Built on Facts

Lasers and Battlefields

Missiles are a problem if you’re fighting a modern war. You can get out of the way or you can hide behind something, but that’s about it. Now anti-missile technology has had some success dealing with mid-range missiles. The Patriot system whose success was limited during the Gulf War has since been improved into a system that’s quite effective in dealing with the large and somewhat lumbering tactical ballistic missiles fielded by a number of adversaries.

But smaller missiles and mortars remain an intractable menace. It takes mere seconds for something like a Qassam rocket to travel its short-range trajectory of a few miles. There’s no anti-missile countermeasure that can adequately address such a threat. For defense of very small targets like individual ships, high-speed machine guns have had some success, but it’s a desperation move that’s even less effective against multiple incoming missiles.

On the other hand, what about a laser? Lasers are pretty useless as an offensive weapon of war by virtue of the fact that a cannon shell does the job much better at a microscopic fraction of the cost. But at defending against incoming rockets and mortars, we may have a different story. Lasers operate instantly, are easy to aim, and generally don’t require any resupply other than a power line. The problem has been power. To destroy an incoming threat requires a tremendous amount of heat delivered in a very small window of time. 100 kW has generally been the accepted “threshold” for usefulness. Last time I wrote about this subject, the state-of-the-art lasers of this type were in the 10 kW range.

Not anymore. Northrop-Grumman just announced successful tests of a 105 kW solid state laser. They suspect it can be pushed to 120 kW without much difficulty.

Each building block for the laser consists of a laser amplifier chain, with each chain producing approximately 15 kW of power in a high-quality beam. Seven laser chains were combined to produce a single beam of 105.5 kW. The laser already has been operated at above 100 kW for a total duration of more than 85 minutes. A government team reviewed results of the demonstration during a System Test Data Review held Feb. 10 at Northrop Grumman’s Directed Energy Production Facility in Redondo Beach.

The laser’s seven beams are combined by “tiling” them in a row and matching their phases, thus coherently combining them, says Wildt…

The technology could be deployed in as quickly as a year for a demo, says Wildt, and in a few years for a fieldable weapon system. The resulting laser weapons would be able to shoot down many types of enemy targets, including rockets, aircraft, unmanned aerial vehicles, missiles, mortar rounds, and swarming boats (an attack consisting of many small, explosives-laden boats that converge on a single ship).

This would be an immense advantage for whatever military can field such a system. Modern militaries (and the US Navy in particular) are almost certainly much more vulnerable than they’d like to admit to mass missile attack by an advanced opponent. Even a technically adept military like the IDF has been able to make very little progress in stopping the most primitive in Soviet-era rocketry. It was not too many years ago that a US commander playing the role of Iran more or less routed the US Navy in a 2002 wargaming exercise with a tactic amounting to launching saturation missile attacks.

This kind of anti-missile laser technology could have the capability to render those tactics impossible. It’s about time.

Comments

  1. #1 rob
    March 23, 2009

    they can also use lasers to shoot down malaria ridden insects:

    http://www.physorg.com/news156423566.html

  2. #2 Eric Lund
    March 23, 2009

    I’m not convinced. Two issues I can think of right away (and I have zero military experience) are duty cycle/recharge (i.e., how long do you have to wait after shooting the thing before you can shoot again) and scalability (how many do you need to ensure that the enemy can’t overwhelm you by lobbing lots of missiles in your general direction). A laser antimissile system will work well if your goal is to protect your base from rocket attacks, because there are ways of overcoming those two issues. If you are a mobile infantry unit, you still need to worry about incoming missiles, in part because the need for portability works against solving the other two problems.

  3. #3 JM
    March 23, 2009

    I could be really picky here, but instead I’ll point out a couple of fallacies.

    There are in fact counter-battery defences to incoming missiles, morters and shells and Israel has them. You detect an incoming projectile and trace it back to its launch point, you then target that launch point.

