Date: Fri, 7 Aug 92 05:00:07 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V15 #079 To: Space Digest Readers Precedence: bulk Space Digest Fri, 7 Aug 92 Volume 15 : Issue 079 Today's Topics: Calendar and Zodiac Energiya's role in Space Station assembly Home made rockets More TSS information from NASA Select NASA Tools (2 msgs) Origin of Life article Red-blooded ET's : ) Shuttle launch Soyuz as ACRV (3 msgs) Soyuz as ACRV (Posting of previous discussion data) (2 msgs) Star Trek (anti-)realism Tether Questions Whats wrong with this CONDUCTOR (was: Tethered Satellites) 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: 4 Aug 92 03:58:32 GMT From: "Gregory N. Bond" Subject: Calendar and Zodiac Newsgroups: sci.space >>>>> On 30 Jul 92 02:31:37 GMT, roberts@CMR.NCSL.NIST.GOV (John Roberts) said: John> By the way, the Orthodox church still uses the Julian calendar John> (in the US and Russia, anyway, and presumably elsewhere). I John> believe the skew is currently 14 days, and should remain so John> until AD 2100. Since the determination of the date of Easter is John> partly a function of the phase of the moon, the lag between the John> two observations of Easter is variable. Easter is defined as (from memory) the first new moon after March 21st (equinox? Coincidence? Wrong date?). The orthodox easter uses the Julian March 21st, the western church uses Gregorian. So the easters will either coincide or differ by 28 days, in some fixed but not obvious pattern. I think. Greg. -- Gregory Bond Burdett Buckeridge & Young Ltd Melbourne Australia ``USL has never sold long distance. You're going after the wrong men in black hats. (Or, in the case of Plan 9, black space suits)'' - Tom Limoncelli ------------------------------ Date: Wednesday, 5 Aug 1992 18:45:44 CET From: "Hugh D.R. Evans" Subject: Energiya's role in Space Station assembly Newsgroups: sci.space In article <1992Aug5.132915.10235@samba.oit.unc.edu>, cecil@physics.unc.edu (Gerald Cecil) says: > >Re the radiation loads: if you get 4-13 rads/30 days INSIDE a Space Station >module, how much worse is the cumulative exposure during the assembly phase, >in suits? Presumably you want to keep this well below 80 rads/30 days if >the 50% mortality dose is 250-300 rads/30 days. >-- Firstly, for the 28.5 degree orbit, the proton radiation dose is only significant for about 10 % of the 13 orbit repeating trajectory (as the right ascension precesses about the Earth, it take ~ 13 orbits to return to about where it was initially). On most of these orbits, the SSF will miss the SAA, as the highest latitude point of these orbits will be at the same longitude as the SAA, and the lowest latitude point will be on the other side of the Earth. I don't know what NASA's policy is regarding EVAs, but one of their require- ments is probably that no EVAs will be performed on the orbits that traverse the SAA. So, there really isn't much of a problem with EVAs, except for the time limitations imposed by the orbital characteristics. I would, however be very interested to know the safety levels NASA imposes on the shuttle crew for radiation levels. As far as Mir goes, who knows what the Russians considered a safe level? Regards, Hugh ESTEC * Inet: hevans@estwn4.dnet.estec.esa.nl P.O. Box 299 * or hevans@estec.esa.nl 2200 AG Noordwijk * SPAN: ESTCS1::HEVANS The Netherlands * BITNET: HEVANS@ESTEC ------------------------------ Date: 6 Aug 92 10:57:04 GMT From: "Frederick A. Ringwald" Subject: Home made rockets Newsgroups: sci.space In article <1992Aug5.173606.202216@uctvax.uct.ac.za> htcric01@uctvax.uct.ac.za writes: > I have recently got into the field of making home-made rockets and have > been experimenting with various types of cheap, readily availible fuels and > cannisters. [...] > Launch sites have > proved to be a bit of a problem as with the current state of political > affairs here, we are a touch scared of being arrested. > > If anyone has any new/different ideas for fuels, chemical components, > homemade flares, please let me know. Please DO NOT DO THIS, for the sake of your safety and the safety of everyone around you. This is a very good way to get KILLED or SEVERLEY MUTILATED. I know a former bass player and chemistry enthusiast who was making his own solid rocket engines. He blew off all the fingers on his right hand. I think he's wised up about homemade rockets/explosives manufacture, often known as "basement bombing." He doesn't play bass any more, either: can you guess why? If you enjoy building and flying rockets, please see the newsgroup rec.models.rockets. Their FAQ gives a good introduction to the hobby of model rocketry, which if practiced carefully, is safe and a lot of fun. Model rocketry isn't expensive: I paid for, built, and flew my first models when I was 10. Model rockets aren't really toys, either: good ones can fly over 1000m high, can glide or parachute down, and you can have multistaged rockets or even flying scale models of famous spacecraft, such as the Saturn V. But DON'T make you own engines, and follow their safety rules. I also know