Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from beak.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests) ID ; Wed, 18 Apr 90 02:48:25 -0400 (EDT) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Wed, 18 Apr 90 02:47:55 -0400 (EDT) Subject: SPACE Digest V11 #281 SPACE Digest Volume 11 : Issue 281 Today's Topics: Re: Listening to the Star (was RE: Drake Equation) Re: Earthbound Asteroid.....trying again! Re: Galileo Update - 04/13/90 Re: Drake Equation (was Re: Interstellar travel) Earthbound Asteroid.....trying again! Questions about the Voyagers RE: Reach What happened with the Barium drop Re: Fermi Paradox Re: Energy consumption Re: The effects of decompression Re: Interstellar travel Re: Discovery's Spin in 2010 (Was Re: Artificial gravity) ---------------------------------------------------------------------- Date: 17 Apr 90 16:44:43 GMT From: idacrd!mac@princeton.edu (Robert McGwier) Subject: Re: Listening to the Star (was RE: Drake Equation) From article <1494@gara.une.oz.au>, by pnettlet@gara.une.oz.au (Philip Nettleton): > From vn Tue Apr 17 10:55:55 1990 > > The point that people are forgetting is the impracticality of advanced > civilisations using radio signals, especially if they're technologically > advanced enough to have colonised other worlds and thereby need to keep in > contact. We are acting like American Indians a couple of hundred years ago > looking for smoke signals from a neighboring tribe to indicate they're > presense when they're using CB radios. > I couldn't agree more. While visiting JPL a couple of years ago, I met with the folks who were doing advanced research for the Casini (Saturn orbiter, titan probe) mission. Even at that time they were working on single photon laser detectors so that LIGHT could be used as the data link back to earth achieving incredible data rates. If coherent light and incredible data rates (and fiber optics etc.) is the mainstay of communications of another world, SETI, as now envisioned, is probably a waste. We have moved from radio to planning the use of light and even now making massive moves to fiber, in under 100 years. I think radio SETI is a waste, and Cyclops would certainly be a waste. Bob -- ____________________________________________________________________________ My opinions are my own no matter | Robert W. McGwier, N4HY who I work for! ;-) | CCR, AMSAT, etc. ---------------------------------------------------------------------------- ------------------------------ Date: 17 Apr 90 22:36:53 GMT From: usc!cs.utexas.edu!ut-emx!grads@ucsd.edu (Feulner ... Matt Feulner) Subject: Re: Earthbound Asteroid.....trying again! In article <6122@rayssdb.ssd.ray.com> bea@rayssdb.ssd.ray.com (Brian E. Alber) writes: > >Sorry for my screw up before...it was pilot error. The message should be: > >I had heard that sometime last year or the year before that a large asteroid >or some other LARGE (I mean really BIG) object nearly hit the Earth. It >supposedly came within 250,000 miles and scientists (astronomers?) here on >Earth only knew of its existence after it had passed us. > >Questions: > > 1.) Is there any truth to this? Yes. > 2.) When did this happen (where is it documented)? It was in the daily papers. I don't know if it was anywhere else. > 3.) How large was it? Big enough for 4) > 4.) What would have happened if it hit? If it landed in water (80% or so) it would create tidal waves covering much of the California coast (if it went into the Pacific). If it landed on land, it would have made a REALLY big crater, and the resulting dust in the atmosphere would be around for quite a while. > 5.) Why didn't we see it coming? We weren't looking. > 6.) How often do things this big come our way? Maybe once a year. That one was supposed to be in about a 1 year period, and others have come close. > 7.) etc... It was supposedly twice as far out as the moon. Matthew Feulner I love short, concise answers. grads@emx.utexas.edu ------------------------------ Sender: "Jack_Bacon.WBST897ai"@Xerox.COM Date: 17 Apr 90 06:22:54 PDT (Tuesday) Subject: Re: Galileo Update - 04/13/90 From: "Jack_Bacon.WBST897ai"@Xerox.COM Cc: "Jack_Bacon.WBST897ai"@Xerox.COM As I read it, the ubiquitously-mentioned DC Voltage inbalance seems to increase every time that certain thrusters are fired after a long idle period. Could someone close to the project tell us whether the two events are directly related? (ie, some form of magnetohydrodynamic coupling of ionizing exhaust gasses with the spacecraft?). Is this some sort of static charge that is built up on Galileo, or is it an overproduction of voltage by the power supply? What instruments are sensitive to this inbalance? ------------------------------ Date: 17 Apr 90 02:43:03 GMT From: cs.utexas.edu!news-server.csri.toronto.edu!clyde.concordia.ca!mcgill-vision!quiche!calvin!msdos@tut.cis.ohio-state.edu (Mark SOKOLOWSKI) Subject: Re: Drake Equation (was Re: Interstellar travel) Since the above subject is highly philosophical, if not of a sci-fiction nature, let's talk about the martians!!! I think that the fact that our