rifle, even in the hands of a specialized soldier like a sniper. The ammunition is all hand-loaded. If you aren’t familiar with benchrest-quality reloading…you just would not believe all the prep that goes into the ammo. While SEALS may have made such long-range shots for practice, there’s no way they would take such a shot on a real mission. It’s just too risky. That enemy general isn’t going to sit around and give him a second shot, either.

This is not intended as a flame, just wanted to share some info with you. In this case anyway, I find the truth to be much more fascinating than a vague reference to what is likely a military myth.