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China’s ‘land aircraft carrier’ charges flying drone with microwave beam (www.scmp.com)
submitted 6 months ago by to c/technology@lemmy.world
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Scientists in China have demonstrated a wireless power transmission system that uses a ground-based microwave emitter to beam energy to an antenna array mounted on the aircraft’s underside. Importantly, they were able to do this while both the drone and charging system were in motion.

In tests, the car-mounted system kept fixed-wing drones in the air for up to 3.1 hours at an altitude of 15 metres (49 feet). The key challenge that the team overcame was maintaining alignment between the emitter and the drone during flight, wrote Song Liwei, the project’s leader.

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[–] 28 points 6 months ago (26 children)

Neat but 3 hours of loitering is nothing for a fixed wing drone. We have drones that stay in flight for a month or more.

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  • [–] 13 points 6 months ago (9 children)

    I have a 6 year old electric car that takes 40ish minutes to charge, now BYD has batteries that will go from 10% to 70% in 5-10 mins.

    In a few years time these drones will be getting charged from a microwave stream of power from a solar array floating in the upper atmosphere.

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  • [–] 5 points 6 months ago* (4 children)

    Yes but you are charging through a conductive cable. It's not even remotely the same as charging something with microwaves.

    The power delivered decreases exponentially with distance. I'm sure you've heard the phrase "inverse square law".

    Because you divide the effect and gain by 4pi(r^2) meaning your output is decreased by 75% every time you double the distance.

    You're going to need ridiculously powerful hardware and an enormous amount of electricity to run it on any meaningful distance.

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  • [–] 6 points 6 months ago (3 children)

    A concentrated, collimated beam doesn't act like a point source. There's of course some amount of scattering and absorption loss due to atmospheric particles, but other than that a fully collimated wireless energy transmission doesn't lose intensity over distance. Kind of obvious, really, because "where would the energy go?".

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  • [–] 5 points 6 months ago (2 children)

    We already have concentrated microwave beams. And they do suffer immense energy loss on longer distances.

    If you want to transfer energy via microwaves, your efficency will reach single digits real fast on any meaningful distance.

    You are right that the inverse square law doesn't realistically apply with concentrated beams. But you still have energy loss. Lots of it.

    But don't take my word for it. https://www.nature.com/articles/s41598-022-25251-w

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  • [–] 2 points 6 months ago (1 child)

    Quickly glancing through the paper it doesn't really seem to support your claim. They attribute their major losses to the parabolic reflector (meaning they don't have very well concentrated microwave beams?), and say that developing higher efficiency focusing components is important work for the future. I'm kind of guessing that's one thing the Chinese are doing.

    Still, I'm sure there are relevant losses even in properly focused microwave beams. How much that is, I have no clue, and didn't see it addressed in the paper. Might have missed it - it was a very quick glance. :)

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  • [–] 1 point 6 months ago

    I'll be honest, I didn't exactly proof read every word either.

    I think what they meant with parabolic reflector is the reciever. They mentioned they 3d printed a reciever to achieve recors breaking efficency (short range). It's not so easy to gather and convert the microwaves into electric energy. And it's probably not very easy to create a concentrated beam either.

    But that was my interpretation. I'm not going to pretend I understand everything about this. I could be wrong.

    I think the technology to have satellites charge drones in the sky is at least 50 years away.

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  • [–] 3 points 6 months ago*

    The difference is likely size and expense.

    Now you don't need a 100 million dollar Boeing 737 sized drone to loiter for 3 hours.

    Previously small and cheap drones could loiter for 40 mins on an internal battery. Now they can stay up for 3 hours. That can be useful.

    Of course these mobile wireless recharging stations will become military targets for the opposition. So the overall combat math isn't obvious to me, but it's not a tech I see as obviously useless.

    This could be much more straightforwardly a win for civilian applications.

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  • [–] 6 points 6 months ago (14 children)

    Solar power is still more practical

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  • [–] 1 point 6 months ago (6 children)

    not nearly enough surface area to power a drone.