galaxy could be colonized in a time span ranging from 3 million (high speed at 0.1c) to 30 million years (chemical propulsion at 0.01c) proves at least to me that no other advanced civilization exists in our galaxy, since this later object is at least 12 billion year old. This is more than enough time for hundreds of planets having some form of life to reach some kind of "maturity" comparable to our own technical level... Therefore, I will have this DEFINITE conclusion: We are alone, and I am very pleased with that (We're already 6 billion here!!!!), notwithtanding the fact that space is VOID, COLD, DEAD in general, which means that any INTERSTELLAR civilization (including us in a few hundred years...) will be so imperialistic and so energy thirsty that I won't want to live in there (but some others surely will...) and if they come here, we're all dead, PERIOD! ------------------------------ Date: 17 Apr 90 16:42:10 GMT From: rayssd!bea@decuac.dec.com (Brian E. Alber) Subject: Earthbound Asteroid.....trying again! Sorry for my screw up before...it was pilot error. The message should be: I had heard that sometime last year or the year before that a large asteroid or some other LARGE (I mean really BIG) object nearly hit the Earth. It supposedly came within 250,000 miles and scientists (astronomers?) here on Earth only knew of its existence after it had passed us. Questions: 1.) Is there any truth to this? 2.) When did this happen (where is it documented)? 3.) How large was it? 4.) What would have happened if it hit? 5.) Why didn't we see it coming? 6.) How often do things this big come our way? 7.) etc... Any comments out there? Brian ALBER bea@rayssdb.ssd.ray.com ================================================================================ ------------------------------ Date: 18 Apr 90 02:32:25 GMT From: ogicse!cs.uoregon.edu!spencer.cs.uoregon.edu!solana@uunet.uu.net (David Solana) Subject: Questions about the Voyagers Could someone out there please answer these questions about the Voyagers? * What are their positions in this moment? * Where are they heading for? At what speed? * Why didn't they visit Pluto? I read in Sky & Telescopes that this decade would be ideal for sending a probe to Pluto. Are there any plans to build such a probe? * What kind of data do the Voyagers transmit? * What can it be expected from these data? Are all of them "routine science cruise data" as baalke@mars.jpl.nasa.gov (Ron Baalke) describes them? Are all the data lost due to lack of Deep Space Network (DSN) coverage? * For how long will the probes be transmitting? Thanks in advance. David Solana Computer Science Department University of Oregon ------------------------------ Date: Tue, 17 Apr 90 22:52 CST From: "Kim J. Trull" Subject: RE: Reach X-Envelope-To: space+@andrew.cmu.EDU Patrick Horgan asks: >Has anyone else read Reach? Well, Patrick, it just happens to be one of my favorites!! I had the opportunity to ask Gibson why he decided to write a fiction story when so many astronauts choose to write fact. His reply, (paraphrased) was that he started to write a factual story based on his experiences, but he got bored with it himself. He also made another comment that I really liked: "I remember -- but then I realize that I'm remembering memories and not the way it really happened anyway." Any way, his analogy about the war between Data and Judgment is one of my favorites parts of the book!! I hope you enjoy the ending... KJ Trull TRULL@cl.uh.edu ------------------------------ Date: 18 Apr 90 03:06:56 GMT From: netnews.upenn.edu!linc.cis.upenn.edu!vinson@rutgers.edu (Jack Vinson) Subject: What happened with the Barium drop What happened with the barium canister that was to be released from PegSat Sunday morning? I haven't seen anything in the local newspaper or any quick blurbs here. Did I miss it when skipping one of the long Headline postings? Jack vinson@linc.cis.upenn.edu ------------------------------ Date: 17 Apr 90 17:42:19 GMT From: cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo!henry@tut.cis.ohio-state.edu (Henry Spencer) Subject: Re: Fermi Paradox In article <1990Apr16.172643.20403@ncsuvx.ncsu.edu> noble@shumv1.ncsu.edu (Patrick Brewer) writes: >... For an alian race to make something we would actually notice >it would have to be large. Large as in "light week" measurements. It would >have to be larger than the solar system. Never mind that a structure this >size probably could not be built because of its own gravity! I'd suggest doing some reading about Dyson spheres and their more ambitious relatives. Works of engineering many light*years* across are not at all beyond imagining. They are beyond what we could do in the immediate future, but we routinely do things now that were pure fantasy a century ago. (Try telling the Wright brothers that less than a century after their first flight, the average human population of the Earth's skies would be several hundred thousand people... 