While armies still rely on diesel trucks and kerosene tankers, US defence researchers are quietly testing a different idea: sending electricity itself through the air, using lasers and high‑flying aircraft as airborne power pylons.
From fuel convoys to flying power lines
Modern warfare runs on fuel. Tanks, generators, surveillance radars, drones and armoured vehicles all depend on steady supplies of petrol, diesel or jet fuel.
Those supplies move along long, vulnerable routes. Convoys of tankers remain prime targets for missiles, mines and drones. Disrupt the fuel, and much of the fighting power collapses.
The US Defense Advanced Research Projects Agency (Darpa) wants to loosen that dependency. Its programme, called Persistent Optical Wireless Energy Relay – conveniently shortened to Power – aims to beam energy by laser across tens or even hundreds of kilometres.
Instead of guarding fuel lines on the ground, the concept imagines electric “power lines” drawn in light across the sky.
The new call for proposals, named Power Receiver Array Demonstration (Prad), focuses on the most fragile link in that chain: the final receiver that turns the incoming laser into usable electricity.
A 10 kW beam crossing 200 km of air
The requirement is clear and surprisingly ambitious. Darpa wants a system that can deliver about 10 kilowatts of electrical power over a distance of roughly 200 kilometres.
That power would arrive not by cable, but via a laser beam bouncing from one aircraft to another, before being captured by equipment on or near the ground.
The planned architecture looks less like a single spotlight and more like a relay race in the sky.
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- A ground station generates laser power and fires it upward.
- High-altitude aircraft at around 18,300 metres receive and redirect the beam.
- A final aircraft or relay sends it down to a receiver on the battlefield.
- The receiver uses photovoltaic cells tuned to the laser wavelength to turn light into power.
According to the project outline, three aircraft or drones would form the initial test network, acting as flexible, mobile nodes in this airborne grid.
The target: 10 kW of usable power at the far end, enough to feed a small radar, charge drones, or support a forward operating base.
Why lasers, and not microwaves or cables?
Long-distance wireless power transfer is not new as an idea. Microwaves have been studied for decades for space‑based solar power concepts.
Lasers bring a different mix of advantages and challenges. A laser beam can be focused very tightly, limiting the spread of energy and allowing higher energy density on the receiver.
That tight beam also means less interference with anything outside the direct path, which matters in crowded airspace.
On the other hand, lasers can be strongly affected by weather. Fog, clouds, dust or smoke can scatter or absorb the beam. High-altitude relays at 18,300 metres sit above most of that turbulence, which is one reason the Power programme relies on aircraft operating near the edge of the stratosphere.
Efficiency: emitting 50 kW to get 10 kW
One number in the Darpa concept stands out. To deliver around 10 kW at the end of the chain, the source might need to emit roughly 50 kW of laser power.
That gap reflects all the losses along the way. Energy is lost in converting electricity into laser light, again in redirecting and refocusing the beam, and finally in converting the light back into electricity at the receiver.
| Stage | Process | Main loss source |
|---|---|---|
| Generation | Electricity → laser light | Laser efficiency limits, heat |
| Propagation | Laser beam through air | Scattering, absorption, misalignment |
| Relay | Aircraft redirecting beam | Optical imperfections, tracking |
| Reception | Laser light → electricity | Photovoltaic conversion limits |
This may sound wasteful, but for the military, the comparison is different. Fuel convoys burn fuel just to move fuel, then require armoured protection and human crews. If a beamed system cuts the need for daily tanker runs into a contested area, lower efficiency at the generator may be an acceptable trade.
What 10 kW actually means on the battlefield
Ten kilowatts does not power a tank, but it is far from trivial. A small family house can run on that average level of power.
On a battlefield, 10 kW could support:
- a network of surveillance cameras and sensors around a remote outpost
- a tactical radar system tracking drones and missiles
- a bank of fast chargers for small uncrewed aerial vehicles (UAVs)
- communications equipment, including satellite terminals and encrypted radio relays
Power could also be buffered. A constant 10 kW beam might feed batteries or supercapacitors, which then deliver brief surges to more demanding systems such as directed-energy weapons or short-takeoff drones.
The vision is not a flying power station for tanks, but a persistent, flexible trickle charger for distributed, electronic warfare and surveillance assets.
Technical hurdles behind the sci‑fi image
The concept sounds like science fiction, but the toughest work lies in mundane engineering details.
Pointing and tracking a hair-thin beam
At a range of 200 kilometres, even a small misalignment can mean the beam completely misses the receiver.
The aircraft relays must hold position, angle and focus within very tight margins, despite turbulence and wind shifts.
This calls for advanced optics, real-time tracking sensors, and control systems that constantly adjust mirrors and lenses to keep the beam locked on target.
Safety and rules of engagement
High-power lasers raise obvious questions. Eyes can be damaged by much lower intensities than those used for power transmission.
Systems must avoid striking civilian aircraft, satellites or unintended objects. That implies geofenced corridors, automatic shutdown features and coordination with air traffic authorities for any real deployment outside combat zones.
There is also the risk of the beam being detected or jammed. Adversaries might attempt to dazzle or disrupt the optical relays, or simply shoot them down.
Beyond war: could this feed remote communities?
Although designed for military scenarios, the underlying technology could find civilian uses.
Remote research stations, high-altitude observatories or disaster zones often lack reliable power links. Building new transmission lines is slow and politically complex.
In theory, a beamed system could send energy to a temporary camp in the Arctic, or to emergency shelters after an earthquake, without waiting for grid repairs.
Commercial applications would demand higher efficiency and strong safety guarantees. They might also blend with renewable generation, such as pairing ground-based solar farms with airborne relays that bypass damaged infrastructure.
Key terms and what they mean
The technology involved can sound opaque, so a few core ideas help frame the discussion.
Photovoltaic receiver: Instead of a regular solar panel that captures broad sunlight, the receiver uses cells tuned to a specific laser wavelength. That targeted design can squeeze more electricity from each photon, lifting efficiency compared with a general-purpose solar panel.
High-altitude platform: The aircraft at around 18,300 metres sit above most commercial traffic and weather. These could be large drones, solar-powered aircraft, or modified jets that loiter for long periods. They effectively act as mobile towers, not for signals, but for power.
Optical relay: Each relay receives the beam, stabilises it and sends it on with minimal loss. Think of it as a mirror with a brain, constantly tweaking its angle and focus so that the next node gets exactly what it expects.
Scenarios: how a beamed grid might operate
Picture a contested region where ground infrastructure has been destroyed. A generator hundreds of kilometres away feeds a high-power laser pointed at a loitering drone.
That drone, acting as the first node, receives the beam and passes it on to a second aircraft closer to the frontline. A third aircraft sits over a forward base, sending the last leg straight down to a compact receiver unit beside a radar trailer.
The base commander sees none of this. What they experience is simply a steady 10 kW feed available day and night, regardless of cloud cover at ground level, as long as the airborne chain remains intact.
In another scenario, a swarm of small drones rotates through a charging zone under the beam, each landing for a quick top-up before rejoining patrols. The beam becomes less a static cable replacement and more a shared, wireless charging lane in the sky.
These scenarios highlight both the promise and the fragility of the idea. Lose one aircraft, and the chain breaks. Yet if the system matures, planners might accept that fragility in exchange for removing long, exposed fuel columns from the map.
