Date: Wed, 14 Oct 92 05:04:39 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V15 #315 To: Space Digest Readers Precedence: bulk Space Digest Wed, 14 Oct 92 Volume 15 : Issue 315 Today's Topics: Controversy over V-2 anniversary Diesen sphere or Strungen Sphere (2 msgs) Gallileo's antenna HRMS/SETI Answers Math programs with arbitrary precision for the Mac? NASA workshops on detection and interception (was Re: asteroid impact) Roswell SETI functional grammar SETI functional grammer the development and change of the soft-and-hardwsre programms for electronic computers and microcontrollers. Too thin for light pressure? (was Re: Diesen sphere or Strungen Sphere) Two-Line Orbital Element Sets, Part 2 Welcome to the Space Digest!! Please send your messages to "space@isu.isunet.edu", and (un)subscription requests of the form "Subscribe Space " to one of these addresses: listserv@uga (BITNET), rice::boyle (SPAN/NSInet), utadnx::utspan::rice::boyle (THENET), or space-REQUEST@isu.isunet.edu (Internet). ---------------------------------------------------------------------- Date: Wed, 14 Oct 1992 05:15:20 GMT From: Henry Spencer Subject: Controversy over V-2 anniversary Newsgroups: sci.space In article jbh55289@uxa.cso.uiuc.edu (Josh 'K' Hopkins) writes: >>... they made some 65,000 modifications to delay >>mass production. > >I've seen numbers like this too, but it's not clear to me whether they made >so many modifications because they wanted to or because, never having built a >ballistic missile, it took a few tries to get things right. Actually, according to some of the more detailed histories, it was neither. They were constantly having to revise the design because one material or another featured in the original design had become unavailable. They found this frustrating, and said so. However, it also appears to be true that they never did get complete and final convergence on the build-test-analyze-revise cycle for the mass- produced version. -- MS-DOS is the OS/360 of the 1980s. | Henry Spencer @ U of Toronto Zoology -Hal W. Hardenbergh (1985)| henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 14 Oct 92 00:19:05 GMT From: Steve Linton Subject: Diesen sphere or Strungen Sphere Newsgroups: sci.astro,sci.space |> A Dyson sphere with a radius of one A.U. (as postulated in the Start Trek |> episode to which the poster refered - it's also a nice round number) and 1 km |> thick would require about 10e17 cubic km of materials. |> |> Earth has a volume close to 10e12 cubic km. Jupiter is about 100 times bigger. |> |> Where is there enough stuff to build out of? The answer of course is that you don't build it 1km thick. Using all the available matter we get about 1m thick, which would be plenty to plate solar collectors on. Indeed a metre of solid rock, spread out would make plenty of levels of low-g living space. However there is another problem. A rigid spherical shell cannot all be in orbit, the poles would fall in. There are two solutions to this that I have heard 1) instead of rigid shell you have a large number of small (asteroid like) bodies in carefully arranged orbits. These can deply very thin solar collectors like wings to ensure that no energy is allowed to escape. 2) have a VERY thin shell, supported by the light pressure inside and perhaps passing power to external orbitting habitats. A 1AU shell for the sun would be about 3 microns thick (if made of rock) and would mass no more than a medium sized moon. ------------------------------ Date: 14 Oct 92 05:20:07 GMT From: Henry Spencer Subject: Diesen sphere or Strungen Sphere Newsgroups: sci.astro,sci.space In article jbh55289@uxa.cso.uiuc.edu (Josh 'K' Hopkins) writes: >A Dyson sphere with a radius of one A.U. (as postulated in the Start Trek >episode to which the poster refered - it's also a nice round number) and 1 km >thick would require about 10e17 cubic km of materials. > >Earth has a volume close to 10e12 cubic km. Jupiter is about 100 times bigger. So don't make it 1 km thick. There really isn't any reason to make the thing any thicker than what you need to hold atmosphere and provide shielding. You're not going to get any useful amount of gravity out of any practical thickness. In practice, if you look at Dyson's *original* proposal, he wasn't suggesting a solid one-piece sphere at all, partly because it presents tremendous structural challenges. He was proposing a swarm of smaller bodies, each individually in orbit, which together would intercept almost all of the output of the star. -- MS-DOS is the OS/360 of the 1980s. | Henry Spencer @ U of Toronto Zoology -Hal W. Hardenbergh (1985)| henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 13 Oct 92 17:42:53 GMT From: Douglas Stevens Subject: Gallileo's antenna Newsgroups: sci.space Does anyone know if NASA has managed to get Gallileo's antenna open yet? ------------------------------ Date: 14 Oct 92 02:27:09 GMT From: Jeff Bytof Subject: HRMS/SETI Answers Newsgroups: sci.space >From: alg@is.morgan.com (Al Guintu): >Q: "WHAT IF ETI STOPS SENDING?" > what about a hypothetical eti civilization that stopped > transmission for example, because their government > cut off the resources for the work ;-> ? would the current > research ignore observation of the tail end of such a > transmission? What if ETI sends brief signals at highly infrequent intervals? For us to successfully receive such a signal, either we must observe the sky omnidirectionally at all times, or somehow guess the timing rule as a function of search direction. A prudent and efficient ETI might transmit to us along the following lines: 1. They do not broadcast omnidirectionally, and not unless they have evidence the target system has a habitable planet. 2. They are aware of the structure of our Solar System and the existence of Earth from their astronomical observations. 3. They broadcast at a specific moment, guessable by us. 4. The "guessable moment" or timing rule must determined by a (preferably) cyclical phenomena that we and they can both observe. 5. The orbital motion of Jupiter can be used to construct a timing rule. One possible mode: construct a vector from the Sun to Jupiter. Then construct a vector from the Sun to a particular direction (towards a solar-type star, for instance). Observe in that direction at times when the angle between the two vectors is a minimum, which occurs every 11.86 years. If ETI lies in the observed direction, their task is to send a signal to arrive at our Solar System when we are looking in their direction, as governed by the timing rule. 6. ETI must have a "pretty good telescope" to get Jupiter's orbit and the distance to our Solar System nailed down well. I assume that they are more advanced than we (a common assumption). 7. There will be error in the arrival time of the signal, so ETI will have to set the length of the their transmission to match the expected error. We know when to look with greater accuracy, and catch part of the message. If we aren't looking in the right direction at the right time, we can catch it later at modulo 11.86 year intervals. 8. The information content of the message from ETI in this strategy might be limited to instructions for sending our reply. 9. ETI can reduce the amount of time they listen for our reply by the instructions given in their message. If they provide us with the values they've obtained for determining the orbit of Jupiter (the timing rule) and their estimate of the distance to our Solar System (which they get from long baseline astrometry), we can solve for a more precise value of the Solar System-ETI distance. With a more precise distance value in hand, we can transmit a reply that it will arrive at ETI at an expected time. 10. A major fault of this strategy is the assumption that ETI is local (they can see our Solar System). If the number of communicating civilizations in the Galaxy is small, SETI is doomed if we are all "misers". On the other hand, the "effective" number of communicating ETIs would be increased by dispatching automatic stations out into the Galaxy, placed in orbits counter-revolving with respect to the general Galactic rotation. Such stations would drift along, mainly conducting passive astronomical observations of the Galaxy and transmitting data back to the home planet of the ETI. 11. Being power limited, these stations could not act as omni- directional beacons, and a power-efficient strategy like the one presented here may be utilized. 12. One automatic station may be followed by another. If we are detected by the first, instructions could be beamed to the second to alter its cross-velocity slightly and intercept the Solar System ("A Bracewell Probe"). 13. The content of the initial communication would be limited to the purely functional requirements of signal timing. The content of our reply (determined by the ETI) may be required to be a simple "password" that advances the "conversation" to the next level. If we can decode their instructions for proper content and timing for our reply, we have passed the "first test". --------------------- rabjab@golem.ucsd.edu ------------------------------ Date: 14 Oct 92 01:27:10 GMT From: "Frederick A. Ringwald" Subject: Math programs with arbitrary precision for the Mac? Newsgroups: sci.space In article seal@leonardo.Jpl.Nasa.Gov (David Seal) writes: > other mac programs or ways of computing pi? You mean like this? N[Pi, 1000] 3.1415926535897932384626433832795028841971693993751058209749\ 4459230781640628620899862803482534211706798214808651328230\ 6647093844609550582231725359408128481117450284102701938521\ 1055596446229489549303819644288109756659334461284756482337\ 8678316527120190914564856692346034861045432664821339360726\ 0249141273724587006606315588174881520920962829254091715364\ 3678925903600113305305488204665213841469519415116094330572\ 7036575959195309218611738193261179310511854807446237996274\ 9567351885752724891227938183011949129833673362440656643086\ 