Homing In On Laser Weapons

Bloodmoon1 writes "I just came across this article at GlobalSecurity.org that gives a very good summary of the current status of solid-state lasers as weapons. It gives you a good idea of where the JSF Laser system is at and just how much time, effort, and money has went into this project. Also has some basic, but very sufficent, explanations of some of the science behind the technology."

The Airborne Laser

[Tikiman]

Check out the Airborne Laser Homepage [airbornelaser.com]. It's a project to strap a giant laser to a 747 that will fly around enemy launch sites and shoot down missles right after they launch.

Not a feasible weapon

[PhysicsGenius]

Lasers work by creating an inversion of atoms into an excited state and then releasing that exciting energy in a burst. But exciting the atoms obviously takes energy and, by E=mc^2, it takes a LOT. Industrial and scientific lasers can manage this by being plugged in to a dedicated power supply capable of delivering the gigawattage required for even small lasers, but a soldier in the field clearly doesn't have the luxury of an outlet needed to power his weapon.

Wavelength?

[Cutie Pi]

Does anyone know what wavelength these lasers are operating at? The article mentions that the lasers have a hard time piercing through clouds. It seems to me that an infrared laser would be more effective at piercing clouds than a visible one. Infrared solid-state laser technology definitely exists (the laser used in green laser pointers is in fact a 1064nm IR laser diode that is frequency doubled to 532nm).

You're right...

[doru]

Roughly, a laser works by changing one form of energy (provided by a "pump") into another (coherent light radiation). No "atomic particle" is turned into anything.

Re:targeting system?

[FeloniousPunk]

The answer to your question is called AN/TPQ-36 and AN/TPQ-37 "Firefinder" target acquisition radars. We've had them for 20 years - the -36 is designed to track mortar shells and the -37 other types of artillery (though IIRC, the -37 has all the functionality of the -36).
They are very effective. They calculate the location of the firing tubes, and that information is passed to artillery units tasked to provide counterbattery fire (usually MLRS rocket artillery). This all happens very quickly - 30 seconds to a few minutes' time.

Re:Tactically Flawed

[FeloniousPunk]

Military lasers do not lase in the visible spectrum; you're not going to see the beam. And they would fire a pulse of energy lasting only a fraction of a second.
If the target had a laser sensor, it could figure out where the fire is coming from, but I suspect the target is going to be having other concerns once it receives the laser pulse.

Re:targeting system?

[Unipuma]

The advantage of a laser system is that you do not need to calculate the trajectory. Since you are firing at the object with the speed of light, the object will be (almost) in the same location from the moment you fire till the moment the beam hits.

Re:targeting system?

[mikewas]

A daunting task, but one that has been solved by systems such as Aegis. Presently, systems must track an incoming threat which may either be an umguided weapon traveling in an arc such as a mortar round, a guided but unpowered weapon such as a bomb that uses fins to alter it's ground course as it drops, or a powerred guided weapon such as a missile which can turn in any direction at any time.

Present systems not only have to aquire the target, catagorize the target, determine the best weapon to use in response. Then there's the same problem with the weapon you use to retaliate -- it also doesn't travel in a straight line so you must compensate not only for the threat's non-straight-line behaviour but also your own countering weapon's non-straight-line behaviour.

Is you use the LASER, the second half of the problem goes away!

BTW: Aegis solves the problem in a manner that is elegent or brute force, depending on your point of view. It uses an electronically steered RADAR to track incoming targets, shoot a gattling gun in the direction of the target, then tracks both the incoming target & the outgoing rounds, uses this data to modify the direction the guns are pointed. Elegent in the simplicity of its concept, brute force due to the fact it applies massive processing power to allow it to track an enormous number of targets.

Re:Soon (wrings hands)

[JKR]

A 40W laser could weld steel plate - it all depends on the beam spot size. Think about it - a 10 mW laser pointer isn't eye safe; a 40 W laser focused to a 2 mm spot would burn a hole straight through the eyeball and out the other side.

Jon.

Re:targeting system?

