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Scientists beam solar power to Earth from space for first time ever

84 points by JoachimS 3y ago

wiz21c 3y ago
What if there are clouds ? What if some space debris hits it ? what's the outlook of this ?
- iso1631 3y ago
  Clouds don't stop your satellite TV working. Some types of clouds can cause rain fade on certain frequencies. If space debris hits it's the same as any other satellite
- JumpCrisscross 3y ago
  > What if there are clouds MAPLE "radiates microwave energy at 9.884 GHz" [1]. At this frequency, water vapor attenuates, but by less than dry air [2]. > What if some space debris hits it It breaks. [1] https://www.its.caltech.edu/~sslab/PUBLICATIONS/2022%20IEEE%20Paper%20%231570826333.pdf https://www.its.caltech.edu/~sslab/PUBLICATIONS/2022%20IEEE%... [2] https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.676-9-201202-S!!PDF-E.pdf https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.676-9-201... Figure 5
- JoeAltmaier 3y ago
  Re: debris. A real problem. It's made of cheaper flexible lightweight components. Have some spares; lift some more. It'll all be about the MTBF
JumpCrisscross 3y ago
No, they didn't. [EDIT: Nvm.]
- alt227 3y ago
  The very next paragraph in the article says: The instrument then beamed energy from a tiny window installed in the unit to the roof of Gordon and Betty Moore Laboratory of Engineering on Caltech’s campus in Pasadena.
saiya-jin 3y ago
Hmm, I am sure the physicists involved did their part, but it sounds like a complex process up there with many components, each susceptible to ie micrometeorites. Why do all these various energy transformations (and transfer it then 'wirelessly', LOL) and not just make some sort of lens / mirrors and focus it on specific point on Earth, that would collect it efficiently? Or does atmosphere do too much dispersion/absorption for it to be effective, compared to microwaves?
- JumpCrisscross 3y ago
  > does atmosphere do too much dispersion/absorption for it to be effective, compared to microwaves Exactly. Water vapor attenuates visible light more than microwaves. One way to think about SBSP is as an orbital lens converting sunlight into a form that better penetrates the atmosphere.
- melagonster 3y ago
  this probably kill someone.
radoomi 3y ago
Imagine planes with a receiver (that fly above the clouds) and are closer to the satellites. Probably not needed anymore with the recent breakthroughs in battery density but still a nice future we have ahead...
- tenpies 3y ago
  It's more than being imagined, it seems it might even be tested, we just won't know about it for a while: https://www.thedrive.com/the-war-zone/33339/x-37b-space-planes-microwave-power-beam-experiment-is-a-way-bigger-deal-than-it-seems https://www.thedrive.com/the-war-zone/33339/x-37b-space-plan...
- JeanMarcS 3y ago
  Well less weight is less power needed so why not, it's still a good idea.
- Gravityloss 3y ago
  This was on NASA's reference roadmap around the year 2000. First X-33, then something air breathing and finally flying saucers powered by ground and space lasers.
__jambo 3y ago
What is the advantage of microwaves over sunlight? Seems like it would be better to just make better solar panels, sunlight is already pretty high-wattage.
- schnitzelstoat 3y ago
  You can beam it to remote areas where there is little sunlight (or it is night-time) and where they may not have access to cheaper energy supplies.
- Chris2048 3y ago
  Surely sunlight is less filtered above the atmosphere than below/in it? Also, maybe microwaves pass through the atmosphere with less absorption? The current plan for solar power stations entail using mirrors to focus it to one spot anyway, so the evolution of that might be space mirrors that convert it to a single frequency before beaming it down to a focal point. Also, the panels/mirrors can be sun-synchronous to receive sun all the time, reducing the amount of them needed (surface panels would not get peak sunlight all the time, and half the time will be shadowed by earth).
- DennisP 3y ago
  From a geostationary satellite you have 99.5% uptime over the course of a year, with most days having 24 hours of full power. Unlike ground solar you don't need batteries, long-distance wires, excess capacity, or demand management. Over 24 hours, a panel in orbit collects five times as much energy as it would on the ground.
  - Jeff_Brown 3y ago
    > 99.5% uptime over the course of a year I had no idea geostationary satellites were so far away! (Per Google, 36,000 km -- about 6 times the radius of the Earth.)
    - DennisP 3y ago
      Plus the equator is tilted with respect to the Earth's orbit, so it's only around the equinoxes that a geostationary satellite is shadowed at all.
henearkr 3y ago
So what are your bets for the year of start of the build of a Dyson swarm? Humanity will probably create an Earth-orbiting swarm first, to prove the concept.
- Chris2048 3y ago
  Would a "Earth-orbiting swarm" be orbiting earth, or share earths orbit?
  - WillAdams 3y ago
    Share earth's orbit --- we could start with a series of units which block a small amount of sunlight --- directly converting that into usable power should be a help in reducing the earth's warming up from the absorption of solar energy.
    - twobitshifter 3y ago
      We’d actually have more heat on earth due to our use of the suns energy at higher output than it hits the earth. We could build a mirror to reflect it back into space though.
      - henearkr 3y ago
        Not all energy use leads to heat production. And also, we could move large parts of our industry to outside our biosphere.