0213949463952247371907021798609437027705392171762931767523\ 8467481846766940513200056812714526356082778577134275778960\ 9173637178721468440901224953430146549585371050792279689258\ 9235420199561121290219608640344181598136297747713099605187\ 0721134999999837297804995105973173281609631859502445945534\ 6908302642522308253344685035261931188171010003137838752886\ 5875332083814206171776691473035982534904287554687311595628\ 6388235378759375195778185778053217122680661300192787661119\ 590921642 This was done in about 4 seconds just now, read by me from a clock on-screen, so it might be better, on a Mac II with 5 Megs of RAM, a 68030 chip with a 68881 coprocessor (which I'm not sure is even used), under System 7.0.0 with virtual memory disabled, because it has never worked on this machine - i.e., not the greatest Mac around, probably slower than a new Classic II - with Mathematica 2.0.3 Enhanced. It's no wonder Mathematica is rapidly emerging as the standard, at least in academia. Not only was I able to redo all the math I had in all of high school, college, and grad school in an afternoon (my favorite command is still InverseLaplaceTransform[expr, s, t]), but it's also frighteningly easy to use. Pricey, but well worth it, and no, Steven Wolfram didn't pay me to write this. (Perhaps he should...) E-mail me if you're interested in 10,000 or more places, fred.ringwald@dartmouth.edu ------------------------------ Date: 14 Oct 92 05:19:17 GMT From: Bill Higgins-- Beam Jockey Subject: NASA workshops on detection and interception (was Re: asteroid impact) Newsgroups: rec.arts.sf.science,sci.space In article <1992Oct11.000556.2350@techbook.com>, szabo@techbook.com (Nick Szabo) writes: > In article <1992Oct8.102322.6660@arbi.Informatik.Uni-Oldenburg.DE> Onno.Meyer@arbi.informatik.uni-oldenburg.de (Onno Meyer) writes: >>I read a newspaper notice concerning an asteroid (or some other >>kind of rock) passing the earth with ... million miles distance. >>The paper said that a rock that would hit the earth could be deflected >>with nuclear arms. > > [Nick's discussion of deflection problem deleted] > > A couple projects if funded could remedy our ignorance. > These projects would cost only $70 million apiece, or in total > 1/10 of 1% -- one-one-thousandth -- the cost of NASA's space > station. The first is Spacewatch, to find and track all dangerous > earth-approaching asteroids. The second would be a survey to use big > telescopes and spectroscopy to determine the composition of these bodies. > These projects are also critical to getting raw materials from these > asteroids in the future, so we kill two birds with one stone (so to speak :-) People seriously interested in these questions will want to get hold of *The Spaceguard Survey: Report of the NASA International Near-Earth-Object Detection Workshop*. The group was chaired by David Morrison of the University of Hawaii. It met a number of times during 1991, and the report was released earlier this year. I believe copies can be obtained from NASA Headquarters in Washington; start by asking the Public Affairs Office, NASA Headquarters, 600 Independence Avenue, Washington, DC 20546 (202)453-1549. To quote from the press release: > The NASA-sponsored Near-Earth-Object Detection Workshop >judged asteroids with diameters 1 km or larger the most >dangerous objects in terms of potential for causing catastrophic >global effects on Earth. Impacts of such asteroids are extremely >rare and can be detected with current ground-based technology, >most likely decades in advance of any collision. Later, in January 1992, Los Alamos National Laboratory hosted a Near-Earth-Object Interception Workshop. This group worked on the question of how to *prevent* asteroid collisions. Their report isn't out yet, having run into both political and budgetary problems (they ran out of money to pay their editor). Short overviews of both workshops, authored by some of their participants, appeared in the May/June 1992 issue of *Mercury*, the magazine of the Astronomical Society of the Pacific. They were accompanied by an article by Fran Smith of the *San Jose Mercury News*, "A Collision over Collisions: A Tale of Astronomy and Politics." According to Smith's account, Morrison persuaded Congressional committees "that you didn't have to be a nut or a tabloid editor to contemplate cosmic collisions." Thus NASA's FY 1991 authorization bill included a requirement to report to Congress on the asteroid hazard; that's how these two workshops got started. Smith describes a disagreement between Morrison and John Rather, assistant director for space technology at NASA Headquarters, and a member of the SDI community before he came to NASA. Morrison's group emphasized large objects, bigger than a kilometer in diameter, which could cause regional or global cataclysm-- but which are eminently detectable in ground-based telescopes. Rather's group, which included weapons physicists from Livermore and Los Alamos, was more