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Navy declares weapon is ready for defensive use against hostile foreign craft

The U.S.S. Ponce (AFSB(I)-15), a U.S. Navy Austin-class floating dock, has been floating the high seas since 1971, but after three decades it's carrying out perhaps its most exciting mission, testing out the Navy's Laser Weapons System (LaWS) in live firing tests at sea.  Now the Navy is sharing details of the results and bragging how well its most mature direct energy weapon performed.

I. LaWS vs. MLD -- What's Under the Hood

Unlike chemical lasers which need to be recharged with expensive and often toxic gases, solid state lasers (SSLs) don't need recharging.  Chemical lasers produce their high energy beam via a violent reaction which produces photons as a byproduct.  By contrast an SSL produces photons via passing electricity from an external power source through a glass or crystal.  The active media (the crystal or glass) is typically doped with rare earth elements.

Pumped laser design
The solid state laser (SSL) design uses doped fiber optics to create high energy (HE), high intensity (brightness) laser beams. [Image Source: Ching Na Ing; Thesis]

LaWS is a fiber laser (FL), a special kind of SSL).  More precisely, the LaWS system is believed to use double-clad fiber optics, a scheme where light is pumped itno the system from a high power, low-brightness diode laser.

Fiber solid state laser
Dual-clad fiber lasers can reach a maximum power of 10 kW in lab testing.
[Image Source: Laser World]

Light is pumped into the larger radius undoped standard glass fiber optic core.  Internal reflection funnels some of the photons into an inner core doped with ytterbium, a rare earth element.  The ytterbium produces more high energy photons in a multiplicative effect that increases the brightness (intensinty) of the light, amplifying its power.

LaWS uses six 5.5 kW fiber laser beams, which are incoherently combined to form a beam with a theoretical maximum outputted power of 33 kilowatts (kW).  During sea firing tests it's believed to be operating in the 10-15 kW range.  It has roughly a 25 percent wall plug efficiency and requires 400 kW of input power to operate.

LaWS graphic
Laws fires six incoherently combined beams at its targets. [Image Source: Unknown/Bing Images]

The fiber lasers used in LaWS are virtually identical to those used in commercial welding applications.

During the incoherent combining process, sextet of beams is focused upon the target object via the beam director.  The outputted beams are in the near infrared (reddish) range at 1.06 µm.  This is a good range to be at because beams at this range suffers relatively little atmospheric absorption other than small transmission losses from absorption by water molecules.

The laser is designed by Raytheon Comp. (RTN), under an $11M USD contract that was awarded in 2010.  Overall the system cost around $40M USD in defense contracts to build.

The design is subtly different from the Maritime Laser Demonstrator (MLD), a rival design which is being developed under a $98M USD Northrop Grumman Corp. (NOC) contract.  The MLD is a somewhat different kind of laser -- a slab solid state laser (SSSL).  The MLD combines seven 15 kW beams coherently to produce a 105 kW beam.

MLD at sea
Northrop Grumman's 105 kW MLD uses slab solid state lasers and coherent beam combining -- a more complicated and difficult design to ready for field action. [Image Source: U.S. Navy]

The MLD is not only more powerful than LaWS; it also has a better beam quality, with an estimated quality of 3 or lower.  LaWS is estimated to have a beam quality closer to 15-17.  Beam quality is an important determinate of how much power a laser loses as it travels through the atmosphere.  The higher the number, the lower the quality and the more the scattering and power loss.  With that in mind LaWS is confined to a rangle of a couple kilometers, at most, where MLD could potentially fire at targets a couple miles away.

The big problem with the MLD is that it relies on more expensive technologies and finnicky technologies (namely high energy SSSLs and coherent beam combining).  Aside from the cost, the SSSLs are harder to cool, which is likely one reason we haven't seen the MLD fielded on an active naval vessel (it's done firing tests at sea, but on a static platform).


II. Theatrics and Endurance Testing

LaWS is the Navy's less power, lower quality direct energy beam weapon, but it's cheaper, easier to cool, and more reliable.  Thus it's not surprising that it would be chosen over the MLD for execises on the U.S.S. Ponce, an active ship.

LaWS
LaWS is mounted on a structure above the bridge of the U.S.S. Ponce. [Image Source: ONR]

The U.S. Office of Naval Research (ONR) announced on Wed. that LaWS had wrapped up several months of testing, including live fire exercises at sea.  This is an important milestone as never before has any nation's navy fielded such a laser weapon in live testing at sea aboard an active naval vessel.

The latest round of test follow live fire tests in 2011 against boat engines.  Those tests were performed from a decomissioned destroyer stalled at sea.  Similar tests were performed int 2012, shooting down UAVs.

The new test sent it on a course to the Persian Gulf, also known as the Arabian Gulf.  