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  • [–] 2 points 6 months ago (5 children)
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  • [–] 2 points 6 months ago (1 child)

    That thing is just a dollar panel with the bare minimum amount of motors to hold up the solar panel. That not practical at all for someone that also needs to move quickly and fire munitions

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  • [–] 1 point 6 months ago* (last edited 6 months ago)

    If you think that's not practical, wait until you see something microwave powered trying to make quick moves. I want to see what you think it will do when it suddenly has to pass through an urban environment with a ton of obstacles. Are you gonna MIMO the damned microwave beam!?!?!? With millisecond trajectory updates!?!?!?

    Not mention that a microwave power transmitter in war will die faster than any mobile radar station because it's so god damned trivial to detect and lock onto, you're losing that bullshit in seconds of turning it on

    The only scenario where this wouldn't be total bullshit is perimeter monitoring drones flying a fixed path, where you for some reason really don't want to have to have multiple drones in rotation (which honestly doesn't make much sense either but at least that's just 80% BS instead of 100% BS)

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  • [–] 1 point 6 months ago (1 child)

    That drone has no mass and uses all its energy to hold up the solar array. Good luck in winds.

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  • [–] 1 point 6 months ago

    Considering everybody talking about using these things in war it has the benefit of not being a suicide beacon visible to instruments for many many miles, unlike the microwave transmitters everybody else here want to carry with them

    Also see;

    https://www.pv-magazine.com/2024/05/09/powering-drones-with-ultra-thin-flexible-perovskite-pv-cells/

    If you actually want to extend the lifetime of high performance autonomous drones in the field then it's more practical to do battery swaps

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  • [–] -2 points 6 months ago* (6 children)

    You can have solar panels and batteries on the ground, and use them to charge the microwave emitter, which can then charge the aircraft, which now does not need to carry solar panels and as much batteries, and thus has increased payload / range.

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  • [–] 0 points 6 months ago (4 children)

    The microwave receiver will not be small or efficient

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  • [–] 1 point 6 months ago* (last edited 6 months ago) (3 children)

    Oh, ok.

    Even though this entire post is... about how it is small enough to fit on a drone, and efficient enough to power it for 3 hours.

    Ok.

    Gotcha.

    I'm not sure if you're aware of this, but densely packed explosive bombs and missiles and warheads tend to be pretty heavy.

    ... the entire problem with purely onboard solar powered vehicles of any kind is that they have to be absurdly lightweight, flimsy.

    That isn't practical.

    It might be purely efficient, in a sense, but it isn't very useful.

    Being able to actually move stuff, that is practical.

    Most transportation modes involve the ability to haul stuff.

    You know, do work, aka the capacity to make stuff move.

    You picking a fight that makes no sense to pick.

    You can have solar and batteries be more stationary, and use microwaves to power things that are more mobile, this post is literally the proof of that concept... you can charge a battery with a any kind of power source.

    Look heres another massive potential application of this, if you science fiction extend the accuracy/capability of this:

    Plop a bunch of solar panels/batteries in the L1 point between the Earth and the sun.

    Now, via a set of satellites in something like concentric orbits, you can get absurd amounts of power, beam it back along chains of satellites, snd then beam it to recieving stations on Earth. Or the Moon. Or orbital infrastructure.

    Microwave transmission power loss will be waaaay less in space, because there's no atmosphere.

    Same with solar panel efficiency!

    Solar Power + Microwave Transmission = Very Good, Actually.

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  • [–] 2 points 6 months ago* (2 children)

    The only two metrics that matter here are W/m^2 and weight.

