8 ms·

1km through the atmosphere is probably all you need to verify that the approach would work for Space Based Solar. I know the military is interested in that. Ima

1km through the atmosphere is probably all you need to verify that the approach would work for Space Based Solar. I know the military is interested in that. Imagine being able to deploy energy anywhere on Earth and not have to setup a logistics chain to facilitate it. That's priceless. The economics for SBS don't really make sense to me, for domestic energy consumption. But economics are irrelevant if it enables you to project power deeper into hostile territory.

walrus01 4y ago
space based solar probably works fine outside the atmosphere, but any space based "power beaming" system would need to contend with the entire thickness of the atmosphere for path loss. > Imagine being able to deploy energy anywhere on Earth and not have to setup a logistics chain to facilitate it. theoretical setups for receiver arrays for space based solar power beamed over microwave are very large, if you're going to go to the trouble to erect a big receiving array somewhere in an empty piece of land, you might as well just build a large ground mount photovoltaic system based on commodity 72-cell monocrystalline Si 400W rated panels.
- DennisP 4y ago
  The atmosphere is fairly transparent to microwaves, so the loss shouldn't be much worse. The book The Case for Space Solar Panel cited net efficiency of 40% with the tech at the time it was written, with a theoretical maximum of 60%. It's a pretty good deal given that a panel in geostationary collects five times as much energy in 24 hours as the same panel on the ground, and the power flows 24/7 for most of the year with no need for storage.
  - scythe 4y ago
    We're a long way from geostationary orbit with this tech, though. They got 1 km, now you need 35,000.
    - giantg2 4y ago
      I guess it depends on how tight the maser beam stays. Most of that 35k km has little to no atmosphere, so that part is a little less important.
      - scythe 4y ago
        There's an equation for that. The effective range of a Gaussian beam is roughly equal to (beam width)^2 / wavelength. I'm not sure what wavelength or beam width they used here, though.
        engineer_22 4y ago
        10Ghz from the article, and photo of the target appears to be 3 meters square
        scythe 4y ago
        That means they're right at the Rayleigh length. You'd need a significantly wider beam or higher frequency to send power from orbit. https://en.wikipedia.org/wiki/Rayleigh_length https://en.wikipedia.org/wiki/Rayleigh_length
        DennisP 4y ago
        In fact, SPS designs involve receivers measured in square kilometers. But they'd be mostly wire and would only contribute about 0.7 cents/kWh to the cost.
      - deleted 4y ago
        [deleted]
      - pfdietz 4y ago
        Why do you think it's a maser? High power microwave beams are a thing in radar. We don't use masers to make them. We don't use masers in microwave ovens, either, or in industrial applications requiring high power microwaves.
  - walrus01 4y ago
    I'd question whether anyone writing "the atmosphere is fairly transparent to microwaves" has calculated the link budget, then implemented in the real world an FCC part 101 licensed microwave radio system (example: 1024QAM modulation, 11 GHz standard FDD band plan, +16 Tx power, 80 MHz channels H&V dual linear, 35 km, 180 cm high performance dishes both ends) and seen the path loss in reality. I think anyone that's done terrestrial point to point microwave telecom professionally will take a very skeptical view of things like 10 GHz band, 1 km power "beams". the reality is that the atmosphere absolutely eats microwave, and when it's not eating it, you have temperature inversions, ducting and diffraction effects to take into account at long distances as well. this is why their demo only works at 1.0 km.
    - DennisP 4y ago
      Indeed. Such a writer may, however, have read up on studies on expected losses for the frequencies proposed for SPS. The book I mentioned covers a lot, but a paper I just googled is available on scihub at your discretion. Here's the abstract: https://www.tandfonline.com/doi/abs/10.1080/00222739.1970.11688771 https://www.tandfonline.com/doi/abs/10.1080/00222739.1970.11... The paper is published in the Journal of Microwave Power, proposes using a wavelength around 10 cm, and with a vertical beam calculates a loss of 1% in clear skies and up to 10% loss with rain.
sillysaurusx 4y ago
My imagination is limited. Care to help me out? 1.6kW deployed to any area in the world. I’m not sure how to visualize that, or what the implications are. Could this power a drone indefinitely with no need to land?
- _s 4y ago
  Yes, any vehicle that can be drive with a motor. Here’s an out there scenario - a few power generating aircraft or satellites in high orbit sending power down to drones at lower altitudes, and vehicles on the ground that just have inverters and motors. No costly batteries, let alone the logistical supplies required for fuel and maintenance for combustion. You are no longer limited by the slow moving fuel vehicles; a blitz is a whole other thing now. Generators and solar arrays are the backbone of most forward operating bases - no longer. You have so much more freedom and space as you are no longer restricted by your power / fuel requirements. It will shift the balance of war, vehicles, infrastructure, logistics. For less military uses - imagine doing away with power cables entirely. No more costly infrastructure built above or below the ground. Just a few towers (much like mobile phone towers) transmitting to households. Depending on where the technology goes, imagine not needing batteries in anything anymore. You’re just hooked up to the wireless grid for power too. It’s still in its infancy, but this is pretty significant.
