tag:blogger.com,1999:blog-7494544263897150929.post5986639954725144703..comments2024-03-28T00:36:19.403-07:00Comments on Rocketpunk Manifesto: Solar Power from SPAAACE ??!Rickhttp://www.blogger.com/profile/16932015378213238346noreply@blogger.comBlogger56125tag:blogger.com,1999:blog-7494544263897150929.post-22279970086101411392012-01-18T19:58:13.474-08:002012-01-18T19:58:13.474-08:00Fair point!
A cost of $1 million/ton is not out o...Fair point!<br /><br />A cost of $1 million/ton is not out of line if all the 'ifs' work out, especially traffic demand. That has always been the frustrating circular bootstrapping problem.Rickhttps://www.blogger.com/profile/16932015378213238346noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-7301558182013497532012-01-13T04:26:15.761-08:002012-01-13T04:26:15.761-08:00yes - of course the proof of the pudding is in the...yes - of course the proof of the pudding is in the eating .. <br /><br />but - otoh & afaik - spacex is the only launching company that is actually willing to write a price per launch onto its homepage ... which speakes of a certain confidenceagricola64https://www.blogger.com/profile/15520306118805972674noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-29421392959672147482012-01-12T18:42:00.079-08:002012-01-12T18:42:00.079-08:00Welcome to the discussion threads!
I wouldn't...Welcome to the discussion threads!<br /><br />I wouldn't call myself so much a pessimist as conservative about costs. This is largely a reaction to the notorious history of cost lo-balling by space advocates, going back to von Braun himself. <br /><br />If SpaceX can actually hit that cost target, more power to them! But Falcon Heavy hasn't actually flown yet, let alone entered regular commercial service. So it may turn out more expensive than they are hoping (or hyping).Rickhttps://www.blogger.com/profile/16932015378213238346noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-35405418746299725752012-01-10T14:39:03.052-08:002012-01-10T14:39:03.052-08:00i strongly suspect that the cost to LEO for F9H is...i strongly suspect that the cost to LEO for F9H is already including stage recovery ..agricola64https://www.blogger.com/profile/15520306118805972674noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-69716209833144304872012-01-10T14:33:12.245-08:002012-01-10T14:33:12.245-08:00I've discovered your blog a few weeks ago, by ...I've discovered your blog a few weeks ago, by way of atomic rockets, and I'm going through all your posts from day one.<br /><br />Somthing that strikes me is how pessimistic you are re launch costs.<br /><br />SpaceX is already selling their falcon heavy for $100m, or $2,000/kg to leo. We can reasonably expect their prices to get cut in half when they start recovering their first stages, so we're looking at launch costs dropping below $1,000/kg before the end of this decade.<br /><br />A great many unaffordable projects are going to suddenly become realistic.leridanhttps://www.blogger.com/profile/02831735654564441964noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-1893748968781279762011-07-29T04:01:32.185-07:002011-07-29T04:01:32.185-07:00Power beaming with microwaves has the problem of t...Power beaming with microwaves has the problem of the large scale needed due to the rather long wavelength. You end up with power plants in the gigawatt range. It's hard to do pilot projects.<br /><br />This has led people to look at laser power beaming. The issues here are lower efficiency of producing the photons, and then of converting them back to electricity.<br /><br />My suggestion: look at terrestrial applications of photons, so you can skip one step (conversion of laser light back to electricity) and so the terrestrial competition has to pay for the other step (conversion of electricity to photons).<br /><br />An example is the photochemical process for the production of caprolactam, the precursor of Nylon-6. This process mixes cyclohexane and nitrosyl chloride, then uses light to dissociate the NOCl into NO and Cl radicals. The cyclohexane is converted to an oxime, which can then be converted to caprolactam by a Beckman rearrangement.<br /><br />Another possible application would be pump radiation for the dye lasers for laser isotope separation.<br />The threshold for dissociation of NOCl is in the near IR, so any visible frequency laser should work (although the dissociation cross section is much higher at shorter wavelengths.)Paul D.noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-56860784243924250002009-08-16T00:21:05.133-07:002009-08-16T00:21:05.133-07:00ok ..