a father who, with his son, was making homemade rockets and not bothering to test them for flightworthiness (also called aerodynamic stability), and furthermore was igniting them in a non-standard and patently unsafe manner (instead of using a safety-certified electrical launcher, they were sticking lit punks into the rocket engines' nozzles). One of the rockets shot up and burned his eye, damaging his cornea severely. I hope he was eventually all right: he sure didn't look it when I last saw him. What you describe doing is amazingly dangerous. If you persist in it, I hope you do get caught and arrested, as you are a public menace, if you're still alive to read this post! Fred Ringwald Department of Physics & Astronomy Dartmouth College Hanover, NH 03755-3528 USA P.S. Real rocketeers are usually meticulous about safety: because when they aren't, things like the Challenger disaster happen. ------------------------------ Date: 6 Aug 92 05:47:44 GMT From: John Roberts Subject: More TSS information from NASA Select Newsgroups: sci.space Notes: STS-46 8/5/92 Mission Status Briefing (paraphrased) Chuck Shaw Dr. Nobie Stone Billy Nunley ............................................. Chuck Shaw - lead flight director - Fabulous success - everything worked except the actual mission [ :-) ] - It didn't work, but we learned a lot. - The dynamics of the deploy and rewind were very good - very controllable, and much more stable than expected. The material of the tether tended to damp out vibrations, which was hoped for but not counted on. Calculated minimum stable tether length was 300 meters - they only got to 256 meters, but it was still stable at that point. - On attempt this morning, the upper tether control mechanism (a motor with a clutch) at the top of the boom wouldn't work. It wouldn't move forward, and it wouldn't put tension on the reel. It also wouldn't pull the tether in, and it wouldn't disengage. Driving the reel motor put tension between the reel and the top of the boom, but wouldn't pull in the tether through the upper mechanism. The ingenious method that was finally used to unstick the upper mechanism was to retract the boom and take up the slack using the reel motor, then put the brake on the reel and re-extend the boom, thus using the deploy motors of the boom to pull on the tether between the reel and the upper mechanism. The tension rose to 40 [80?] newtons, then suddenly dropped to 6 N as the upper mechanism unjammed. Having gotten the tether loose, they started to retrieve the satellite. Retrieval went very well, and the satellite was very stable. While of course the full mission was not carried out, the dynamics people got a lot more experience than planned at the least stable and trickiest portions of the deploy and retrieval. - The thrusters on the satellite worked very well. - Control of libration worked exactly as expected. Vibrations were very small. The inline thrusters didn't have to be used until ~60 m. - (There was also mention of a vernier motor with a pinch roller above the upper controller mechanism, so that might be three motors involved. Or that may be the upper control motor mentioned elsewhere - I'm not sure. This morning, they also discussed the passive damping mechanism, which is a small ring on the upper boom through which the tether passes. The ring is attached to a surrounding frame by bungee cords, so motion of the tether that moves the ring from side to side eventually causes the energy of oscillation to be absorbed by the bungee cords.) ............................................. Billy Nunley (TSS Project Manager): - Most of the hardware worked very well. - Post-flight analysis of the failed hardware is planned. - Science was significantly less than expected. ............................................. Dr: Nobie Stone (TSS Mission Scientist): - The primary objectives of the mission science were missed completely. The voltages and currents produced were not large enough for most of the experiments. - The Italian satellite worked "perfectly". The new conductive paint was successful. It remained stable over time in vacuum, unlike the old paint. - One instrument was noisy, and one of the four electron guns failed due to a pressure surge from the orbiter. - The data collection and display systems worked. Scientific measurements show that gyrations induced during deploy damped out over the course of about 10 minutes. - Even at the shorter distance, the tether was able to generate about 40 volts at about 15 milliamps. Voltage is directly proportional to tether length. - The tether offers a unique tool for space plasma physics and many other applications. ............................................. Q&A: Q: Once you got it unstuck, why didn't you try to extend the tether further? A: Unlike the previous day, the new failure mode was not well understood. Though there was plenty of battery power[?], the "GN2" (gaseous nitrogen, used as a propellant on the satellite) was getting low. It is needed for the inline thrusters. There's a workaround to reduce or avoid the