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 Post subject: Re: Space Solar Power
PostPosted: May 12, 2014 3:10 pm 
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Unfortunately, the elns idea does not work. The problem is the sun is not a point source. The resulting image on the ground is about 250km in diameter. Oh well.

I do like the LLNL laser transmission SBSP proposal.


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 Post subject: Re: Space Solar Power
PostPosted: May 12, 2014 4:03 pm 
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I hate to say anything to encourage the discussion about the insanity that is space solar power (for the ground) but I will say something encouraging about the magnifying glass idea (which is also bonkers):

It does get past one of the biggest problems with space solar power, namely the need to convert visible light photons to electricity, back to microwave photons for transmission, and back to electricity. It is these repeated conversions that are at the heart of the problem with SSP, and if you simply reflected (or even concentrated) visible light photons to your converter on the ground, you would have done yourself a real favor.


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 Post subject: Re: Space Solar Power
PostPosted: May 13, 2014 12:01 am 
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Would the recent discovery of room temperature continuous wave solid state masers (which need a laser to excite, so maybe solar pumped lasers) be enough to change the game? JAXA in the past even seriously considered solar pumped lasers for laser transmission of space power as well.

Speaking of lasers, there was that recent Project Icarus update for a pulsed fusion starship that uses the otherwise unwanted neutron output of the fusion reaction to pump a nuclear laser to ignite the next reaction.

http://www.icarusinterstellar.org/project-icarus-workshop-update-34-the-ghost-ship/

For a nuclear pumped laser's neutron source, putting the laser in the center of a doughnut shaped thorium reactor with something like a zoetrope shield to pulse neutrons into the lasing chamber through briefly opening shield windows, would get you a pulsed laser. Though one could just skip the constant shield rotation and go for a continuous wave nuclear laser. One could then fire a laser up to a laser mirror relay satellite, then back down to something equivalent to a SPS terrestrial laser receiver. Which sorta fits into some indian SPS proposals for a "space power grid" in terms of a long range transmission network.


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 Post subject: Re: Space Solar Power
PostPosted: May 13, 2014 1:31 am 
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Lenses would never be used, way too expensive and heavy.

Similarly this crazy concept, if it is ever attempted, will not use imaging optics in the first place.

The most likely (actually least crazy) concept would probably use fresnel arrays of reflectors.

There is still the huge problem of cost. The economics just don't work out. This is actually the biggest problem of space solar. Even with zero conversion the launch cost is crazy. Advocates say launch cost will come down, but it will always be a high energy, high materials affair. Future civilizations will still value this highly.

There is another problem with sending the photons in their solar energy wavelength to the earth. It is called cloud cover. At least microwaves make it through most of the clouds. CSP has near zero output with cloud cover, PV is only slightly better.


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 Post subject: Re: Space Solar Power
PostPosted: May 13, 2014 1:49 pm 
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alexterrell wrote:
Trouble is, no one knows when humanity will become space-faring. Hopefully before the next scheduled major asteroid impact.
Personally, I'm a bit more worried about the next UNscheduled strike! ;)

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PostPosted: Apr 29, 2016 10:01 am 
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New Scientist - 24 September 2010
Out-of-this-world proposal for solar wind power
By Charles Choi

Forget wind power or conventional solar power, the world’s energy needs could be met 100 billion times over using a satellite to harness the solar wind and beam the energy to Earth – though focussing the beam could be tricky.

The concept for the so-called Dyson-Harrop satellite begins with a long metal wire loop pointed at the sun. This wire is charged to generate a cylindrical magnetic field that snags the electrons that make up half the solar wind. These electrons get funnelled into a metal spherical receiver to produce a current, which generates the wire’s magnetic field – making the system self-sustaining.

Any current not needed for the magnetic field powers an infrared laser trained on satellite dishes back on Earth, designed to collect the energy. Air is transparent to infrared so Earth’s atmosphere won’t suck up energy from the beam before it reaches the ground.

Back on the satellite, the current has been drained of its electrical energy by the laser – the electrons fall onto a ring-shaped sail, where incoming sunlight can re-energise them enough to keep the satellite in orbit around the sun.

A relatively small Dyson-Harrop satellite using a 1-centimetre-wide copper wire 300 metres long, a receiver 2 metres wide and a sail 10 metres in diameter, sitting at roughly the same distance from the sun as the Earth, could generate 1.7 megawatts of power – enough for about 1000 family homes in the US.