  - henearkr 3y ago
    I was thinking of a swarm orbiting Earth. As a first test.
nomercy400 3y ago
Like SimCity's microwave power plant?
- nickpeterson 3y ago
  What a great game.
aaron695 3y ago
[dead]
stepbeek 3y ago
Eat your heart out Mark Lawrence. All we need now is a shipheart!
anArbitraryOne 3y ago
Not true. I aimed a mirror in the sunlight toward the azimuth once back when I did science research instead of just write code that pretends to be scientific
ChrisMarshallNY 3y ago
That sounds like an excellent bird barbecuer. You thought windmills were bad? Hold my beer.
- ben_w 3y ago
  Less so than you might expect. Because it's a single wavelength, ground stations can be much more efficient than solar; this means 80-90% for the relevant frequencies rather than 20-45% for typical solar PV. Given the size of the ground stations are necessarily enormous, the energy can be quite dilute and still "interesting" power output. I don't think it'll pass the geopolitics test, as you need to prove to your enemies that it can't be abused; and I have yet to hear any proponents seriously consider what can go wrong if there's more than one over the horizon at any one time (that reminds me, I do need to write this up properly…), but if there's only one then the maths says it's probably safe. Unfortunately, the very thing that makes it safe is another reason for pessimism (on Earth): a back-of-the envelope calculation suggests the ground stations have to use about 50,000 tons of aluminium given the size constraints are based on wavelengths, regardless of the power going through them. That's not much for one, but if you need four thousand of them then it's comparable to a 2 TW antipodal power grid which would make space beaming redundant anyway. I can easily see this being used on a Mars colony to get past the global dust storms, but I don't really see it becoming a major player on Earth thanks to the political issues and the alternatives.
  - dabluecaboose 3y ago
    >I can easily see this being used on a Mars colony to get past the global dust storms, but I don't really see it becoming a major player on Earth thanks to the political issues and the alternatives. I could see it becoming analogous to current-day satellite phones. Some very specific uses in remote areas, but not the standard for everyone.
thatcherc 3y ago
Weird article. This section stuck out: > Hajimiri, who led the Caltech that developed MAPLE, explained how the wireless transmission of energy through space is based on a quantum phenomenon called “interference.” And then they go on to describe classical wave interference. I think the point they were trying to make is that the satellite uses a digital phased array antenna to direct its energy downward, but there's nothing quantum about that - it's the same technology used in Starlink terminals and new-ish wifi routers (among many other applications). They also don't list how much power was received! That's the one figure that matters here I think. I'm curious whether it was watts, milliwatts, or kilowatts.
- marginalia_nu 3y ago
  To be fair, technically optical interference is a quantum phenomenon, it's just we've known about it for a long while since photons in the radio and visible light end of the spectrum is toward the wave-like side of the wave/particle duality and we've been modelling it as entirely a wave as a result. Although describing it as a "quantum phenomenon" does admittedly dress it up to be far more exotic than it is, since it's an effect that appears in all waves.
  - abdullahkhalids 3y ago
    There is a very specific metric that is used to distinguish whether a beam of light/EM wave is "classical" or "quantum". The metric is called the second order correlation function, labelled g^(2). If a EM wave has g^(2)>1 then experiments that demonstrate quantum phenomena cannot be successfully performed with this wave. Hence, the EM wave is called classical. Only if g^(2) < 1 can you start doing quantum stuff with it. In this case, almost certainly the waves have g^(2) > 1.
    - marginalia_nu 3y ago
      Coherence is a function of time/length though. At a sufficiently short time interval, all waves are coherent. It's effectively a measure of the time (or equivalently distance) between phase shifts. Since they're claiming to use interference, which only exists in coherent waves, I think it's safe to say in g(2)<1 for the scale they're utilizing interference at. Coherence is so inexorably linked to interference, it's measured using an interferometer.
jmkni 3y ago
Wasn't this the plot of a Bond movie? I recall a villain who did exactly this
- Yizahi 3y ago
  Twice even, in two different movies :)
reportgunner 3y ago
Headline makes it seem like they just pointed a mirror to reflect sun rays to earth.
- dylan604 3y ago
  Maybe they were confusing how the Egyptians lit the pyramids and how we're getting solar energy from space. Seems innocent enough /s
onetimeuse92304 3y ago
A constellation of autonomous mirrors made of spinning metalised film. Can be made cheaply (cheaper than solar panels on Earth surface) and used to beam energy from space or as a weapon to burn enemy installations and troops.
- nine_k 3y ago
  Getting it to the orbit is hard, and destroying / disorienting it there is easier (requires a smaller rocket). The whole thing is not very maneuverable, and cannot effectively defend itself either. Unlike a comm or spy satellite, it has no use except during an active "hot" conflict, so its useful life against any modern military would be pretty limited. Could be used against forces that lack an ability to reach orbit: against guerilla groups maybe, or to burn opium and coca plantations.
