Developing a High-Energy Laser for the Navy

141115-N-PO203-057The Navy’s new Laser Weapon System became the world’s first deployed tactical laser weapon aboard USS Ponce (AFSB [I] 15) at the end of 2014.  (Photo by John F. Williams)

By Peter Morrison and Dennis Sorenson

We all know the old saying about the unfortunate soul who brought a knife to a gunfight. In the not-too-distant future, we should be able to say we bested our adversaries because we had lasers and they showed up with only a gun. As former Chief of Naval Operations Adm. Gary Roughead said, “I never, ever want to see a Sailor or Marine in a fair fight. I always want them to have the advantage.”

Laser weapons will give warfighters options unlike any other system. The same weapon that can be used to identify and then issue a non-lethal warning to an approaching unmanned aerial vehicle can then set a drone ablaze and send it crashing to the ground. With lasers, aim becomes more precise and engagement happens at the speed of light. This goes beyond “fire and forget.” This is all about knowing before you fire, knowing as you are firing, providing the warfighter with a graduated response, and then knowing and having evidence that you were effective in your last shot.

The military began experimenting with laser weapons in the late 1970s. Carbon dioxide lasers were initially used to engage airborne and land targets. Although they performed efficiently at megawatt output levels, these systems often were very large, difficult to integrate, costly, and had insufficient target engagement ranges. With the advent of solid-state laser technologies approximately 10 years ago, the Defense Department shifted its focus away from chemical lasers. Although producing considerably less power than chemical lasers, solid-state lasers—which use solid mediums such as glass or crystal rather than a gas or liquid to initiate the lasing process—require only electricity and cooling to operate. The technologies used to develop solid-state laser weapon programs began with the Department of Defense High-Energy Laser Joint Technology Office program called the Robust Electric Laser Initiative, which fostered technology development for several types of lasers in cooperation with industry.

High-energy laser weapons cost about $1 per shot to fire—a highly cost-effective approach for countering the threat from unmanned aerial vehicles, which can be manufactured for as little as $50,000 apiece. Defending today’s warships with only guns and missiles is a very expensive means of fighting inexpensive threats. A laser would modify this equation in the defender’s favor by giving ships what the Navy calls a “deep magazine,” reducing the need for replenishing. A ship’s existing electrical system can power the laser, and missiles and ammunition can be saved for use against larger and more difficult targets, such as manned aircraft and ships. Laser weapons complement kinetic weapons currently aboard surface combatants and offer a few specific advantages, such as the ability to:

• Engage with precision without the associated collateral damage of an exploding warhead—and firing depth is limited only by power and cooling
• Offer a measured response, allowing friendly forces first to warn a threat and later to change to a lethal engagement if the threat does not heed the warning
• Complement conventional kinetic-energy weapons such as guns or missiles through accurate laser targeting, ranging, and illumination
• Achieve significant cost savings—against specific threats, the cost per engagement is orders of magnitude less than comparable missile engagements.

ENABLING TECHNOLOGIES

Laser technologies have many commercial applications and provide significant benefits to society. Industrial lasers are commonly used to weld, cut, and anneal metal structures to improve durability. Low-power lasers are commonly used for communication or precision distance and angular measurements, such as surveying. Medical uses for lasers are common for surgery and to improve eyesight. Emerging uses of lasers include direct transmission of energy that can be converted into electrical power.

The ability to field high-energy laser systems has been aided by the rapid and substantial improvements of high-power fiber lasers (which are used to form the laser beam) over the past few years by the commercial manufacturing and telecommunications industries. During testing two years ago, the fiber lasers used did not allow a good quality beam to be formed. The latest fiber lasers permit a 10-fold improvement in beam quality and a much increased effective range.

The Office of Naval Research (ONR) maintains a broad portfolio of directed-energy weapon programs comprising shipboard, airborne, and ground-based systems. The way forward toward operational capability is integrating seaworthy and affordable systems through partnerships with the Naval Sea Systems Command, Naval Air Systems Command, Defense Advanced Research Projects Agency, and other services.

Recent Navy investments in laser technology include the ONR-funded demonstration of the first high-energy laser aboard a Navy surface combatant at sea, as well as demonstrations and investments in the Laser Weapon System and the Mk-38 Tactical Laser System. ONR continues to invest in rapid-fielding initiatives and technical demonstrations, including a successful test of the Laser Weapon System against unmanned aerial systems during exercises off the coast of Southern California in 2012.

These efforts highlight the Navy’s ability to prototype, rapidly field, and demonstrate shipboard high-energy laser systems. Widespread use of directed-energy weapons aboard Navy and Marine Corps platforms will continue to be introduced as the technology matures.

WHAT IS THE NAVY DOING TODAY?