24 hours a day, 7 days a week.) We can guess at our own capabilities a hundred years from now, but most of the guesses will probably be wrong. A thousand years out, even guessing is silly. A race that has had a technological civilization for a million years would probably be capable of doing many things we are certain are impossible. -- With features like this, | Henry Spencer at U of Toronto Zoology who needs bugs? | uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: 17 Apr 90 19:11:24 GMT From: cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo!henry@tut.cis.ohio-state.edu (Henry Spencer) Subject: Re: Energy consumption In article <1496@gara.une.oz.au> pmorriso@gara.une.oz.au (Perry Morrison MATH) writes: >> Energy costs are *not* the major cost of spaceflight today... > >These postings have been concerned with the desirability or otherwise >of space tourism. Given the energy requirements of the average >third worlder (if there is such a thing) all of this is still a terrible >waste of resources- especially to fulfil what is effectively an individual's >whim. So is Earth tourism; the energy costs of air travel to Australia are roughly the same as the energy costs of reaching low orbit. If one is acceptable, what's wrong with the other? > Show me a space vehicle that gets simpler and I'll show you a unicorn. >The shuttle shows us how complex these things really are becoming and >how chronically unreliable they are. Most of the plans for successors to the shuttle envision simpler vehicles, not more complex ones. The shuttle was an aberration. And yes, there are instances of high-tech hardware getting simpler -- military jet engines have many fewer parts than they used to, for example, and it's for the same reason, higher reliability. >> As for "exotic alloys": "exotic" is relative to our technical >> abilities. Aluminum was once an exotic, expensive material. Today, >> it's mundane. The same thing is happening today to composites, >> ceramics and other materials. > >Oh. So newer space vehicles won't use any new "exotic" alloys? They'll >stick with the tried and true? That's not what he said. In any case, many newer space vehicles probably *will* use old alloys. Hermes will be mostly aluminum, for example, not titanium like the shuttle. The fact is, tried and true alloys are quite adequate for spaceflight unless you are pushing the state of the art for its own sake, e.g. NASP. -- With features like this, | Henry Spencer at U of Toronto Zoology who needs bugs? | uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: 17 Apr 90 20:08:20 GMT From: shlump.nac.dec.com!quik07.enet.dec.com!burch@decvax.dec.com (Ben Burch) Subject: Re: The effects of decompression In the book "Suiting Up For Space: The Evolution of the Space Suit" (Author presently unremembered) is shown a mechanically-pressurized suit from the mid-1950's. This was an elastic pressure garment which used the skin as the vapor barrier and which used skin evaporation for thermal regulation. It had a separate oxygen pressurized helmet. No doubt the pressures in the helmet were of the order of 3.5 psi to minimize leakage and the amount of mechanical force required to keep the helmet mantlet gasket on the shoulders. This is one of those really elegant ideas that one looks at sometimes, unable to understand what, besides social inertia, killed it. Oh yes, the fingers were encased in what looked like rubber finger cots. - Ben Burch (burch@quik07.enet.dec.com) "Views expressed herein are not those of Digital Equipment Corporation." ------------------------------ Date: 17 Apr 90 17:49:30 GMT From: cs.utexas.edu!samsung!rex!rouge!dlbres10@tut.cis.ohio-state.edu (Fraering Philip) Subject: Re: Interstellar travel I don't have references, but studies on Interstellar travel have looked at the possibility of using a dust or gas cloud put in front of you while you are coasting to cut down on the amount of gas or dust likely to collide with you. Imagine the dust in interstellar space colliding with an exhaust plume or cloud of ice particles put out by a lowly RL-10. Of course, it depends on how long the cloud holds together. Doubtlessly something could be done with electrostatics or a magnetic field holding the dust in place. Scotty, raise the shields... :-) Philip Fraering dlbres10@pc.usl.edu "I'm trobled, I'm dissatisfied, and I'm Irish."- Marianne Moore ------------------------------ Date: 17 Apr 90 17:28:44 GMT From: clyde.concordia.ca!mcgill-vision!quiche!calvin!msdos@uunet.uu.net (Mark SOKOLOWSKI) Subject: Re: Discovery's Spin in 2010 (Was Re: Artificial gravity) >One thing that has always impressed me about 2001 was the lack of >sound in the outer-space (ie outside of spacecraft) shots; no >Star Wars-like deep, low freq rumble of powerful thrust engines. >Any other such movies with silent space? Even Alien, with "in space >no one can hear you scream", you could hear the engines from "outside". For Alien, I think the film is still very realistic, the noise coming probably from the small athmosphere (a few billions of our surface pressure down here) of iniozed material that transmists some noise... ------------------------------ End of SPACE Digest V11 #281 *******************