Persian Gulf
LaWS is being tested in the Persian Gulf, which borders Iran. [Image Source: Focus Group Persian Gulf]


Most of the nations boardering the Persian Gulf are among the U.S.'s allies in the Middle East -- Saudi Arabia, Qatar, the United Arab Emirates, Bahrain, Iraq and Kuwait.  But the nation with the biggest stretch of coastline bordering the Persian Gulf -- Iran -- is both technologically advanced and somewhat hostile to the U.S.

The presences of LaWS may have been partially a theatrical gesture towards Iran who has been actively developing combat UAVs, including one design that was colorfully dubbed "the Messenger of Death".  But theatrics aside, this long term deployment was also a very serious test to see how the LaWS system would hold up during a multi month deployment that exposed it to the elements.

Iran drone bomber
Iran is testing a drone bomber around the same region.  The drone's name translates roughly to "Messenger of Death". [Image Source: Reuters]

By all accounts, LaWS performed remarkably well in the harsh ocean environment.  The release said the LaWS system performed above expectations both in terms of reliability and maintainability.  The ONR was particularly proud of how well the system did in adverse weather conditions, including "high winds, heat and humidity."

III. LaWS Scores More Hits, But There's a Bit of a Catch

In a live fire exercise the LaWS system is seen tracking and destroying a UAV and two seaborne targets.  



The first sea target was an exposed fuel tank be towed on a floating platform behind a speedboat.

LaWS sea target
[Image Source: U.S. Navy/YouTube]

The second target was a fuel tank mounted to pipes held up over the speedboat by a frame.  

LaWS sea target
[Image Source: U.S. Navy/YouTube]

The airborne target was a ScanEagle, a mid-size fixed-wing drone made by the Boeing Comp.'s (BA) Insitu unit.  The ScanEagle is mostly used by the Navy as a surveillance tool.  The ScanEagle in the test was humorously modified to carry a small warhead on its nose. Clearly that helped LaWS when it came to the shootdown, which it successfully performed.

LaWS ScanEagle
[Image Source: U.S. Navy/YouTube]

Clearly the trickery used to help LaWS with the shootdowns calls into question how well it would do in a scenario where it doesn't have such a juicy target.  That said, the test wasn't completely unrealistic, as cheap speedboats like the ones commonly used in terrorist attacks on warships or in piracy often have exposed engines and/or fuel tanks.  Further, if it's a terrorist craft, it's likely loaded with explosives.

The ONR's chief of naval research, Rear Adm. Matthew L. Klunder said of the test:

Laser weapons are powerful, affordable and will play a vital role in the future of naval combat operations.  We ran this particular weapon, a prototype, through some extremely tough paces, and it locked on and destroyed the targets we designated with near-instantaneous lethality.

At less than a dollar per shot, there's no question about the value LaWS provides.  With affordability a serious concern for our defense budgets, this will more effectively manage resources to ensure our Sailors and Marines are never in a fair fight.

The plan is to by around 2020 deploy a second-generation LaWS system in the 60-100 kW range aboard the upcoming Littoral Combat Ship and on Arleigh Burke-class guided-missile destroyers.

IV. A Gun Fight: How Lasers Stack up to Kinetic Machine Gun Autocannons

The Navy is lusting for direct energy weapons due to its need for a weapon to effectively counter the growing threat posed by small, fast attacking ships and enemy UAVs.  Such targets can, of course be countered with traditional mounted machine guns -- which typically fire 20 or 25 mm shells.

LaWS targets
LaWS is designed to counter UAVs and small ships. [Image Source: ONR]

When it comes to neutralizing small targets, missiles are a high accuracy solution but not very cost effective.  Missiles can run anywhere from hundreds of thousands into the millions of dollars for more sophisticated tracking missile designs.

Machine gun autocannons cost an order of magnitude less, but also suffer some accuracy issues.  Their costs are primarily in the cost of ammo, which while relatively inexpensive is definitely not free.  Machine gun autocannons can fire anywhere from 100 to 1,000 rounds in different scenarios to neutralize a target.  All those shells can cost anywhere from $5,000 to $50,000 USD per neutralization [source].

US Navy shells
U.S. Navy autocannons typically fire 25 mm shells. [Image Source: Engaging Photography]

By contrast, direct energy weapons could neutralize many targets for just dollars.  The LaWS system is powered by a small diesel generator and is separate from the ships' main power systems.  The laser is only limited by the amount of fuel that can be brought to power it.  The ONR estimates that during the recent testing, the solid state laser cost roughly $0.53 USD worth of fuel per shot -- less even than a 20 mm chain gun.