so lets say 30 cm wavelength and a quarter...ok .. <br /><br />so lets say 30 cm wavelength and a quarter wave antenna - this gives us a wire every 7 cm and a (very substancial) 0.5 cm wire diameter ..<br /><br />this means the power input to a solar power station sitting under the rectenna is reduced by 1/15 or about 7% by shadowing <br /><br />if we can reduce the wire diameter (which i think is possible) to 0.25 cm the power loss will be 3.5% <br /><br />7% power loss hurts ..<br /><br />otoh - the land for either the rectenna or the solar thermal power station will essentially be "free" - you only have to purchase it once <br /><br />.. you only need one connection to the electric grid, you need only one transformer station, only one administration and control building and you have to jump through the legal and regulatory hoops only once <br /><br />i think the last point will be especially interesting to the company building the thing .. 8-)agricola64https://www.blogger.com/profile/15520306118805972674noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-32599075877090381622009-08-15T19:57:37.728-07:002009-08-15T19:57:37.728-07:00Thanks for the fill-in!
To return to the start p...Thanks for the fill-in! <br /><br />To return to the start point, the cool thing is that we may well find out how good Solaren's engineers are, and whether they can build a credible tech demonstrator. To paraphrase a familiar saying, engineering talks, BS walks.Rickhttps://www.blogger.com/profile/16932015378213238346noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-31383367166753750042009-08-15T10:37:36.006-07:002009-08-15T10:37:36.006-07:00"does anyone has some data on rectenna design..."does anyone has some data on rectenna design? how far away from each other do the wires have to be, etc ..<br /> ...don't know many details, but IINM putting the wires farther apart than the wavelength of the EM radiation will let a lot of it through rather than converting it to electricity."<br />Yes, to have an effective rectenna the spacing between elemens (the wires) must be no further apart than one wave length...a quarter wave length would be better, but one wave length will do. The effecency of the rectenna is a function of the conductivity and the 'coupling' (the amount of power the conductor absorbs)...so, for example, an aluminum wire (a poor conductor) is set up in as a full wave rectenna (each wire is one wave length away from the next) would be more effective than a steel wire rectenna whose wires are just a bit over one wave length apart. So, the cost of the wire material, the size of the rectenna, and the frequency of the microwave beam would be some of the primary concerns in building a solar powersat system. Actually, since the microwave beam will be optimized to pass through the atmoshere with minimum loss, then the rectenna will be built to maximize coupling efficency to the beam. I guess we'll see how competent Solaren's engineers are...<br /><br />FerrellAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-21965404187051645842009-08-14T12:46:32.459-07:002009-08-14T12:46:32.459-07:00Jim's point makes sense, so we're probably...Jim's point makes sense, so we're probably talking about rectenna wires on order of a foot apart (0.3 m). Which probably does not come to all that much wire, as wire goes - a few thousand wires, each a few km long. I imagine the equipment to 'clean up' the power and feed it into the grid will cost more than the rectenna itself does.Rickhttps://www.blogger.com/profile/16932015378213238346noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-67011694045523942282009-08-14T07:44:26.509-07:002009-08-14T07:44:26.509-07:00I don't know many details, but IINM putting th...I don't know many details, but IINM putting the wires farther apart than the wavelength of the EM radiation will let a lot of it through rather than converting it to electricity.Jim Baergnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-51670814480275664752009-08-13T20:54:18.442-07:002009-08-13T20:54:18.442-07:00does anyone has some data on rectenna design? how ...does anyone has some data on rectenna design? how far away from each other do the wires have to be, etc ..Unknownhttps://www.blogger.com/profile/13269227244479951158noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-40126558940207279042009-08-13T17:46:13.296-07:002009-08-13T17:46:13.296-07:00True. I guess the question is how much the rectenn...True. I guess the question is how much the rectenna itself costs. Wire is cheap, but presumably a rectenna multiple km on a side has LOTS of wire.Rickhttps://www.blogger.com/profile/16932015378213238346noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-63966938722402198282009-08-13T12:47:25.950-07:002009-08-13T12:47:25.950-07:00the space under a receiving wire rectenna is perfe...the space under a receiving wire rectenna is perfectly suited for a solar-thermal power station (of the mirror trough type) or a pv cell power station<br /><br />agricola64Unknownhttps://www.blogger.com/profile/13269227244479951158noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-66676172967350078022009-08-13T11:19:47.465-07:002009-08-13T11:19:47.465-07:00I have no earthly idea (so to speak!) of how much ...I have no earthly idea (so to speak!) of how much rectennas cost - though surely much less than a BIG satellite at geosynch!<br /><br />There is also cutting edge work being done on big, cheap storage batteries, which might make fully Earth-based solar competitive. (Biofuels are of course another way to store solar power!)Rickhttps://www.blogger.com/profile/16932015378213238346noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-50194431663417558272009-08-13T08:11:02.934-07:002009-08-13T08:11:02.934-07:00I still don't believe is solar power satellite...I still don't believe is solar power satellites to generate power for use on earth.<br /><br />See<br />http://www.energyfromthorium.com/forum/viewtopic.php?f=39&t=929<br />& go down the page a bit to the post by Kirk Sorenson at Nov 30, 2006 3:30 pm.<br /><br />The basic problem is that microwave transmission from Clarke orbit means the antennas have to be several km across (for any power level), which kills the economics.<br /><br />On earth intermittency & the low power density of solar greatly reduce the usefulness of solar power. In space solar is continuous and concentrating mirrors of aluminum foil can be really cheap & flimsy, unlike on earth where gravity & winds have to be dealt with.<br /><br />So barring some other much cheaper power beaming tech, I think it will be solar power in space, & nuclear power on planetary surfaces.Jim Baergnoreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-70563846621793601132009-08-06T11:20:52.651-07:002009-08-06T11:20:52.651-07:00Jim: i follow your math ..
