Experimental Design of a UCAV-Based High-Energy Laser Weapon

Until now, unmanned combat aerial vehicles (UCAV) have used only conventional missiles (i.e., Hellfire), but the rapid growth of laser weapon technology suggests that the day of the first deployable UCAV armed with a high-energy laser (HEL) weapon is not far away.

The deployment of an airborne platform armed with a High Energy Laser (HEL) weapon has been a major challenge for several decades. Attempts in the past included mounting a HEL weapon in large aircraft like a Boeing 747, mainly for strategic missions like defense against tactical ballistic missiles. Despite being very promising in their initial phases, these trial configurations presented various technical and economic issues that resulted in their cancellation.

Recently, the focus has shifted from strategic missions to tactical missions. That means that HEL weapons of lower power and, consequently, decreased size and weight would be sufficient for these missions while also being more suitable for airborne applications. Additionally, the improvements in laser weapon technology in terms of size, weight, and power (SWaP) promise that soon a HEL weapon could be deployable from an unmanned aerial vehicle (UAV).

The purpose of this research was to model a UAV-based HEL weapon by applying a model-based system engineering (MBSE) approach and simulate its performance. Two alternative HEL design configurations were selected, and their corresponding weight requirements were estimated. Finally, the endurance of the UAV for these different configurations was calculated.

Utilizing Vitech CORE software, the architecture of the UAV-HEL system was modeled, starting from the system capabilities required for a Close Air Support (CAS) mission execution along with the operational system requirements. Next came the functional and physical architecture, showing the functions that each physical component is to accomplish. Finally, the UAV's endurance and the HEL's lethality were identified as the technical performance measures of the overall system.

The first phase of the simulation experiment focused on exploring how the different operational tactics and HEL design configurations affect the lethality of the system as measured by the irradiance delivered to the target and the power accumulated in a bucket on the target's surface, with a radius of 5 cm and thickness of 3 mm. Exploring these parameters at the same time, rather than one factor at a time, called for application of the Design of Experiments (DOE), a well-structured mathematical process that allows for the determination of the significance of each factor and potential interactions among them by analyzing the simulation's experiment results. The selected parameters in this simulation are the HEL's power; the beam director size; and the UAV altitude, speed, and direction. Having defined the mission of the UAV, the target damage criteria was determined by calculating the required irradiance and power in bucket (PIB) for different dwell times. Specifically, it was found that for an aluminum surface target, an irradiance of 11 MJ/m2 and PIB of 85 kW for a dwell time of 6 seconds would be sufficient to melt the target.

The simulation results clearly showed the importance that the operating altitude of the UAV has on the HEL's lethality. The results showed that operating altitude has the greatest effect on both irradiance and PIB. Following altitude in importance is the beam director size and then output power. Speed and direction of UAV show no significant effect. Another important simulation result showed that under certain circumstances a 150 kW HEL deployed by a UAV flying at altitudes higher than 3000m could have the same performance as a 250 kW HEL operated from lower than 500m of altitude.

Having determined those two power levels as possible alternatives and measured their performance, the corresponding weight and power requirements were estimated for each alternative. These estimations, which were based on commercially developed systems and provided a nominal approximation, showed that a 150 kW HEL would weigh approximately 1670 kg whereas a 250 kW HEL would weigh 2635 kg. Therefore, both alternatives could be mounted and supported by a UAV similar in size and capability to the Predator B.

By consulting a subject matter expert on UAVs, it was determined that a simple mathematical relationship existed between the endurance of the UAV and its payload weight. Using this relationship, it was determined that the lower power HEL would allow an endurance of around 25.5 hours, whereas the bigger one would allow only for 23 hours, or a 10 percent decrease in endurance.

This work was done by Antonios Lionis for the Naval Postgraduate School. For more information, download the Technical Support Package below.

This Brief includes a Technical Support Package (TSP).
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Experimental Design of a UCAV-Based High-Energy Laser Weapon

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