...100 MW of Space Solar Power ...per single launch!
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From: Pat Flannery on 15 Dec 2009 03:35 Sylvia Else wrote: > Making a very large antenna that is sufficiently rigid not to collapse, > but light enough to be launched, doesn't seem such a straigthforward > proposition. Yes, there are tidal effects to be taken into account due to it not being a point source in orbit. There's a trick that might be usable here; since objects with like electrical charges tend to repel each other, you might be able to charge the whole thing and have it use electrostatic repulsion to keep it rigid as the individual parts try to move away from each other. This converts the structure into something that can be held together by thin wires in tension rather than structural framework. The NRO reportedly used the flip side of this concept many years back by deploying the collapsible framework of a large parabolic antenna of a signal intercept satellite in orbit, and having electrostatic attraction suck the thin covering material (probably something like a aluminized mylar sheeting) down onto the framework to give it smooth reflective surface. Pat
From: Peter Fairbrother on 15 Dec 2009 11:47 Sylvia Else wrote: > Pat Flannery wrote: >> Peter Fairbrother wrote: >> >>> >>> Most designs don't use a mesh, but rather a matrix of transmitting >>> elements in a solid plane. The individual elements are closely >>> spaced, and even if a grid was used it would be fairly full. Think of >>> a phased array antenna rather than a loose grid of wires. >> >> Something like a huge version of this: >> http://www.bharat-rakshak.com/NAVY/Images/MR-775.jpg >> Unlike a big parabolic dish, you can steer the microwave beam from a >> flat array electronically without having to physically move the antenna. >> >> Pat > > Imagine a large square in orbit over the equator, oriented so that its > surface is horizontal, (w.r.t. the surface of the Earth immediately > below) and so that it has one of its four sides (the "front") > perpendicular to the direction of motion. > > It seems to me that all four sides experience a force with a component > towards the centre of the square, and a component away from the centre > of the Earth. The forces on the front and rear arise because they are > travelling too fast for the orbit they are in. The forces on the left > and right arise because of that, and also because they are not actually > in an orbit about the centre of the Earth. These forces tend to make the > square crumple into a ball. Yes, though it's more a prolate spheroid than a ball. BTW, an antenna will probably be round, not square, though that doesn't change much. > The forces on the front and rear sides can be eliminated by making the > square curved, but the forces on the left and right sides remain. Indeed. but this is in GEO, so the forces will be quite a lot smaller than in, say, LEO. A flat antenna is however best. Also it spins once per day in order to keep it pointed at the Earth, around an axis at right angles to the motion through the plane of the antenna, which gives a bit of fore-aft tension. Electronic beam steering is only used for fine adjustments. It could also be spun about an axis perpendicular to the plane to keep it in tension. It wouldn't need to spin fast, maybe once per hour (I haven't worked it out, that's a wild guess). There are also possible electrostatic and other tricks, as mentioned by Pat. The mirrors may have to spin too, and the support beams between the mirrors and the transmitter/power station are also a weight problem. > Making a very large antenna that is sufficiently rigid not to collapse, > but light enough to be launched, doesn't seem such a straigthforward > proposition. Agreed, it isn't straightforward, especially at todays launch capacities and costs - a new, much cheaper, high-capacity per annum (though not necessarily per launch) launch system is needed for it to be economically viable. However the potential market is in the trillions, so capital to develop a new launch system is chickenfeed really (though we are still talking about a large amount of money). [Hmm, I think I described such a launch system here a few months ago, 30,000 tons per year capacity for $7 billion or so ...] BTW there are a lot of studies available at http://www.nss.org/settlement/ssp/library/index.htm if you are interested, though I think many of them seem to miss the point a bit - for instance, providing power to forward troops is not going to work well politically, inciting claims of cooking the enemy etc. The real money is in supplying fixed domestic and industrial power, which has very few unwanted domestic (and pretty well zero international) political consequences if done right. And no greenhouse gases, or very few, and no nuclear waste, and almost zero environmental impact (except for some at the ground sites, which IMO should be situated in deserts or otherwise empty areas). Personally I'd go for 100 GW Brayton cycle turbine systems rather than a 400 MW direct semiconductor conversion system, with maybe 5 km diameter space antennas and 8 km ground antennas - though I haven't done any detailed studies on this, it's very BOTE. -- Peter Fairbrother
From: Sylvia Else on 15 Dec 2009 18:45 Peter Fairbrother wrote: > It could also be spun about an axis perpendicular to the plane to keep > it in tension. It wouldn't need to spin fast, maybe once per hour (I > haven't worked it out, that's a wild guess). That axis would be continuously changing because of the need to keep the antenna pointed at Earth. So you would need to find a continuous torque from somewhere (gyroscope effect), as well as deal with the structural implications. I suspect that spinning it to put it in tension would create more problems than it solves. > > There are also possible electrostatic and other tricks, as mentioned by > Pat. > > The mirrors may have to spin too, and the support beams between the > mirrors and the transmitter/power station are also a weight problem. They're presumably less of a problem in that they point at the sun, meaning that their axis of rotation is going through a complete turn once per year rather than once per day. > > >> Making a very large antenna that is sufficiently rigid not to >> collapse, but light enough to be launched, doesn't seem such a >> straigthforward proposition. > > Agreed, it isn't straightforward, especially at todays launch capacities > and costs - a new, much cheaper, high-capacity per annum (though not > necessarily per launch) launch system is needed for it to be > economically viable. > > However the potential market is in the trillions, so capital to develop > a new launch system is chickenfeed really (though we are still talking > about a large amount of money). I remain sceptical of the economics. It's not sufficient for the system to be financially possible - it has to be cheaper than alternatives that achieve the same general goals. For example, even though land based solar has issues with availability which have to be addressed, the fact that they don't need to be launched represents a huge saving. Sylvia.