    You can't make a reasonable microwave receiver lighter than solar film and efficiency peaks around 50% in FIXED installations and you can easily assume less than a quarter (under 10%) when the target isn't just moving, but is also changing angles and distance (you'd have to put the receiver on a gimbal like for cameras) and now it's also interfering with flight (propeller airflow, unless you do weird propeller geometries or tilted body flight

    Tldr DUMB

    Microwave power transfer only make sense between distant fixed line of sight locations with minimal infrastructure available. On earth that's literally just island mountain tops. Even then it's easier and cheaper to still just install solar

    On the moon, it would basically just mean you have one big generator and everything gets powered by the sun when in sunlight and switch to microwave from the generator when in shadow, which is pretty much the only configuration that even make sense

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  • [–] 1 point 6 months ago (1 child)

    You can't make a reasonable microwave receiver lighter than solar film and efficiency peaks around 50% in FIXED installations

    https://www.sciencedirect.com/topics/engineering/microwave-power-transmission

    In JPL 30 kW power was transmitted for 1.54 km with reception conversion array having an efficiency of 80%

    That was 8 years ago.

    What I'm describing are... currently extremely active areas of research.

    Microwave power transfer has been used for many applications since its inception by Maxwell. Wireless charging of EVs and UAV using microwave power are some of the widely researched examples.

    you can easily assume less than a quarter (under 10%) when the target isn't just moving, but is also changing angles and distance (you'd have to put the receiver on a gimbal like for cameras)

    You should maybe look into the level of precision that things like Phalanx CIWS systems have at tracking a moving target, with the ability to throw bullets at it, and hit it.

    Or basically any SPAAG type platform that throws rounds down range.

    Or I dunno, MASERs used in deep space transmission.

    Or all the research that has gone into developing tracking gimbal systems that do intentionally use lasers or some kind of DEW to shoot down small drones, or damage aircraft in flight, or burn out incoming missiles.

    Hell of a lot easier to track a friendly aircraft.

    and now it's also interfering with flight (propeller airflow, unless you do weird propeller geometries or tilted body flight

    Genuinely no clue what you are talking about.

    Are you assuming only like, quadcopters here?

    We've had RQ 4 drone aircraft the size of WW2 medium bomber planes, with jet engines, for 20 years now.

    I'm fairly sure that a jet engine produces a considerable amount of consistent heat.

    Do... you think aircraft engineers... do not know... how to handle... heat?

    Shall I describe a ramjet to you?

    Or maybe we could go with something like the Space Shuttle's reentry tiles?

    In conclusion, you are vastly uniformed as to the state of... not even state of the art technology, that would be incredibly relevant to this discussion.

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  • [–] 1 point 6 months ago* (last edited 6 months ago)

    Those efficiencies are for large senders and receivers. When you have to make it small for a drone the numbers gets worse.

    None of those make continous evasive maneuvers. All the things you mention works because the flight path is fully known in advance and you have full synchronization and ability to lock orientation. None of this works on a drone in urban environments where you'll constantly lose line of sight.

    Dude I'm not talking about heat I'm talking about literal about the literal MW receiver's physical LOCATION on the drone body AND THE ACTUAL PROPULSION IN FORM OF MOVING AIR, because the receiver has to be large, and oriented to the sender at all times, which means there are orientations in which it will block at least some propellers from pushing air physically downwards, unless those also are built to extend far out AND CAN TWIST THEIR ORIENTATION TOO

    (remember that propeller flight obeys the laws of Newton, pushing air down keeps you up and if you tilt your drone to align with the microwave center then you must tilt your propellers or you'll be flying sideways, unless you put receiver on a gimbal in which case it's stupidly complex and you now have to adjust airflow across non-blocked propellers when the receiver is below some of them)

    You can not win an argument by misunderstanding the counterarguments. You lose by not even being able to imagine how a drone actually flies physically in the air, not to mention your lack of ability to just read

    Not to mention that you didn't even ask yourself what happens to a microwaved power transmitter in war. Guess what? It gets targeted and destroyed in seconds. You're dead now. Bye.

    And you can't even make a drone swarm work. Either you have a dozen transmitters (lol good luck) or a phased antenna array in which lol fucking lmao that thing will spew out heat losses and get banned from operating near any remotely populated area due to radio interference

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