  - Retric 4y ago
    It might have value in a military setting, but it’s got to be really really stupidly cheap to compete in the civilian space. Which seems extremely unlikely.
  - reaperducer 4y ago
    No costly batteries, let alone the logistical supplies required for fuel and maintenance for combustion And if the enemy captures your vehicles, you can simply deauthorize them and they won't work anymore.
  - thinkmassive 4y ago
    Sounds cool, but also like that satellite is a massive single point of failure
ghostly_s 4y ago
> 1km through the atmosphere is probably all you need to verify that the approach would work for Space Based Solar. How so? Wouldn't a space-based-solar facility need to transmit through the full height of the atmosphere which is much more than 1km?
- coenhyde 4y ago
  It is. I guess I was extrapolating without explaining. Whatever results they get from this test at sea level, they should be able to predict the efficiency for a Space Based Solar System. I wasn't necessarily saying their test verifies that Space Based Solar would work, but just that they have the information to determine if it would.
  - lazide 4y ago
    We already know the efficiency - terrible. Actual end to end efficiency even of this system was more like 2%
    - b112 4y ago
      But this just proves it, don't you see? Only if the government has alien power generating tech, would they care so little about power loss.
      - lazide 4y ago
        Hah, more like if the infinite money machine is going, even 2% is fine - not like they have to worry about the 98% losses?
  - paranoidrobot 4y ago
    So what you're proposing is: - Gather a whole shitload of power on-orbit - Build a massive fleet of power-shunting satellites - Deliver all of that down to the ground I think you may have watched too many James Bond movies. What seems to be missing is consideration of what happens to all that 'lost' power. In their test, they sent 91kW, and received 1.6kW, over a distance of 1km. That missing power doesn't just up and disappear, it's heating the air and water between it. You'd have to scale this up, massively -- I'm not good enough at the math or physics, but I can't imagine it gets any easier at longer distances. So what you're really describing is a death-beam that even if you don't cook the people on the ground, is going to be dumping huge amounts of heat into the atmosphere.
pmoriarty 4y ago
If Space-Based Solar becomes a thing and starts being used in war zones, then it seems almost inevitable that warfare will move in to space... and that could lead to a catastrophic chain reaction of exploding satellites (aka the Kessler syndrome[1]) leading to an impenetrable field of space junk around Earth, which will prevent or at least greatly delay further use/exploration of space. [1] - https://en.wikipedia.org/wiki/Kessler_syndrome https://en.wikipedia.org/wiki/Kessler_syndrome
- TechBro8615 4y ago
  How would space-based solar increase the risk of warfare in space more than space-based communications and geolocation infrastructure already risks it? Knocking out GPS satellites seems like it’d be nearly as effective as knocking out power-supplying satellites. I guess maybe the difference is there is redundancy in the GPS network – taking out one satellite wouldn’t do much damage, but with power supplying satellites I presume it would.
  - Jeff_Brown 4y ago
    There's also a symmetry concern. All parties to any conflict would be using something like GPS. But if only one has access to SBS, the others have less to lose by taking the fight into space.
    - neltnerb 4y ago
      Of course, a country that can shoot down a satellite can probably already launch a nuke, if they have one. And they likely have a bunch of stuff in space as well. There are a few counterexamples, but they wouldn't be, for instance, Russia or China or the US. They'd be mad to do that over a power delivery system that they can utilize or hack.
    - JaimeThompson 4y ago
      The US Military can degrade GPS performance of a selected area while keeping the military encrypted accuracy at standard levels which they did during the Kargil War IIRC.
gerdesj 4y ago
"Imagine being able to deploy energy anywhere on Earth and not have to setup a logistics chain to facilitate it." Logistics is quite a complex beast and you mention "the military". Out of POL (Petrol, Oil, Lubricants) you now have one item nearly sorted - "petrol" ie power source. Your machines also need a few other things to work. Then there is food and water - your army's people need a power source too. Oh and they need a few things to throw at the opposition - munitions. There's a major war being fought in Ukraine right now. Ukraine is bloody huge and it's all about logistics. Russia cannot possibly "win", where win is take and hold all of Ukraine. There was a huge armoured convoy headed for Kyiv and it stalled because it could not possibly have had enough of anything to run for more than a few days. As my dad always used to say (Col. (Retd) RAOC): "An army marches on its stomach". That means that Russia may continue to commit acts of barbarism but it cannot possibly achieve its original aims. They have not got the legs. That's not much comfort for the peoples of Ukraine suffering massive indignity and savage brutality, day after day.
- MobileVet 4y ago
  Logistics (fuel, food, tires etc) were definitely a contributor to the convoy’s stalled assault. As it turns out, there were also a group of Ukrainian Special forces that pestered and attacked that column relentlessly. Kudos to them and their efforts. https://www.theguardian.com/world/2022/mar/28/the-drone-operators-who-halted-the-russian-armoured-vehicles-heading-for-kyiv https://www.theguardian.com/world/2022/mar/28/the-drone-oper...
  - krisoft 4y ago
