Military forces have been aspiring to fight at the speed of light ever since lasers were developed 60 years ago. So far, the services have succeeded in fielding lasers for targeting and other nonlethal purposes. These are helpful tools for troops on the battlefield, but far short of technologists’ desire of shooting down missiles, rockets, artillery and mortar rounds with destructive light energy beams.
Harnessing high-powered lasers in a deployable weapon system has remained an elusive endeavor outside of laboratory experiments and prototyping efforts. Scientists have struggled with the paradoxical challenges of making lasers small and hardy, yet powerful enough to destroy targets in seconds. Solutions are slowly forthcoming, but patience is running low for defense officials who want to start seeing results in operational settings.
The Navy expects to incorporate lasers onto most ship classes in its surface fleet, including amphibious ships, cruisers and destroyers. “The continuing goal is to deploy ships with an appropriate weapons mix, possibly one day including directed energy weapons, to engage and defeat any potential adversary across the spectrum of naval warfare,” said Rear Adm. Frank Pandolfe, director of surface warfare on the Navy staff.
Experts believe that of all the services the Navy holds the most promise for helping directed energy weapons become operationally viable systems in the near future. Its warships can provide adequate spaces for hosting the current generation of power-hungry and coolant-needy lasers.
Armed with guns and missiles, the Navy’s surface ships can defend themselves from current airborne and surface threats. But officials have been pushing research and development programs in directed energy in hopes of yielding future weapons to bolster ship defenses against new threats including high-speed boats and unmanned aircraft. Those efforts have blossomed into prototypes that are being tested this year.
The Naval Sea Systems Command in May demonstrated the feasibility of using commercial fiber lasers to knock down small unmanned aircraft from the sky. This fall, the Office of Naval Research plans to demonstrate a high-energy laser weapon system prototype at sea for the first time. If that demonstration proves successful at destroying a high-speed boat target, then Navy officials could decide to procure a system and become the first service to incorporate high-powered lasers into its weapon inventory.
Long the darlings of research laboratories and widely used in manufacturing, medicine and forensics, lasers come in a variety of wavelengths and power levels. The methods for creating and propagating those beams are often not conducive to operation in war zone environments. But recent advances in electric laser technologies are opening up some possibilities.
Lasers are generated inside a reflective optical cavity by passing light energy multiple times through a gain medium — a material in gas, liquid, solid or plasma state — which amplifies the light. Solid-state lasers rely on gain mediums comprising crystals that are “doped” with ions to help excite light particles to higher energy states.
A team from Northrop Grumman Corp. is developing a solid-state laser system for the Office of Naval Research’s maritime laser demonstration program. Powered by electricity, the system sends light through a series of microscope slide-shaped media of yttrium aluminum crystals doped with neodymium. The solid-state laser generates a 15-kilowatt beam, which is directed to the target by a set of optics designed to track the target, select an aim point and hold the beam on the aim point until the desired effect is achieved.
“It’s like a high-powered sniper rifle, except with much more range,” said ONR’s Peter Morrison, program manager, naval air warfare and weapons department.
The laser is based upon the same technology that the Northrop Grumman team previously developed for the Defense Department’s joint high-power solid-state laser program, said Dan Wildt, Northrop Grumman’s vice president for directed energy systems. That program last year achieved a power level of more than 105 kilowatts — a first for solid-state lasers — and the minimum required for military weapon applications. The light ray was produced via seven laser “building blocks” — groups of 15-kilowatt laser beams that were combined into one.
For the maritime laser demonstration prototype, engineers are using an eighth chain that was built but not needed for the program’s 105-kilowatt demonstration. More of the 15-kilowatt building blocks can be added to scale the maritime laser prototype power level up to address various threats, Wildt added.
The maritime laser’s beam control technology is derived from the Defense Department’s tactical high-energy laser program, a joint U.S.-Israeli effort that yielded a prototype that shot down a total of 46 rockets, artillery shells and mortar rounds in flight. Pinpoint accuracy and the ability to tailor lethality to the target give the maritime laser weapon an advantage over its kinetic energy brethren, said Morrison.
Engineers beefed up the laser’s optical mounts to operate in sea-state 3 environments and to survive in sea-state 5 conditions. Sea state is a scale that characterizes the frequency and height of waves. Sea-state 5 involves rough-looking waves that are eight to 13 feet tall.
The prototype in November will go to sea aboard a Navy vessel for demonstrations in the Pacific Ocean. It will shoot at small boat targets in a live-fire test area, officials said.
“This is really the first time we’ll take a laser system into that realistic environment with realistic targets on a real Navy ship,” said Morrison.
In a video from a previous test, the laser tracked a small boat target and maintained its crosshairs on the gunwale, or upper side edges of the vessel, at a distance of thousands of yards, Morrison pointed out.
“It’s ready to operate in the maritime environment,” said Wildt.
Engineers in June completed integration of the major hardware pieces. They are preparing the system for a land-based test that will fire at targets on the water prior to taking the laser to sea.
By 2016, the system could become an initial capability put onto Navy ships, said Morrison. “This is a pave-way program for Navy directed energy systems,” he said. “We’re definitely not talking megawatts of power, which we’ll have in the future. We’re not talking the most advanced [lasers] just coming out of the research labs. We’re talking about advanced technology mature enough to go to that marine environment.”
While developing the maritime laser, program officials looked at a large number of ship classes to evaluate whether such a system could be installed. “We found without exception that every ship class that we’ve looked at could accommodate an entry-level system based on this,” said Wildt.