    Israel is actually fond of using this capability as an excuse for “accidentally” hitting civilian targets – their argument goes that they trace back and then shell the launch point “instantly” and therefore are likely to hit civilians if the bad guys are hiding inside a civilian target. This is the common excuse for hitting schools, hospitals and UN compounds.

    However, there is a problem with this argument – which is relevant to whether or not a laser weapon can shoot down a missile in flight. It takes time to calculate the trajectory of the missile (or mortar) and co-ordinate with the retaliating weapon (whether aimed at the launch point or the projectile itself).

    Retaliation isn’t instant. Currently, the state-of-the-art (as represented by actually deployed equipment) is for about a 10 minute delay.

    Far too long for a laser weapon even if it could be built both powerful enough to do the job and light enough to track a fast moving target.

  4. #4 James Brennan
    March 23, 2009

    JM the Phalanx system can acquire and lock onto a target in seconds. However, I wonder about the power supply issue in a field deployable version. This thing is not going to run on a few flashlight batteries.

  5. #5 Joshua Zelinsky
    March 23, 2009

    Is this substantially better than something like the Phalanx? It isn’t clear to me that there’s really a major advantage. Obviously the laser does travel faster but recharge is an issue and for machine guns the ammo issue is easily dealt with- you just have lots of ammo ready. I haven’t crunched the numbers but it isn’t clear to me how long a 120 kilowatt laser is going to need to focus on a missile in order to shoot it down. Moreover, there’s also the issue of the easy countermeasure of having a reflective coating on missile which if it reflects the right frequencies could substantially reduce the effect of the laser.

    Regarding JM’s comment:The Israelis do have to delay before responding. You saw this in the Lebanon war for example where Hezbollah would try to launch rockets and then quickly get out of the area. I fail to see how this in any way retracts from the Israeli claim.

  6. #6 Uncle Al
    March 23, 2009

    1) Mirror warhead. 2) The laser is the target. 3) Business as usual. Given 120 kW of laser, the cost-effective target is long range enemy eyes – no punctilious collimation required. Your close buddy sells electrochromic welder’s goggles abroad and alkaline batteries…

    “Mother sells cheap prophylactics.
    She punctures each head with a pin.
    Father takes care of abortions.
    My god how the money rolls in!” (re Oscar Brand)

    (A transparent diffraction grating that only disperses coherent light is the second generation upgrade.)

  7. #7 Matt Springer
    March 23, 2009

    “Retaliation isn’t instant. Currently, the state-of-the-art (as represented by actually deployed equipment) is for about a 10 minute delay.”

    The Phalanx CIWS system has been in operation for decades and can successfully aim a Gatling gun at a supersonic missile instantly. Aiming a laser should be even easier – and you don’t have to move the whole laser, just the beam steering components. Communication between components shouldn’t be a problem either. The radar and tracking systems would be embedded with the laser system itself, as they are with the conceptually similar Patriot system. In any case it’s not retaliatory – the systems take aim at the incoming missile itself. Counter-battery systems might take longer, but this isn’t one of those anyway.

    “This is the common excuse for hitting schools, hospitals and UN compounds.”

    Or, I dunno, Hamas could stop launching missiles from schools, hospitals, and UN compounds.

  8. #8 TBRP
    March 23, 2009

    Or, I dunno, Hamas could stop launching missiles from schools, hospitals, and UN compounds.

    Hamas would need some incentive to do that. Right now when they do it, their enemy gets painted as a monster for bombing schools, hospitals, etc. Why stop doing something that gets you sympathy? Of course there’s the moral reason, but when you’re lobbing explosives indiscriminately, you probably don’t care about the “collateral damage,” such as schools, hospitals…

  9. #9 CS
    March 23, 2009

    Mirrors are not 100% efficient — ordinary mirrors still absorb a few % of visible light. Might need to aim the laser a little longer, but you can still get some energy on mirrored objects. How much energy would it take to burn away that mirrored surface?

