Date: Mon, 19 Oct 92 05:02:12 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V15 #326 To: Space Digest Readers Precedence: bulk Space Digest Mon, 19 Oct 92 Volume 15 : Issue 326 Today's Topics: DCX Status? Dyson Spheres and Cosmic Spaghetti Earth's two moons Recognizing a Dyson sphere if you saw one (2 msgs) Sundrive Weather satellites & preventing property damage 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: 19 Oct 92 06:13:55 GMT From: Scott Fisher Subject: DCX Status? Newsgroups: sci.space aws@iti.org (Allen W. Sherzer) writes: >Things are going on pretty well. My countdown may be off by a day or two >but there have been no serious problems with deisgn or construction. > Allen >+---------------------------------------------------------------------------+ >| Allen W. Sherzer | "A great man is one who does nothing but leaves | >| aws@iti.org | nothing undone" | >+----------------------192 DAYS TO FIRST FLIGHT OF DCX----------------------+ Q: Why is the DCX designed to take off and land vertically, taking off I can perhaps understand, but landing?? What are the advantages? Thanks in advance Scott. _______________________________________________________________________________ Scott Fisher [scott@psy.uwa.oz.au] PH: Aus [61] Perth (09) Local (380 3272). _--_|\ N Department of Psychology / \ W + E University of Western Australia. Perth [32S, 116E]--> *_.--._/ S Nedlands, 6009. PERTH, W.A. v Joy is a Jaguar XJ-6 with a flat battery, a blown oil seal and an unsympathetic wife, 9km outside of a small remote town, 3:15am on a cold wet winters morning. ------------------------------------------------------------------------------- ------------------------------ Date: 19 Oct 1992 01:33 PDT From: Donald Arseneau Subject: Dyson Spheres and Cosmic Spaghetti Newsgroups: sci.astro,sci.space In article <1992Oct18.212301.1597@m.cs.uiuc.edu>, carroll@cs.uiuc.edu (Alan M. Carroll) writes... >Niven proposed a different form of this which was sort of neat. >Instead of multiple O'Neil colonies, you just build one that's >extensible. You extend it until it wraps all the way around. If it's >thin enough (say, ~10km with a 1AU radius) the rotation stresses are >negligible. So you can spin it for gravity. Nope. Niven had to invent yet-another-impossibly-strong-material for his ringworld. Scrith, I think he called it. Oh! Re-reading, perhaps Alan means the ring is a torus, and spins around its small circle. In that case the stresses *are* negligible, but it wasn't Niven's ringworld. Donald ------------------------------ Date: 19 Oct 92 09:21:10 +1000 From: apm212a@vaxc.cc.monash.edu.au Subject: Earth's two moons Newsgroups: sci.space In article <1992Oct16.231928.11845@sfu.ca>, palmer@sfu.ca (Leigh Palmer) writes: > In article cocking@csugrad.cs.vt.edu (Cara > Cocking) writes: >> >> I took an astronomy class in high school and my teacher told us that >> Earth really has two moons but that the other one can't be seen unaided >> because it's a lot smaller and farther out. >> >> I've been telling some people that Earth has two moons but no one >> believes me. Could someone please confirm this? > > Question Authority. > > Leigh As far as I can gather Eath has several thousand moons. Indeed, many of them are very small. They are called artificial satellites. Most are with in the orbit of Earth's natural satellite. +-------------------+--------------------------------+-------------------------+ | Stuart Robinson | In any hierachical bureaucracy | My opinions are my own. | | Mathematics Dept. | the bitchiness expands to fill | | | Monash Uni. | the egos available. | They are not those of | | Clayton 3168, | | Monash University. | | Victoria, +--------------------------------+-------------------------+ | Australia | apm212a@vaxc.cc.monash.edu.au |Ph : +61 3 565 4501 (BH) | +-------------------+--------------------------------+-------------------------+ ------------------------------ Date: 19 Oct 92 03:58:45 GMT From: "Frederick A. Ringwald" Subject: Recognizing a Dyson sphere if you saw one Newsgroups: sci.astro,sci.space So, how can one recognize a Dyson sphere, among astronomical objects? Has anyone ever published anything serious about this? Seriously, this seems a lot more promising than other types of SETI. So what would it look like, to a ground-based astronomer? A G dwarf with an infrared excess, maybe also a narrow-band radio excess (dead giveaway there, although even Arecibo won't be sensitive enough to detect leakage radiation, unless