  - fnordpiglet 3y ago
    The question, long term, will be can this be built in-situ with regolith materials on the moon and moved to stationary earth orbit. The deltaV of that is considerably less and would allow for extreme scales.
  - onetimeuse92304 3y ago
    How is getting it to orbit hard? SpaceX is already sending satellites in bulk and those are large and complex communication satellites. And soon they will at least 10x if not 100x their capacity to send things. Even just a cursory estimation shows it is going to be much cheaper to send things to space (even high orbit) than buy land on Earth. And as a weapon it is essentially free. Because when you don't use it as a weapon you just beam that power to your power station. You just divert it temporarily when you need to make your enemy to a crisp. It more than pays for itself.
- forgotusername6 3y ago
  Reminds me of this https://en.wikipedia.org/wiki/Znamya_%28satellite%29?wprov=sfla1 https://en.wikipedia.org/wiki/Znamya_%28satellite%29?wprov=s... I was so disappointed when it didn't launch. Iirc they said on the news that it would be visible from the UK had it been successful. Part of me always wondered whether the goal was a golden eye style beam rather than merely illuminating Siberia.
Tade0 3y ago
That's a great demonstration, but I doubt it will become cost-effective anytime soon, or ever. To me it looks like building a sufficiently thick undersea HVDC line wrapping around the globe and connecting all the solar installations on the ground would be an easier route. The sun always shines somewhere.
- toast0 3y ago
  Don't forget to factor in a floating solar array in the pacific ocean somewhere. There's a good period of the day where that's really the only place getting usable sun.
p0w3n3d 3y ago
I wonder how flying animals would feel when they fly through such beam...
- dmd 3y ago
  I wonder how those animals feel right now, given what we currently do to the atmosphere to generate power.
toss1 3y ago
Two things I'd like to know: How detectable is "detectable"; what power level did the experiment yield? Microwave satellite transmissions have been "detectable" and very useful for decades. I don't hold it against them if they are 6 orders of magnitude lower than would be useful (yet), but I'd like to know they are getting in the are of transmitting power vs information. When this is scaled up, what is the energy density in the sky along the beam? Is it enough to have a detrimental effect on insects, birds, airplanes, etc., or can it be kept truly de minimus and still be useful? This is a key question related to considering whether we should just because we can.
coffeeblack 3y ago
Isn't the sun doing that already pretty successfully?
- dotnet00 3y ago
  The idea is to be more efficient with harvesting it into electricity and beaming it down in wavelengths less absorbed by the atmosphere. It also allows for power production without weather getting in the way. So in some hypothetical space solar based future, a rainy region might still be able to rely on solar by having energy beamed down to a farther out station. Although yeah, there's so much room down here to place panels that doing it from space is probably not economically worthwhile just yet.
  - Chris2048 3y ago
    Also, sunlight intercepted outside of earths footprint (e.g. further ahead, or behind, earths orbit around the sun) will receive/redirect light that otherwise wouldn't reach us.
- NegativeK 3y ago
  There are benefits, such as increased insolation and decreased ecological impact under installed panels. Obviously there are a bunch of downsides, because space.
  - Jeff_Brown 3y ago
    > downsides I dread the weaponization of this tech.
ronaldoCR 3y ago
Could they make a constellation of geostationary satellites that send energy down via a cable? Perhaps a way to minimize cable tension if at right height + assisted by some space craft?
- empyrrhicist 3y ago
  The weight of the cable is problematic in earth gravity. See e.g. space elevators.
- ben_w 3y ago
  Yes, provided you can mass produce sufficiently long carbon nanotubes or similar; but the power cable going down that space elevator is also about the length needed to encircle the earth if it was on the ground, so if you can build that part alone you don't need the tower. This isn't a "no": if you're building a space elevator anyway you probably do want to put solar on the top. It's just you don't want to build one only for the solar on the top.
ZeroGravitas 3y ago
There used to be a popular graphic that charted gas vs battery costs and showed what price for each made Hybrids and then full BEV sensible financially. In a well organised world, we'd have raised gas prices steadily to force a changeover. We only did that in patches, but luckily the cost of batteries dropped much faster than anyone expected, so we're firmly in the BEV wins quadrant. You could do similar for space launch costs vs battery cost to map when space solar makes sense. Launch costs have plummeted unexpectedly, but the reduction in battery costs have I think even further tipped the balance so this is less economically sensible than it was before.
- ianburrell 3y ago