need for inline thrusters, called centrifugal operations. GN2 is also used for attitude control, but very little is needed for that - only 3kg of the original N2 load was budgeted for that. However, they were running out of time, and they wanted to make sure the satellite was retrieved, so that was what they concentrated on. Q: What was the EVA contingency plan? A: If the jam couldn't be undone, two crew members would be sent out, one on the RMS, one on a sill, with the reel used for payload bay door contingencies, to pull the tether over to the reel, and reel it in by hand. Another option was to fly the Shuttle over to the satellite, and just gather in the loose tether. There was a period of 24 hours to decide the best way to do it. Since the tether was unjammed by control from inside, an EVA was not necessary. Q: What was the margin for the nitrogen and the batteries? A: 10-12 minutes GN2 margin, down from 42 minutes margin at the start of retrieval. If there hadn't been enough GN2, they would have started centrifugal operations to maintain tension on the tether. Battery margin was "almost half the mission" - plenty. Q: (What caused the jam?) A: When the boom trick pulled the tether free, the astronauts looked specifically for anything unusual about the tether, i.e. a kink. They didn't see anything. Q: Speculate on cause of jam. How might it have been prevented? A: (General description of possibilities mentioned above.) This was all tested and simulated many times on the ground, always with success. Q: Would it be wise for future missions to use stronger motors? A: Maybe. More analysis is needed. Stronger thrusters on the satellite are probably not needed. Q: How strong are the current motors? A: Vernier motor - ~30 newtons - just intended to overcome friction from the reel motor out. 12-17 newtons was predicted for normal operation - that's what they saw. During the reel jams, force rose to ~25 newtons. Q: How successful was the science part of the mission? A: None of the primary or secondary objectives of the mission were accomplished. (No high voltage.) Some of the objectives of opportunity were met - shuttle glow, interaction of electron beams with gas clouds and the orbiter, etc. The low-voltage performance was shown to be as expected, and the hardware for data collection worked. Q: With no more tethers at least for years, why not "go for it"? A: No indication that they could get far enough out for more meaningful science, and the risk was great, so they decided to retrieve the satellite and hope for another mission sometime. Q: How about a reflight? A: They'd sure like one. The science instruments apparently were chosen with the correct ranges of sensitivities, and they'd be happy to use the same instruments on a second flight. Q: Was it three separate problems, or could they have been related? A: That's yet to be determined - it's one of the things they've been looking for. Important to remember that zero-G and vacuum do strange things to heat flow, materials, etc. The satellite paint is an example of something that was anticipated and solved ahead of time. ......................................................... Comments: - The TSS people seem to be really pinning their hopes on a future tether mission. They're now calling this "the first experimental flight of the tether". The question is whether the results of this mission will allow sufficient political support for further efforts. (It's undesirable when a failure on a first try discourages later attempts, but that's often the case.) The fact that almost everything appeared to work, and that the stability and vibration problems turned out to be much less severe than expected may help with this. - It sounds like they really need to work on tension control. Ideally, reel tension would be kept constant, even during deployment of the boom, so that buried loops would not be formed. That was *not* a feature of the current design, apparently. This may turn out to be one of the main things to watch out for on all deployed tether systems. - I thought the presentation was just a little more "slick" than it needed to be, though of course they have to put a good face on things to win support for future efforts, and they did accomplish a lot. The failure to meet the main science objectives is a significant failure, and intensive engineering investigation is warranted even aside from plans for further missions. I wouldn't say the presentation neglected to mention any of the shortcomings, but they laid it on a little thick when discussing the limited successes. - The use of the data from the science instruments to support the engineering analysis is a good idea. I guess that shows the value of the space flight and science teams talking to one another. - On the basis of the parts that look good, I hope they are able to continue the work with tethers. John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: Thu, 6 Aug 92 12:40:03 BST From: amon@elegabalus.cs.qub.ac.uk Subject: NASA Tools > Actually, they have Gaffer's tape and not duct tape. Gaffer's