# Experimental study of laser scattering protection system for low-speed aircraft

## TL;DR

This paper presents a laser scattering system to protect low-speed aircraft by reducing laser intensity targeting aircraft sensors.

## Contribution

The study introduces a practical laser protection system using Mie scattering with water aerosols for low-speed aircraft.

## Key findings

- Laser intensity decreased by 17.9% under static conditions with water aerosols.
- Reduction in laser intensity was consistent across different flow speeds and flow uniformity.
- The system showed potential for practical defense against laser threats in dynamic conditions.

## Abstract

This study introduces a laser scattering system to protect a low-speed aircraft. Scattering was selected to reduce the laser’s intensity targeting the sensor of an aircraft and simultaneously maintaining the functionality of aircraft optics. Mie scattering, known for effectively decreasing short-wave infrared light, was employed by utilizing water aerosols having a diameter of 1 to 5 μm. Experimental results regarding the decrease of the laser intensity via scattering confirmed that the theoretical and experimental values resulted in a similar decrease rate under static conditions. To validate the theoretical values, the path length, which the laser passing through water aerosols, was changed. To assess the system’s feasibility in flow conditions, a low-speed wind tunnel was employed to generate two flow speeds: 5.5 m/s and 17.6 m/s. Remarkably, the reduction of laser intensity was only affected by the path length, and was somewhat unaffected regardless of flow speed and the uniformity of the flow, only to the path length. In all cases, the initial laser intensity was set to 10 mW. Under static conditions, the intensity dropped to 8.21 mW, showing a decrease of 17.9%. In flow conditions of 5.5 m/s, 17.6 m/s, and in distorted flow, the laser intensity decreased by 18.3%, 18.1%, and 18% respectively. As a preliminary study, these results demonstrate the system’s capability to protect a low-speed aircraft targeted by lasers even under dynamic flow conditions, may suggest a possibility of providing a practical defence solution.