Reflected energy hazards from high energy lasers (HEL): Field testing in support of HEL mobility demonstrator (HEL MD)

Abstract

A methodology is developed to perform laser hazard analyses to support field tests of high-energy lasers. This methodology considers realistic worst-case event analyses of specular reflections from planar and cylindrical targets. Our approach uses three models of event data for hazard estimation: Beam propagation to determine the size of the laser beam on the target; Reflected irradiance, which depends on the target shape and bi-directional reflectance distribution function; Exposure time, which is used to calculate the maximum permissible exposure and depends on the locations and velocities of the laser, target, and observer. For HEL field testing, the reflected laser hazard analysis was performed using the Specular Methodology; atmospheric attenuation is not included in the analysis since the resulting hazard distances are not sufficiently long for emissions from these tests. This methodology considers only specular reflections to derive analytical expressions for the irradiance and exposure time at observer locations. The hazard or injury distance is derived from these values. Specular reflections have the longest hazard distances, and this methodology determines more realistic and thus less restrictive exposure times compared to assuming the events and risks at longest exposure time. While the Specular Methodology is an approximation of reflected laser light compared to high-fidelity simulations, it performs calculations much more rapidly and can allow real-time assessment and attenuation of laser during use.Reflected Nominal Ocular Hazard Distances (R-NOHD) were calculated and presented for several targets for the HEL.A methodology is developed to perform laser hazard analyses to support field tests of high-energy lasers. This methodology considers realistic worst-case event analyses of specular reflections from planar and cylindrical targets. Our approach uses three models of event data for hazard estimation: Beam propagation to determine the size of the laser beam on the target; Reflected irradiance, which depends on the target shape and bi-directional reflectance distribution function; Exposure time, which is used to calculate the maximum permissible exposure and depends on the locations and velocities of the laser, target, and observer. For HEL field testing, the reflected laser hazard analysis was performed using the Specular Methodology; atmospheric attenuation is not included in the analysis since the resulting hazard distances are not sufficiently long for emissions from these tests. This methodology considers only specular reflections to derive analytical expressions for the irradiance and exposure time at o...