interested in objects 4 to 20 meters across-- hard to find with telescopes, but more common, and easier to destroy or deflect with SDI-derived technology plus nuclear weapons. Names of such prominent SDI advocates as Edward Teller, Lowell Wood, Roderick Hyde, and Gregory Canavan appear in the article, but it's not clear to me who among them were actually involved with the "Interception" workshop (Canavan was). "Several months ago, after several astronomers got their hands on a near-final draft calling for `star-wars' technology and nuclear bombs," Smith writes, "they angrily demanded that NASA revise these recommendations-- or drop their names from the report." She does not name these people, but long-time opponents of SDI like Louis Friedman and John Pike are among the members of Morrison's workshop. My impression, from Smith's article, is that a number of specialists in asteroid astronomy believe that organizing a search for possible collisions is a good idea, but is difficult enough to sell without getting connected to a weapons-development project. Odds are that if the search finds a large asteroid or comet due to collide with the Earth, there will be years or decades of warning. One could bet that there would be plenty of time to develop a defense *after* such detection. Yet it might make sense to have collision-defense development proceed in parallel with the search, at least at a modest level. In the same issue of *Mercury*, Gregory Canavan and Johndale Solem of Los Alamos write in their summary, "Interception of Near-Earth Objects:" "The premiums for such insurance vary. A few million dollars per year could support observations and theory on detection and interception. A few tens of millions per year could provide research on the technologies for interception, the dedicated instruments needed to search for large Earth-threatening NEOs, and research on the sensors needed to detect smaller asteroids at the ranges desired. A few hundred million dollars could develop and test the robotic spacecraft missions needed to characterize NEOs of all sizes. Unfortunately, confusion over the relative priorities of detection and interception has thus far delayed action on either, although preliminary estimates indicate that either would justify the research." O~~* /_) ' / / /_/ ' , , ' ,_ _ \|/ - ~ -~~~~~~~~~~~/_) / / / / / / (_) (_) / / / _\~~~~~~~~~~~zap! / \ (_) (_) / | \ | | Bill Higgins Fermi National Accelerator Laboratory \ / Bitnet: HIGGINS@FNAL.BITNET - - Internet: HIGGINS@FNAL.FNAL.GOV ~ SPAN/Hepnet: 43011::HIGGINS ------------------------------ Date: 14 Oct 92 01:43:01 GMT From: "Frederick A. Ringwald" Subject: Roswell Newsgroups: sci.space In article henry@zoo.toronto.edu (Henry Spencer) writes: > Come now. If you're going to reprint stuff from Air&Space, [...] > at least summarize the whole article, rather than taking part of it out > of context. Much the most interesting thing in that article was the > observation that a crash of a hush-hush *US* project could easily account > for the fuss and the secrecy... especially since the location was ideal for > such a thing to happen. Roswell is in the middle of an area that includes > White Sands Missile Range, Los Alamos, and an airbase that then housed the > world's only operational nuclear-bomber force. > > It's silly to invoke crashed UFOs when Earthly causes provide quite an > adequate explanation. It may well also explain the alleged "spook hangar" - number 19, if memory serves me right - at Wright-Patterson AFB. I must say "alleged", since I have not seen it myself, although I've heard one can see a building that doesn't look like much. Let's see, a building that doesn't look like much: now that's convincing! ;-) If such a building actually exists, and it does house something dreadfully embarrassing to the USAF, you have your pick of nasties - nuclear, chemical, or even biological - before you get to anything extraterrestrial. Then there's the idea that's where the Arc of the Covenant wound up... ;-) ;-) ;-) ------------------------------ Date: 14 Oct 92 04:45:10 GMT From: John Roberts Subject: SETI functional grammar Newsgroups: sci.space -From: jbh55289@uxa.cso.uiuc.edu (Josh 'K' Hopkins) -Subject: Re: SETI functional grammer -Date: 13 Oct 92 20:40:01 GMT -Organization: University of Illinois at Urbana -I ran across a thought experiment once where the prototype teleporting machine -ends up on an alien planet and won't come back. How do you tell the aliens -to press the right (manual override) button and not the left (self destruct) -button? I couldn't figure a way out. There's a way, but it involves some subtleties of nuclear physics - I don't remember the details. You may have to assume the aliens are made of normal matter rather than antimatter, but given that your machine didn't turn into gamma rays, that's probably a pretty good assumption. John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: 13 Oct 92 23:42:12 GMT From: Steve