Combat Applications of Laser Weapons

(Lecture 5 of the Laser Weapon Science Popularization Series)

In the 1960s, laser weapons were referred to as "death rays." In 1978, science fiction writer Tong Enzheng published Death Ray on a Coral Island [1], which depicted several laser weapon combat scenarios. The novel was adapted into a film of the same name in 1980, featuring an impressive scene where a red laser instantly destroyed a submarine. The development of laser weapons has spanned nearly 60 years. Have the laser weapons imagined in the movie become a reality? Are the rumors circulating online about laser weapons being used in actual combat true?

I. Damage Mechanisms of Laser Weapons

The so-called laser damage mechanism refers to the cause and conditions under which lasers induce target destruction, serving as a critical physical foundation for the combat application of laser weapons. Laser weapons inflict damage through the interaction between laser light and matter, as introduced in the first article of this series. The primary mechanisms are the photoelectric effect, thermal effect, and thermomechanical coupling effect.

Table 1: Typical Damage Thresholds of Laser Weapons Against Different Combat Targets

To effectively damage targets, laser weapons must meet certain conditions: sufficient power density, irradiation duration, and beam coverage area are essential. Table 1 presents typical laser damage mechanisms and thresholds for various targets. The damage thresholds listed represent the minimum required on-target power density. Additionally, sustained laser irradiation is necessary to achieve target destruction:

• Electro-optical systems require only milliseconds to seconds of exposure.

• Other damage mechanisms typically need 1–10 seconds of sustained irradiation.

II. What Targets Can Laser Weapons Engage?

Based on damage mechanisms, laser weapons can engage a wide range of targets—from crowd-dispersal laser rifles to missile-intercepting and satellite-attacking laser cannons. The table below outlines potential applications across operational domains.

Table 2: Potential Applications of Laser Weapons Across Operational Domains

Although laser weapons theoretically have a broad operational domain and promising prospects, their practical application remains challenging. In the 1990s, foreign chemical lasers addressed the issue of usability, but their large size limited deployment in real combat. Over the past 30 years, diode-pumped solid-state and fiber lasers have been tackling the issue of practicality, but their power and beam quality still fall short, restricting their combat utility. The instant destruction of targets depicted in Death Ray on a Coral Island is astonishing but remains unattainable.

While the combat effects portrayed in the film are unrealistic, lasers as weapons are feasible. Current high-energy laser technology has advanced rapidly, and there have been numerous reports of laser systems successfully intercepting drones, artillery shells, and small boats abroad. However, most laser weapons reported online are still in the testing phase. Officially deployed systems are primarily electro-optical countermeasure weapons. For example, Russia's "Peresvet" laser weapon system, unveiled in 2018, is likely designed to disrupt or blind optical reconnaissance satellites. Many of the alluring potential applications of laser weapons remain distant.

III. What Are Tactical and Strategic Laser Weapons?

Many documents and news reports categorize laser weapons as tactical or strategic, though there is no strict definition. Generally, tactical laser weapons refer to short-range air defense systems targeting aircraft and missile electro-optical systems, rockets, artillery shells, cruise missiles, small drones, and boats (excluding laser guns for crowd dispersal in counterterrorism). Strategic laser weapons are used to intercept ballistic missiles, counter hypersonic vehicles, or attack satellites.

Laser weapons targeting electro-optical systems can be tactical when used for short-range missile or aircraft defense but become strategic when employed to disrupt or blind reconnaissance satellites. Thus, the classification depends on the operational scenario and target, not the system's technical specifications.

IV. What Factors Must Be Considered in Laser Weapon Deployment?

To achieve effective target destruction, laser weapon design must account not only for laser power, beam quality, aperture size, and atmospheric transmittance but also for wavelength absorption selectivity. Different materials exhibit varying absorption properties, leading to orders-of-magnitude differences in damage thresholds. Beginners in laser weapon development often overlook these factors, focusing narrowly on one aspect.

Additionally, the following practical considerations are crucial for laser weapon deployment:

1. Engagement Distance
   Laser beams can theoretically travel vast distances, but the effective strike range is determined by the weapon system's specifications and the target's damage threshold—it is not a fixed value. The same system may have vastly different engagement distances for different targets due to varying damage thresholds.

   Unlike kinetic weapons (e.g., artillery, missiles), multiple laser weapons can collaborate to extend engagement range (kinetic weapons cannot achieve this by increasing numbers). For example, four identical laser systems working together can double the engagement distance. Theoretically, the laser power density (a measure of combat effectiveness) on the target is inversely proportional to the square of the distance—a critical principle in operational planning.

   Laser weapons employ an "engagement range table" specifying effective distances for different targets. Insufficient range can render a system impractical. For instance, the U.S. Airborne Laser (ABL) program, launched in the 1990s, successfully intercepted a simulated ballistic missile at 50 miles in 2012 but failed at 100 miles. This $5+ billion program—the largest laser weapon research effort in history—was canceled for failing to meet operational requirements.

2. Battlefield Environment
   Atmospheric effects cannot be ignored in atmospheric combat. Rain, fog, or haze significantly degrade laser weapon performance. Clouds can block laser transmission entirely, forcing ground- or sea-based anti-satellite lasers to avoid overcast conditions. Smoke and dust in land battles also impair effectiveness.

   Platform conditions also impact system reliability and safety. For example, shipboard vibrations complicate high-precision beam control, while salt spray and humidity in marine environments corrode systems and disrupt laser transmission, necessitating robust protective designs.

   Another critical factor is battlefield sustainability. The U.S. Tactical High-Energy Laser (THEL) program was shelved partly because chemical laser logistics were deemed impractical for combat.

3. Command and Control Systems
   Laser weapon systems typically lack independent target detection capabilities or rely on external guidance. The precision of this external command system must align with the weapon's requirements to ensure target acquisition—a demand often prohibitively high.

4. Response Time
   In real combat, response time is paramount, especially against hypersonic missiles. The delay from receiving an attack order to full-power laser emission must generally be under one second, as engagement windows may last only seconds or even milliseconds.

   For example, a shipboard laser intercepting a Mach 2.5 anti-ship missile at 3 km has less than 3 seconds to act. A one-second delay could be fatal. This requirement poses a major challenge for high-energy laser designers and is frequently overlooked by beginners. Some test systems prove unusable in combat solely due to slow response times, even if power, beam quality, and tracking precision meet standards.

Afterword

At the invitation of Optics World, I undertook this science popularization series on laser weapons, striving to explain their technology and applications in non-technical language. Today, the task is complete—but have I succeeded? Do you understand? I cannot say for certain.

In 1979, after reading Death Ray on a Coral Island, I chose laser science for my university studies. I was fortunate to begin researching high-energy laser technology under my mentor, Professor Zhao Yijun, starting with my master's degree. Since 1989, I have dedicated myself to studying high-energy laser physics, technology, and applications. Thirty years of trial and error have deepened my appreciation for the philosophical interplay between science, technology, engineering, and application.

Laser weapons are among the modern weapon systems with the longest development cycles from concept to deployment (surpassed only by railguns, to my knowledge). Their challenges are difficult to grasp without deep involvement, so I cannot predict how many unanswered questions readers may have after these lectures.

In closing, I extend special thanks to Assistant Researcher Yang Weiqiang, Researcher Xu Xiaojun, Professor Hua Weihong of the National University of Defense Technology, my academic assistant Engineer Du Xueyuan, and Dr. Zhang Jun of Optics World. Without their contributions, this series would not have been possible.

(Note: Citations like [1] are preserved as placeholders for source references in the original text.)