High-energy laser (HEL) weapons are receiving increasing interest from armed forces around the globe. Technology has reached a point where HEL weapons are being exploited by peer competitor nations due to the higher potential of mission success and lower operational cost when compared to traditional weapons.

China’s Guorong anti-drone system is a shortrange ground-to-air laser weapon system.

The use of these weapons will affect our naval tactics and necessitate new solutions to manage the threat. U.S. naval tactics use forward-deployed unmanned aerial vehicles (UAVs), putting them in close proximity to adversaries. This makes naval UAVs more susceptible to being targeted and damaged by HELs. Once HEL weapons are integrated into the littoral and maritime environments, U.S. naval assets must be capable of protecting themselves against such threats.

This research focused on characterizing future adversarial-directed energy weapon (DEW) threat environments and evaluating solution concepts for countering, evading, and neutralizing the threat. In particular, this study focused on HEL weapon systems as the directed energy threat and their effects on naval UAVs. The results of the research provide an understanding of projected UAV susceptibility to future HEL threats and identified countermeasure, or counter-directed energy weapon (CDEW), concepts that can be applied to protect naval UAV assets.

HEL weapon systems focus a beam of electromagnetic radiation onto a small spot to burn through the target material and render a target incapable of accomplishing its mission. Directed energy weapons (DEWs) have been under development since the 1960s, but recent developments indicate that they will soon be fielded in combat operations. A HEL’s ability to precisely deliver energy at the speed-of-light targeting, low per-engagement cost, and “unlimited” magazine (limited only by the power available) make it a desirable weapon. Unclassified new reports have indicated that countries such as China and Russia have been demonstrating this weapon technology operationally; therefore, the U.S. must be prepared for such threats.

The research began by characterizing the DEW threat environment, which included studying the limitations and strengths of HEL systems. The HEL requires a finite amount of time, referred to as dwell time, to achieve a hard or soft kill on the target. A “hard kill” refers to structurally damaging the UAV whereas a “soft kill” may disrupt the function but not permanently damage the target. The length of the required dwell time can be impacted by the output power of the HEL, the distance to the target, the line-of-sight requirements, the atmospheric conditions, and the material of the target.

The atmosphere itself poses significant limitations for HEL weapons. Limitations include the effects of molecular and aerosol absorption and scattering of the laser beam. Turbulence, which is due to air cells of varying temperature and density along the beam that can act as tiny “lenses,” limits the effect of HEL by causing the beam to break apart or wander. Thermal blooming, which is due to heating of air in a column along the beam, can also limit HEL by defocusing the beam. Atmospheric effects also include scattering due to smoke particles, which could be used in expendables to exploit in the counter-measure solution. Other factors affecting HEL lethality are the thickness, thermodynamic properties, and reflectivity of the target material. All of these target characteristics will affect the required HEL dwell time needed for a soft-kill or hard-kill. A general rule for a hard-kill is on the order of five to ten seconds per target.

Naval UAVs were evaluated in terms of their vulnerabilities in a HEL threat environment based on their type and assigned missions. Possible destructive effects were considered, and component-based evaluation was performed to determine which UAV components would have the highest probability of being targeted and the type of damage that would be inflicted. The team identified four specific UAVs as use-cases for countermeasure concepts based on the potential to operate in a DEW environment, the general operating altitude, the maneuverability, the missions employed, the general operational conditions, and the aircraft material. The four UAVs that were identified as use cases were the MQ-4C “Triton,” the X47B “Pegasus,” the MQ-8C “Fire Scout,” and the STUAS “ScanEagle” aircraft.

Information gathered on HEL weapons and UAVs as targets was used to develop CDEW solution concepts. The CDEW solution concepts depended on the operational environment; atmospheric conditions; the size weight and power (SWaP) of the UAVs; and the UAV missions that dictated operational altitudes, maneuvers, and proximity to HEL threats.

This work was done by James A. Ansley Jr., Kyle Buffin, Victoria E. Couture, Eranga A. Gonaduwage, Stephen A. Hakimipour, and Lisa Nguyen for the Naval Postgraduate School. For more information, download the Technical Support Package (free white paper) below. NPS-0019

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This article first appeared in the September, 2021 issue of Aerospace & Defense Technology Magazine.

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