there's one right nearby or they're leaking in a prodigious manner, by our standards)? Maybe also laser leakage signals (another dead giveaway, although has anyone done a calculation of how much excess power to expect, assuming leakage; directionality may well be a major problem)? Would I recognize a Dyson sphere if I saw one? Might there be one or more lurking in the IRAS database? (I'm sure this has occurred to someone: got any literature references?) I hear funding may be stalled (I applied for a job, and I got back a nice "sorry, but we didn't get funding for that position - try again next year"), but what about the 2MASS survey? The 10-100 micron region sounds like a better place to search, though, being a more likely temperature regime. What's been done or thought about, or do I have to do this one myself? Seriously, a large-scale search for ten-micron radiation from F-K dwarfs might be a project I could do, if I could get it past a funding committee... Please e-mail, and I'll post a compilation in a week or so, fred.ringwald@dartmouth.edu ------------------------------ Date: 19 Oct 92 05:50:05 GMT From: Steve Linton Subject: Recognizing a Dyson sphere if you saw one Newsgroups: sci.astro,sci.space You`re looking for a body with a diameter of a few AU's radiating a black-body spectrum at a few hundred K, for a total power output roughly the same as that of a star. The spectrum might not be spot on, and deviations from black-body would like very unlike anything you might expect naturally - might have very sharp spikes, or sudden chops. ------------------------------ Date: 19 Oct 92 01:36:26 GMT From: Ian Stirling Subject: Sundrive Newsgroups: sci.space Re the idea of putting a reflective sphere with a window in round a star and using as a drive. using the sun as an example. I can't find a figure for the energy output by the sun, but I found a figure of 4*10^9 kg mass loss per second(by fusion) assuming 50% total system efficiancy this gives the system a engine power of 2 (4*10^9)*(3*10^8) = 4*10^9 * 9*10^16 = 4.5*10^26 W Assuming this is all in the form of photons going the right way, this gives a force of 2*10^10 N. The sun has a mass of 1.9*10^30 Kg so the acceleration is simply 2*10^10 N ___________ = 1.05*10^-20 M/s/s 1.9*10^30 This is not much , 3.1*10^7 * 1.05*10^-20 = 3.2*10^-13 M/s/year Till the sun goes nova is maybe 15*10^9 years so the final speed will be a massive 4.5 milimeters/sec. And you would have moved the sun a bit outside the current orbit of mercury. Pity, it looked such a nice concept, maybe the numbers are better for small, hot stars? How could you focus the beam to make it hit a interstellar probe? Any problems with my math? Mail to either |PLEASE do not send large Printf@cix.compulink.co.uk First try |(>20K)mail messages without Printf%cix@ukc.ac.uk Second try |asking, as I may get charged Printf@cix.uucp Last hope |for them. one of these may work. | ------------------------------ Date: 19 Oct 92 04:10:24 GMT From: "Frederick A. Ringwald" Subject: Weather satellites & preventing property damage Newsgroups: sci.space Does anyone have figures for how much property damage has been prevented because of data from weather satellites? More interestingly, does it justify the entire NASA budget, for all time? I'm not sure I want to get into a discussion about lives (because sooner or later, someone will put a monetary value on a human life, something I do not in any way feel qualified to do); let's stick with property damage. Similar contentions could be made for military surveillance satellites; LBJ, for one, was said to have thought that the entire NASA expenditure was justified by them, plus Carl Sagan may have expressed sentiments to the effect, but let's leave them out of consideration, for now. Likewise for Earth observation satellites, such as LANDSAT or SPOT: besides, it's been rumored that while they are useful, they have a long way to go before they're commercially justifiable. Ditto for space manufacturing, although there seems to me to be a great deal of potential here. Comsats, of course, are making profits, although I'm not sure they justify all space activity, although on the other hand I'm not sure it's relevant, being a commerical concern. Let's stick with government funding of weather satellites. Please e-mail, and I'll post a compilation in a week or so, fred.ringwald@dartmouth.edu ------------------------------ End of Space Digest Volume 15 : Issue 326 ------------------------------