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Warships May Get Lasers For Close-In Defense
King Louie writes "Raytheon and the US Navy have successfully tested a ship-borne laser capable of shooting down aircraft. Video at the link shows the 32-kilowatt solid-state laser shooting down an unmanned aerial vehicle. The technology is apparently mature enough to be deployed as part of ships' short-range missile defenses, a role currently filled by the Basic Point Defense Missile System (based on the Sea Sparrow missile) and the Close-In Weapons System (based on a 20mm Gatling gun)."
*) Longer range
Not really. Lasers are strongly attenuated in air, especially in the humid air in marine environments. Trying to get around this problem is the reason we're just getting weapons like this now, as opposed to thirty years ago, and even now they're limited to short ranges.
*) Better accuracy
Yes and no. In order to heat up the target's surface enough to cause destruction, you either need to focus the laser on the exact same spot for long enough time, or just crank the power up and/or widen the beam enough so that it doesn't matter. The first has proven almost impossible, and so we've resorted to the second.
*) Unlimited ammunition
No. There are two kinds of lasers in consideration by the military: chemical and solid-state. Chemical lasers need tons of (duh) chemicals to form the reaction that generates the laser light, and when you run out, you're done shooting. Solid-state lasers require heavy amounts of electricity, which needs to come from somewhere.
*) No pollution from spent weapons
Again, no. Chemical lasers leave behind highly toxic waste products when the reactants are expended; that's the main reason why they're not in heavy use in the military today. Solid-state lasers leave behind pollution from whatever power source you use to generate the electricity.
I'm not saying lasers are awful tools, they're certainly useful in specific applications. But they're not the Wunderwaffen you're making them out to be.
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Presumably, the reason for replacing 20mm Gatling guns with lasers is, ultimately, about missiles. 20mm DU rounds, in quantity, move pretty fast compared to aircraft; but substantially less fast than one would like compared to decent missiles. Photons, while they lack the punch, are much zippier...
Now, since the only reason to adopt this(no doubt more expensive and power hungry) system is that offers hope against missiles, why testing against UAVs? Well, if I were an optimist, I would say that this is just one of the tests in the development process. If I were a pessimist, I would say that the fine folks at Raytheon are following in the time-honored tradition of anti-missile systems, and responding to the fact that the problem is hard by moving the goalposts until their system is up to the "task"...
Hopefully, well before deployment, it will see proper "red team"/"green team" type testing, where the opposing force, made up of the most devious and talented people at their disposal, is free to try every sneaky, optically confusing, silver plated, ablative armor protected, etc. hypothetical near future threat that they can come up with against the system. A very valuable learning exercise....
Bullets and lasers deliver this energy differently - the bullet's energy is transferred to the target in a much shorter time (milliseconds, I assume) which produces more chaotic results than the laser (for the same energy), which is waiting until the target ignites or a hole forms, wrecking the aerodynamics. Even so, I was curious how the energy payloads stack up.
A 32 kilowatt laser delivers (not surprisingly) 32kJ during a one-second pulse. I'm not sure how long this laser pulses, but from the video, it appears to be several seconds.
By way of comparison, a .50 Browning has a muzzle energy of 15kJ, which is about the same as a half-second exposure to the laser.
The Phalanx gun which this the laser purports to replace, on the other hand, shoots 20mm rounds - these could weigh 100g each, for a muzzle energy of 30.25kJ, comparable to the one-second pulse. Of course, the Phalanx shoots 50-75 rounds a second, for a total muzzle energy/second of firing of a whopping 2269kJ.
By coincidence, this is the same as the food energy in two Big Macs.
While energy weapons are gosh-wow sexy, their effects depend on maintaining the beam on the incoming missile for some undetermined length of time, until it either ignites the fuel or destroys the guidance systems. As modern ship-killer missiles tend to be supersonic, keeping the beam focused on a particular spot on an incoming missile is far from trivial, and of course will vary from missie to missile, so the defensive sytems have even more variables to account for. Phalanx and other gun systems use radar to track the incoming missile as well as the stream of outgoing rounds, and adjusts the aim until the tracks intersect.
Another problem is that destroying the missile's guidance system alone won't cut it. If it's already locked in the terminal phase chances are it will be blind, but still hit the target. This is the major reason that CIWS tend to use multi-barrel cannon with extremely high rates of fire (20mm/6,000 rounds per minute in the case of Phalanx, 30mm/4,000 rpm in the Dutch Goalkeeper system, which is built around the gun used in the A-10 aircraft). The intention is to cause as much structural damage to the incoming missile as possible, either destroying it or rendering it incapable of remaining on course, and with a missile like the SS-N-19 Shipwreck, which masses 7,000 kg and travels at Mach 2.5, even if the guidance systems and warhead are nullified, impact, even from large fragments, can still cause catastrophic damage to the defending vessel.
Then there's the energy requirements of a powerful laser, along with the transmission and control systems, massive cabling, fire-suppression, safety etc., versus self-contained units like Phalanx or Goalkeeper which basically just plug into a hole in the deck (oversimplification of course, but not by much). I am not a weapons expert, but personally I don't see the advantage of energy weapons over traditional gun systems for close-in defense.