Countries around the world are rapidly developing high-energy laser weapons for military missions on land and sea, and in air and space. Visions of swarms of small, cheap drones filling the skies or skimming the waves are motivating militaries to develop and deploy laser weapons as an alternative to costly and potentially overwhelmed missile-based defense systems.
Laser weapons have been a staple of science fiction since long before lasers were invented. More recently they have also featured prominently in some conspiracy theories. Both types of fiction emphasize the need to understand how laser weapons actually work and what they are used for.
How lasers work
A laser uses electricity to generate photons or light particles. The photons pass through a gain medium, a material that creates a cascade of additional photons, rapidly increasing the number of photons. All these photons are then focused into a narrow beam by a beam director.
In the decades since the first laser was unveiled in 1960, engineers have developed a variety of lasers that generate photons at different wavelengths in the electromagnetic spectrum, from infrared to ultraviolet. The high-energy laser systems that find military applications are based on solid-state lasers that use special crystals to convert the input electrical energy into photons. An important aspect of high-power solid-state lasers is that the photons are created in the infrared part of the electromagnetic spectrum and therefore cannot be seen by the human eye.
When a laser beam interacts with a surface, it generates different effects based on the photon wavelength, the power in the beam, and the material of the surface. Low-power lasers that generate photons in the visible part of the spectrum are useful as light sources for pointers and light shows at public events. These rays have so little power that they simply reflect off a surface without damaging it.
Higher power laser systems are used to cut through biological tissue in medical procedures. The highest power lasers can heat, vaporize, melt and burn through many different materials and are used in industrial processes for welding and cutting.
In addition to the power level of the laser, its ability to deliver these different effects is determined by the distance between the laser and the target.
Laser weapons
Based in part on advances made in high-power industrial lasers, militaries are finding more and more applications for high-energy lasers. A key advantage of high energy laser weapons is that they provide an ‘infinite magazine’. Unlike traditional weapons such as rifles and cannons, which have a limited amount of ammunition, a high-energy laser can continue to fire as long as it has electrical power.
The US military is deploying a truck-based, high-energy laser to take down a range of targets, including drones, helicopters, mortars and missiles. The 50-kilowatt laser is mounted on the Stryker infantry fighting vehicle, and the Army deployed four of the systems for battlefield testing in the Middle East in February 2024.
The US Navy has deployed a ship-based, high-energy laser to defend against small and fast-moving surface ships, as well as missiles and drones. The Navy installed a 60-kilowatt laser weapon on the destroyer USS Preble in August 2022.
The Air Force is developing high-energy lasers for aircraft for defensive and offensive missions. In 2010, the Air Force tested a megawatt laser mounted on a modified Boeing 747, which hit a ballistic missile as it was launched. The Air Force is currently working on a smaller weapon system for fighter aircraft.
Russia appears to be developing a high-energy ground-based laser to “blind” its opponents’ satellites.
Limitations of laser weapons
One of the main challenges facing militaries using high-energy lasers is the high power required to create useful effects at a distance. Unlike an industrial laser that may be only a few centimeters from its target, military operations span significantly greater distances. To defend against an incoming threat, such as a mortar shell or a small boat, laser weapons must engage their targets before they can do any damage.
However, to burn through materials at safe distances, tens to hundreds of kilowatts of power are required in the laser beam. The smallest prototype of a laser weapon consumes 10 kilowatts of power, roughly equivalent to an electric car. The latest high-powered laser weapon in development consumes 300 kilowatts of power, enough to power 30 homes. And because high-energy lasers are only 50% efficient at best, they generate a huge amount of waste heat that must be managed.
This means that high-energy lasers require extensive power generation and cooling infrastructure that places limits on the types of effects that can be generated by different military platforms. Army trucks and Air Force fighter planes have the least space for high-energy laser weapons, so these systems are limited to targets that require relatively low power, such as shooting down drones or disabling missiles. Ships and larger aircraft can accommodate larger, high-energy lasers that can burn holes in boats and ground vehicles. Permanent ground-based systems have the fewest limitations and therefore the highest power, making it potentially feasible to blind a distant satellite.
Another major limitation for platform-based high energy laser weapons relates to the infinite magazine concept. Because the truck, ship or plane must transport the power source for the laser, and that limits the capacity of the power source, the lasers can only be used for a limited time before they need to recharge their batteries.
There are also fundamental limitations to high-energy laser weapons, including reduced effectiveness in rain, fog and smoke, which scatter laser beams. The laser beams must also remain focused on their targets for several seconds to cause damage. Current prototype laser weapons are also proving challenging to maintain in combat zones.
No fire from the sky
In recent years, a new breed of conspiracy theory has emerged, claiming that nefarious entities have used high-energy lasers in the air to start wildfires in California, Hawaii and Texas. This is very unlikely for several reasons.
First, the power level required to ignite vegetation with a high-energy laser from the air would require a large power source installed in a large aircraft. An aircraft of that size would have been clearly visible just before the fire broke out. Second, in some of the images that claim the fires started, the laser beams are green. Beams from high-energy lasers are invisible.
What comes next
In the future, high-energy laser weapons will likely continue to develop with higher power levels, increasing the range of targets they can be used against.
Emerging threats posed by cheap, weaponized drones, such as those used in conflicts in the Middle East and Ukraine, make it more likely that high-energy lasers will also find non-military applications, such as defending the public against terrorist attacks.
This article is republished from The Conversation, an independent nonprofit organization providing facts and trusted analysis to help you understand our complex world. It was written by: Iain Boyd, University of Colorado Boulder
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Iain Boyd receives funding from the US Department of Defense and Lockheed-Martin Corporation.