Aucbvax.4431 fa.space utzoo!decvax!ucbvax!space Thu Oct 15 11:03:09 1981 SPACE Digest V2 #15 >From OTA@S1-A Thu Oct 15 10:43:23 1981 SPACE Digest Volume 2 : Issue 15 Today's Topics: SPS vs. Fusion - A response to REM capital for SPS Re: booze money Budget cutting SPS and radiation pressure SPS continued "When the Sun goes, we all go"? Booze Budget ---------------------------------------------------------------------- Date: 14 Oct 1981 1158-PDT From: Paul Dietz Subject: SPS vs. Fusion - A response to REM To: space at MIT-MC REM misses the point when we says that there are many ways to build an SPS. What I was doing was this: look at the potential points of vulnerability in each concept. With solar sattelites, the big problem is not technical feasibility. The big problem is that any low cost SPS is going to require asteriodal or lunar material. We don't really know how hard it is to build a full scale lunar materials processing plant. We have no experience in extraterrestrial industry. We have never built a factory that works in zero g or in a vacuum. We have never built a factory that uses extraterrestrial materials. This is not to say that we shouldn't build such factories. What I am saying is that we have no idea how hard it is, or how much it will cost, or what the hidden snags are. I suspect that the only way to find out is to go up and do it. And this is very expensive. With fusion, the problem is not building the plants after we're sure they work. The problem is designing the plant in the first place. The problems in fusion designs tend not to be common to all designs. Many that are common have already been addressed in other types of power plants. And for those who argue that the japanese or the russians will develope SPS first: compare how much they are spending on fusion research to how much they're spending on SPS research. The japanese are spending large amounts of money on the tokamak idea. Their feeling is that they better get a new energy source on line damn quick, before the oil gets expensive. So, to reiterate, SPS's all share a common problem that may make them uneconomical, or, may make them require too much start-up capital. The whole SPS idea can be killed by a single bullet. Fusion does not share this problem. The problems that fusion does have seem much more amenable to quick technical solution. We will get SPS if and when we get lunar or asteroidal materials - not the other way around. ------- ------------------------------ Date: 14 Oct 1981 10:34:29-EDT From: cjh at CCA-UNIX (Chip Hitchcock) To: space at mit-mc Subject: capital for SPS Cc: rem at mit-mc $1 million to establish a Lunar catapult? Dream on!$ And if it just throws dirt, how will the dirt be sorted out into worthwhile metals? (That's probably safer to do on the moon than in zero-G; the latest I've heard, the "traveling bucket" design has been dropped, and capsules of refined material (with enough magnetic metal to respond to the electric catapult) are what would be flung.) ------------------------------ Date: 14 Oct 1981 10:01:07-EDT From: cjh at CCA-UNIX (Chip Hitchcock) To: POURNE at MIT-MC Subject: Re: booze money Cc: space at MIT-AI In response to your message of Wed Oct 14 03:46:08 1981: Any suggestions as to how we bell that particular cat? ------------------------------ Date: 14 Oct 1981 0959-PDT From: Tom Wadlow Subject: Budget cutting To: space at MIT-MC Several space advocacy groups, including the L-5 Society, are attempting to approach Congress with proposals designed to reduce government red tape involving spaceflight. The attitude of: ''Well, if you don't intend to go, at least don't make it so bloody hard for us to go.'' is a much more productive one than another popular outlook: ''You are all assholes for not going.'' The World Space Foundation has a proposal for an ''Earthport'', duty free spaceport and industrial park that is being designed with some of these problems in mind. What is really needed is some production-line engineering to bring down the cost of space travel. Jerry Pournelle mentioned recently that a standard Shuttle pressure suit costs 14 megabucks. Clearly a spacesuit is not as complex as the piece of a jet fighter that 14 megabucks will buy. A Shuttle has about the same number of parts as a 747. But a Shuttle is built by large numbers of highly trained craftsmen, each being a separate work unlike any other shuttle. A 747 is built on an assembly line, turned out by the dozens, and is reliable as hell (especially compared to a Shuttle). If humanity's move into space reaches its third generation, we can expect to see those ticket to LEO base get a lot cheaper. ------------------------------ Date: 14 Oct 1981 01:37:27-PDT From: E.jeffc at Berkeley To: v.space@Berkeley, u:minsky@mit-ai Subject: SPS and radiation pressure While plausable, I'm not wholly satisfied that the problem has been explained away. You were considering