Linton Subject: SETI functional grammer Newsgroups: sci.space Organization: U of Cambridge, England Lines: 32 Nntp-Posting-Host: bootes.cus.cam.ac.uk Source-Info: Sender is really news@CRABAPPLE.SRV.CS.CMU.EDU Source-Info: Sender is really isu@VACATION.VENARI.CS.CMU.EDU |> |> Saying this is very hard is an understatement :-) And rember that it may take |> a few centuries to say "Sorry, I didn't catch that..." What you don't do is wait for a response. Having found evidence of someone out there, you send them everything you can think of, on every frequency you can think of and just keep talking. After a few centuries they will (hopefully) reply, and if they ask any questions you haven't already sent answers to you put the answers in straight away. Even if it takes them decades to crack your language it's a safe bet that they'll have recordede what you sent so far, so they can go back and translate it all. By all means send them clever codes and mathematics and so on, but also send them encyclopedias and newspaper back issues and TV game shows. Who knows what'll be the key to them cracking the language? Meanwhile of course we have to crack their codes, mathematics, language and TV dating ads. |> |> I ran across a thought experiment once where the prototype teleporting machine |> ends up on an alien planet and won't come back. How do you tell the aliens |> to press the right (manual override) button and not the left (self destruct) |> button? I couldn't figure a way out. This is a fundamental physical problem. The easy answer is to refer them to some assymetry in the machine, or in the distribution of quasars or something. Failing that you can send them a helically polarised radio beam. Failing all those, you have to describe a rather complicated piece of particle physics which demonstrates that the universe is not symmetrical. I don't recall the details, but it can be done (as long s you agree on the direction of time). Steve Linton ------------------------------ Date: 14 Oct 92 06:44:26 GMT From: "Tahsin I. Alam" Subject: the development and change of the soft-and-hardwsre programms for electronic computers and microcontrollers. Newsgroups: sci.space,sci.research,sci.physics,sci.med,sci.engr.chem,sci.chem,sci.astro Hi: Is there any algorithm or any research paper on calculating volumes of n-dimensional convex polyhedra? Any info would help. I would appreciate it if you could send the reply directly to me at the following address: tahsin@cs.brandeis.edu Thanx, -- ma'as-salama (Goodbye in Arabic, literally "With peace ... ") Tahsin I. Alam ------------------------------ Date: 13 Oct 92 19:38:09 GMT From: Bill Higgins-- Beam Jockey Subject: Too thin for light pressure? (was Re: Diesen sphere or Strungen Sphere) Newsgroups: sci.astro,sci.space In article <1992Oct14.001905.25147@infodev.cam.ac.uk>, sl25@cus.cam.ac.uk (Steve Linton) writes: [uh-oh, Steve lost the antecedents, but he was referincing a Josh Hopkins(tm) posting...] > |> A Dyson sphere with a radius of one A.U. (as postulated in the Start Trek > |> episode to which the poster refered - it's also a nice round number) and 1 km > |> thick would require about 10e17 cubic km of materials. [...] > have a VERY thin shell, supported by the light pressure inside and perhaps > passing power to external orbitting habitats. A 1AU shell for the sun would be > about 3 microns thick (if made of rock) and would mass no more than a medium > sized moon. I doubt whether 3 microns is enough to be reasonably opaque, let alone a nearly perfect reflector (which you want when building a solar sail.) I don't have a handbook handy, but I think you need dozens of microns of aluminum to make a good reflector. Eric Drexler ran into the transparency problem when he was trying to design the most lightweight possible sail (in his previous life, before he achieved fame as Mr. Dinky). During the first and second stage Bill Higgins flights of the vehicle, if a serious Fermi National Accelerator Laboratory irretrievable fault should occur and HIGGINS@FNALB.BITNET the deviation of the flight attitude of HIGGINS@FNAL.FNAL.GOV the vehicle exceeds a predetermined SPAN/Hepnet: 43011::HIGGINS value, the attitude self-destruction system will make the vehicle self-destroyed. --Long March 3 User's Manual Ministry of Astronautics, People's Republic of China (1985) ------------------------------ Date: Wednesday, 14 Oct 1992 09:00:24 CET From: TNEDDERH@ESOC.BITNET Subject: Two-Line Orbital Element Sets, Part 2 Newsgroups: sci.space Sorry, but we are in mid of october and the last state of EUVE is again for august 19th. Is it not anymore tracked by NORAD? -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Thorsten Nedderhut | Disclaimer: mbp Software & Systems GmbH | c/o ESA/ESOC/FCSD/OAD/STB | Neither ESA nor mbp is responsible Darmstadt, Germany | for my postings! tnedderh@esoc.bitnet | ------------------------------ End of Space Digest Volume 15 : Issue 315 ------------------------------