Part 2 of 3 Parts (Please read Part 1 first)
The use of lasers to power small Unmanned Aerial Vehicles (UAVs) has been an area of research for the U.S. military for years. The U.S. Air Force started testing lasers to propel small “lightcraft” as early as the 1980s. They were able to send a small cone-shaped craft hundreds of feet through the air propelled only by laser beams. The latest concept of laser propulsion is different because the beamed power UAVs that the U.S. Navy is working on will make use of traditional propulsion systems such as propellers. The UAVs will utilize rectennas that capture energy from the directed energy beams and use it to constantly replenish their electrical power reserves that are powering the propellers.
In 2011, research at the NASA’s Glenn Research Center on laser power-beaming system was published. Funding was supplied by the Air Force Research Laboratory's Revolutionary Munitions Directorate at Eglin Air Force Base. The research was dedicated to the examination of “long-range optical ‘refueling’ of electric platforms such as micro unmanned aerial vehicles (MUAV)”. Rand Corporation published a study conducted by the Air Force in 2011. The study concluded that though the concept of laser beamed power was sound, atmospheric interference from clouds could impose limitations on flight paths and ceilings.
DARPA held a power beaming roundtable in 2015 which included representative from top defense contractors, research universities and various DoD-operated laboratories. Then, in 2018, DARPA held a demonstration of its latest prototype laser-powered aircraft which was named the Silent Falcon. Joseph A. Abate was the project lead. He said that the aircraft was meant to “demonstrate that remote electric refueling of DoD systems via high energy laser power beaming to extend mission operation time in contested and remote environments.”
While lasers have been tested for use in beaming power to UAVs, these tests have usually involved ground-based or airborne lasers to beam the power. Sending the source of power generation and transmission into Earth orbit is a new use of this concept. It offers superior lines of sight and a continuous, renewable source of energy which is the Sun.
Low Earth orbit satellites travel around the Earth at extremely high speeds. Their maneuverability is very limited so the Navy’s latest beamed power system will also be limited. As a proof of concept, it is useful and necessary. A constellation of satellites would be needed to really have a 24/7 power supply. The UAVs would be “passed” from satellite to satellite for continuous or tightly scheduled recharging. The same could be said for any receiver applications on the Earth’s surface.
Thomas Mehlhorn is the superintendent of the Naval Research Laboratory’s Plasma Physics Division. In 2014, he published a paper in the IEEE Transactions on Plasma Sciences. This paper gave an overview of plasma physics and pulsed power as they related to national security. The article covered a wide range of topics which included nuclear weapons, inertial confinement fusion, and high energy laser weapons. In the paper, the author also mentions the Navy’s beamed power UAV research taking place at that time. He said that continuous flight times offered by beamed power systems could change surveillance, reconnaissance, and communications gateway/relay mission forever.
Please read Part 3 next