[sql*kitten]

I would like to know how such a weapon will acquire/track/target an incoming projectile. (That was not sarcasm; I really would like to know.) Mortar rounds generally travel in a high parabolic path - think of the St. Louis arch. Larger artillery shells - such as those fired from a battleship - follow a flatter trajectory. The targeting system would have to acquire a small incoming object, predict the path it will follow, and fire within a few seconds. That looks like a daunting task.

It's a solved problem. The Sea Wolf [mbda.net] point defence system can shoot down 4.5-inch shells as well as supersonic missiles. Sea Wolf was first deployed in combat in 1982. Of course, you are likely to run out of missiles before they run out of cannon ammo, but maybe you can buy enough time to hit them with an Exocet [mbda.net].

Warships are expensive, so a lot of money has been spent on ways to protect them!

The problem with mirrors...

[caldaan]

Would be finding one that woulnd't be instantly vaporized when touched by a laser of that magnitude. Certainly paint isn't going to work as it would instantly oxidize and loose all reflective properties. Polished metals might help but they too would loose structural integrity. The mirror would have to be close to if not 100 percent reflecive of all the radiation being pointed at it and remain so for the duration of the attack. As far as using smoke cloud around missles as protection, they too need to see for guidance purposes, plus it would be almost impossibly to keep a leading smoke edge on something moving that quickly as the drag on the particles would loose the impulse of the rocket engine as soon as they were ejected, leaving the rocket exposed.

Just for your information

[Crasoum]

A kilowatt is 3,600,000 joules, 10 kilowatts in respect is 36,000,000.

Lightning is 1,000,000,000 to 10,000,000,000 joules.

Basically they are trying to make a weapon that could blast the hell out of that tree in your front yard, but right now will have to settle for your cat.

To put this in prespective, the adverage person uses 64,800,000 joules a month, or 18 kilowatts... So for every time they fire this baby, they are blowing 50-100 bucks....

They essentially are what cause the blackouts in California.

Re:targeting system?

[bheilig]

You're right. I used to work on the AEGIS weapon system's SPY radar. Once a projectile is completely ballistic it's trajectory is easily predictable. It's more difficult to determine the trajectory of a missile that is still burning fuel. In this case the radar must determine the type of missile.

In AEGIS we would fire an interceptor missile at a threat. The interceptor has mid-course guidance capability with a window of opportunity, so you can't fire the thing in the wrong direction and expect it to still hit the target. Therefore, your predictions must be highly accurate, accounting for wind, earth coriolis (the earth is moving underneath the projectiles), non-constant heterogenous gravity (weaker as the projectiles move further away from the earth, not in a straight line, and different for different parts of the earth).

The equation for filtering in this case is quite a mess. I'd imagine predicting for a laser is much easier because your interceptor is much faster, more stearable, etc.

If you're really interested in how it works, get a book on the Kalman filter. By the way, this technique is also useful in enemy AI development for games!

Re:Tactically Flawed

[quick_dry_3]

From October edition of Aerospace Internation journal (strange this gets posted just after i'd finished reading this article)

"beam is expected to take anywhere from five to ten seconds to burn through the casing"

That was from an article about the ABL mounted on a 747.

But as you said, if you're getting hit with a megawatt laser beam, you've got bigger problems than finding out where it came from.

And when that something firing is the size of a 747, finding it probably isn't such a huge problem.

Re:Not a feasible weapon

[Phosphor3k]

A 15 watt Argon Ion laser will punch holes in aluminum cans. It will also cause severe burns to peolple and go through clothes like mad.

Re:Mirrors

[Idarubicin]

Wouldn't a couple of mirrors ruin the whole thing?

In principle, yes. In practice, no. If you were to put a very high quality coating of silver (for visible wavelength lasers) or gold (for IR lasers) on your missile, in principle you could reflect 95 to 98% of incident light. Special optical coatings can result in >99% reflectance, but only over narrow wavelength ranges.

