Lasers at Sea Part 1

One of the weapons currently on the horizon of naval warfare is the laser. While laser weapons have been discussed since the 60s, and the first laser weapons went to sea in the early 80s, it's only in the last decade that there's been a serious prospect of deploying lethal lasers in action. But there's a great deal of confusion around the potentials and limitations of laser weapons. How do they work, and what will they do to naval warfare?¹

An Argentine aircraft attacks the British in the Falklands

Before I get to those questions, I should probably address something I'm sure many of you are asking about. Yes, the first operational laser weapons were deployed in the early 80s, aboard the ships of the Royal Navy. This device, known as Outfit DEC, was not designed to directly damage attackers. Instead, it was a blue-light optical dazzler, designed to blind the pilots of incoming aircraft. Even looking away wouldn't be enough, as the wavelength would cause the canopy to fluoresce. It is claimed that some ships deployed with Outfit DEC to the Falklands, and there are persistent rumors that several Argentine aircraft crashed while attacking the fleet as a result of their pilots being blinded. I am skeptical of this, as the air war has been extensively studied and every loss analyzed in detail. No Argentine aircraft flew into the terrain inside San Carlos water, and reports on Outfit DEC don't give the names of the pilots involved.²

The British kept Outfit DEC in service for another two decades, deploying it during the Persian Gulf War, although there are no solid reports of combat service. Growing concern over the danger of lasers causing permanent blindness lead to the Protocol on Blinding Laser Weapons in 1995, which bans any weapon intended to permanently blind the target. Temporary dazzlers are still allowed, and have seen some service, and this prohibition also does not apply to laser weapons intended to attack optical equipment, opening the way for systems like the Directional Infrared Countermeasures (DIRCM), a laser designed to blind IR-guided anti-air missiles. Of course, if a person were to end up looking at one of these systems, they would probably be blinded, and it's unclear to what extent laser attacks on devices like binoculars are allowed. In practice the effects of the ban are further limited because many systems designed for other purposes, such as rangefinding, are also capable of causing blindness at close range. Lasers are also a deniable weapon in operations short of war, and there are persistent reports of Russian and Chinese vessels and aircraft using lasers against ships and aircraft operating nearby. To counter this, laser-resistant glasses, which filter out specific frequencies, were developed and have been in reasonably wide use for the last quarter-century.

DIRCM turret on a C-17

But dazzlers are ultimately rather boring, and the new wave of weapons offers the capability to do direct damage. But before we start looking at these systems in detail, it's worth going into the basics of lasers and laser weaponry. Lasers are coherent light, with all of the waves lined up with each other, which allows them to be focused much more precisely than ordinary non-coherent light. A laser weapon requires both a system to generate a high-powered beam, and optics to direct said beam onto a target that could be several miles away. Until recently, high-powered lasers had to get their energy directly from chemical reactions, which meant using toxic and dangerous fuel. The current generation, drawing on technologies developed for the manufacturing industry, are solid-state and require only electricity and cooling, making them far easier and cheaper to operate. One of the key attractions of laser weapons is the possibility of disabling targets for a few dollars in fuel, instead of requiring a missile that costs hundreds of thousands or millions.

But that requires getting the beam from the ship to the target, which is more complicated than you might think. Sure, in space light travels in a straight line and you just need to make sure that your optics focus it at the correct point on the target.³ Things in an atmosphere, particularly when firing from a ship, are more complicated, as a number of effects make it hard to get the beam to the target in a state to do damage. The largest effect comes from the fact that changes in the density of the air that the beam passes through tend to spread it out. Some of this comes from normal, naturally-occurring turbulence, but far more is the result of the laser beam itself. Air isn't perfectly clear, even to visible light,⁴ and energy absorbed from the passing beam tends to turn it into a lens that spreads out the beam, a process known as blooming. Blooming is usually due to either water vapor or aerosols such as dust and soot. The aerosols also reduce beam strength in another way, as they tend to scatter energy out of the beam, particularly at shorter wavelengths. Adaptive optics hold the possibility to deal with some, although probably not all, blooming by distorting the mirror to compensate for the effects of density gradients.⁵

The AN/SEQ-3 aboard USS Ponce

But what happens when the beam reaches its target? Depending on power and duration, lasers can have all sorts of effects, but all current and projected naval lasers that are capable of doing serious material damage will use simple heating, depositing energy on the target until something bad happens to it. Exactly how long this takes will depend greatly on the target and the range, a subject I look at in more detail in a future installment, but reports suggest that the 30 kW laser deployed to the Persian Gulf aboard USS Ponce required on the order of 15 seconds to disable a drone. More power will be needed to be effective against missiles and airplanes, and work is underway on such systems.

But lasers have the potential to do more than just destroy things, and their flexibility is likely to prove vital in missions short of war. During her deployment, Ponce found that the optical system designed to focus the laser worked both ways, giving them an unprecedented view of anything nearby and making it significantly easier to figure out what a potentially hostile boat or aircraft was up to. Nor is that the only less-than-lethal capability that comes with the laser. It can be fired at low power to provide a harmless "warning shot" or to temporarily blind electro-optical surveillance equipment. These roles would generally involve routing the beam through a frequency-doubling crystal to place it in the visible spectrum instead of IR. There are also some other options beyond simple melting on the more destructive end of the spectrum. Many forms of electro-optical equipment, such as missile seekers, are quite vulnerable to laser damage, and if that isn't enough, the ability of a laser to heat the target can be used to make it easier for a traditional IR-homing missile to see even if it's too far for direct laser damage.⁶ And when simple destruction is the objective, the laser gives new capabilities thanks to its precision. It can easily disable the motor of a potentially hostile boat, while leaving the crew unharmed, or cook off the warhead of an RPG, multiplying its direct effect among nearby enemies.

But all of this still leaves the question of what these lasers are actually capable of. Public sources are long on generalities about UAVs, boats and missiles, and short on any sort of hard numbers. Fortunately, this is a case where most of the information we need to get a much better handle on the situation is already in the public domain, provided you know where to look, and next time, I will unpack what we might be able to expect from current and future naval lasers.