A year ago I read the book The Case for Space Solar Power, which goes into the engineering in detail.
The old SPS designs from the '70s were monolithic beasts that would have been ridiculously expensive. Current designs would use a large number of identical parts, of about eight types, which would self-assemble in space. That way they can be mass produced in factories.
The basic design was PV with microwave transmission, which has already been tested over distances of ten kilometers or so. (Iirc it was between a couple Hawaiian islands.) The receiving station sends a sort of homing signal for a phased array transmitter, which makes it difficult to redirect to somewhere without the homing signal and keep a reasonably focused beam, though you could switch between multiple receiving stations (which are fairly cheap). The station would be in GEO.
The book did some detailed cost analysis and found that with pre-SpaceX launch costs, the SPS could provide power at 15 cents/kWh retail.
Elon Musk has said that at scale the BFR could ultimately get to a $50/lb launch cost, so for grins I plugged that number into the book's calculation and got 4 cents/kWh.
Since this type of solar would work through the night, with little or no need for storage, it could be pretty competitive.
As the article mentions, the station will beam the collected energy down to Earth. Whether in visible light, microwave or any other spectral band, it will need two things for everyday operations:
- ability to point the beam at an arbitrary point on Earth, to track the collector ground installation, and
- ability to focus the beam to proper size
The second capability is crucial; if it's fixed focus - and one with sufficiently large footprint at that - and fixed orbit, it would be safe.
However having either adjustable focus, or adjustable orbit[1] makes this a proper weapon, due to the possibility of pointing multi-megawatt beam of energy at any point on the ground, with little to no countermeasures available. Whether "rogue hackers", or actual owners of the station, somebody would have the capability to destroy, without warning, large swaths of infrastructure on the ground.
I sure hope I'm very wrong about this - that somebody have figured out a way of inherently neutralizing the danger. But for now I treat the project as a doomsday weapon in space.
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[1] the later is a given to an extent, due to the need for orbital stationkeeping, and only possible to limit via provision of weak engines and/or limited fuel loadout
It's a pretty shitty weapon because many countries have the capability to launch a bomb to the satellites and the satellites are way more expensive than the bomb.
Based on a book I read on the subject, there's a way to make a phase-array microwave transmitter, which achieves the required focus by tuning into a reference signal from the receiving station on Earth. Using this system, if you try to transmit to an arbitrary spot you'll have a much more diffuse beam, and even the tight beam is only concentrated enough to raise the temperature several degrees. The receiving station is about the size of a ground-based solar array, but cheaper because it's just microwave antenna.
Another approach is to use a laser, at a frequency that gets absorbed by the atmosphere. Beam it to a high-altitude receiver station, which beams microwaves to a receiver directly below. But that way is a lot more expensive.
It'll be the largest most fragile thing in the sky - kilometers wide and trivially destabilized/neutralized. Think black paint.
We seem to be arguing It'll be terribly expensive and difficult to make work, on one hand, and It'll be trivially easy to make into a weapon, on the other.
> pointing multi-megawatt beam of energy at any point on the ground, with little to no countermeasures available.
Can't you use a mirror to reflect a significant part of that energy back, wrecking the transmitter? If it is several mirrors focusing on the same point on earth (like a solar thermal power station), just jiggle the mirror on land to sweep the mirrors with a beam of energy.
They intend to beam the energy to earth through a laser. I wonder if building a space-mirror and focussing a beam of sunlight would be a much easier and scalable solution.
Though I guess you would need multiple base stations to beam it somewhere where there's no clouds?
Using a wavelength transformation to send this through the non-absorption windows means more energy hits the ground and you aren't hacking terrestrial albedo in a bad way. That global warming is about absorption of sunlight, so putting a lot more sunlight on the same absorption percent means more heat retained. It doesn't do any good to cut gwp materials in the air, then increase sunlight hitting the atmosphere in a way that makes heat retention higher.
I did a quick search on the Energy Returned on Energy Invested calculations. The following site https://dothemath.ucsd.edu/2012/03/space-based-solar-power/
gave an ERoEI of 10:1 for solar panels on earth vs ERoEI of 4.2:1 for solar panels in space. Which would indicate that we would still be better laying solar panel on the ground as long as we got the appropriate empty space.
What did I missed? Have we realized enough progress since 2012 energy-wise, that the threshold has been crossed, or does it only make sense economically due to lower launch prices.
With regards to climate change and global warming, what about putting this in between the sun and the earth to block some of the energy reaching the planet to allow it to cool?
If you have "fusion in a bottle" and don't want to share, this is a decent way to make it harder to steal/damage/use-for-terrorism.
Also, giant beam transmission facilities and giant beam weapons aren't so different from each other. There are going to be detectable critical differences, but with some modifications one can be made into the other.
Radiation damage is going to be a challenge but satellites do with solar for a long time. Onboard robots?
>China's proposal, meanwhile, appears to suggest converting solar energy into electric energy in space, before beaming back to Earth using a microwave or laser and feeding into the grid via a ground receiving system.
Do they need to? I wonder how feasible it would be to put large computational centers in space and have space solar farms powering these computational centers. So if we want to test complex or long-running programs/models/algos, we can just beam it to the computational centers orbiting earth and wait for the results when it's finished.
DennisP|7 years ago
The old SPS designs from the '70s were monolithic beasts that would have been ridiculously expensive. Current designs would use a large number of identical parts, of about eight types, which would self-assemble in space. That way they can be mass produced in factories.