In other words, if the enemy knows the wavelength at which your laser operates, he can reduce the effectiveness of your laser weapons. For ground based installations, this still isn't a big problem--you just need a laser that's an order of magnitude more powerful, and you can cook even the reflective coatings on the other guy's missiles. I've done research work involving lasers in both physical chemistry and medicine, and I've seen a number of purportedly highly-reflective optical elements get toasted by a powerful enough beam. Also, high-quality optical coatings usually aren't meant to handle the stresses (physical and thermal) experienced by your typical missile (ballistic or tactical).

Re:Interesting, but is it legal?

[jandrese]

I certainly hope not. Almost all of our smart bombs these days are laser guided. That provision wouldn't make sense anyway. Laser guided weapons tend to be much more accurate than their dumb counterparts (you can't radar or IR guide a bomb on cold ground building), so they tend to reduce civilian casualties by letting the military only blow up military targets. The system isn't perfect (especially when armies hide behind their civilians), but it's certainly a lot better than carpet bombing.

Re:Unlimited use in battle!

[sql*kitten]

This would be the first weapon mounted on aircraft/heavy machinery that the pilot/operator wouldn't have to worry about running out of ammo in combat! That's a pretty serious advantage, no matter what other shortcomings the weapon may have.

Assuming he has an infinite energy source on board too, of course. Otherwise firing the weapon will decrease range/endurance by increasing fuel consumption. Currently the opposite it true, because it reduces weight.

Re:Not a feasible weapon

[Idarubicin]

Lasers work by creating an inversion of atoms into an excited state and then releasing that exciting energy in a burst. But exciting the atoms obviously takes energy and, by E=mc^2, it takes a LOT. Industrial and scientific lasers can manage this by being plugged in to a dedicated power supply capable of delivering the gigawattage required for even small lasers, but a soldier in the field clearly doesn't have the luxury of an outlet needed to power his weapon.

Okay, I'll bite. Where does E=mc^2 come into this? I've worked with lasers for a number of years, and I have yet to see any of my lasing medium converted directly to energy. Lasers operate by kicking atoms into an excited state (usually an excited electronic state) and then emitting light when excited atoms relax back to ground state.

For the record, small lasers don't require "gigawattage" to operate. I have a laser pointer that runs on one AA battery--I'll be giving a talk using it in a couple of hours. A laser designed for a weapons application would be larger. Still, I could assemble a carbon dioxide laser that could start fires from several hundred feet away and still be light enough to carry--and operate for a while on a moderately hefty battery back.

Granted, I couldn't destroy missiles with it, but the article discussses lasers that are mounted on aircraft or vehicles, or are part of fixed installations. You don't need a large power supply for even an extremely powerful laser if it only fires the very short pulses (microseconds or nanoseconds) that would be most useful for military purposes.

Re:targeting system?

[FeloniousPunk]

The radar actually detects the projectiles in flight; it analyzes the location, trajectory, and speed of the projo, accounts for atmospheric factors and determines where the artillery must be in order to fire a projectile with that flight path. What is being detected and tracked is the projectile; all the bits about targetting the firing battery is derived from that. If a radar beam can track a small projectile that accurately, so can a laser. And with a laser weapon, acquisition/ tracking and firing are essentially the same act.

Re:targeting system?

[quick_dry_3]

as a few others have posted in regards to the shipboard Aegis systems currently in use - basically a fast tracker and a gatling gun - here is the method used by the ABL.

Sensors detect a target (e.g. infra-red senssors pick up exhaust plumes or radar picks up missile)

Kilowatt class Active Ranger System laser acquires and tracks target.
Tracking data goes to the Tracker Illuminator Laser, which locks onto the missiles body and determines the best position to hit the missile.

A third laser the Beacon illuminator bounces light of the laser to determine atmospheric interference.

Interference data allows the optics to be altered to 'correct' the COIL's beam so it is properly focused when it arrives on target.

Then the COIL (Chemical Oxygen Iodine Laser) fires, and hopefully burns a hole in the target. Destroying it ouright, disabling it, or blowing its fuel tanks.

Re:Just for your information

[KFury]

"A kilowatt is 3,600,000 joules, 10 kilowatts in respect is 36,000,000."

What are you talking about? A kilowatt is a measure of power, and a joule is a measure of energy. The two are not directly comparable without a time factor thrown in. Do you mean a kilowatt hour is 3,600,000 joules?

