The U.S. Navy declared its first laser weapon operational on board the USS Ponce (AFSB[I]-15), shown here, in 2014 after several months of testing. An
advanced version of that system will be tested by the USS Portland (LPD-27) later this year.
Defense contractor Lockheed-Martin received a Navy contract this year to deliver a high-energy shipboard laser system with two separate but linked capabilities by 2020. The “high energy laser and integrated optical-dazzler with surveillance” (HELIOS) system will combine the ability to attack and destroy unmanned aircraft and small boats with an intelligence, surveillance, and reconnaissance (ISR) capability linked to a long-range, high-resolution camera. The camera system includes a laser with the ability to damage—“dazzle”—sensors on unmanned aircraft.
The Navy previously deployed an operational laser to counter small boats, on board the interim afloat forward staging base USS Ponce (AFSB [I]-15) from 2014–2017. When the Navy first assessed the Laser Weapon System (LaWS) in 2014, it realized that the optical aiming system was valuable for examining and classifying potential threats. (The Office of Naval Research plans to test an upgraded prototype of LaWS on the USS Portland [LPD-27] later this year.) HELIOS, unlike LaWS, will be designed for eventual integration with the Aegis system on board cruisers and destroyers and may turn out to be the first of a series of increasingly powerful directed-energy weapons.
The initial emphasis on countering unmanned aircraft reflects the need to be able to engage large numbers of targets. Though an Arleigh Burke– (DDG-51) or Ticonderoga- (CG-47) class ship’s missiles could destroy almost any unmanned aircraft, in most instances the cost of the missile is disproportionate to the threat, and the number of missiles is limited. An enemy might employ inexpensive drones either to exhaust a ship’s air defenses or to threaten directly the ship’s sensors or hull. Low-performance, flimsy drones are inexpensive and often can loiter for extended periods. Small boats operating in swarms can likewise saturate close-in defenses. Lasers in effect have bottomless magazines, bounded only by the electrical output of the ship.
The Navy and other services also hope that lasers will provide a capability to respond to high-performance targets, particularly missiles. An antimissile laser system would not need to distinguish between decoys and actual missiles and instead could employ its nearly unlimited capacity to attempt to destroy all of them without needing to husband scarce defensive missiles.
The promise of electric weapons—including not only lasers but also particle beams—largely motivated the Navy’s move toward all-electric ship propulsion with the Zumwalt- (DDG-1000) class destroyers. The hope was that in combining propulsion with auxiliary power plants, ships would gain electric power capacity sufficient for such weapons.
With both the Russian and Chinese governments developing hypersonic antiship cruise missiles, the need for new antiaircraft weapons has become more urgent. A defensive missile ought to be at least as fast as its target, so that it can maneuver into position to intercept. (Faster is better.) Navy Standard Missile air defense interceptors have speeds ranging from Mach 2.5 up to about Mach 4, depending on the specific variant. (Antiballistic missile interceptors are much faster.) “Hypersonic” missiles by definition travel no slower than Mach 5, with China’s DF-17 having a claimed speed of Mach 10. At such rates of travel, the time available for an engagement would be extremely short. A defender responding to a Mach-10 missile launched at a range of 1,000 miles would have eight minutes to acquire, classify, engage, and destroy the threat.
To turn the hope of instant antimissile firepower into reality, the Navy and contractors have to solve several problems.
For many years, the most pressing problem for laser designers was power generation, and chemical reactions appeared to offer the best solution. Power affects two aspects: range (the laser beam loses intensity as it travels) and destructiveness (the degree to which the laser can damage or destroy a target). The Mid-Infrared Advanced Chemical Laser (MIRACL), developed by the Navy in the 1970s, produced megawatt-scale power using deuterium fluoride, and such lasers were proposed as a weapon for Knox- (FF-1052) class frigates. But the exhaust proved too toxic for use on ships. (Whether or not the laser would have killed an incoming missile, it surely would have killed everyone on the bridge.)
LaWS and HELIOS solve the power problem by generating multiple smaller beams from solid-state fiber lasers and grouping them to produce a useful amount of energy at the focal point. The basic principles of these systems should scale up to create still-more-powerful lasers with more efficient conversion of electrical energy into laser energy. (LaWS generated as much as 100 kilowatts [kW] in testing on the Ponce but officially was rated for around 30 kW.)
A second problem related to the damage a laser could inflict—would it pack enough power not only to reach but also to destroy or disable a target? Soviet antiship missiles—about the size of fighter aircraft—were vulnerable to U.S. surface-to-air missiles, which would shred large sections of their targets. Whether a single beam (MIRACL) or a “gang” of beams (LaWS and HELIOS), a laser weapon inflicts damage by heating a small spot on a target. In physics, power is a time-based function: The longer a beam stays on a spot, the more damage it inflicts. The more energy in the beam, the less time it needs to stay on the target. In just the right place, even a very small hole can be devastating, but elsewhere it might not be enough, especially for older missiles primarily made of metal. However, modern materials such as fiber-reinforced composites may be more vulnerable, as heating may cause delamination and lead to structural failure.
Particularly at sea, there is a third problem. As the laser beam burns its way through the air, it may bend. At low altitude close to sea level, the atmosphere above the water is layered as a result of several causes, including evaporation. These layers refract, or bend, light. (Desert mirages and shimmering roads also are caused by refraction.) This effect is apparent when, for example, a ship is visible despite being beyond the horizon. Radar suffers heavily from this sort of refraction, called ducting.
Laser refraction is more complicated than that of ordinary visible light because the laser beam heats the air it passes through, altering the structure of the atmosphere. In other words, whatever refraction already exists is made worse by turning the laser beam on. It will require significant computational power to compensate for this—suggesting an additional reason to integrate HELIOS with the Aegis system and its substantial microprocessor capability.
HELIOS probably is conceived as an initial step toward something more powerful. Its range will be limited by its relatively low power (media reports suggest 60–150 kW), and it is unclear how capable it will be of compensating for refraction and other atmospheric effects. But positive results from the upcoming tests might lead fairly soon to a HELIOS successor replacing the current Phalanx and SeaRAM close-in weapons—and longer term to a directed-energy weapon capable of defeating hypersonic antiship missiles.
Dr. Friedman is the author of The Naval Institute Guide to World Naval Weapon Systems, available from and published by the Naval Institute Press at www.usni.org.