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China wants to put a solar farm in space by 2025

engadget.com

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Re: China wants to put a solar farm in space by 2025

#41

Post by adrianN »

GistNoesis wrote: post #34

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 enou…

Solar panels in space also work during the night and while it's cloudy. Did your calculation include the energy costs of storage?

Re: China wants to put a solar farm in space by 2025

#42

Post by dexen »

adrianN wrote: post #29
dexen wrote: post #25

A doomsday weapon in space. 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 fix…

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.

It takes a good while to detect preparations for an attack with this kind of weapon & take the decision ("Mr President, the station has slightly shifted around, should we nuke it now?"), and it takes long time for any physical weapon to reach it.

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.

Re: China wants to put a solar farm in space by 2025

#43

Post by AstralStorm »

DennisP wrote: post #27

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 transmis…

It would be competitive, if there were no nuclear power or maintenance costs or manufacturing costs. These are not counted in launch costs.

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.

Re: China wants to put a solar farm in space by 2025

#44

Post by adrianN »

dexen wrote: post #42
adrianN wrote: post #29

Earlier quoted context omitted.

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.

It takes a good while to detect preparations for an attack with this kind of weapon & take the decision ("Mr President, the station has slightly shifted around, should we nuke it now?"), and it takes long time for any physical weapon to reach it. 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 stati…

That's all true, but a 2h window for destruction of single targets is not very useful against a modern military. There are enough ICBM silos that you can't destroy all of them before someone kills you DEATH STAR and then you still have to win the war that follows.

Re: China wants to put a solar farm in space by 2025

#45

Post by steve76 »

DennisP wrote: post #27

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 transmis…

Pharmaceuticals:

- Dump all the pollution into space

- Crash that energy back to Earth in a capsule

- Comparatively light for what it sells for

- If it blows up, it won't poison a hemisphere

That, or mine an asteroid or the moon and build some spinning flywheel or hit a turbine with a molten ball of dirt.

Re: China wants to put a solar farm in space by 2025

#46

Post by dexen »

audunw wrote: post #33
dexen wrote: post #25

A doomsday weapon in space. 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 fix…

> with little to no countermeasures available. 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

>In a world with ICBMs

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.

Re: China wants to put a solar farm in space by 2025

#47

Post by DennisP »

AstralStorm wrote: post #43
DennisP wrote: post #27

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 transmis…

It would be competitive, if there were no nuclear power or maintenance costs or manufacturing costs. These are not counted in launch costs. 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 probl…

The costs I quoted include everything, including manufacturing and maintenance. The book breaks down all these costs. In the 4 cents/kWh scenario, launch isn't the dominant cost anymore, and dropping that further wouldn't make much difference.

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.

Re: China wants to put a solar farm in space by 2025

#49

Post by AstralStorm »

adrianN wrote: post #44
dexen wrote: post #42

Earlier quoted context omitted.

It takes a good while to detect preparations for an attack with this kind of weapon & take the decision ("Mr President, the station has slightly shifted around, should we nuke it now?"), and it takes long time for any physical weapon to reach it. 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 stati…

That's all true, but a 2h window for destruction of single targets is not very useful against a modern military. There are enough ICBM silos that you can't destroy all of them before someone kills you DEATH STAR and then you still have to win the war that follows.

Indeed, it is not a useful weapon in an all out war. I'd expect it to be used as surgical strike capability instead. Special operations. You can blame its use on inclement weather due to amount of electric charge this will paint on anything in path and resulting lightning storm.

Re: China wants to put a solar farm in space by 2025

#50

Post by AstralStorm »

adrianN wrote: post #41
GistNoesis wrote: post #34

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 enou…

Solar panels in space also work during the night and while it's cloudy. Did your calculation include the energy costs of storage?

You do know that one can build the panels on the other hemisphere, right? It is all a small matter of building a long enough high voltage DC line. Mostly a political problem. Or you can use microwaves on ground if it is easier to build a bunch of antennas.

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.

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