(Source: Atomic Gator)
Goal is to reach a 50 KW blast sustainable for 2 minutes

Currently, U.S. Marine Corps' Humvees or trucks typically pack a light, mounted machine gun.  While good against ground based troops, that weapon is in danger of becoming obsolete in this era of modern drone based warfare.

I.  Navy's New Laser Project Takes Aim at Land-borne UAVs

Whether its captured U.S. drones that fall into the wrong hands or home-grown varieties under development in hostile nations like Iran, the Pentagon is concerned that UAVs may be used in future conflicts to spy on or attack U.S. troops.

Its current plan is to counter drones with high-energy lasers.  The U.S. Navy's Office of Naval Research has published details about its plan to award up to $400,000 for contracts to build a so-called "Ground-Based Air Defense Directed Energy on the Move" (GBAD-DE-OTM).

Lengthy name aside, the vehicle is basically an anti-UAV laser war wagon.  The goal is to build it up from pre-existing vehicles like military trucks or Humvees.  The ONR has ambitious plans for the power of the laser and duration of the blast.

The laser will replace the M60 (currently being phased out), M240G, or similar mounted projectile cannons.  The Navy's laser efforts are reportedly ahead of schedule, which is a bit of surprise given their ambitious goals.

II. From 2.5 kw Towards Megawatt "Superlasers"

Early efforts involved 2.5 kw trailer-mounted lasers being used by the U.S. Air Force to shoot down lightly armored UAVs.  A 2009 test at the Naval Air Warfare Center, China Lake, Calif. saw five successful kills.  The U.S. Navy has since fielded a more powerful 15 kw laser at sea, which can cut through 20 ft of steel per second.

The seaborne laser is used in the Navy's laser weapons system (LaWS), which is an upgrade to the projectile based MK 15 Close In Weapon System (CIWS), a.k.a. the Phalanx gun, a radar-guided autocannon.  Raytheon Comp. (RTN) is looking to replace current projectile Phalanx autocannons with either missile or laser-based varieties.

The Navy is also working with another defense contractor -- Northrop Grumman Corp. (NOC) -- on the boxy Maritime Laser Demonstrator (MLD), which is meant to target ships.  Several prototypes have been delivered, bumping the beam power, and the laser successfully braved choppy surf to sink a lightly armored boat target.  

MLD system
The Navy will field the MLD at sea on an active surface vessel for the first time later this year.
[Image Source: US Navy]

The $98M USD MLD project's goal for the next several years is to reach 100 kw using advanced solid-state lasers, then bump the power to megawatt-class designs with electron-injection lasers.  The Navy expects electron-injections lasers to be ready by the 2020s; a megawatt beam could theoretically damage enemy cruisers and other armored vessels.

III. Navy Wants 50 kw Laser War Wagon

On land, the Navy wants its wagon laser to weigh less than 2,500 lb and achieve a "minimum" 25 kw beam strength, capable of shooting down modestly armored enemy UAVs.  The long-term goal is to sustain a 50 kw blast for 2 minutes with optics capable of adjusting to "all environmental conditions" (humidity, smoke, etc.).  The beam is also expected to have a fast turn-around time -- ""a 20 minute recharge to 80% of total capacity (power and thermal)."

To get there the Navy will need to carry a lot of batteries and/or powerful chemical charges, likely.

The Navy solicitation does not constrain the users to the type of laser used.  That leaves two primary possibilities [PDF].  Modern fiber-lasers are typically around 25 percent efficient at converting DC current to light.  Thus a 50 kw, 2 minute blast would require over 6 kw-hours of juice -- or roughly 10 car batteries worth of power (car batteries are typically around 1.2 kw-hour theoretical capacity, 50% efficient in the real world).  However, fiber lasers are bulky so may not be applicable to a vehicle setting.  Chemical lasers (aka "solid state lasers") are perhaps a more likely possibility, but are expensive on a per-shot basis.

The biggest problem will likely be the cooling.  The Navy's seaborne 15 kw lasers already need heavy advanced cooling systems.  That will suck down yet more power, while increasing the system size and weight.

III. Laser Weapons Have Their Advantages

It's hard to say just how soon the GBAD-DE-OTM laser wagon will hit the battlefield, but it appears to be top objective for the Navy and the Marines, as military rivals like Iran race to develop war-ready UAVs.

The Navy does plan to deploy a seaborne laser aboard the U.S.S. Ponce later this year, according to Rear Adm. Matthew Klunder, the Navy’s chief of research.  The deployment will be the first time a laser weapon is actually tested on a mobile navel vessel -- the MLD test attack on the ship was performed by a weapon mounted to the stationary decommissioned destroyer USS Paul Foster, albeit performed at sea.

USS Ponce
The U.S.S. Ponce [Image Source: US Navy]

While expensive, finicky, and hard to reload, and constrained by line of sight, laser weapons do have some unique advantages.  On the ground they remove the friendly fire danger of a "shower" of unexploded rounds that miss the target and hit the ground, detonating. They also are faster allowing them to target fast moving targets like UAVs with precision strikes.

Nevin Carr, a retired two-star admiral and former head of the ONR, describes to Wired, "It’s a good capability for softer targets like UAVs [unmanned aerial vehicles] and boghammers — small, fast-swarming boats."

He says the costs may eventually become an advantage, given that the laser is powered by generated electricity.  He describes, "In a sense, it’s more economical — but more than just theoretically economical, it’s a way to have deeper magazines, because your fuel tanks become your mags. “Now that refueling becomes rearming, it changes the logistics trail.  Think of all the ships that carry weapons."

In addition to ground-vehicle and ship mounted lasers, the U.S. Air Force is also testing out airborne lasers.  The armed forces are also looking towards a variety of other future weapons like a locust-like swarm of small autonomous killing robotslightning gunsmicrowave Humvee cannons, and the ever-popular rail guns.

Sources: U.S. Navy via FBO, Wired, FAS

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