A satellite with the same-sized receiver at the same distance from the sun but with a 1-kilometre-long wire and a sail 8400 kilometres wide could generate roughly 1 billion billion gigawatts (1027 watts) of power, “which is actually 100 billion times the power humanity currently requires”, says researcher Brooks Harrop, a physicist at Washington State University in Pullman who designed the satellite.

Since the satellites are made up mostly of copper, they would be relatively easy to construct. “This satellite is actually something that we can build, using modern technology and delivery methods,” Harrop says.

Satellites laden with solar panels that can beam their energy down 24 hours a day have been discussed for decades. California agreed last December to a deal involving the sale of space-based solar power. Solar panels cost more per pound than the copper making up the Dyson-Harrop satellites, so according to Harrop, “the cost of a solar wind power satellite project should be lower than a comparative solar panel project”.

So far so good, but there is one major drawback. To draw significant amounts of power Dyson-Harrop satellites rely on the constant solar wind found high above the ecliptic – the plane defined by the Earth’s orbit around the sun. Consequently, the satellite would lie tens of millions of kilometres from the Earth. Over those distances, even a sharp laser beam would spread to thousands of kilometres wide by the time it reached Earth.

“Two megawatts spread across areas that large are meaningless, less than moonlight,” says John Mankins, president of consultancy firm Artemis Innovation which specialises in space solar power. To beam power from a Dyson-Harrop satellite to Earth, one “would require stupendously huge optics, such as a virtually perfect lens between maybe 10 to 100 kilometres across,” he says.

He also points out that the wire could burn out due to the huge current coursing through it, although he has not performed the calculations to gauge the probability of that occurring. But he does say that a smaller version of this “clever and interesting” satellite could help power some space missions. “I could imagine uses for this idea outside of the plane of the ecliptic, such as helping generate power for something like the Ulysses spacecraft, which went around the poles of the sun.”

Journal reference: International Journal of Astrobiology, DOI: 10.1017/S1473550410000066

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PostPosted: Apr 30, 2016 11:50 am 
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Cyril R wrote:
I think the real issues are to do with the intermittency . . .
Wow! So my posts about space solar power were totally ignored. How nice.

Boeing, PG&E/Solaren and others fully intend to demonstrate continuous solar power transmitted by geosynchronous satellites in the microwave to ground rectennae that can be located anywhere on earth and generally in the midst of the existing grids. The sun always shines out there and it's a lot more intense. Space solar power can provide NONINTERMITTENT baseload power by wireless power transmission--already demonstrated technologies.

This forum is about thorium energy and we are (as far as I know) the guests of Kirk Sorensen. As long as he keeps this going, I am going to cast my posts in context. It is clear that his company's thorium burner has a huge utility in parallel with all energy generation technologies.

I think S.2795 is a good bill. It does innovate the nuclear regulatory process and should receive the budget appropriations, pass the house, get to our president's desk ASAP to become law. It has bipartisan support. Everyone here ought to read it, make input, and get the show on the road. It will modernize the US nuclear industries and pave the way for advanced reactor makers and especially Flibe Energy to get it's LFTR parts tested under operating conditions and the machine licensed to operate.

If that were done, y'all'd be talking here about solar collection in addition to thorium power. Besides, the whole world has recognized "all of the above" in this arena. Surface collection is misunderstood in the general electorate because most people were allowed to graduate without a satisfactory in their high school science.

Kurt Sellner wrote:
Assuming that they find the money . . .
They? Really. Once a 250 MWe space solar power installation is demonstrated, we'll see what investors and governments will do with private and public funds. Free markets work for the most part.

Kurt Sellner wrote:
This basic aspect of economics will control growth.
Since the health of human economies depend on energy technologies, the stakes are as high as they can get. Market competition is going to be very keen.

Kurt Sellner wrote:
I have to laugh when I see people claim solar power is going to take over any day now. I just don't know how I can explain to these people the problems that must be overcome for solar power to grow with any speed. I just went over the manufacturing problems but that is just a fraction of the issues.
Meanwhile, Boeing and others are building the systems.

Kurt Sellner wrote:
Unless someone can show where I went wrong then I'll stick with my stance that solar power growth will be very slow if it grows at all.
Okay. You went wrong when you didn't read the links I posted. How about that?

We don't know each other. Let's assume we're of good spirit and humor and are predisposed to like one another; and especially laugh at our foibles in this great and honorable endeavor to leave our children with a better future. Let's not get too lost in the thicket. The last of eleven rules-of-thumb in The Art of the Deal is: "Have fun." Good advice coming from a camp that likes to get scrappy.