From: Jonathan on 15 Dec 2009 19:30 "Sylvia Else" <sylvia(a)not.at.this.address> wrote in message news:00a2f7ab$0$23810$c3e8da3(a)news.astraweb.com... > Jonathan wrote: >> "Sylvia Else" <sylvia(a)not.at.this.address> wrote in message >> news:00a1528c$0$26889$c3e8da3(a)news.astraweb.com... >>> Jonathan wrote: >>>> "Sylvia Else" <sylvia(a)not.at.this.address> wrote in message >>>> news:00a09904$0$23357$c3e8da3(a)news.astraweb.com... >>>>>> Solaren has not provided details on just how its technology >>>>>> works, citing intellectual property concerns. >>>>> Meaning it wouldn't stand up to the inevitable expert scrutiny if they got >>>>> a >>>>> patent. >>>>> >>>> Maybe, but keeping a secret could mean fraud or it could mean >>>> a breakthrough, we don't know for sure. >>> If they have a breakthrough, they should get a patent on it, ASAP. As long >>> as >>> it's merely secret, they're exposed to industrial espionage, accidental >>> leaks, >>> you name it. >> >> >> They claim to have a patented 'system'. But that's all I found, no details. > > http://www.freepatentsonline.com/7612284.html > > Usual case of patenting the bleedin' obvious, while not identifying a solution > to the technical difficulties involved. Well would you expect them to? It doesn't make for good business to give your product 'details' away for free. The test of their ideas will be if it can go public and convince institutional investors to buy their stock. > > Sylvia.
From: Sylvia Else on 15 Dec 2009 19:37
Jonathan wrote: > "Sylvia Else" <sylvia(a)not.at.this.address> wrote in message > news:00a2f7ab$0$23810$c3e8da3(a)news.astraweb.com... >> Jonathan wrote: >>> "Sylvia Else" <sylvia(a)not.at.this.address> wrote in message >>> news:00a1528c$0$26889$c3e8da3(a)news.astraweb.com... >>>> Jonathan wrote: >>>>> "Sylvia Else" <sylvia(a)not.at.this.address> wrote in message >>>>> news:00a09904$0$23357$c3e8da3(a)news.astraweb.com... >>>>>>> Solaren has not provided details on just how its technology >>>>>>> works, citing intellectual property concerns. >>>>>> Meaning it wouldn't stand up to the inevitable expert scrutiny if they got >>>>>> a >>>>>> patent. >>>>>> >>>>> Maybe, but keeping a secret could mean fraud or it could mean >>>>> a breakthrough, we don't know for sure. >>>> If they have a breakthrough, they should get a patent on it, ASAP. As long >>>> as >>>> it's merely secret, they're exposed to industrial espionage, accidental >>>> leaks, >>>> you name it. >>> >>> They claim to have a patented 'system'. But that's all I found, no details. >> http://www.freepatentsonline.com/7612284.html >> >> Usual case of patenting the bleedin' obvious, while not identifying a solution >> to the technical difficulties involved. > > > Well would you expect them to? It doesn't make for good business > to give your product 'details' away for free. The test of their ideas will > be if it can go public and convince institutional investors to buy their > stock. > I don't see why not, if you have a patent. What it appears they've done is to patent something that's obvious, for the purpose of using the existence of the patent, without providing detail, as a way of giving themselves undeserved credibility. Sylvia. |