  Space solar also has an availability problem. The closer the orbit means more time in shadow. The farther out orbits have more availability but then have larger antennas. I haven't seen analysis on what orbits are practical, geosynchronous is probably too far. The result is that you need multiple satellites to provide reliable power to any place on Earth. If they are high enough, they can provide power to other places on Earth. It may mean that still need batteries to store power during the night or when satellites aren't available. The question is if better to have space solar with batteries or ground solar with batteries. Or multiple space solar or multiple ground solar. My guess is that ground solar will always be cheaper and has the advantage of being more reliable. Also, building long-distance transmission lines might be cheaper than launching solar into space.
iambateman 3y ago
I see in the article that they think solar panels could be more efficient in space, but could they ever be so much more efficient to justify the added cost of flying them to space?
- ianburrell 3y ago
  Solar power satellites made a lot more sense back when solar panels were expensive. If the launch costs were lower, then would get the most bang for efficient panels by launching them into space and getting more utilization from them. Solar panels are now so cheap that the expensive part is mounting them. There are more efficient panels but they aren't worth the cost. The result is that can put panels on a much larger area.
twobitshifter 3y ago
I thought lasers would work better so I did some searching and found this article from DOE. It seems lasers are easier to construct, but the problem with lasers is that it’s a high powered laser in space which might as well be a weapon. https://www.energy.gov/articles/space-based-solar-power https://www.energy.gov/articles/space-based-solar-power ——- Microwave transmitting satellites orbit Earth in geostationary orbit (GEO), about 35,000 km above Earth’s surface. Designs for microwave transmitting satellites are massive, with solar reflectors spanning up to 3 km and weighing over 80,000 metric tons. They would be capable of generating multiple gigawatts of power, enough to power a major U.S. city. The long wavelength of the microwave requires a long antenna, and allows power to be beamed through the Earth’s atmosphere, rain or shine, at safe, low intensity levels hardly stronger than the midday sun. Birds and planes wouldn’t notice much of anything flying across their paths. The estimated cost of launching, assembling and operating a microwave-equipped GEO satellite is in the tens of billions of dollars. It would likely require as many as 40 launches for all necessary materials to reach space. On Earth, the rectenna used for collecting the microwave beam would be anywhere between 3 and 10 km in diameter, a huge area of land, and a challenge to purchase and develop. ——- Laser transmitting satellites, as described by our friends at LLNL, orbit in low Earth orbit (LEO) at about 400 km above the Earth’s surface. Weighing in in at less than 10 metric tons, this satellite is a fraction of the weight of its microwave counterpart. This design is cheaper too; some predict that a laser-equipped SBSP satellite would cost nearly $500 million to launch and operate. It would be possible to launch the entire self-assembling satellite in a single rocket, drastically reducing the cost and time to production. Also, by using a laser transmitter, the beam will only be about 2 meters in diameter, instead of several km, a drastic and important reduction.
hathym 3y ago
how many solar panels can you build with that investment?
SillyUsername 3y ago
I have questions. 1) Will this heat the atmosphere from the contact with water vapour in clouds? 2) Could a plane passing underneath inadvertently reflect or absorb some of this power, if it's banking and it enters a window, turn into a microwave oven? 3) Really it's a weapon in disguise isn't it, like James Bond villain, or the failed Star Wars programme of the US gov? 4) For the levels of power needed, this is going to add many more satellites around Earth, why is this not being considered even compared to fusion or improving existing processes?
tzs 3y ago
Almost all discussion of beaming power between space and Earth is in the context of power generated in space (such as via solar panels) and beaming it to Earth. I wonder if it would ever make sense to beam power from Earth to space? For example there are places on Earth that would be great for large solar farms but don't have sufficient transmission lines to get that power to where it is needed. Perhaps power from those Earth-based solar farms could be beamed to relays in space that would them beam it down to receivers on Earth that can get the power to where it is needed.
- ben_w 3y ago
  I think that only makes sense when the constraints are political; the antennas have to be huge, which means they use a lot of metal, which could be used for a very very long transmission line. A re-run of the Berlin Wall might do it, but only if the city to which that is an apt analogy is OK with totally enclosing it's entire land area in antenna.
tzs 3y ago
> “To the best of our knowledge, no one has ever demonstrated wireless energy transfer in space, even with expensive rigid structures,” Hajimiri added. Technically, haven't the anti-satellite weapons tests that the US, Russia, China, and India have conducted involved wireless energy transfer in space? It was kinetic energy and destroyed the receiver but it was energy transfer. :-)
hulitu 3y ago
> A space solar power prototype has demonstrated its ability to wirelessly beam power through space and direct a detectable amount of energy toward Earth for the first time. I thought that this is what the first communication satellite did.
hulitu 3y ago
> This was used to light up a pair of LEDs. So 4 mW received. Without saying how much they transmitted does not tell much.

