Countries around the world are rapidly developing high-energy laser weapons for military missions on land, sea, air and space. Visions of swarms of small, cheap drones filling the skies or soaring over the waves motivate militaries to develop and deploy laser weapons as an alternative to costly and potentially overwhelmed missile-based defenses.
Laser weapons were a staple of science fiction long before lasers were invented. Recently, they have also come to the fore 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 do lasers work?
A laser uses electricity to produce photons or light particles. Photons pass through a gain medium, which is a material that creates a train of additional photons that rapidly increases the number of photons. All these photons are then focused into a narrow beam by a beam steerer.
Over the decades since the first laser was introduced in 1960, engineers have developed a variety of lasers that produce photons of different wavelengths across the electromagnetic spectrum, from infrared to ultraviolet. High-energy laser systems in military applications are based on solid-state lasers that use special crystals to convert input electrical energy into photons. An important feature of high-power solid-state lasers is that photons are created in the infrared part of the electromagnetic spectrum and are therefore invisible to the human eye.
When a laser beam interacts with a surface, it produces different effects depending on the photon wavelength, the power of the beam, and the material of the surface. Low-power lasers, which produce photons in the visible part of the spectrum, are useful as light sources for beacons and light shows at public events. These rays have such low power that they reflect off a surface without damaging it.
Higher power laser systems are used to cut biological tissue in medical procedures. The highest power lasers can heat, vaporize, melt and burn many different materials and are used for welding and cutting in industrial processes.
In addition to the laser’s power level, its ability to deliver these various effects is determined by the distance between the laser and its target.
laser guns
Based in part on the progress made in high-power industrial lasers, militaries are finding an increasing number of uses for high-energy lasers. One of the most important advantages of high-energy laser weapons is that they provide an “infinite magazine”. Unlike traditional weapons such as guns and cannons, which contain a limited amount of ammunition, a high-energy laser can continue to fire as long as it has electrical power.
The U.S. Army uses a truck-based high-energy laser to hit a variety of targets, including drones, helicopters, mortar rounds and rockets. 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 U.S. Navy has used a ship-based high-energy laser to defend against small, fast-moving ocean surface ships, as well as missiles and unmanned aerial vehicles. The Navy installed a 60-kilowatt laser weapon on the destroyer USS Preble in August 2022.
The Air Force is developing high-energy lasers on aircraft for defensive and offensive missions. In 2010, the Air Force tested a megawatt laser mounted on a modified Boeing 747 to hit a ballistic missile as it was launched. The Air Force is currently working on a smaller weapons system for fighter jets.
Russia appears to be developing a ground-based high-energy laser to “blind” rivals’ satellites.
Limitations of laser weapons
One of the key challenges for militaries using high-energy lasers is the high levels of power required to produce useful effects from a distance. Unlike an industrial laser, which can be only inches away from its target, military operations require significantly longer distances. To defend against an incoming threat, such as a mortar shell or a small boat, laser weapons must reach their target before they can do any damage.
But burning materials at safe distances requires tens to hundreds of kilowatts of power in the laser beam. The smallest prototype laser gun draws 10 kilowatts of power, roughly equivalent to an electric car. The latest high-power laser weapon in development draws 300 kilowatts of power, enough to power 30 households. Since high-energy lasers are only 50% efficient at best, they produce a huge amount of waste heat that must be managed.
This means that high-energy lasers require extensive power generation and cooling infrastructure, which limits the types of effects that can be generated from different military platforms. Army trucks and Air Force fighter jets have the least space for high-energy laser weapons, and so these systems are limited to relatively low-power targets such as shooting down drones or disabling missiles. Ships and larger aircraft can accommodate larger high-energy lasers that have the potential to punch holes in boats and ground vehicles. Persistent ground-based systems have the fewest restrictions and therefore the most power, making it potentially possible to dazzle a distant satellite.
Another major limitation to platform-based high-energy laser weapons relates to the infinite magazine concept. Because the truck, ship, or plane must carry the power supply for the laser, which will limit the capacity of the power supply, lasers can only be used for a limited time before recharging their batteries.
High-energy laser weapons also have fundamental limits, including reduced effectiveness in rain, fog, and smoke that disperse laser beams. Laser beams also need to stay locked on their target for several seconds to deal damage. Maintaining existing prototype laser weapons in combat zones also poses a challenge.
There is no fire from the skies
In recent years, a new breed of conspiracy theory has emerged, claiming that nefarious entities are using airborne high-energy lasers to start wildfires in California, Hawaii and Texas. This is unlikely for several reasons.
First, the level of power required to ignite vegetation from the sky with a high-energy laser would require a large power supply mounted on a large aircraft. An aircraft this size would be highly visible just before any fire broke out. Second, in some images purportedly showing fires starting, the laser beams are green. The beams of high-energy lasers are invisible.
What’s next
In the future, high-energy laser weapons are likely to continue to evolve with increasing power levels that will expand the range of targets they can be used against.
Threats posed by low-cost, armed drones, such as those used in conflicts in the Middle East and Ukraine, raise the possibility that high-energy lasers may also find non-military applications, such as defending the population against terrorist attacks.
This article is republished from The Conversation, an independent, nonprofit news organization providing facts and authoritative analysis to help you understand our complex world. 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.