"It was much too big and fantastical," said Robert Zubrin, president and
founder of Mars Society, a non-profit that promotes human settlement of
Mars.

I too am not sure that satellite power stations are necessary. We can
generate huge amounts of solar power on Earth (at least in the tropical
regions.)

With BFR available may be SPS could become practical??

The important thing is that space *does* get industrialized. Not how it does.More important still is saving the earth. Ground based solar seems to be onthe way to doing that... assuming of course it can be done soon enough...and they can get over the problem of storage.I've never believed in SBSP, to be frank. Aside from the huge costs, thereare things having nothing to do with costs.There is the necessity of bathing the earth in terawatts of microwaves, whichhas always given me the willies. The company-line response to this is thatthese only will hit the collectors. Nope. Some of it won't. No matter how big theemitter and collectors are, there is beam scatter and some of it is going to spread all over the place.There's really not much savings in ground use of collectors vs. PV panels at least in the U.S. If PV efficiencies improve, there won't be any.Another selling point of SBSP advocates is, something like chicken wire couldbe used for the collectors, and so use the land underneath as farm or ranchland. After reading into it my findings were: no this is snake oil.

If ground-based PV becomes more efficient, then the PV used on powersats also gets more efficient. Also, places like the UK or Norway have bigger problems with ground-based solar than the Sahara or even (most of) the US.
As for what to put under the rectenna: factories, greenhouse agriculture, production of synthetic hydrocarbons. You've got some basic structure there, and scads of electricity.
But if building hotels or starships or such gets the job done better than powersats, then by all means build hotels and starships or mining colonies or whatever.

Combs, Mike wrote:> Point to a scientific study detailing the harmful effects of microwave> exposure (below the level of cooking the organism, of course!)>> There aren't any. Federal regulations regarding "acceptable" exposure to> microwaves are not based on any scientific finding.The first is a list of over 100 studies done. You might question the validity ofthese studies, but that there are plenty of them is not in doubt.http://mercola.fileburst.com/PDF/123ReviewsNonthermalEffectsMicrowaveLowerFrequencyEMFs-MartinPall.pdfhttps://articles.mercola.com/sites/articles/archive/2010/05/18/microwave-hazards.aspxhttps://www.goodhealthinfo.net/radiation/health_efx_western.htm> Can you be more detailed? If you're just arguing that a person can't> literally string up chicken wire and convert microwaves to rectified DC, then> sure, but that's a straw man. (This reminds me of the guy who cautioned me> that getting useful elements out of regolith would never be as easy as just> shining some concentrated sunlight on it. Well, yes, but who literally said> that?) I don't think you can mean that a rectenna could never be designed> which would let water through, or even the bigger fraction of the sunlight,> given the vast difference in wavelengths between microwaves and visible light.> Again, could you please share your findings?No I did *not* suggest literally chicken wire, that is why I said "somethinglike".Maybe I could have stated it better by saying: something like a mesh thatcaptures microwaves but lets all, or almost all, the light through. Of therectennas I've seen, none of them look anything like this. They are all mostly,if not almost completely, opaque solid surface.Here is a google image search for "rectenna array element":https://www.google.com/search?q=rectenna+array+element&source=lnms&tbm=isch&sa=XHere is a NASA study done on rectennas. See the picture of the rectenna on page 10:http://www.nss.org/settlement/ssp/library/1987-NASACR179558-RectennaTechnologyProgram.pdfHere's a page, at the bottom of which is (small) picture of a rectenna surface:http://www.spaceset.org/p.solar.mmHere's another rectenna page and picture, from the Japan space program:https://www.ijser.org/paper/Renewable-energy-Spaced-based-solar-Power-transmission.htmlhttps://www.ijser.org/paper/Renewable-energy-Spaced-based-solar-Power-transmission/Image_007.jpgHere's another picture of an actual rectenna:http://www.solarsat.org/Bill%20Brown%20tuning%20Rectenna.png">

solar power sats have imho a problem ..

sailor.barsoom wrote:> If ground-based PV becomes more efficient, then the PV used on powersats also gets> more efficient. Also, places like the UK or Norway have bigger problems with> ground-based solar than the Sahara or even (most of) the US.Improvements in cost would hardly affect the cost of SBSP, almost all of whichof course, would be the enormous cost of getting the PV arrays up into space.Not making them.Improvements in efficiency would hardly make a dent in making SBSP as affordableas ground-based solar, because of said cost. Yes it would reduce the amount ofvolume and weight needed to be carried into space by a corresponding ratio. Butanywhere near enough? Like someone trying to empty Lake Tahoe with a waterbucket, by saying they now have a water bucket twice as large.Nor would those efficiency improvements reduce the size of the rectenna arrays.Also, the types of PV panels used in space are not the same types as the onesused on earth. Space presents a far harsher environment. They're many times asexpensive. And they effectively last about half as long as ground-based ones. Sosome new cheap or efficient type of PV might -- or might not -- be adaptable tospace.> As for what to put under the rectenna: factories, greenhouse agriculture, production> of synthetic hydrocarbons. You've got some basic structure there, and scads of> electricity.You can do the same for ground-based solar right now. Unlike SBSP, you own the power instead of having to buy it from someone else. Unlike SBSP, you can putthe structure anywhere, or anywhere there is enough sunlight. You can make thestructure as big or little as you want. Which is another advantage of ground-based solar: it is the most decentralized power source there is, whereas SBSPwould be *highly* centralized. And depending on your views of such things, you don't have to worry about notgoing onto the roof.SBSP would offer the advantage of continuous power. However if it's for theproduction synthetic hydrocarbons, this is would be a kind of energy storage.

Combs, Mike wrote:> Yes, as you anticipated, I was not at all impressed with these sources. Looks> like the same people who are going on about power lines, cell phones, and> WIFI, and those concerns are groundless as well.I thought so.> Science is controlled, double-blinded experiments. That's what I'm looking> for.You think that none of the over 100 studies were done this way?> You might have a better point about rectennas (although the structure in that> last picture showing Bill Brown looks like it would let rainfall through, and> maybe about a quarter of the sunlight). I would only make 2 points here. 1.> The fact that all rectenna components built to date look a certain way may or> may not mean they can't be built a bit differently, if there's a compelling> economic reason for doing so.Possibly. But the weight of the evidence, as of right now, is what we see. Andwhat we see is, mostly or almost completely opaque.> 2. Even if it is overselling SPS to say that one could farm or ranch under a> rectenna, I would comment that one cannot do either under a fossil fuel or> nuclear power plant.Yes. However, a moot point. That's a strike against SBSP: a large supposedadvantage, that turns out not to be. (At the very least, for the time being.)

Sent from your computer it's clickable. And thank you for it; it's worth seeing.

Of course my favorite place for a wind farm is 50 Km off-shore: you can't see it, it produces scads of electricity, the supports can also support reefs, and it weakens hurricanes.