    > As it turns out, there were also a group of Ukrainian Special forces that pestered and attacked that column relentlessly. I mean yeah? That is the nature of millitary offensives. The opposition tends to make your life harder every way they can. When someone says that the attack stalled because the attacking force botched the logistics, that doesn’t mean that they forgot that tanks run on fuel. It means that they couldn’t deliver the supplies needed because their logistics were not resilient to enemy action. In the very micro level this might mean that a particular Ukranian soldier shot dead a particular Russian fuel truck driver. (Or they blown up the truck, or trapped it, or misrouted it, or caused them enough fear the truck driver decided to run away instead of getting the supplies to the troops.) On the macro level the details don’t matter, there you can say that the logistic failed. Similarly if during an excercise in your own country the fuel trucks show up a day late that’s not a problem. You spend the day camping next to your tank and the fuel arrives when it arrives. But if the same happens during a real invasion you are a sitting duck the enemy is trying to kill. Logistics failing and the Ukrainan forces pestering and attacking the column are not two different things. They are one and the same, but on two different levels of abstraction.
ta8645 4y ago
Isn't this more likely just the cover story for a space based death ray? Why pass energy to the ground for your troops, if you can just kill your targets from space?
- ReactiveJelly 4y ago
  An electric drone with a few bombs and endless range might be able to blow up tougher things than a 1 kW microwave alone
chris_va 4y ago
No, the ionosphere does weird things, including self-lensing at high enough power densities (frequency dependent too), so there's probably a bit more to test
- coenhyde 4y ago
  Thanks, I wasn't aware of that.
- zo1 4y ago
  Where would one learn about that?
  - chris_va 4y ago
    A bit old, but fun read: https://ntrs.nasa.gov/api/citations/19810019084/downloads/19810019084.pdf https://ntrs.nasa.gov/api/citations/19810019084/downloads/19... ... there are newer sources, but I'd have to dig through notes, nothing very concrete.
- DennisP 4y ago
  Power density for a beam from geostationary would be quite low. Receiving stations would be kilometers wide.
Renaud 4y ago
I doubt it's never going to be practical enough to be useful, at all. I might be wrong and someone can do the calculation to prove me wrong, but I don't think there is any way you're going to power an army or even a single regiment with that (or even more than a couple of toasters). First, Low Earth Orbit is at least 160km above the Earth. You could do it at 100km but now you have to fight atmospheric drag on top of everything else and constantly need to readjust your orbit to avoid burning up. Forming a beam tight enough that it stays focussed on your small target is the first challenge. Talk about fraction of a degree. You'll get much worse energy loss just there, because your target will always be smaller than the energy spot. If you have to build large targets, then there is a point where it would be more advantageous to just use solar panels on the ground. Second, since you'd be using a low orbit, you'd still be in the dark at night, so no power for you. Third, the lower the orbit, the faster the satellite is going to zoom past in the sky. You'd need a constellation of these to constantly reshape their beam to all their targets. As their distance from the target increases, the power received will also vary a lot. It also means the satellite will have to know the precise location of the target at all times. Might be workable for a static unit, but if you're talking drone/autonomous system, then they will need a way to transmit this information somewhere, very, very accurately too so the beam can find it. It's not something you could deploy anywhere in an instant unless you have thousands of satellites covering all areas of interest. The solar panel size you would need to ensure some decent minimum power received on Earth would be pretty big. Say you have a super efficient solar panel that can get you 30% efficiency, you'd get max of 300W/m2. So you would need very large arrays of panels just to get a few kW on the ground. Now if instead of solar panels you want to beam up energy to bounce from the satellite back to the target, you'd double your problem space: need lots of large emitters that would need to target a constellation of fast moving satellites. Not great unless you know you can deploy them exactly where they are needed, which probably limits the use cases in foreign territories. So, I'd say this will remain a niche application on Earth, where the size of the transmitting arrays depends on the distance to the target, and will probably never go beyond a trial in space if they manage to convince someone to get funding for it.
- newjersey 4y ago
  > First, Low Earth Orbit is at least 160km above the Earth. You could do it at 100km but now you have to fight atmospheric drag on top of everything else and constantly need to readjust your orbit to avoid burning up. I am just thinking out loud but what if we went out further and added an array of satellites in the geostationary orbits, not to power anything on earth but rather to power each other. I was thinking if we had enough of these satellites and they were in line of sight between each other, could they kind of send power to each other in case one of them was in the dark? Just thinking out loud.
egsmi0 4y ago
> Imagine being able to deploy energy anywhere on Earth and not have to setup a logistics chain to facilitate it. I suppose. But on the other hand, let's say "anywhere on Earth" is a PCB inside an attacking enemy jet fighter. I haven't designed any PCBs for the military, so I don't know what their standards are, but I can say every low voltage circuit I've designed would not appreciate even 10W being dumped into any arbitrary net...