The focus of the ONR Solid-State Laser program is to address threats such as small suicide boats carrying explosives, intelligence/surveillance/reconnaissance and unmanned aerial systems, or inexpensive armed drones. As power levels increase, the potential exists to defeat more difficult targets—threats aimed at the Navy’s surface combatants, amphibious ships, and aircraft carriers. The precision of solid-state lasers and the low cost per shot make these systems an effective and affordable way to counter many potential threats facing deployed naval forces.

Through careful planning, developing key technologies, applying lessons learned from two at-sea demonstrations over the past two years, and leveraging investments made through other Defense Department services and agencies, the U.S. Navy has significantly improved the practicality and capability of shipboard high-energy laser systems. These improvements have resulted in lasers with increased ruggedness, power, and beam quality, which has yielded improvements in laser weapon system overall effectiveness, increased engagement ranges, and decreased time to defeat targets.

Our nation’s adversaries are pursuing inexpensive ways to try to restrict our freedom to operate. Spending about $1 per shot of a directed-energy source that never runs out makes more sense than firing costly munitions at a $50,000 threat.
—Former Chief of Naval Research Rear Adm. Matthew Klunder

In 2014, Naval Sea Systems Command installed a solid-state laser gun aboard USS Ponce (AFSB[I] 15) for a deployment in the Arabian Gulf. Operational tests are under way with this weapon, and the knowledge gained will help to develop a prototype system that can be tailored for any ship, from littoral combat ships to destroyers.

“This is a revolutionary capability,” said former Chief of Naval Research Rear Adm. Matthew Klunder. “This very affordable technology is going to change the way we fight and save lives.”

The 30-kilowatt Laser Weapon System is a capability demonstrator that bundles six commercial fiber lasers. Their beams converge at the target, which is burned or ablated (i.e., the removal of a material’s surface). In demonstrations, earlier versions of the system downed several unmanned aerial vehicles and disabled a number of small boats. This team effort brings together the best talent from ONR, Naval Sea Systems Command, Naval Research Laboratory, and Naval Surface Warfare Center Dahlgren Division to make powerful directed-energy weapons a reality.

LASERS OF THE FUTURE

ONR’s Solid-State Laser Technology Maturation (SSL-TM) program is focused on developing the next generation of high-energy laser weapon systems and transitioning that technology to an acquisition program of record. SSL-TM’s goal is to design and build an advanced development model prototype solid-state laser weapon (or weapons), install it on a naval vessel, and test it at sea by 2016.

Data regarding accuracy, lethality, and other factors from Ponce’s deployment will guide the development of the SSL-TM weapon(s). The program is made possible because of collaboration between ONR, Naval Sea Systems Command’s Directed Energy and Electric Weapon Systems Program Office, and Naval Surface Warfare Center Dahlgren Division and the leveraging of contributions from the Department of Defense’s High-Energy Laser Joint Technology Office.

Three Navy contractors—Raytheon, Northrop Grumman, and BAE Systems—were awarded contracts to develop different concepts of solid-state laser weapon prototypes between 100—150 kilowatts. As a result of LaWS performance and knowledge gained, new solid-state-based high-energy laser weapon systems with improved effectiveness could be demonstrated in an operational setting on destroyers or littoral combat ships in approximately five years. If all goes well, full-scale deployment of a solid-state laser weapon aboard a ship could become a reality in the 2020s.

REMAINING CHALLENGES
In the near term, many challenges remain to develop and operate high-energy laser systems in the maritime environment that are unique to the Navy and Marine Corps. Among these challenges is dealing with the heat generated as power levels increase. A second issue is packing sufficient power on the platform, which will require advanced battery, generator, power conditioning, and hybrid energy technologies. Current laser technologies are approximately 30 percent electrically efficient. Corrosion and contamination of optical windows by shipboard salt spray, dirt, and grime also are technical challenges. In addition, atmospheric turbulence resulting from shifting weather conditions, moisture, and dust is problematic. Turbulence can cause the air over long distances to act like a lens, resulting in the laser beam’s diffusing and distorting, which degrades its performance.

Much progress has been made in demonstrating high-energy laser weapon systems in the maritime environment, but there is still much to be done. Additional advances will be required to scale power levels to the hundreds of kilowatts that will make highenergy lasers systems robust, reliable, and affordable. Higher power levels are important for the ability to engage more challenging threats and improve the rate and range at which targets can be engaged.

The programs managed by ONR are addressing these remaining issues while positioning this important warfighting capability toward an acquisition program and eventual deployment with the fleet and force.

About the Authors:

Peter Morrison is the Office of Naval Research’s program officer for the Navy’s Solid-State Laser program. Dennis Sorenson is a contractor with the Office of Naval Research.