tape is > used in film production (hence its name) since it has the desireable > quality of not leaving any adhesive residue behing when you remove it. > It has the undesireable quality of costing a _lot_ more. (about $25 US > in single rolls). My brother uses it by the yard when putting a light on > the wall on location shoots. It is very nice stuff.... > I used to do a lot of theater work and we used the names interchangeably. We just bought it at the local hardware store (incidentally would you believe that you CAN'T get it in DIY stores here in Belfast!!!!) It also has a nice property that it tears predictably. You can put up long runs of cable on the pipes and they stay put until you pull out the safety ties, then you just give it a yank and it pops the tape right down the line... Maybe your brother just uses higher quality stuff. It does leave a residue if it gets really baked onto the pipes. A lot of heat comes out of a 1KW quartz... But it does just about any job. Astronauts used it to construct the "flyswatter" when they attempted to activate the Hughes satellite that failed to fire? I think that was shortly before Challenger. So it even works out in the big dark... ------------------------------ Date: Thursday, 6 Aug 1992 09:30:28 CET From: "Hugh D.R. Evans" Subject: NASA Tools Newsgroups: sci.space In article <9208051253.AA16702@cmr.ncsl.nist.gov>, roberts@CMR.NCSL.NIST.GOV (John Roberts) says: > >-From: Bruce_Dunn@mindlink.bc.ca (Bruce Dunn) >-Subject: NASA Tools >-Date: 5 Aug 92 00:27:47 GMT >-Organization: MIND LINK! - British Columbia, Canada > >-> John Roberts writes: >-> Maybe they need to unpack the Ferrous Portable Leverage Application >-> Mechanism (FPLM), the Passive Maximal Kinetic Transfer Device (PMKTD), >-> and the Linear Metallic Abrasive System (LMAS), and try an EVA. :-) > >-Crowbar, hammer, and file? > >Very good! :-) What I specifically had in mind was crowbar, sledgehammer, >hacksaw. That LMAS acronym needs work - I agree it's ambiguous. > stuff deleted... >and you've got all the basic tools to demolish, er, repair just about >anything. >For the ultimate in luxury, throw in an electric drill, grinder, tin snips, >pop rivet tool. Plus assorted nuts, bolts, washers, and screws, of course. > Waddabout WD40? No self respecting handyman would be without it! On the serious side, anybody know how this miracle drug of mechanics works in the space environment? Hugh. ESTEC * Inet: hevans@estwm8.dnet.estec.esa.nl P.O. Box 299 * or hevans@estec.esa.nl 2200 AG Noordwijk * SPAN: ESTCS1::HEVANS The Netherlands * BITNET: HEVANS@ESTEC ------------------------------ Date: 6 Aug 92 11:05:51 GMT From: "Frederick A. Ringwald" Subject: Origin of Life article Newsgroups: sci.space In article <1992Aug05.163028.91421@cs.cmu.edu> stroxel@cvgs.schools.Virginia.EDU (Steve Troxel) writes: > Why is it so difficult for people who call themselves > scientists to explore the possibility that God created the > earth and all the creatures on it? When Pierre Simon de La Place published his treatise on Solar system dynamics, Napoleon remarked that it did not mention God. La Place replied "I did not require that hypothesis." (There, that gets this discussion back to the topic of space, where it belongs.) ------------------------------ Date: Thu, 6 Aug 92 12:25:49 BST From: amon@elegabalus.cs.qub.ac.uk Subject: Red-blooded ET's : ) > The Sun also has a magnetic field, as do many stars. They have > little iron (all of it vaporized). The interaction of convection > and magnetic fields on these bodies causes all sorts of interesting > effects. > Stars not only have Fe, they are the producers of it. Although when they start producing it in large quantities it is time to act like a fly and leave the stellar system... Fe is the end product of nucleo-synthesis... that is when supernova's happen in big stars. I'm not sure of the exact range of stellar masses that proceed all the way to Fe. I'm sure if Paul thinks about it for a few moments he can write out the equations for a late life O type star... ------------------------------ Date: 6 Aug 92 05:52:42 GMT From: John Roberts Subject: Shuttle launch Newsgroups: sci.space -From: seds%cspara.decnet@Fedex.Msfc.Nasa.Gov -Subject: Re: Shuttle launch -Date: 31 Jul 92 22:53:00 GMT -Organization: University of Houston -...my experiment (Acceleration Measurement System) that I designed lifted off -as a secondary payload (CONCAP III-01) on STS-46. The purpose of this -experiment is to measure the acceleration forces on the shuttle by the -tether and its assocated end mass. We expect the magnitude of these forces -to be about 40 microgee. -Our University also has another secondary payload (CONCAP II-01) which will -expose many samples of superconducting materials to the Atomic Oxygen flow -in order to ascertain if the unique oxidation states of the Atomic Oxygen -are suitable for raising the temperature of the transition state to -superconductivity for the ceramic typ superconducters that were first -invented here at UAH a few years ago. -Dennis Wingo, University of