a two-body problem with the Earth and the SPS as the bodies. However, the Sun must also be taken into account, for the SPS is also in orbit about the Sun, and all of the momentum from radition pressure will be wholly directed to pushing the SPS away from the Sun. Unfortunately, I can't determine from thinking alone whether this revives the problem or not. What is needed is a computer simulation which will take all these factors into account. Does anybody know of one? or does someone know how to do such a simulation? I imagine that the moon would have to be taken into account also. Anyway, even if the SPS is not blown away from the Earth, it will still get knocked out of geosyncronous orbit, and I would hate to see a high power energy beam wandering about the countryside. ------------------------------ Date: 14 October 1981 03:59-EDT From: Jerry E. Pournelle Subject: SPS continued To: CSVAX.tuttle at UCB-C70 cc: "TO:" at MIT-MC, minsky at MIT-AI, CSVAX.space at UCB-C70, e.jeffc at UCB-C70 You have pleaded for the validity of philosophical arguments, and your prayer has been answered; but that doen't make bad philosophy valid. Nor does re-inventing the wheel. I can well believe you are "shocked" to discover that SPS might act as a solar sail, but I assure you others have thought of it as well; and long ago. As to the sheer volume of material, per kilowatt SPS takes up about 1% of the mass of a dam to deliver the same power. (Actually a 3-metere slice of the 1270 metere Grand Coulee Dam would if put up as an SPS deliver the same power, some 9 gigawatts.) If the sheer volume of material for SPS will bankrupt us then we are bankrupted; for the entire US power plant must be replaced over the next thirty years wqhether we have growth or not; power plants don't last a lot longer than thirty years. And SPS is the SMALLEST system that would do that job. It is expensive because the people to build it are expensive; but of course the money is not "spent in space", there being no one there to cash checks... ------------------------------ Date: 14 October 1981 18:48-EDT From: Robert Elton Maas Subject: "When the Sun goes, we all go"? To: CSVAX.upstill at UCB-C70 cc: SPACE at MIT-MC Forwarding info: From: CSVAX.upstill at Berkeley From menlo70!hao!woods Tue Oct 13 17:45:03 1981 To: menlo70!ucbvax!upstill GREG (ucbvax!menlo70!hao!woods) I certainly hope not!!! If this species has any desire to survive, and any intelligence, it won't carefully arrange that when the Sun dies we'll all kill ourselves. Within 100 years, unless we do something stupid like have a nuclear war or like declare it illegal to go into space, we'll have an awful lot of our population (more than a thousand, probably more than a million, possibly more than 1E9) living in space colonies. Within another 100 years we'll have colonies orbiting not just the Earth/Moon system but freely orbiting the Sun. We'll also have some probes out to other nearby stars such as Alpha Centauri, Epsilon Eridani, Tau Ceti, Barnards Star. Within 1000 years we'll have colonies living around some of these other stars. Within 10,000 years we'll have populated all the major stars in our local part of the galaxy. Within 100,000 years we will have filled the whole Milky Way galaxy, not stuffed full, more like the pioneers of North America have now "filled" the whole continent, "from sea to shining sea", plenty of living space, just no major areas remaining that are untouched by man. Within 10,000,000 years (less if we can exceed 0.1 c) we'll have populated the Andromeda galaxy (M31) too. Within 500,000,000 years we'll have accomplished my goal of conquering the "final frontier", the whole Virgo supercluster of galaxies. Then in about 5,000,000,000 years, when the Sun burns itself out, the people living on Earth and in colonies around the Sun will have to move to some other star or perish. (Those who colonized faster-burning stars like Sirius will have to move much much sooner. I'd worry about them not the people of Earth/Sol.) ------------------------------ From: MINSKY@MIT-AI Date: 10/15/81 00:15:12 Subject: Booze Budget MINSKY@MIT-AI 10/15/81 00:15:12 Re: Booze Budget To: SPACE at MIT-AI Of course, if one were to consider the cost of booze, in illness and automobile accident and injury -- the latter might come to the order of 50,000 deaths and crippling injuries which at a cost of, say, 500,000 each -- adds a few real, non-taxable costs. ------------------------------ End of SPACE Digest ******************* ----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen of http://communication.ucsd.edu/A-News/ This Usenet Oldnews Archive article may be copied and distributed freely, provided: 1. There is no money collected for the text(s) of the articles. 2. The following notice remains appended to each copy: The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 Bruce Jones, Henry Spencer, David Wiseman.