walrus01 4y ago

space based solar probably works fine outside the atmosphere, but any space based "power beaming" system would need to contend with the entire thickness of the atmosphere for path loss. > Imagine being able to deploy energy anywhere on Earth and not have to setup a logistics chain to facilitate it. theoretical setups for receiver arrays for space based solar power beamed over microwave are very large, if you're going to go to the trouble to erect a big receiving array somewhere in an empty piece of land, you might as well just build a large ground mount photovoltaic system based on commodity 72-cell monocrystalline Si 400W rated panels.

DennisP 4y ago
The atmosphere is fairly transparent to microwaves, so the loss shouldn't be much worse. The book The Case for Space Solar Panel cited net efficiency of 40% with the tech at the time it was written, with a theoretical maximum of 60%. It's a pretty good deal given that a panel in geostationary collects five times as much energy in 24 hours as the same panel on the ground, and the power flows 24/7 for most of the year with no need for storage.
- scythe 4y ago
  We're a long way from geostationary orbit with this tech, though. They got 1 km, now you need 35,000.
  - giantg2 4y ago
    I guess it depends on how tight the maser beam stays. Most of that 35k km has little to no atmosphere, so that part is a little less important.
    - scythe 4y ago
      There's an equation for that. The effective range of a Gaussian beam is roughly equal to (beam width)^2 / wavelength. I'm not sure what wavelength or beam width they used here, though.
      - engineer_22 4y ago
        10Ghz from the article, and photo of the target appears to be 3 meters square
        scythe 4y ago
        That means they're right at the Rayleigh length. You'd need a significantly wider beam or higher frequency to send power from orbit. https://en.wikipedia.org/wiki/Rayleigh_length https://en.wikipedia.org/wiki/Rayleigh_length
        DennisP 4y ago
        In fact, SPS designs involve receivers measured in square kilometers. But they'd be mostly wire and would only contribute about 0.7 cents/kWh to the cost.
    - deleted 4y ago
      [deleted]
    - pfdietz 4y ago
      Why do you think it's a maser? High power microwave beams are a thing in radar. We don't use masers to make them. We don't use masers in microwave ovens, either, or in industrial applications requiring high power microwaves.
- walrus01 4y ago
  I'd question whether anyone writing "the atmosphere is fairly transparent to microwaves" has calculated the link budget, then implemented in the real world an FCC part 101 licensed microwave radio system (example: 1024QAM modulation, 11 GHz standard FDD band plan, +16 Tx power, 80 MHz channels H&V dual linear, 35 km, 180 cm high performance dishes both ends) and seen the path loss in reality. I think anyone that's done terrestrial point to point microwave telecom professionally will take a very skeptical view of things like 10 GHz band, 1 km power "beams". the reality is that the atmosphere absolutely eats microwave, and when it's not eating it, you have temperature inversions, ducting and diffraction effects to take into account at long distances as well. this is why their demo only works at 1.0 km.
  - DennisP 4y ago
    Indeed. Such a writer may, however, have read up on studies on expected losses for the frequencies proposed for SPS. The book I mentioned covers a lot, but a paper I just googled is available on scihub at your discretion. Here's the abstract: https://www.tandfonline.com/doi/abs/10.1080/00222739.1970.11688771 https://www.tandfonline.com/doi/abs/10.1080/00222739.1970.11... The paper is published in the Journal of Microwave Power, proposes using a wavelength around 10 cm, and with a vertical beam calculates a loss of 1% in clear skies and up to 10% loss with rain.