The entire laser comprises a space not much larger than a table and fits inside a standard shipping container. “We can put everything except for the beam director in an optimal spot on the ship,” Wildt said. The beam director, which guides the high-energy laser onto a fine-point target, would have to be exposed to the outside environment. All of the other components can be stationed below deck.
The laser is designed to tie into the Navy’s existing shipboard combat systems, where a single operator can control its operations. The operator needs specialized training, similar to the instruction that Navy crews receive for the MK 15 Phalanx close-in weapon system or the MK 45 lightweight gun. Sailors will be able to maintain the laser themselves. “It won’t require a Ph.D. nuclear physicist right there babying it along,” said Morrison.
Concurrently with the maritime laser demonstration, the Navy also is funding the development of another laser weapon system for potential shipboard use. Officials at Naval Sea Systems Command initiated a program to develop a weapon system based on commercial fiber laser technologies. Fiber lasers are solid-state lasers that rely on optic fibers as the gain medium.
Navy engineers in May used a system comprising six fiber lasers strung together to shoot down two unmanned aerial vehicles flying in the maritime environment at San Nicholas Island, Calif. The 100-kilowatt laser’s electronics were integrated with the MK 15 Phalanx close-in weapon system, a 20mm rapid-fire gun found aboard most Navy ships.
The same laser last year shot down five UAVs during a test at China Lake Naval Air Warfare Center, Calif. The UAVs were made of carbon-fiber composites that are representative of the threat, said Capt. David Kiel, program manager for directed energy and electric weapons at Naval Sea Systems Command.
The existing low-fidelity prototype could be taken to sea by the end of 2012, or the program office could build a better prototype and take that to sea by 2014, said Kiel. If funding is secured in the Navy’s 2012 budget, the program office could field an initial capability as early as 2017.
The Defense Department in decades past pursued lasers to destroy supersonic targets in flight. The Navy succeeded in shooting down such targets in experiments. But the technology failed to transition to a weapon program. Other efforts, such as the Air Force’s pursuit of the megawatt-class airborne laser as an anti-missile capability aboard a 747 aircraft, have been under development for years. But that program was highly criticized and eventually came under fire by Defense Secretary Robert Gates, who cut funding for a second prototype last year.
With the services under pressure to reduce spending, programs attempting to develop new weapon systems are falling under increased scrutiny. Budgetary experts warn that the Navy’s maritime laser programs are no exception.
“In the present fiscal and economic climate, this is really not a propitious time for a major new weapons system like that,” said Barry Watts, senior fellow at the Washington-based Center for Strategic and Budgetary Assessments. Laser weapons, he said, would be most effective against an enemy onslaught of precision weapons, such as guided missiles, rockets and mortars.
“Until something really nasty like that happens, it will be a lot of research and development and demonstrators,” said Watts.
Navy officials contend that a laser weapon system could allow the service to buy fewer missiles and permit ships to access areas that may have been off-limits previously because of their traditional shipboard firepower.
In order for laser weapons to find their way onto ships, the technology has to be technically mature, affordable and fill a performance gap, said Stan Crow, business development director for directed energy at Northrop Grumman. “Maybe it’s a perfect storm right now that we haven’t had before, where all three of those criteria are in place,” he said.
The maritime laser team believes that the at-sea testing will demonstrate the readiness of solid-state laser weapon systems to begin transitioning to the fleet.
“The Navy is not going to procure any system that is not operationally viable,” said Pandolfe. Officials are closely watching the demonstrations and will be evaluating the capability of directed energy systems against operational requirements. Lasers would not supplant existing kinetic energy systems but instead would complement them, they said. The Navy has not made any decisions so far to put lasers aboard fleet units, but a study on the future of maritime directed energy weapon systems is ongoing.
In the meantime, work progresses on both maritime laser demonstration and the fiber laser. Though the two programs are being developed with the same goal in mind — to transition to the fleet — there is more of a collaborative spirit in play as they share systems, components and notes.
“We say that they’re two different systems and two different options for the Navy,” said Morrison.
Solid-state lasers are more powerful and have better beam quality than their fiber laser counterparts. But fiber-optic systems in the future ought to be cheaper, Morrison said. While the fiber laser is being integrated with an existing shipboard weapon system, the maritime laser is likely to remain a separate system unto itself. Keeping a laser weapon independent from the shipboard kinetic system has advantages, such as not having to contend with vibration, smoke and particulate issues from firing the gun, Morrison said. But integrating the fiber laser with the gun system will help introduce directed energy weapons to the fleet at a much lower cost, Kiel said.
One of the challenges for lasers is that they are notoriously power hungry and require cooling because so much of the energy is lost through heat. To run a laser typically requires about four to five times more energy than what the system emits as light. But increasing the efficiency to thirty to 45 percent is not outside the realm of possibility for directed energy systems, noted Morrison.
Most Navy ships can generate megawatts of electricity for powering various radar, electronic warfare and combat control systems and produce enough water to cool all of their systems.
Today’s warships have enough power to support a 100-kilowatt laser, said Kiel. Any surface combatant large enough to accommodate the close-in weapon system could also carry the fiber laser, he added.
The Northrop Grumman team said that the maritime laser demonstration’s design will accommodate upgrades to new solid-state laser technologies. If and when the Navy sets requirements, the team would use its scalable approach to determine the right number of laser chains to build to achieve adequate power levels.
Both laser teams remain optimistic about the prospects for directed energy weapons aboard ships.
“We believe it will pave the way for free electron laser, and a laser in every airplane someday,” Kiel said.