GABRIEL HONRADA
Chinese researchers have invented a way to keep drones airborne indefinitely by recharging them with laser beams, which may one day enable drones to complement or replace military satellites in some scenarios.
This week, South China Morning Post (SCMP) reported that scientists from Northwestern Polytechnic University (NPU) fitted drones with photoelectric conversion modules that could convert light into electricity, enabling high-powered laser beams to power the drones remotely while in flight.
The report notes that the team from NPU’s school of artificial intelligence conducted a drone experiment that combined autonomous charging with intelligent signal transmission and processing technology.
“Highlights of the research are 24-hour intelligent vision tracking system and the autonomous long-range energy replenishment for optics-driven drones (ODD),” the team said in their official WeChat account, as cited by SCMP.
SCMP noted that the researchers mentioned that the first challenge they encountered was tracking the drones in the air. The source notes that the team was able to develop an algorithm based on intelligent visuals that could accurately track ODDs in the air.
The team also overcame the challenges of laser distortion and weakening due to atmospheric conditions and distance by using adaptive beam shaping technology that reportedly can autonomously adjust laser intensity, SCMP says.
Regarding safety features, the SCMP report says that the team added a protection algorithm that automatically adjusts laser intensity to safe levels once an obstacle is detected in its path.
The research team did not disclose specifics of their experiment due to its sensitive military applications, though it did say it had successfully conducted indoor follow-up, outdoor daytime and outdoor night flights.
China’s Northwestern Polytechnical University’s research team says it carried out three field tests. Photo: Northwestern Polytechnical University
China can use ODD drones to create a “low altitude satellite” or “artificial moon” and increase the combat effectiveness of drone swarms, the SCMP report said.
Meanwhile, the US has its own projects to power drones with lasers. In July 2022, The Warzone reported that the US is exploring converting aerial refueling tankers into “airborne energy wells” to recharge battery-powered drones.
The report said that the US Defense Advanced Research Projects Agency requested that same month industry feedback on converting the US Air Force’s existing KC-135 and KC-46 Pegasus tankers with an “underwing beaming pod.”
The Warzone article mentions that the pod should contain a continuous-wave laser that can generate at least 100 kilowatts, have a thermal control unit and be able to cover a “nearly hemispherical field of regard,” to make sure it can charge drones where needed.
The report also cited other requirements for the airborne energy well concept, such as the need to generate more power aboard tanker aircraft with new or existing equipment.
In a September 2018 article, The Byte reported the US Army is developing a ground-based system that can power up drones in mid-flight at 500 meters.
The report said that the system aims a laser precisely at a photovoltaic cell mounted on the drone, which converts light into electricity. However, it notes that any excess laser energy not converted by the photovoltaic cell turns into heat, which can severely damage the drone.
Laser-charging drones face various technological hurdles. In a 2022 article in the peer-reviewed journal Micromachines, Syed Mohsan and other writers enumerate the challenges of powering up drones with lasers. They note that water, dust and air temperature can degrade the performance of lasers and that they grow weaker over distance.
Nevertheless, such technology may be used in drones as stand-ins for satellites. Asia Times has reported on China and Russia’s fielding various anti-satellite weapons, such as microwave-armed satellites, mobile anti-satellite missiles, and electromagnetic pulse (EMP) weapons, and that the US is developing advanced anti-satellite weapons such as ground-based lasers, signal jammers and hunter-killer satellites.
These developments mean outer space is no longer a sanctuary for military satellites, which are costly to launch and difficult to repair or replace when damaged or destroyed.
Drones, on the other hand, are much cheaper to launch, operate and maintain than satellites. They are a feasible option to ensure multi-layered battlefield communication infrastructure, acting to reinforce, provide redundancy or in some situations replace satellite-based command, control, computers, communications, cyber, intelligence, surveillance, and reconnaissance (C5ISTAR) capabilities.
Given those developments, high-flying solar-powered drones may soon be a feasible replacement for military satellites, with laser charging potentially giving drones nearly unlimited endurance.
A 2016 article by Futurism notes that such drones, called “high-altitude pseudo-satellites (HAPS),” can perform all the functions of current satellites but at a lower cost.
Airbus’ Zephyr drone. Image: Airbus Defense and Space
The report notes HAPS have longer operating times than satellites and need to land only for maintenance and upgrades. It notes that these drones can be used for military monitoring, emergency communications, and high-speed internet.
One such drone is the Zephyr made by Airbus. It has a 25-meter wingspan and can fly continuously for months at an altitude of 21,000 meters, placing it above weather conditions and commercial air traffic. Airbus touts the Zephyr as capable of providing mobile connectivity to underserved or remote areas, earth observation and secure tactical communications.
Not to be outdone by Zephyr, in September 2022, SCMP reported that China unveiled its Morning Star 50 HAPS drone, which experts describe as a “pseudo-satellite.” SCMP notes that Morning Star has a 50-meter wingspan that is twice the size of the Zephyr, flies at altitudes above 20 kilometers, and can stay airborne for months or even years.
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