sillysaurusx 4y ago

My imagination is limited. Care to help me out? 1.6kW deployed to any area in the world. I’m not sure how to visualize that, or what the implications are. Could this power a drone indefinitely with no need to land?

_s 4y ago
Yes, any vehicle that can be drive with a motor. Here’s an out there scenario - a few power generating aircraft or satellites in high orbit sending power down to drones at lower altitudes, and vehicles on the ground that just have inverters and motors. No costly batteries, let alone the logistical supplies required for fuel and maintenance for combustion. You are no longer limited by the slow moving fuel vehicles; a blitz is a whole other thing now. Generators and solar arrays are the backbone of most forward operating bases - no longer. You have so much more freedom and space as you are no longer restricted by your power / fuel requirements. It will shift the balance of war, vehicles, infrastructure, logistics. For less military uses - imagine doing away with power cables entirely. No more costly infrastructure built above or below the ground. Just a few towers (much like mobile phone towers) transmitting to households. Depending on where the technology goes, imagine not needing batteries in anything anymore. You’re just hooked up to the wireless grid for power too. It’s still in its infancy, but this is pretty significant.
- Retric 4y ago
  It might have value in a military setting, but it’s got to be really really stupidly cheap to compete in the civilian space. Which seems extremely unlikely.
- reaperducer 4y ago
  No costly batteries, let alone the logistical supplies required for fuel and maintenance for combustion And if the enemy captures your vehicles, you can simply deauthorize them and they won't work anymore.
- thinkmassive 4y ago
  Sounds cool, but also like that satellite is a massive single point of failure

ghostly_s 4y ago

> 1km through the atmosphere is probably all you need to verify that the approach would work for Space Based Solar. How so? Wouldn't a space-based-solar facility need to transmit through the full height of the atmosphere which is much more than 1km?

coenhyde 4y ago
It is. I guess I was extrapolating without explaining. Whatever results they get from this test at sea level, they should be able to predict the efficiency for a Space Based Solar System. I wasn't necessarily saying their test verifies that Space Based Solar would work, but just that they have the information to determine if it would.
- lazide 4y ago
  We already know the efficiency - terrible. Actual end to end efficiency even of this system was more like 2%
  - b112 4y ago
    But this just proves it, don't you see? Only if the government has alien power generating tech, would they care so little about power loss.
    - lazide 4y ago
      Hah, more like if the infinite money machine is going, even 2% is fine - not like they have to worry about the 98% losses?
- paranoidrobot 4y ago
  So what you're proposing is: - Gather a whole shitload of power on-orbit - Build a massive fleet of power-shunting satellites - Deliver all of that down to the ground I think you may have watched too many James Bond movies. What seems to be missing is consideration of what happens to all that 'lost' power. In their test, they sent 91kW, and received 1.6kW, over a distance of 1km. That missing power doesn't just up and disappear, it's heating the air and water between it. You'd have to scale this up, massively -- I'm not good enough at the math or physics, but I can't imagine it gets any easier at longer distances. So what you're really describing is a death-beam that even if you don't cook the people on the ground, is going to be dumping huge amounts of heat into the atmosphere.