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PostPosted: Apr 30, 2016 1:07 pm 
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Run the cost calculations on the launch costs for the titanic space solar arrays.
Then run the costs on these gigantic rectenna assemblies that will probably have to be built in deserts or offshore to gain public acceptance.

Even with SpaceX launch costs and thin film panels you are going to have ridiculously large capital costs, and we don't know how long the arrays will last before they get cooked.


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PostPosted: Apr 30, 2016 1:56 pm 
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Yeah, space solar power just doesn't work economically. It's off by orders-of-magnitude, unfortunately.

We used to have a thread just for this topic, we should probably move this discussion there.

UPDATE: just did...


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PostPosted: Apr 30, 2016 2:16 pm 
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Quote:
Wow! So my posts about space solar power were totally ignored. How nice.


Not at all, space solar power is a reality today - it is used to power most satellites. It will stay there - out into space - for the forseeable future. Its about as relevant today as running cars on Chanel # 5. Technically possible, just too expensive to matter. Burning dirt is much cheaper.

Space solar power is very interesting - it gets re-visited every now and so often. Each time it turns out to be too expensive too matter, which is typically "rediscovered" by the more reasonable researchers. As if that's a surprise. Putting stuff into orbit is expensive, who knew?

In x number of generations things may be different, but right now its not something that can make an impact in our generation.


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PostPosted: May 01, 2016 9:14 am 
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Cyril R wrote:
Not at all, space solar power is a reality today - it is used to power most satellites. It will stay there - out into space - for the forseeable future. Its about as relevant today as running cars on Chanel # 5. Technically possible, just too expensive to matter. Burning dirt is much cheaper.


Excellent analogy Cyril, I may have to steal it for a presentation to some of my old NASA friends, who still hold out hope for SBSP to be the "business case" for a greatly expanded space program.


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 Post subject: Re: Space Solar Power
PostPosted: May 01, 2016 10:05 am 
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Thank you, Mr. Cyril and Mr. Kirk. Success! My posted report elicited clear arguments from people who are truly qualified to judge optimum energy technology policy as far as this former-chemist can tell. Thanks to Gordan McDowell, et. al, I discovered the thorium conferences. My zeal for space solar power was clarified.
Kirk Sorensen wrote:
Cyril R wrote:
Not at all, space solar power is a reality today - it is used to power most satellites. It will stay there - out into space - for the forseeable future. Its about as relevant today as running cars on Chanel # 5. Technically possible, just too expensive to matter. Burning dirt is much cheaper.
Excellent analogy Cyril, I may have to steal it for a presentation to some of my old NASA friends, who still hold out hope for SBSP to be the "business case" for a greatly expanded space program.
Reallocation of public funding for nuclear regulatory innovation and modernization to include the new advanced nuclear energy licensing cost-share grant program seems to be a necessary part of that business case. (Please comment on S.2795: http://energyfromthorium.com/forum/viewtopic.php?f=50&t=4675)

Kirk, NASA is like God in my world. That you regret not having devoted those years rather to the Flibe Energy LFTR troubles a person who is about 17 years your senior and FAR less accomplished. I thought it was the space probe power systems work for NASA that took you to Oak Ridge? Didn't that ignite this great innovation?

Our human process is to take notice of the object emerging from the background, this subject of (surface) solar just further clarifies the founding point of this forum: the thorium burner deserves re-prioritization upward. Our best candidate is the Flibe Energy LFTR in my view for one.

Thanks, rgvandewalker, alexterrell, E Ireland, Burghard, Kurt Sellner, KitemanSA, especially Kirk, and Cyril The Great.

Closing out this topic on solar growth changing the energy technology landscape: The answer is that it is disqualified for immediate baseload power plants. Public funding ought to be reallocated. (Advanced reactor development requires first-mover support that the private sector has not born in the history of our nation but greatly benefits from the results of those first-mover efforts.)

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PostPosted: May 01, 2016 10:28 am 
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Kirk Sorensen wrote:
We used to have a thread just for this topic, we should probably move this discussion there.

UPDATE: just did...
Thanks, Mr. Kirk, for keeping my posts and adding them to the proper thread (moved from Is solar energy use increasing exponentially?).