  10. #10 Moopheus
    March 23, 2009

    As Uncle Al (hey, I have an Uncle Al) points out, the logical flaw of all missile-defense schemes is that ultimately there’s no undefeatable defense–it just continues the arms race into another level. Each scheme generates a counter-scheme. And the game does not provide you with much of an advantage: it’s cheaper to harden/camouflage/deflect than to build lasers and anti-missile missiles.

  11. #11 rob
    March 23, 2009

    the 100 kW laser operates at something like 20% efficiency. that means the total power needed is about 1/2 megawatt. it would have to be mounted on something the size of a heavy tank. you won’t have humvees with frickin’ lasers any time soon.

  12. #12 Joshua Zelinsky
    March 23, 2009

    CS, yes but if the time is getting that much longer it could be a problem. Let’s say for example it normally takes 1 second to fry a missile (to pull a number more or less out of nowhere), then if the mirror reduces the energy absorption to 10% (which is a conservative estimate) then this takes now at least 10 seconds, even before we get into other issues like the missile radiating heat in the meantime. Mirroring could thus make a practical system much less effective.

  13. #13 Anthony
    March 23, 2009

    Half a megawatt is only 670 horsepower, I don’t think a HMMWV has that much power, but it’s not really a power level that’s a problem for a truck.

    In terms of overwhelming the system, it’s almost certainly doable, but the basic point of defensive systems like this isn’t invulnerability, it’s to raise the cost to the other side. If you have to launch two missiles to get one through, it means each attack you launch is twice as expensive, and appreciably more likely to get detected before you can fire it off at all.

  14. #14 Matt Springer
    March 23, 2009

    I’d have to disagree, #10. Countermeasures do breed countermeasures, but either way the most advanced army usually wins. You want to be that army.

    And that’s one way of looking at the issue in general. However, I think lasers specifically will be more resistant to countermeasures than most weapons. It’s intrinsically very, very difficult to make an undetectable missile. No one has ever done it as far as I know, and there’s good reasons for thinking it might be impossible. Materials science is also such that it’s intrinsically almost impossible for an object absorbing hundreds of kilowatts of energy in one location to remain airborne. Even mirror coatings vaporize under those kinds of loads.

    But really all that’s only relevant against relatively technologically equal opponents anyway. Hamas is not going to be putting some super-stealth anti-laser countermeasures in their unguided Soviet era rust buckets.

    For the power issue a few people have brought up, that’s definitely a problem. On the plus side though, it doesn’t need that megawatt continuously. It only needs it when actually firing. Access to a local power grid or even a big generator/capacitor might be able to do it.

  15. #15 Eric Lund
    March 23, 2009

    Access to a local power grid or even a big generator/capacitor might be able to do it.

    This is the issue I was trying to get at in my earlier post. If you are a base, you have enough generator capacity to deal with this. If you are infantry, you don’t, and since you are in the middle of a war zone, you cannot count on access to a working power grid. A big capacitor will let you get off one shot, but then you have to recharge it somehow, and that’s going to take time when all you have is portable generators. Meanwhile, your enemies launch another missile at you. It may be more expensive, but it’s not vastly more expensive.

    the most advanced army usually wins

    They may be more likely to win a given battle, but recent history tells me the more advanced army does not always win the war. Some counterexamples: USSR vs. Afghanistan, 1980s; USA vs. Vietnam, 1960s; Germany vs. USSR, 1940s; and you can undoubtedly find others. It does help if you choose your fights carefully; there is a reason why getting involved in a land war in Asia is the all-time top classic blunder.

  16. #16 Comrade PhysioProf
    March 23, 2009

    This is an interesting technology, but it cannot be assumed that better tactical missile defense makes one less vulnerable to attack.

  17. #17 CS
    March 23, 2009

    Joshua-

    The mirroring layer is typically very thin. It may not take much to burn it away, at which point the laser can go back to work destroying the missile casing and/or electronics. I do not know exactly how much it takes to overcome mirroring, but just wanted to throw out there that mirroring may not be as much of a countermeasure at it would seem.