84 points by JoachimS 3y ago

wiz21c 3y ago

What if there are clouds ? What if some space debris hits it ? what's the outlook of this ?

iso1631 3y ago
Clouds don't stop your satellite TV working. Some types of clouds can cause rain fade on certain frequencies. If space debris hits it's the same as any other satellite
JumpCrisscross 3y ago
> What if there are clouds MAPLE "radiates microwave energy at 9.884 GHz" [1]. At this frequency, water vapor attenuates, but by less than dry air [2]. > What if some space debris hits it It breaks. [1] https://www.its.caltech.edu/~sslab/PUBLICATIONS/2022%20IEEE%20Paper%20%231570826333.pdf https://www.its.caltech.edu/~sslab/PUBLICATIONS/2022%20IEEE%... [2] https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.676-9-201202-S!!PDF-E.pdf https://www.itu.int/dms_pubrec/itu-r/rec/p/R-REC-P.676-9-201... Figure 5
JoeAltmaier 3y ago
Re: debris. A real problem. It's made of cheaper flexible lightweight components. Have some spares; lift some more. It'll all be about the MTBF

JumpCrisscross 3y ago

No, they didn't. [EDIT: Nvm.]

alt227 3y ago
The very next paragraph in the article says: The instrument then beamed energy from a tiny window installed in the unit to the roof of Gordon and Betty Moore Laboratory of Engineering on Caltech’s campus in Pasadena.

saiya-jin 3y ago

Hmm, I am sure the physicists involved did their part, but it sounds like a complex process up there with many components, each susceptible to ie micrometeorites. Why do all these various energy transformations (and transfer it then 'wirelessly', LOL) and not just make some sort of lens / mirrors and focus it on specific point on Earth, that would collect it efficiently? Or does atmosphere do too much dispersion/absorption for it to be effective, compared to microwaves?

JumpCrisscross 3y ago
> does atmosphere do too much dispersion/absorption for it to be effective, compared to microwaves Exactly. Water vapor attenuates visible light more than microwaves. One way to think about SBSP is as an orbital lens converting sunlight into a form that better penetrates the atmosphere.
melagonster 3y ago
this probably kill someone.

radoomi 3y ago

Imagine planes with a receiver (that fly above the clouds) and are closer to the satellites. Probably not needed anymore with the recent breakthroughs in battery density but still a nice future we have ahead...

tenpies 3y ago
It's more than being imagined, it seems it might even be tested, we just won't know about it for a while: https://www.thedrive.com/the-war-zone/33339/x-37b-space-planes-microwave-power-beam-experiment-is-a-way-bigger-deal-than-it-seems https://www.thedrive.com/the-war-zone/33339/x-37b-space-plan...
JeanMarcS 3y ago
Well less weight is less power needed so why not, it's still a good idea.
Gravityloss 3y ago
This was on NASA's reference roadmap around the year 2000. First X-33, then something air breathing and finally flying saucers powered by ground and space lasers.

__jambo 3y ago

What is the advantage of microwaves over sunlight? Seems like it would be better to just make better solar panels, sunlight is already pretty high-wattage.

schnitzelstoat 3y ago
You can beam it to remote areas where there is little sunlight (or it is night-time) and where they may not have access to cheaper energy supplies.
Chris2048 3y ago
Surely sunlight is less filtered above the atmosphere than below/in it? Also, maybe microwaves pass through the atmosphere with less absorption? The current plan for solar power stations entail using mirrors to focus it to one spot anyway, so the evolution of that might be space mirrors that convert it to a single frequency before beaming it down to a focal point. Also, the panels/mirrors can be sun-synchronous to receive sun all the time, reducing the amount of them needed (surface panels would not get peak sunlight all the time, and half the time will be shadowed by earth).
DennisP 3y ago
From a geostationary satellite you have 99.5% uptime over the course of a year, with most days having 24 hours of full power. Unlike ground solar you don't need batteries, long-distance wires, excess capacity, or demand management. Over 24 hours, a panel in orbit collects five times as much energy as it would on the ground.
- Jeff_Brown 3y ago
  > 99.5% uptime over the course of a year I had no idea geostationary satellites were so far away! (Per Google, 36,000 km -- about 6 times the radius of the Earth.)
  - DennisP 3y ago
    Plus the equator is tilted with respect to the Earth's orbit, so it's only around the equinoxes that a geostationary satellite is shadowed at all.

henearkr 3y ago

So what are your bets for the year of start of the build of a Dyson swarm? Humanity will probably create an Earth-orbiting swarm first, to prove the concept.