pmoriarty 4y ago

If Space-Based Solar becomes a thing and starts being used in war zones, then it seems almost inevitable that warfare will move in to space... and that could lead to a catastrophic chain reaction of exploding satellites (aka the Kessler syndrome[1]) leading to an impenetrable field of space junk around Earth, which will prevent or at least greatly delay further use/exploration of space. [1] - https://en.wikipedia.org/wiki/Kessler_syndrome https://en.wikipedia.org/wiki/Kessler_syndrome

TechBro8615 4y ago
How would space-based solar increase the risk of warfare in space more than space-based communications and geolocation infrastructure already risks it? Knocking out GPS satellites seems like it’d be nearly as effective as knocking out power-supplying satellites. I guess maybe the difference is there is redundancy in the GPS network – taking out one satellite wouldn’t do much damage, but with power supplying satellites I presume it would.
- Jeff_Brown 4y ago
  There's also a symmetry concern. All parties to any conflict would be using something like GPS. But if only one has access to SBS, the others have less to lose by taking the fight into space.
  - neltnerb 4y ago
    Of course, a country that can shoot down a satellite can probably already launch a nuke, if they have one. And they likely have a bunch of stuff in space as well. There are a few counterexamples, but they wouldn't be, for instance, Russia or China or the US. They'd be mad to do that over a power delivery system that they can utilize or hack.
  - JaimeThompson 4y ago
    The US Military can degrade GPS performance of a selected area while keeping the military encrypted accuracy at standard levels which they did during the Kargil War IIRC.

gerdesj 4y ago

"Imagine being able to deploy energy anywhere on Earth and not have to setup a logistics chain to facilitate it." Logistics is quite a complex beast and you mention "the military". Out of POL (Petrol, Oil, Lubricants) you now have one item nearly sorted - "petrol" ie power source. Your machines also need a few other things to work. Then there is food and water - your army's people need a power source too. Oh and they need a few things to throw at the opposition - munitions. There's a major war being fought in Ukraine right now. Ukraine is bloody huge and it's all about logistics. Russia cannot possibly "win", where win is take and hold all of Ukraine. There was a huge armoured convoy headed for Kyiv and it stalled because it could not possibly have had enough of anything to run for more than a few days. As my dad always used to say (Col. (Retd) RAOC): "An army marches on its stomach". That means that Russia may continue to commit acts of barbarism but it cannot possibly achieve its original aims. They have not got the legs. That's not much comfort for the peoples of Ukraine suffering massive indignity and savage brutality, day after day.

MobileVet 4y ago
Logistics (fuel, food, tires etc) were definitely a contributor to the convoy’s stalled assault. As it turns out, there were also a group of Ukrainian Special forces that pestered and attacked that column relentlessly. Kudos to them and their efforts. https://www.theguardian.com/world/2022/mar/28/the-drone-operators-who-halted-the-russian-armoured-vehicles-heading-for-kyiv https://www.theguardian.com/world/2022/mar/28/the-drone-oper...
- krisoft 4y ago
  > As it turns out, there were also a group of Ukrainian Special forces that pestered and attacked that column relentlessly. I mean yeah? That is the nature of millitary offensives. The opposition tends to make your life harder every way they can. When someone says that the attack stalled because the attacking force botched the logistics, that doesn’t mean that they forgot that tanks run on fuel. It means that they couldn’t deliver the supplies needed because their logistics were not resilient to enemy action. In the very micro level this might mean that a particular Ukranian soldier shot dead a particular Russian fuel truck driver. (Or they blown up the truck, or trapped it, or misrouted it, or caused them enough fear the truck driver decided to run away instead of getting the supplies to the troops.) On the macro level the details don’t matter, there you can say that the logistic failed. Similarly if during an excercise in your own country the fuel trucks show up a day late that’s not a problem. You spend the day camping next to your tank and the fuel arrives when it arrives. But if the same happens during a real invasion you are a sitting duck the enemy is trying to kill. Logistics failing and the Ukrainan forces pestering and attacking the column are not two different things. They are one and the same, but on two different levels of abstraction.

ta8645 4y ago

Isn't this more likely just the cover story for a space based death ray? Why pass energy to the ground for your troops, if you can just kill your targets from space?

