At 12:00 PM 4/16/2008, Dan M wrote: >(Keith wrote) > > > > At 12:00 PM 4/11/2008, Dan M wrote: > > > > (Keith wrote) > > > >Takes 10 200 ton payload > > > > rockets each flying once a day to do it and with a blank check > > > > perhaps under 5 years to work up to this production rate and 6-7 > > > > years from start to get to a $50 billion a year revenue stream > > > > increasing at $25 billion a year. > > > > > >OK, let's do the math on that. At the present time, the cost of lift to > > >geosynchronous orbit is $20,000 per kg or $20M per metric ton. Ten 200 > > ton > > >payloads would be about 40 billion per day or 14.6 trillion per year. > > >That's roughly the GDP of the US. > > > > And the analogy would be how impossible it is to build a dam sending > > all the contents in Fed Ex envelopes. > > > > >The trick is, as it always has been, to lower launch costs. > > Unfortunately, > > >even in inflation adjusted dollars, launch costs haven't dropped much > > over > > >the past 40 years. > > > > I agree with you. The question is why? > >I wrote a blog on that general topic at the Scientific American website > >http://science-community.sciam.com/blog-entry/Dan-Ms-Blog/Unfortunate-Promin >ent-Misconception-Concerning-Tech/300004870
It was an interesting blog, though *social problems* are in a very different class than engineering ones like going to the moon. At least they are now. Ask and I will point you to a dark story about how they might be solved. >The essence is that when the engineering community starts working on >something, it starts working on the obviously solvable problems first. >Then, progress slows as the easy problems are solved and harder problems are >faced. The point at which this happens, and the manner in which it happens >is based on what is found. The speed of sound barrier is rather >significant, and we have not found a way to develop efficient planes that go >at Mach 1.1 almost 60 years after we first went above Mach 1. > > >It's not the cost of energy. > >No, it's the cost of the system. > > >A nearly hundred percent efficient space > >elevator lifts about 2400 mt a day (on less than a GW) snip >I've invented a few things that are used worldwide and am still engaged in >practical science/engineering. I've worked close to guys who's inventions >have reduce world costs for producing oil by about 250 million/day. Since there are around 80 million barrels a day produced, that's a reduction of about 3%. >So, I >think I'm fairly familiar with processes that are economical and that work. >I have not seen anything in what you have written on this subject that gives >an indication of an understanding of the nature of practical solutions to >problems. What do you want? The current 747 cost about $300 million and dry masses out to about 185 mt or $1.6 million a ton. Produced in similar tonnage, do you see any reason these rockets would cost more than per ton than a 747? If so, why? First and second stage mass 619 tons, (third stage is mostly power sat parts) so if they cost on a par with a 747, they would cost just a hair over a billion each, with one coming off the production line every 20 days, or about 31 mt a day. That might sound like a lot, but I have worked in a locomotive factory that made 30 times that much a day in product (8-9 locomotives a day at 113 mt each). At peak production 747s were coming off the line at a slightly higher tonnage per year. If you use them for 200 flights the capital cost per flight is $5 million /200,000kg or $25/kg. This number is excessively rough, but could be refined without a lot of trouble. At a nickel a kWh, a kg of power sat generates $200 of electricity a year. > > Done with rockets of this sort > > http://www.ilr.tu-berlin.de/koelle/Neptun/NEP2015.pdf the energy > > input is about 15 times that high, or from $15 /kg down to $1.50 as > > you get less and less expensive energy. > >I went to this website, and it looked like a speculative conference. >Vaporware is easy to build. Doing something that works is hard. Most >things we wish we could do we do not know how to do. The .pdf was recommended as a good reference by Hu Davis of Eagle Engineering. Look him up. >I think that this is the absolutely fundamental difference you have with >folks who argue for nuclear reactors vs. space based solar power. We've >demonstrated > > > > >>safety mechanisms, > > > > Can you be specific about what you mean here? > >Sure, to be effective, power would have to be transmitted down in a fairly >dense fashion. One needs mechanisms that provide feedback to turn the power >off should the aim stray. The power level for power sats was set at about 1/4kW/square meter back in the 70s so it could not be used as a weapon. There was also concern that the ionosphere could go non-linear and short out the beam. As far as sending the beam down densely, it's an optical problem--see the math behind Airy's disk. If you want to get a tighter beam you have to go to a larger transmitter or higher frequency or both. The beam requires a pilot beam up from the center of the receiving array to stay phased. Otherwise it goes non-coherent, and the power scatters into a half space from the antenna. The power level, 5-10 GW, is set by the waste heat limits on the a km disk of transmitter klystrons. > > > > >Plus, > > >it costs money to build the actual arrays. > > > > That's true, but with just mild concentration you can get at least 10 > > times more power out of a solar cell in space. > >We have an overwhelmingly fundamental difference here. I have looked at the >solar arrays for the space station and they are expensive. There is a presumption that if you are buying them at 300 GW/year, you get a price break. Plus you get a lot more energy over a year out in GEO. Much of this is discussed on the power satellite wikipedia page--which seems fairly up to date. >If concentration >were trivial in space, don't you think they would have used it? I don't know what the tradeoffs were. It may be that they can't keep it pointed well enough. With tens of square km of solar cells, you better be able to keep it pointed at the sun. In any case, it's not obvious to me that solar cells are even the way to go. In this range, steam turbines might be less expensive. >We know on >earth that techniques that use concentration have practical problems that >have prevented them from being cost effective. There sure are a lot of installed concentrators in thermal solar systems. > > >If you can find a way to drop > > >launch costs a factor of 100 to 500, then space based solar becomes a > > >player. There is nothing like that on the horizon. > > > > There doesn't seem to be any reason a really huge throughput > > transport system should not be able to give you that much > > reduction. > >Then, why hasn't it happened with the scores of airline industries? 747s >were brought online in the '60s....almost 40 years ago. 747s remain >competitive. The airline industry is huge, and we've only seen incremental >improvements over the past 40 years. A 747 is economical even at current fuel prices. Think about that every time you buy grapes grown in Chilli. The amount of energy used per kg isn't a lot different from lifting the same grapes to GEO. The main point is that there are very few options that are big enough and possibly low enough in cost to replace the bulk of fossil fuels. Keith _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