The basic design was PV with microwave transmission, which has already been tested over distances of ten kilometers or so. (Iirc it was between a couple Hawaiian islands.) The receiving station sends a sort of homing signal for a phased array transmitter, which makes it difficult to redirect to somewhere without the homing signal and keep a reasonably focused beam, though you could switch between multiple receiving stations (which are fairly cheap). The station would be in GEO.
The book did some detailed cost analysis and found that with pre-SpaceX launch costs, the SPS could provide power at 15 cents/kWh retail.
Elon Musk has said that at scale the BFR could ultimately get to a $50/lb launch cost, so for grins I plugged that number into the book's calculation and got 4 cents/kWh.
Since this type of solar would work through the night, with little or no need for storage, it could be pretty competitive.
book: https://www.amazon.com/Case-Space-Solar-Power-ebook/dp/B00HN...
AstralStorm|7 years ago
You have to launch replacement panels pretty often due to trash collisions or put them in a less than convenient orbit.
The space solar module with a good enough battery and emitter would cost about as much as half a radiotelescope... Because it is one.
And consider we have problems covering sizable area with wires and cheap panels which are easy to maintain.
steve76|7 years ago
[deleted]
dexen|7 years ago
As the article mentions, the station will beam the collected energy down to Earth. Whether in visible light, microwave or any other spectral band, it will need two things for everyday operations:
- ability to point the beam at an arbitrary point on Earth, to track the collector ground installation, and
- ability to focus the beam to proper size
The second capability is crucial; if it's fixed focus - and one with sufficiently large footprint at that - and fixed orbit, it would be safe.
However having either adjustable focus, or adjustable orbit[1] makes this a proper weapon, due to the possibility of pointing multi-megawatt beam of energy at any point on the ground, with little to no countermeasures available. Whether "rogue hackers", or actual owners of the station, somebody would have the capability to destroy, without warning, large swaths of infrastructure on the ground.
I sure hope I'm very wrong about this - that somebody have figured out a way of inherently neutralizing the danger. But for now I treat the project as a doomsday weapon in space.
--
[1] the later is a given to an extent, due to the need for orbital stationkeeping, and only possible to limit via provision of weak engines and/or limited fuel loadout
adrianN|7 years ago
DennisP|7 years ago
Another approach is to use a laser, at a frequency that gets absorbed by the atmosphere. Beam it to a high-altitude receiver station, which beams microwaves to a receiver directly below. But that way is a lot more expensive.
https://www.amazon.com/Case-Space-Solar-Power-ebook/dp/B00HN...
JoeAltmaier|7 years ago
We seem to be arguing It'll be terribly expensive and difficult to make work, on one hand, and It'll be trivially easy to make into a weapon, on the other.
JetSpiegel|7 years ago
Can't you use a mirror to reflect a significant part of that energy back, wrecking the transmitter? If it is several mirrors focusing on the same point on earth (like a solar thermal power station), just jiggle the mirror on land to sweep the mirrors with a beam of energy.
audunw|7 years ago
In the short term, maybe. But it wouldn't take much time to put in place comprehensive defense for such a system.
In a world with ICBMs, a weapon like this is not really something I'd be worried about. It'd be a pretty stupid weapon to use for an initial attack
The only thing I'm worried about is accidents or hacks.. if that's made impossible it should be fine
neals|7 years ago
Though I guess you would need multiple base stations to beam it somewhere where there's no clouds?
En_gr_Student|7 years ago
AstralStorm|7 years ago
The mirror is a fine grid which makes it much lighter and more resilient, and it is much easier to convert into electricity than light.
GistNoesis|7 years ago
What did I missed? Have we realized enough progress since 2012 energy-wise, that the threshold has been crossed, or does it only make sense economically due to lower launch prices.
adrianN|7 years ago
fredley|7 years ago
fouronnes3|7 years ago
0xcde4c3db|7 years ago
dalbasal|7 years ago
En_gr_Student|7 years ago
If you have "fusion in a bottle" and don't want to share, this is a decent way to make it harder to steal/damage/use-for-terrorism.
Also, giant beam transmission facilities and giant beam weapons aren't so different from each other. There are going to be detectable critical differences, but with some modifications one can be made into the other.
Radiation damage is going to be a challenge but satellites do with solar for a long time. Onboard robots?
kdmedev|7 years ago
I bet spaceX might do something similar in the future. When they are not as encumbered with star link and the BFR.
AstralStorm|7 years ago
2) The costs, on top of super expensive solar panels, make this totally pointless economically. Solar panels are hard enough to maintain on Earth.
3) It's a multi gigawatt level microwave gun in space. Want to blast some lightning onto someone? Sure, now you can. Or fry it.
44Aman|7 years ago
NikolaeVarius|7 years ago
A small part of me wants to see this turn into China deploying a solar powered death laser under the guise of a green energy initiative.
cf141q5325|7 years ago
>China's proposal, meanwhile, appears to suggest converting solar energy into electric energy in space, before beaming back to Earth using a microwave or laser and feeding into the grid via a ground receiving system.
rohan1024|7 years ago
porpoisely|7 years ago
ovi256|7 years ago
Internet points to anyone who computes:
- how expensive that makes the marginal kWh returned to earth likes this.
- how low launch and return-to-earth costs must go for this to become competitive with current kWh costs.
izzydata|7 years ago
Edit: Apparently this is a stupid question, but I still don't know the answer.
thecopy|7 years ago
electricityUser|7 years ago
clojurestan|7 years ago