ReactiveJelly 4y ago
An electric drone with a few bombs and endless range might be able to blow up tougher things than a 1 kW microwave alone

chris_va 4y ago

No, the ionosphere does weird things, including self-lensing at high enough power densities (frequency dependent too), so there's probably a bit more to test

coenhyde 4y ago
Thanks, I wasn't aware of that.
zo1 4y ago
Where would one learn about that?
- chris_va 4y ago
  A bit old, but fun read: https://ntrs.nasa.gov/api/citations/19810019084/downloads/19810019084.pdf https://ntrs.nasa.gov/api/citations/19810019084/downloads/19... ... there are newer sources, but I'd have to dig through notes, nothing very concrete.
DennisP 4y ago
Power density for a beam from geostationary would be quite low. Receiving stations would be kilometers wide.

Renaud 4y ago

I doubt it's never going to be practical enough to be useful, at all. I might be wrong and someone can do the calculation to prove me wrong, but I don't think there is any way you're going to power an army or even a single regiment with that (or even more than a couple of toasters). First, Low Earth Orbit is at least 160km above the Earth. You could do it at 100km but now you have to fight atmospheric drag on top of everything else and constantly need to readjust your orbit to avoid burning up. Forming a beam tight enough that it stays focussed on your small target is the first challenge. Talk about fraction of a degree. You'll get much worse energy loss just there, because your target will always be smaller than the energy spot. If you have to build large targets, then there is a point where it would be more advantageous to just use solar panels on the ground. Second, since you'd be using a low orbit, you'd still be in the dark at night, so no power for you. Third, the lower the orbit, the faster the satellite is going to zoom past in the sky. You'd need a constellation of these to constantly reshape their beam to all their targets. As their distance from the target increases, the power received will also vary a lot. It also means the satellite will have to know the precise location of the target at all times. Might be workable for a static unit, but if you're talking drone/autonomous system, then they will need a way to transmit this information somewhere, very, very accurately too so the beam can find it. It's not something you could deploy anywhere in an instant unless you have thousands of satellites covering all areas of interest. The solar panel size you would need to ensure some decent minimum power received on Earth would be pretty big. Say you have a super efficient solar panel that can get you 30% efficiency, you'd get max of 300W/m2. So you would need very large arrays of panels just to get a few kW on the ground. Now if instead of solar panels you want to beam up energy to bounce from the satellite back to the target, you'd double your problem space: need lots of large emitters that would need to target a constellation of fast moving satellites. Not great unless you know you can deploy them exactly where they are needed, which probably limits the use cases in foreign territories. So, I'd say this will remain a niche application on Earth, where the size of the transmitting arrays depends on the distance to the target, and will probably never go beyond a trial in space if they manage to convince someone to get funding for it.

newjersey 4y ago
> First, Low Earth Orbit is at least 160km above the Earth. You could do it at 100km but now you have to fight atmospheric drag on top of everything else and constantly need to readjust your orbit to avoid burning up. I am just thinking out loud but what if we went out further and added an array of satellites in the geostationary orbits, not to power anything on earth but rather to power each other. I was thinking if we had enough of these satellites and they were in line of sight between each other, could they kind of send power to each other in case one of them was in the dark? Just thinking out loud.

egsmi0 4y ago

> Imagine being able to deploy energy anywhere on Earth and not have to setup a logistics chain to facilitate it. I suppose. But on the other hand, let's say "anywhere on Earth" is a PCB inside an attacking enemy jet fighter. I haven't designed any PCBs for the military, so I don't know what their standards are, but I can say every low voltage circuit I've designed would not appreciate even 10W being dumped into any arbitrary net...