By your calculation, lightning is 280-2,800 kilowatts (0.3-2.8 megawatts). As we all know, lighting is more in the range of 1.21 gigawatts (humor intended, but general priniciple remains the same). It's not like lightning strikes last for an hour.

------
"To put this in prespective, the adverage person uses 64,800,000 joules a month, or 18 kilowatts... So for every time they fire this baby, they are blowing 50-100 bucks....

They essentially are what cause the blackouts in California."

What the fuck are you talking about? This [enron.com] causes the blackouts in California, not some sergeant flipping the switch on $100 of electricity.

Re:We`ll have to

[caveat]

if you hit a mirror with a powerful enough beam of laser light, the small fraction of light that's absorbed (no such thing as an ideal reflector) will rapidly ablate the mirror coat, and then you're screwed. we have problems with this with our pulsed IR laser at work - we need solid polished aluminum mirrors with heatsinks on the back, ad that's for a 500mJ, 500ns pulse; they don't last that long, either. a 100KW IR laser will vaporize pretty much anything that's not *perfectly* reflective, i.e. anything we can build with current technology.

Re:The Airborne Laser

[TheSync]

Chemical lasers are really the short-term answer to laser weaponry. Solid state is a ways out (>10 years). Chemical oxygen-iodine (COIL) lasers can produce 10-100 megawatts CW today.

The Air Force Airborne Laser (ABL) mentioned above will soon be joined by the ATL [flightdailynews.com] (Airborne Tactical Laser) of the Army. The ATL weighs between 4,500kg and 6,750kg [aeronautics.ru], and can be mounted on a C-130 transport, CH-47 Chinook helicopters, USN P-3 maritime patrol aircraft, or Osprey V-22s for ground attack purposes. Or it could be mounted on US Army tracked or wheeled vehicles.

ATL will have a "sealed exhaust system" and will not exhaust poisonous fumes like the ABL. It could defend against cruise missiles, intercept incoming artillery shells of up to 300mm, knock out SAM sites, or be used for ground attack. It has a maximum range of about 25km, and can be shot 100 times before reloading the chemicals.

Both the ABL and the ATL should be operational by 2006.

Re:Interesting, but is it legal?

[cduffy]

Anti-personnel lasers are illegal -- not laser-guided weapons or weapons meant to be deployed against shells, missiles, aircraft or what-have-you.

Spinning

[ek_adam]

You could spin the missile to reduce spot heating, but that's going to complicate guidance considerably.

Some missiles spin anyway. The Sidewinder missile was intentionally slightly unstable and spun so that it flew in a spiral. Its seeker had one degree of control, up-down relative to the center of the spiral. When the heat source it was looking at was near the center of the spiral, the spiral would narrow down towards the target. When the heat source was not near the center of the spiral, the spiral would broaden out in a cone until it reacquired the heat source. Fairly early in its development a filter was added so that it would ignore anything with the precise infrared signature of the sun.

Re:Next Gen & Counter

[NetFusion]

(remember when we spent millions coming up with a pen that would write in zero-G and the Russians just used pencils?)

The notion the space pen R&D was paid by taxpayers is an urban legend, NASA didnt pay for the research, the Fisher pen co did and owns the patent. But NASA does buy em, but not nearly as many as space enthusiast do.

Space Pen History [spacepen.com]

Re:Simple fix

[Brown]

So you make your mirror subsystem disposable, and eject the spent mirrors like shells.

I think the guy's point was that the mirror isn't good for one shot; it'll pretty much vanish, and the laser'll keep going. A laser isn't like a projectile; a projectile is expended when it hits something. With a laser, only the time spent cutting through the shield is 'wasted'; the remaining milliseconds (or even seconds, possibly) of the pulse after it's done with the shield will slice into your fuel/warhead/guidence/crew.
Bang.

- Chris

Re:Next Gen & Counter

[Guppy]

(remember when we spent millions coming up with a pen that would write in zero-G and the Russians just used pencils?)...

There's a page for this on the Urban Legends Reference Page [snopes.com].