The laser system has a few additional advantages over kinetic alternatives.  First, if the target is overhead, (e.g. a drone hovering over the ship), the laser can fire at will, without fear of shells that miss falling down and damaging the deck.  Second, it can potentially damage small, lightly armored targets that are wildly maneuvering -- for example, a small drone with a bomb strapped to it, that's performing evasive maneuvers.

Another advantage of the laser systems are that they can be operated at lower power for a nonlethal deterrent.  Such a solution could use a blinding, but non-lethal pulse to blind or "dazzle" the pilot of an enemy craft.  Similar tactics could be used on UAVs' optics, leaving them open to conventional fire.

Lastly, as long as the laser doesn't overheat it can continuously fire, where as autocannons need to be reloaded.  When dealing with a swarm of airborne or seaborne threats, the laser's lack of reloading needs could free up crew to perform other duties like repair and targeting,

Accuracy-wise lasers can be more precise than kinetic autocannons in good circumstances.  In adverse weather, problems such as thermal bloom, turbulence, atmospheric scattering, and atmospheric absorption can cumulatively make the laser less accurate than an autocannon.  Higher energy lasers could perform somewhat better in such cases, but it's a serious limitation for the craft.

A lesser limitation is the need for line of sight.  This prevents lasers from competing with heavy artillery functionality.  But lasers lack the distance and power of heavy kinetic weapons, so that's kind of a moot point.  Machine gun autocannons may not technically suffer line of sight issues, but at sea these issues seldom occur at such close ranges.  Further, with small arms, generally you want to see what you're shooting at, whether you're using a kinetic weapon or a direct energy one, given the risk of collateral damage.


Phalanx cannon
A machine gun autocannon is seen here, firing using the Phalanx CIWS. [Image Source: Navy]

One thing to point out is that there's a fair amount of synergy and reuse between machine gun autocannons and lasers in terms of targeting systems.  LaWS actually uses the same Phalanx Close-In Weapons System (CIWS) as kinetic turrets.  The ubiquitous targeting system -- designed by General Dynamics Corp. (GD) and Raytheon -- is mechanically compatible.

The only major modification necessary is on the software side as kinetic tracking algorithms are required to adjust to account for the time it takes for the shell to reach the target.  By contrast, a laser's beam reaches the target virtually instantly, so the Phalanx CIWS can use a simpler naive tracking alogrithm.

The compatibility of LaWS and the Phalanx CIWS could lower the cost of retrofitting existing warships with direct energy weapons.  It also opens the door for hybrid kinetic weapon plus direct energy weapon solutions.  Boeing and BAE Systems plc (LON:BA) tested a hybrid system which paired a BAE Mk-38 autocannon with a 10 kilowatt laser.  Developed under a $2.8M USD contract, the system was tested off the coast of Florida in Sept. 2011.

V. LaWS is Authorized to Lay Down the Law, Fire in Self Defense

Aside from MLD and aWS, another type of laser -- the free electron laser (FEL) -- is undergoing development in the U.S. military labs.  Nearly scrapped by Congress, this project is pricey and years away from possibly producing feasible weapons.  But experts say it's the best hope of creating a direct energy weapon with a high quality beam in the megawatt range.  Such a beam could do real damage, even to lightly armored vehicles, boats, and planes.
Free Electron Laser
Free Electron lasers are pulsed through a magnetic undulator, pumping up the power and brightness.
[Image Source: Eli-Beams.edu]

Until the development of the FEL matures, though, the various armed services will be looking to field cruder fiber optic or slab solid state laser designs.  The deployment of LaWS aboard the U.S.S. Ponce is far from over.  It will accompany the vessel for at least the next year and a half, during which time more tests are expected to be performed at sea.

Thanks to the success it saw in recent tests, LaWS has been declared an "operational asset", which is basically the Navy's way of saying it's ready for real world combat.  It's authorized to fire in "self defense" against a variety of hostile craft, including UAVs, helicopters, and fast patrol craft.

LAWS in action
LaWS has yet to see real combat at sea. [Image Source: AP]

It's possible it could even skirmish with pirates that frequent the seas around the Arabian peninsula and nearby Africa.  It could also see hostile encounters with Iranian drones, which are increasingly attempting surveillance flyovers of U.S. Navy ships in the Persian Gulf.

USS Ponce
LaWS is now officially part of the defensive arsenal of the U.S.S. Ponce and may see combat action.
[Image Source: U.S. Navy]

During its remaining year of action at see, the current LaWS system is expected to gradually be tested at higher firing powers.  This process should test the limits of the onboard cooling system and the fiber optics.

By the time LaWS is reevaluated near the end of 2015, it should have seen a lot of interesting action.  Depending on how all that goes, the Navy may opt to purchase more LaWS weapons for other vessels and to deploy them in a more permanent capacity.

Source: ONR





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