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Drone triggers -- then survives -- lightning strike

A Japanese telecommunications company has built a wire-connected drone that attracts lightning and survives if struck due to its uniquely built lightning protection cage.

Lightning strikes are one of the most destructive natural phenomena affecting human society. While the NTT Group, based in Tokyo, has implemented various lightning protection measures for critical infrastructure, including telecommunications facilities, lightning-related damage remains a persistent issue.

In Japan alone, the estimated annual cost of lightning damage ranges from 100 to 200 billion yen. Building on its long-standing expertise in protecting communications equipment from lightning, NTT is now working to advance this technology further, with the aim of eliminating lightning strikes on infrastructure and urban areas altogether.

Traditionally, lightning protection has relied heavily on lightning rods. However, their protective range is limited, and in some cases -- such as wind turbines or outdoor event venues -- it may not be feasible to install them. At NTT, researchers are exploring the use of drone technology to create a new approach: drone-triggered lightning. This method involves flying drones into optimal positions beneath thunderclouds to actively trigger lightning strikes and then guiding the discharge safely away from vulnerable areas.

Overview and key findings of the experiment
From December 2024 to January 2025, a lightning-triggering experiment using drones was conducted at an elevation of 900 m in a mountainous area of Hamada City, Shimane Prefecture, Japan. In this experiment, a device called a field mill was used to monitor the electric field at ground level. When the electric field strength increased due to the approach of a thundercloud, a drone equipped with a custom-designed lightning protection cage was launched to attempt lightning triggering.

On December 13, 2024, during the approach of a thundercloud, the electric field strength observed by the field mill increased. At that moment, a drone equipped with a conductive wire was flown to an altitude of 300 m. The drone was then electrically connected to the ground via a switch installed on the ground (Figure 2). As a result, a large current was observed flowing through the wire, accompanied by a significant change in the surrounding electric field strength (Figure 3).

Just before the lightning strike, it was confirmed that a voltage of over 2,000 V had developed between the wire and the ground. This rapid increase in local electric field strength triggered a lightning strike directed at the drone. The company says this experiment marks the first successful case in the world of triggering lightning using a drone.

At the moment of the strike, a loud cracking sound was heard, a flash was observed at the winch, and partial melting occurred in the drone's lightning protection cage (Figure 4). However, the drone equipped with the protective cage continued to fly stably even after the lightning strike.

Some technical highlights
To successfully trigger lightning using a drone, the drone must remain operational even after being struck. Moreover, simply flying a drone under a thundercloud is not sufficient to attract lightning; an active triggering method is required. To address these challenges, the researchers at NTT proposed and demonstrated the following two key technologies.

1. Lightning protection technology for drones
NTT developed a lightning protection cage design that prevents malfunction or damage even if the drone is directly struck by lightning. This cage, which can be mounted on commercially available drones, is made of conductive metal and functions as a shield. It redirects the high current from the lightning strike away from the drone's internal components, preventing it from flowing through the drone itself. Additionally, the cage is designed to distribute the lightning current radially, which cancels out the strong magnetic fields generated by the current and minimizes electromagnetic interference with the drone (Figure 5).

NTT conducted artificial lightning tests on drones equipped with the lightning protection cage. The results showed the system withstood artificial strikes of up to 150 kA -- five times greater than the average natural lightning strike -- without any malfunction or damage, covering over 98% of naturally occurring lightning conditions.

2. Electric field-based lightning-triggering technology
To actively trigger lightning, NTT devised a method in which a conductive wire connects the drone to the ground, with a high-voltage switch installed on the ground side.

By operating this switch at the optimal moment, the researchers gain the ability to rapidly change the electric field around the drone. This sharp increase in local electric field strength encourages a lightning discharge to occur toward the drone (Figure 6).

Could such systems really be employed in the future?
In short, NTT thinks so. The company aims to protect cities and people from lightning damage by flying drones that are designed to withstand direct lightning strikes to accurately predict lightning-prone locations, actively trigger strikes, and safely guide them away.

To improve the success rate of drone-based lightning triggering, the company plans to continue to advance research and development in two key areas: high-precision lightning location prediction and a deeper understanding of lightning mechanisms. In addition, the researchers want to not only trigger and control lightning, but also -- one day -- be able to harness some or all of its energy. Future efforts have the lofty goal of developing technologies for capturing and storing lightning energy for potential use (Figure 7).

Source: NTT Group

Published October 2025

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