Apparently, there are a number of problems with pencils, including the flammability of wood/graphite in the pure oxygen atmospheres that were used at that time, and that conductive graphite dust could drift into electronics and cause a short.

Re:Next Gen & Counter

[Stonehand]

(*) Do you really think they'll stop firing missiles? Most countries likely to antagonize somebody with effective, field-capable lasers (large powers) are probably bothering somebody likely to remain without them (especially in the case of the US, whose forces are often deployed into an existing conflict)... so missiles won't be obsolete.

(*) There are conflicts today where old weapons -- even as old as spears and machetes -- are side-by-side with moderately old weapons (AK-47s, for instance... and the explosive grenade goes back at least to the late 1700's, as primitive explosive-charges were thrown to detonate the powder magazines in ships... and the general concept of the gunpowder firearm goes back to the late Middle Ages; RPG-7s) and where more modern weapon systems (vehicles with reactive armor, laser-guided missiles, Phalanx CIWS) are practically non-existent.

Hell, have you ever seen a Palestinian fire an automatic rifle -- perhaps a Kalashnikov or a captured Galil or M16 -- at an Israeli Merkava, when the latter is buttoned up? It's futile, as the bullets have neglible chance of finding a spot penetrable by the small rounds (/maybe/ the vision block), but that doesn't mean that they've ditched their rifles and are now swimming in RPGs.

Weapons cost time (training), money (lots), contacts (need to find somebody who'll sell... for an example of a client with problems, I doubt that the radical Islamists can readily buy modern weapon systems from the US, Russia, China, or Israeli as they are all involved in ongoing conflicts with their brethren... well, maybe they can go to France. *shrug*)

The last major weapon system concept to be completely obsoleted was probably the battleship, which yielded to the aircraft carrier battlegroup, and even now there are still gun-armed ships meant for surface engagements, I'm sure.

(*) Remember when Snopes debunked the "NASA Space Pen" nonsense" [snopes.com]?

Mildly Shocked no one has put these up

[anzha]

A bit of Karma whoring here, wish I'd gotten online sooner so that people would see this much earlier:

TheHigh Energy Laser Systems Test Facility [army.mil] (so-called HELSTF). Let's see if Tom's webserver can survive this...This is the laser test facility for the army and navy at White Sands Missile Range. They've got the world's most powerful laser (MIRACL: Mid Infrared Advanced Chemical Laser) there.

Being developed for them, by Livermore by the same guys that are doing the National Ignition Facility is a solid state laser [llnl.gov]. It works.

Also at HELSTF, and the first functional laser weapon, is Tactical High Energy Laser [trw.com] (aka THEL, and I hate that URL, btw...)

Search TRW for more stuff on lasers as well as Lockmart and Boeing, of course.

Re:Next Gen & Counter

[Anonymous Coward]

Gee they used pencils?

That's right, they did, up until they figured out that graphite particles were causing fires. Then they used our pens... which we spent... $0 developing.

Yeah I remember when that happened, that was a terrible waste of money.

Re:Forget Stealth technology then...

[xtheunknown]

Actually, you're both right. The F-117 works both ways. It both reflects radar at odd angles and attenuates the signal by absorbing (hence a weaker return signal) radar.

F-117's are not invisible to radar, they just appear very small, approximately the size of a sparrow, and are usually over-looked by the radar technician as being natural phenomenom.

Also, they have IR emission reducing capabilities too.

The first comment was right. Defeating laser and radar are contradictory goals.

-- Admit nothing, deny everything, and make counter-accusations.
Naval Intelligence Motto

Re:What good would Anti_Missle system

[Stonehand]

Retalliation and deterrence theory

(1) Only works when everybody with sufficient access in the entire WMD system is rational. This is increasingly questionable; for an example, consider North Korea, which appears to prefer being able to hit the continental United States with a nuclear weapon (they have missiles with sufficient range, although accuracy has been questioned) to, say, being able to feed their people.

(2) Ignores the possibilities of accidental launches and launch systems which would have unclear authorship. For instance, it may be unclear who just launched an ICBM if it came from the middle of an ocean...