Chris2048 3y ago
Would a "Earth-orbiting swarm" be orbiting earth, or share earths orbit?
- WillAdams 3y ago
  Share earth's orbit --- we could start with a series of units which block a small amount of sunlight --- directly converting that into usable power should be a help in reducing the earth's warming up from the absorption of solar energy.
  - twobitshifter 3y ago
    We’d actually have more heat on earth due to our use of the suns energy at higher output than it hits the earth. We could build a mirror to reflect it back into space though.
    - henearkr 3y ago
      Not all energy use leads to heat production. And also, we could move large parts of our industry to outside our biosphere.
- henearkr 3y ago
  I was thinking of a swarm orbiting Earth. As a first test.

nomercy400 3y ago

Like SimCity's microwave power plant?

nickpeterson 3y ago
What a great game.

aaron695 3y ago

[dead]

stepbeek 3y ago

Eat your heart out Mark Lawrence. All we need now is a shipheart!

anArbitraryOne 3y ago

Not true. I aimed a mirror in the sunlight toward the azimuth once back when I did science research instead of just write code that pretends to be scientific

ChrisMarshallNY 3y ago

That sounds like an excellent bird barbecuer. You thought windmills were bad? Hold my beer.

ben_w 3y ago
Less so than you might expect. Because it's a single wavelength, ground stations can be much more efficient than solar; this means 80-90% for the relevant frequencies rather than 20-45% for typical solar PV. Given the size of the ground stations are necessarily enormous, the energy can be quite dilute and still "interesting" power output. I don't think it'll pass the geopolitics test, as you need to prove to your enemies that it can't be abused; and I have yet to hear any proponents seriously consider what can go wrong if there's more than one over the horizon at any one time (that reminds me, I do need to write this up properly…), but if there's only one then the maths says it's probably safe. Unfortunately, the very thing that makes it safe is another reason for pessimism (on Earth): a back-of-the envelope calculation suggests the ground stations have to use about 50,000 tons of aluminium given the size constraints are based on wavelengths, regardless of the power going through them. That's not much for one, but if you need four thousand of them then it's comparable to a 2 TW antipodal power grid which would make space beaming redundant anyway. I can easily see this being used on a Mars colony to get past the global dust storms, but I don't really see it becoming a major player on Earth thanks to the political issues and the alternatives.
- dabluecaboose 3y ago
  >I can easily see this being used on a Mars colony to get past the global dust storms, but I don't really see it becoming a major player on Earth thanks to the political issues and the alternatives. I could see it becoming analogous to current-day satellite phones. Some very specific uses in remote areas, but not the standard for everyone.

thatcherc 3y ago

Weird article. This section stuck out: > Hajimiri, who led the Caltech that developed MAPLE, explained how the wireless transmission of energy through space is based on a quantum phenomenon called “interference.” And then they go on to describe classical wave interference. I think the point they were trying to make is that the satellite uses a digital phased array antenna to direct its energy downward, but there's nothing quantum about that - it's the same technology used in Starlink terminals and new-ish wifi routers (among many other applications). They also don't list how much power was received! That's the one figure that matters here I think. I'm curious whether it was watts, milliwatts, or kilowatts.

marginalia_nu 3y ago
To be fair, technically optical interference is a quantum phenomenon, it's just we've known about it for a long while since photons in the radio and visible light end of the spectrum is toward the wave-like side of the wave/particle duality and we've been modelling it as entirely a wave as a result. Although describing it as a "quantum phenomenon" does admittedly dress it up to be far more exotic than it is, since it's an effect that appears in all waves.
- abdullahkhalids 3y ago
  There is a very specific metric that is used to distinguish whether a beam of light/EM wave is "classical" or "quantum". The metric is called the second order correlation function, labelled g^(2). If a EM wave has g^(2)>1 then experiments that demonstrate quantum phenomena cannot be successfully performed with this wave. Hence, the EM wave is called classical. Only if g^(2) < 1 can you start doing quantum stuff with it. In this case, almost certainly the waves have g^(2) > 1.
  - marginalia_nu 3y ago
    Coherence is a function of time/length though. At a sufficiently short time interval, all waves are coherent. It's effectively a measure of the time (or equivalently distance) between phase shifts. Since they're claiming to use interference, which only exists in coherent waves, I think it's safe to say in g(2)<1 for the scale they're utilizing interference at. Coherence is so inexorably linked to interference, it's measured using an interferometer.

jmkni 3y ago

Wasn't this the plot of a Bond movie? I recall a villain who did exactly this

Yizahi 3y ago
Twice even, in two different movies :)

reportgunner 3y ago

Headline makes it seem like they just pointed a mirror to reflect sun rays to earth.

dylan604 3y ago
Maybe they were confusing how the Egyptians lit the pyramids and how we're getting solar energy from space. Seems innocent enough /s

onetimeuse92304 3y ago

A constellation of autonomous mirrors made of spinning metalised film. Can be made cheaply (cheaper than solar panels on Earth surface) and used to beam energy from space or as a weapon to burn enemy installations and troops.