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PostPosted: May 03, 2016 2:54 pm 
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Kirk Sorensen wrote:
Cyril R wrote:
Not at all, space solar power is a reality today - it is used to power most satellites. It will stay there - out into space - for the forseeable future. Its about as relevant today as running cars on Chanel # 5. Technically possible, just too expensive to matter. Burning dirt is much cheaper.


Excellent analogy Cyril, I may have to steal it for a presentation to some of my old NASA friends, who still hold out hope for SBSP to be the "business case" for a greatly expanded space program.


That would be a nice hope - indeeed, one I had some time ago.

My current hope is that might be the other way round. A greatly expanded space program may - eventually - make the business case for space solar power. We'll have MSRs all over the place before then, but solar power will still be cheaper in space.


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PostPosted: May 03, 2016 10:00 pm 
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alexterrell wrote:
We'll have MSRs all over the place before then, but solar power will still be cheaper in space.


I'm not as confident about that as you. Spacecraft need power to do anything, most important of which is usually communications, next in line is likely propulsion. This is true of all spacecraft whether they be manned and unmanned, satellites or deep space probes, they need power. For solar panels to work there must be enough sun, when or if (and it's usually a matter more of when than if) a spacecraft enters a shadow the craft must have an energy store (batteries or capacitors) or an alternative power source.

(Side note: I just wrote a sentence on where solar power is considered the default and something like nuclear power is an "alternative" energy source which seems very odd to me.)

Much like on terra firma it seems odd to invest in an unreliable energy source like solar power and still need a reliable backup when one could simply use that reliable backup as the primary power source and not bother with the solar power. What I expect to happen is that with a large number of MSRs on earth the problem of fission product waste will create a new market for RTGs for space based applications, perhaps even in the normally sunny satellite business.

While Pu-238 could be called a gold standard for RTGs for it's nice balance of energy density and operational lifespan it does require processes specific to producing it. This might take the form of a MSR that extracts Pu from the fuel salt in a way to assure high purity of Pu-238, extraction of Pu from spent fuel (solid or salt) and enriching it, or special purpose non-power reactors for its production. Lesser RTG material like Sr-90 and Cs-137 are effectively "free" since they will be produced by fission regardless of the fuel used and its presence in spent fuel is unavoidable. I expect that we could see businesses that pop up that get paid to take the Sr-90 and Cs-137 from the nuclear power plants and then get paid to sell it as RTGs for satellites and such.

It is conceivable for me that space grade RTGs could be cheaper than space grade solar panels. With RTGs powering satellites then we could see satellites that can be freed from sunny orbits, which I've heard can get crowded. We've already seen satellites collide in space because of the number of them in these favored orbits. When they collide a debris field is created, making these orbits even more dangerous. Also, RTGs are compact while solar panels must have large areas to soak up the sun. A RTG powered satellite could effectively be "armored up" against these collisions, have power sources that last centuries, and travel in less crowded orbits. I'd think this would be seen as beneficial for military, scientific, and commercial satellites.

The RTG can provide power but may also help with propulsion. I don't know if this is just theoretical or is in use but I've seen electric propulsion that uses wires strung out from a satellite where a charge or current can be placed so it can use the earth's magnetic field as a sort of motor to move a satellite. With RTGs this can be done even if in shadow. RTGs can help with traditional station keeping thrusters by keeping the fuel from freezing. With a set of motors and solar sails a satellite or probe can maneuver without expending fuel, making the fuel last longer. Some of this is already done on solar powered satellites where they use the solar panels as sails but an RTG allows this without sacrificing power output.

If we expect to continue with manned spacecraft in orbit I would expect the space stations to get larger and the number of occupants to rise. At some point the ability to power a station like this on solar power alone (assuming we have not already reached this point) will be difficult. Is it inconceivable to have something much like an Ohio class submarine in orbit? Much like the submarine it'd be a military space station with armor and weapons, a crew of over 150 people, powered by a nuclear reactor, used as a means to project power over the globe.

Perhaps a manned space station like that is unlikely any time soon. One point I'd like to make is that earth's orbit is getting dangerous because of debris and crowding, and relying on solar power may become problematic. Should nuclear power become a big business on earth then I can see the fission products from them put to use in space. Taking this idea a bit further we could see a militarizing of space, or merely enough debris from previous satellites, that armoring satellites will become necessary and having large fragile and critical solar panels propped out the side makes a big easy target to hit either deliberately from an attack or just by chance from debris. This makes RTGs look real nice for small craft and nuclear reactors look good for larger ones.

That makes me wonder how one would design a MSR to operate in a low-G environment.

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