    As for powering these things, another article (I can’t recall where, though) suggested the power unit for these lasers could likely be fit on a single truck. The turbine in an M1A1 tank generates more than a megawatt of power (not electric, but could presumably converted at a reasonable efficiency), so generating the power levels needed here in a single vehicle is not unfeasible. Patriot missile batteries involve several large vehicles, so large vehicles are also not unusual.

  18. #18 Matt Springer
    March 23, 2009

    Well no, PP, but it does make you less vunlerable to attack by tactical missiles. And if that’s the main thing your opponent has, it might well be worth the effort.

    Good points by CS. A mirror might reflect 99% of incoming light, but even 1% of 100 kW is enough to almost instantly destroy the reflective properties of any mirror assuming the beam is focused with any precision at all.

  19. #19 Philip Kahn
    March 23, 2009

    I would certainly imagine the first place these would go would be our carriers. After all, they have bloody nuclear reactors on them, a half megawatt is a small fraction of its generating capacity!

    Also, the reason 105 kW is a big deal is because (for a black body) one or two second of that power output melts common metals such as copper and iron. http://en.wikipedia.org/wiki/List_of_elements_by_melting_point

    105e3=(5.674e-8)T^4 -> T=1166.54 K

    Two seconds of laser contact at 105 kW would pretty much take out any warhead. The 120 kW version will reach 1206 K in a second. And finally, as solid-state lasers, they should be able to refire virtually instantaneously.

  20. #20 Joshua Zelinsky
    March 24, 2009

    If the mirroring won’t be that effective this is starting to sound more plausible. Should be interesting to see where this goes.

  21. #21 Moopheus
    March 24, 2009

    “Hamas is not going to be putting some super-stealth anti-laser countermeasures in their unguided Soviet era rust buckets.”

    So, in order for this plan to work, we have to assume the opponent will always only have very limited technology? That no more sophisticated ally would supply them with something better if push came to shove? I mean we know that the Russians have been deploying missiles with anti-SDI technology, and we know they don’t have a lot of qualms about dealing with people we consider our enemies.

  22. #22 rob
    March 25, 2009

    Philip–just because it is solid state doesn’t mean it will be able to be fired rapidly. the first solid state lasers could not be operated in continuous wave mode and had to be cooled with LN2. the heat sinking problem was overcome though, and now we get blue ray players.

    the laser needs about 1/2 megawatt to produce the 100 kW beam. that leave around 0.4 megawatt of power to heat sink. i expect that will be a pretty neat technical hurdle to overcome.

  23. #23 JM
    March 26, 2009

    Matt before I get into the guts of what I’m talking about here, I suggest you look up Qana 1996 where it was concluded that even though Israel used the “but they were shooting from the UN compound” excuse …

    … that in fact the IDF separately targeted both the mortar crew and the UN compound which was 250 yards away. This is a well established fact, the IDF deliberately targeted the UN compound and knew that the mortars were being fired from elsewhere because the targeted the launch site as well.

    Anyrate. My point is that the capability to track mortars and missiles – over land not sea, so there’s a noisy signal – already exists and it’s not very good (at least in terms of integration with fire control).

    The Phalanx is also irrelevant to this discussion for another reason – it is there to protect a single high value point, an aircraft carrier. The Hamas stuff is wildly inaccurate, unguided stuff that spreads over a wide area. So unless you feel like equipping every block in Israel and the West Bank with a Phalanx you aren’t going to get anywhere.

    That would be wildly expensive as each installation would be at least as expensive as a Phalanx.

    And lastly, having spent all that money all that Hamas would have to do is to up their expenditure 10 fold (and they would still be spending a lot less than you) and overwhelm your shiny new defence system.

    Sorry, nice toy, but not practical for its intended purpose.

The site is currently under maintenance and will be back shortly. New comments have been disabled during this time, please check back soon.