nine_k 3y ago
Getting it to the orbit is hard, and destroying / disorienting it there is easier (requires a smaller rocket). The whole thing is not very maneuverable, and cannot effectively defend itself either. Unlike a comm or spy satellite, it has no use except during an active "hot" conflict, so its useful life against any modern military would be pretty limited. Could be used against forces that lack an ability to reach orbit: against guerilla groups maybe, or to burn opium and coca plantations.
- fnordpiglet 3y ago
  The question, long term, will be can this be built in-situ with regolith materials on the moon and moved to stationary earth orbit. The deltaV of that is considerably less and would allow for extreme scales.
- onetimeuse92304 3y ago
  How is getting it to orbit hard? SpaceX is already sending satellites in bulk and those are large and complex communication satellites. And soon they will at least 10x if not 100x their capacity to send things. Even just a cursory estimation shows it is going to be much cheaper to send things to space (even high orbit) than buy land on Earth. And as a weapon it is essentially free. Because when you don't use it as a weapon you just beam that power to your power station. You just divert it temporarily when you need to make your enemy to a crisp. It more than pays for itself.
forgotusername6 3y ago
Reminds me of this https://en.wikipedia.org/wiki/Znamya_%28satellite%29?wprov=sfla1 https://en.wikipedia.org/wiki/Znamya_%28satellite%29?wprov=s... I was so disappointed when it didn't launch. Iirc they said on the news that it would be visible from the UK had it been successful. Part of me always wondered whether the goal was a golden eye style beam rather than merely illuminating Siberia.

Tade0 3y ago

That's a great demonstration, but I doubt it will become cost-effective anytime soon, or ever. To me it looks like building a sufficiently thick undersea HVDC line wrapping around the globe and connecting all the solar installations on the ground would be an easier route. The sun always shines somewhere.

toast0 3y ago
Don't forget to factor in a floating solar array in the pacific ocean somewhere. There's a good period of the day where that's really the only place getting usable sun.

p0w3n3d 3y ago

I wonder how flying animals would feel when they fly through such beam...

dmd 3y ago
I wonder how those animals feel right now, given what we currently do to the atmosphere to generate power.

toss1 3y ago

Two things I'd like to know: How detectable is "detectable"; what power level did the experiment yield? Microwave satellite transmissions have been "detectable" and very useful for decades. I don't hold it against them if they are 6 orders of magnitude lower than would be useful (yet), but I'd like to know they are getting in the are of transmitting power vs information. When this is scaled up, what is the energy density in the sky along the beam? Is it enough to have a detrimental effect on insects, birds, airplanes, etc., or can it be kept truly de minimus and still be useful? This is a key question related to considering whether we should just because we can.

coffeeblack 3y ago

Isn't the sun doing that already pretty successfully?

dotnet00 3y ago
The idea is to be more efficient with harvesting it into electricity and beaming it down in wavelengths less absorbed by the atmosphere. It also allows for power production without weather getting in the way. So in some hypothetical space solar based future, a rainy region might still be able to rely on solar by having energy beamed down to a farther out station. Although yeah, there's so much room down here to place panels that doing it from space is probably not economically worthwhile just yet.
- Chris2048 3y ago
  Also, sunlight intercepted outside of earths footprint (e.g. further ahead, or behind, earths orbit around the sun) will receive/redirect light that otherwise wouldn't reach us.
NegativeK 3y ago
There are benefits, such as increased insolation and decreased ecological impact under installed panels. Obviously there are a bunch of downsides, because space.
- Jeff_Brown 3y ago
  > downsides I dread the weaponization of this tech.

ronaldoCR 3y ago

Could they make a constellation of geostationary satellites that send energy down via a cable? Perhaps a way to minimize cable tension if at right height + assisted by some space craft?

empyrrhicist 3y ago
The weight of the cable is problematic in earth gravity. See e.g. space elevators.
ben_w 3y ago
Yes, provided you can mass produce sufficiently long carbon nanotubes or similar; but the power cable going down that space elevator is also about the length needed to encircle the earth if it was on the ground, so if you can build that part alone you don't need the tower. This isn't a "no": if you're building a space elevator anyway you probably do want to put solar on the top. It's just you don't want to build one only for the solar on the top.