but having many small...Jim: i follow your math .. <br /><br />but having many small units flying around in close vincinity will carry a much higher collision risk then a few larger units ..Unknownhttps://www.blogger.com/profile/13269227244479951158noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-26355070262893335362009-08-06T11:18:44.868-07:002009-08-06T11:18:44.868-07:00rick:
the gimbal for the cable might be lighter ...rick: <br /><br />the gimbal for the cable might be lighter - otoh, so far nobody has managed to manage cables properly for longer periods in zero-g .. <br /><br />yes - i knoe about "a rocket a day" .. and i agree with its premise to a point .. otoh making the payloads smaller and smaller will probably reduce launch cost, but will also increase the "overhead" mass (and associated costs) <br /><br />and finally - who , who has seen the power and glory of a Saturn V, would not immediately fall in love with a SeaDragon launch .. can you already see the fleet of cruise ships at the safe perimeter 8-)Unknownhttps://www.blogger.com/profile/13269227244479951158noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-47065947320839404012009-08-06T09:38:55.324-07:002009-08-06T09:38:55.324-07:00agricola64 - Untwisting the cable ... um, yeah, a ...agricola64 - Untwisting the cable ... um, yeah, a gimbal will be required, but a much less massive one!<br /><br />On SeaDragon, Jim Bowery had a link on his own blog to an article about the <a href="http://www.fourmilab.ch/documents/rocketaday.html" rel="nofollow">virtues of frequent launches</a>. I'm not sure it can be reduced to a formula, but for a given annual tonnage to orbit, I suspect that frequent smaller launches will be cheaper than occasional big ones. It spreads out the development cost across more vehicles, and - even more important, I suspect - means that the launch team is actually doing its job on a daily basis, rather than spending most of their time training to do it a few times a year.Rickhttps://www.blogger.com/profile/16932015378213238346noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-76555915983171460262009-08-06T06:45:53.222-07:002009-08-06T06:45:53.222-07:00agricola64: The situation with a phased array clou...agricola64: The situation with a phased array cloud is very different. Interference is necessary -- its what makes the phased array work.<br /><br />A brief calculation of the orbital slot requirement:<br /><br />tan(.1degrees)*22kmi;140m/satellite;5MW/satellite ? GW<br />= 2.20694 GW<br /><br />What this means is that for each tenth of a degree of geostationary orbit, you can fit a string of satellites, each with a 140m diameter mirror, that can produce 2GW on the ground.<br /><br />This calculation is simplistic but you get the idea.Jim Boweryhttps://www.blogger.com/profile/12686155123469135528noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-28484603135846038462009-08-05T22:25:55.841-07:002009-08-05T22:25:55.841-07:00Jim:
thanks for that document .. i will have to w...Jim:<br /><br />thanks for that document .. i will have to work through that carefully .. lots of material for thought there .. <br /><br />in regards to stationkeeping: i dont get to play with satellites 8-( ... and i based my question on years old memories of comments made by an Astra engineer (european TV sat company that maintains a fleet of tv sats in one orbital slot) who said that they have a small, but noticeable increase in fuel use due to the fact that they have to be much more careful in station keeping to avoid interference between their sats .Unknownhttps://www.blogger.com/profile/13269227244479951158noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-52199618248473537932009-08-05T22:20:02.112-07:002009-08-05T22:20:02.112-07:00rick:
how do you untwist that cable ?
