China wants to put a solar farm in space by 2025(engadget.com) |
China wants to put a solar farm in space by 2025(engadget.com) |
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...
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.
You don't put a battery on a solar power satellite. To whatever extent you need battery, you put it on the ground, but you don't need much because a satellite in geosynchronous is in full sunlight almost all the time.
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
All told, a country that could use this as a weapon doesn’t need to use this as a weapon.
A decent weapon would be space-burst version of ICBM. For intercontinental ground attack, the flight time is typically 20 minutes, but the most reasonable spot for the station is a geostationary orbit - some 36'000 km above equator. With a sensible speed on the order of 8km/s, it would take our missile around 1h25m to reach geostationary orbit assuming a naive straight-up trajectory; with any realistic trajectory it would take way longer. The space weapon would be able to rain terrible destruction in the meantime with impunity.
An alternative would be using ground- or space-based lasers, which give near instantaneous hit, but you'd need to precisely hit a proper part to guarantee fast disabling of the weapon. Merely hitting a random spot on the dish would probably not destroy it outright. You still have to account for the time to make the observations & take the decision. And the current breed of [high power] lasers is single-use only due to the destructive nature of generation of the large energy needed.
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...
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.
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.
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
Quite the opposite. ICBMs have somewhat symmetrical threat and defense model. You use similar technologies for both, and you have actionable amount of time - some 20 minutes - for observation, decision taking, and deployment of countermeasures.
Assuming the station is deployed on geostationary orbit (some 36'000 km above equator), the flight time of the electromagnetic waves is just over 0.1 second. Good luck deploying any countermeasures.
Though I guess you would need multiple base stations to beam it somewhere where there's no clouds?
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.
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.
Ultimately also reflect off space mirrors (meshes) for much cheaper.
The main problem is theoretically weather. Space has the other kind of weather called space junk.
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?
I bet spaceX might do something similar in the future. When they are not as encumbered with star link and the BFR.
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.
And the efficiency! 10X the solar flux outside the atmosphere! And in the right orbit, 2X again because of course night quits being an issue. So a potential 20X better utility per square.
still I have to agree, how do you even maintain something like this. it would probably lead to a full time presence in space unless robotics become just that good. I just don't see the ROI except may be for national pride.
Isn't the main issue that they get dirty, though?
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.
>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.
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.
Edit: Apparently this is a stupid question, but I still don't know the answer.
https://www.google.com/url?q=https://ntrs.nasa.gov/archive/n...
I think debris is not a terrible problem right now. We manage to have a large number of satellites in high orbits.
However space elevators are still soft SF (still missing a material with enough tensile strength), whereas BFR cheap reusable launchers are hard SF, achievable with current known tech.
You do understand you need many more panel fields as opposed to receiving stations that way and half of them is wasted anyway?
I thought the idea is to put them in solar Lagrange or solar synchronous orbit and bend or reflect the maser to stations. 24 hour lit, though a bit trashy if Lsun is used.
The math is suspicious anyway. Wouldn't it mean that the panels would cost 25% of this on ground?
https://corpblog.viasat.com/how-satellites-are-affected-by-t...
This compares pretty favorably to capacity factors of other power sources.
Illumination per square meter averages quite a bit higher than ground solar, and except for the brief times in shadow is 30% higher than ground solar at noon.
The book evaluated other locations including Lagrange points. Everything had pros and cons; the main disadvantage of Lagrange points was the greater distance, requiring bigger antennas. I think more delta-v in deployment was a factor too, though I forget by how much.
Probably would be better to manufacture most of the stuff on some asteroid or on Mercury and have the computation radiation shielded by a significant mass.