ZeroGravitas 3y ago

There used to be a popular graphic that charted gas vs battery costs and showed what price for each made Hybrids and then full BEV sensible financially. In a well organised world, we'd have raised gas prices steadily to force a changeover. We only did that in patches, but luckily the cost of batteries dropped much faster than anyone expected, so we're firmly in the BEV wins quadrant. You could do similar for space launch costs vs battery cost to map when space solar makes sense. Launch costs have plummeted unexpectedly, but the reduction in battery costs have I think even further tipped the balance so this is less economically sensible than it was before.

ianburrell 3y ago
Space solar also has an availability problem. The closer the orbit means more time in shadow. The farther out orbits have more availability but then have larger antennas. I haven't seen analysis on what orbits are practical, geosynchronous is probably too far. The result is that you need multiple satellites to provide reliable power to any place on Earth. If they are high enough, they can provide power to other places on Earth. It may mean that still need batteries to store power during the night or when satellites aren't available. The question is if better to have space solar with batteries or ground solar with batteries. Or multiple space solar or multiple ground solar. My guess is that ground solar will always be cheaper and has the advantage of being more reliable. Also, building long-distance transmission lines might be cheaper than launching solar into space.

iambateman 3y ago

I see in the article that they think solar panels could be more efficient in space, but could they ever be so much more efficient to justify the added cost of flying them to space?

ianburrell 3y ago
Solar power satellites made a lot more sense back when solar panels were expensive. If the launch costs were lower, then would get the most bang for efficient panels by launching them into space and getting more utilization from them. Solar panels are now so cheap that the expensive part is mounting them. There are more efficient panels but they aren't worth the cost. The result is that can put panels on a much larger area.

twobitshifter 3y ago

I thought lasers would work better so I did some searching and found this article from DOE. It seems lasers are easier to construct, but the problem with lasers is that it’s a high powered laser in space which might as well be a weapon. https://www.energy.gov/articles/space-based-solar-power https://www.energy.gov/articles/space-based-solar-power ——- Microwave transmitting satellites orbit Earth in geostationary orbit (GEO), about 35,000 km above Earth’s surface. Designs for microwave transmitting satellites are massive, with solar reflectors spanning up to 3 km and weighing over 80,000 metric tons. They would be capable of generating multiple gigawatts of power, enough to power a major U.S. city. The long wavelength of the microwave requires a long antenna, and allows power to be beamed through the Earth’s atmosphere, rain or shine, at safe, low intensity levels hardly stronger than the midday sun. Birds and planes wouldn’t notice much of anything flying across their paths. The estimated cost of launching, assembling and operating a microwave-equipped GEO satellite is in the tens of billions of dollars. It would likely require as many as 40 launches for all necessary materials to reach space. On Earth, the rectenna used for collecting the microwave beam would be anywhere between 3 and 10 km in diameter, a huge area of land, and a challenge to purchase and develop. ——- Laser transmitting satellites, as described by our friends at LLNL, orbit in low Earth orbit (LEO) at about 400 km above the Earth’s surface. Weighing in in at less than 10 metric tons, this satellite is a fraction of the weight of its microwave counterpart. This design is cheaper too; some predict that a laser-equipped SBSP satellite would cost nearly $500 million to launch and operate. It would be possible to launch the entire self-assembling satellite in a single rocket, drastically reducing the cost and time to production. Also, by using a laser transmitter, the beam will only be about 2 meters in diameter, instead of several km, a drastic and important reduction.

hathym 3y ago

how many solar panels can you build with that investment?

SillyUsername 3y ago

I have questions. 1) Will this heat the atmosphere from the contact with water vapour in clouds? 2) Could a plane passing underneath inadvertently reflect or absorb some of this power, if it's banking and it enters a window, turn into a microwave oven? 3) Really it's a weapon in disguise isn't it, like James Bond villain, or the failed Star Wars programme of the US gov? 4) For the levels of power needed, this is going to add many more satellites around Earth, why is this not being considered even compared to fusion or improving existing processes?

tzs 3y ago

Almost all discussion of beaming power between space and Earth is in the context of power generated in space (such as via solar panels) and beaming it to Earth. I wonder if it would ever make sense to beam power from Earth to space? For example there are places on Earth that would be great for large solar farms but don't have sufficient transmission lines to get that power to where it is needed. Perhaps power from those Earth-based solar farms could be beamed to relays in space that would them beam it down to receivers on Earth that can get the power to where it is needed.

ben_w 3y ago
I think that only makes sense when the constraints are political; the antennas have to be huge, which means they use a lot of metal, which could be used for a very very long transmission line. A re-run of the Berlin Wall might do it, but only if the city to which that is an apt analogy is OK with totally enclosing it's entire land area in antenna.

tzs 3y ago

> “To the best of our knowledge, no one has ever demonstrated wireless energy transfer in space, even with expensive rigid structures,” Hajimiri added. Technically, haven't the anti-satellite weapons tests that the US, Russia, China, and India have conducted involved wireless energy transfer in space? It was kinetic energy and destroyed the receiver but it was energy transfer. :-)

hulitu 3y ago

> A space solar power prototype has demonstrated its ability to wirelessly beam power through space and direct a detectable amount of energy toward Earth for the first time. I thought that this is what the first communication satellite did.

hulitu 3y ago

> This was used to light up a pair of LEDs. So 4 mW received. Without saying how much they transmitted does not tell much.