something...rick:<br /><br />how do you untwist that cable ? <br /><br />something will have to rotate in relation to the other part - and thats by definition a gimbal (no matter if its on a rigid structure or a cable) and gimbals - especially large ones - always were a headache in space<br /><br />as for launching the SPS in one piece - we could do that .. one word: SeaDragon 8-)<br /><br />and your guesstimate on the mass of those "other parts" is a good as mine .. 8-) .. but i do notice that in the history of spaceflight such guesstimates have a long and distinguished history of being too smallUnknownhttps://www.blogger.com/profile/13269227244479951158noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-31017340962164991432009-08-05T21:02:38.811-07:002009-08-05T21:02:38.811-07:00I'm certainly not committed to any particular ...I'm certainly not committed to any particular technology! Mainly I'm rather enchanted that something I always regarded as jive may have some credibility to it.Rickhttps://www.blogger.com/profile/16932015378213238346noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-38328006904040361812009-08-05T17:41:14.505-07:002009-08-05T17:41:14.505-07:00Agricola64, I am specifically making the case for ...Agricola64, I am specifically making the case for using concentrating mirrors rather than PV cells as the primary light gathering surface. How massive do mirrors have to be in a zero-g, zero-weather environment?<br /><br />As for destructive heterodyning at the receiver, see <a href="http://www.ursi.org/WP/SupportingDocument1.pdf" rel="nofollow">section 2.3.5 of Supporting Document for the URSI White Paper on Solar Power Satellite Systems</a>.<br /><br />Only one slot is required in geostationary orbit for all of the satellites in a 3GW constellation -- not because they are in a halo orbit, but because they are all part of the same virtual phased array antenna. Station keeping is also less necessary since all satellites are co-located and subject to the same purturbations -- simply electronically steering the phased array to compensate. Moreover what stationkeeping is required can be a lot more efficient in its use of reaction mass because of the large amount of energy available.<br /><br />Its rather funny because I ran into a similar problem when putting through the first Ka band satellite license (Norstar for Norris Satellite Communications) back in 1992. The "orbital slots" argument came up without regard for the fact that Ka band is a lot higher frequency. Each new generation of technology presents legacy objections that are sometimes made moot by the new regime.<br /><br />Rick, the Fresnel lens merely reduces the cost of terrestrial cells by reducing the amount of PV area. They don't really target mass the way weightless mirrors do.<br /><br />As for the 'plumbing' of solar thermal, the main requirement for mass is in the high temperature and pressure focus. The moment the fluid leaves that chamber it is adiabatically cooled to the maximum degree possible to create a high velocity, low temperature, low pressure gas stream. Then you are dealing with power to mass ratios of turbines. <br /><br />In any event, high flux PV can also be used at the mirror focus to achieve the mass economy that the Fresnel lens approach doesn't (unless there is a new approach to low mass Fresnel lenses with which I'm unfamiliar).Jim Boweryhttps://www.blogger.com/profile/12686155123469135528noreply@blogger.comtag:blogger.com,1999:blog-7494544263897150929.post-61722172302704231692009-08-05T16:15:29.886-07:002009-08-05T16:15:29.886-07:00Jim - I don't have any information on Solaren&...Jim - I don't have any information on Solaren's intended cells, but 'multijunction' cells that concentrate light from mirrors or Fresnel lenses are getting a lot of buzz, and may be what they have in mind.<br /><br />Traditional solar thermal, concentrating light on a boiler, would be plumbing intensive. I just recently read about work with nanosmaterials that could enable efficient thermoelectric cells. I doubt that's what Solaren is thinking of, given the time frame, but it might be a big deal down the road.<br /><br /><br />agricola64 - Presumably smaller payloads could be assembled into one powersat. In fact would have to be, because we certainly won't be launching these things in one piece. OTOH, the smaller the individual payloads the more complicated the on-orbit assembly process.<br /><br />My instinct is that the other parts of the powersat would be no more than a third of total mass and probably less ... but that is sheerest guesswork. <br /><br />But the gimbals you mentioned upthread might not be needed. The cell structure has to face the sun, and the microwave part has to face the Earth, but they could be connected by cable. (Yes, that leaves some tricky stationkeeping subtleties, which are pretty much above my pay grade.)Rickhttps://www.blogger.com/profile/16932015378213238346noreply@blogger.com