Alabama in Huntsville I hope you will keep us posted on these experiments. :-) John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: Thu, 6 Aug 1992 05:09:00 GMT From: seds%cspara.decnet@Fedex.Msfc.Nasa.Gov Subject: Soyuz as ACRV Newsgroups: sci.space In article , henry@zoo.toronto.edu (Henry Spencer) writes... >In article <4AUG199221381894@judy.uh.edu> seds%cspara.decnet@Fedex.Msfc.Nasa.Gov writes: >>By the way someone here stated that COMET could return 750 kg. That is not >>true, COMET Weighs 750 kg. The return capsule payload is only 60 kg. > >As I said, I haven't seen specs for COMET itself, only for some of the >proposals that went into COMET planning... > >But even ignoring that, note that I didn't say that *COMET* had a 750kg >return capability. I said that its *capsule* had such a capability. >Unless COMET has changed radically since the early proposals, only a >fraction of the mass that comes down in its capsule actually counts as >payload. But most of the extra is things that aren't needed for a >dedicated payload-return capsule. ? Henry the extras on the COMET are for the return capsule. The data system and almost everthing else is in the orbiting portion that will not return. The power system & Solar Cells etc. I have a payload that is in the returnable carrier so I do have a feel for this one. The only extra stuff is wiring for the power and data from the main module. > >The way you make things cheap and efficient is to design them to do one >mission and do it well. For example, transporting astronauts to/from >orbit and supporting them for long stays while there are two different >missions that should be done by different equipment; orbiter plus Spacelab >is an insanely inefficient way to do this, if only because of all the mass >that gets hauled up at great cost only to be brought down again a week >or two later. More to the current point, the vast majority of payload- >return requirements -- real ones, not imaginary ones -- can be met with >a simple, small, cheap expendable return capsule. That is exactly what COMET is supposed to be Henry. It is funny how a lot of the vaporware discussed on this net turns into expensive hardware once development begins. Dennis, University of Alabama in Huntsville. PS I also have accelerometers on SpaceHab and maybe on Spacelab in the future. ------------------------------ Date: Thu, 6 Aug 1992 05:26:00 GMT From: University Space Society Subject: Soyuz as ACRV Newsgroups: sci.space In article <1992Aug5.195538.18528@iti.org>, aws@iti.org (Allen W. Sherzer) writes... >In article <1992Aug05.184230.6910@eng.umd.edu> sysmgr@king.eng.umd.edu writes: > >>>Since Soyuz weighs a good deal less than Shuttle it should burn far less >>>fuel. Polution should therefore be lower. > >>Oh. You left out resupply flights. Hm. You'd better go back to the drawing >>board and add those up. > >OK. Since Soyuz and the resuply modules weigh less than the equivalent >Shuttle flights, polution should be lower. > >Polution is furthur reduced since logistic modules are teathered down >which means both fewer burns for logistics AND fewer burns for Freedom >stationkeeping. This also saves additional $$ since less fuel is needed. > >How's that? > > Allen >-- Nothing except ignoring physics. The exaust velocity of the fuel is in the thousands of meters per second which means that neither one will be a pollution producer. I happen to be a tether proponent and if we get over the disaster with TSS 1 we hope to use tethers on SSF no matter what scenario we use for resupply BUT the large payloads that need returning will have to use Shuttle AND any delicate experimental result must also use shuttle due to the much milder G environment than is possible with any type of ballistic trajectory be it a tether or retropropulsion. Allen the dynamics for tethered return are not right to support station reboost You have to have a mass that is a significant fraction of the Station's weight before the reboost scenario becomes attractive. It turns out that the only mass that satisfys this requirement is the SHUTTLE. This will lower the costs of Shuttle ops since the momentum transferred to the station will be subtracted from the Shuttle allowing for a greater payload to be carried up on the Shuttle per flight. Also I have not seen your derated values for your Atlas payloads to 270 nm. I think your numbers are for a 105 nm transfer orbit. Subtract a VERY significant amount for this. Is that right Wales? Allen please look a little closer at the numbers they do not lie. (except in the hands of congressmen and the news media) Dennis, University of Alabama in Huntsville ------------------------------ Date: Thu, 6 Aug 1992 11:56:35 GMT From: "Allen W. Sherzer" Subject: Soyuz as ACRV Newsgroups: sci.space In article <1992Aug05.205023.9149@eng.umd.edu> sysmgr@king.eng.umd.edu writes: >>>Oh. You left out resupply flights. Hm. You'd better go back to the drawing >>>board and add those up. >>OK. Since Soyuz and the resuply modules weigh less than the equivalent >>Shuttle flights, polution should be lower. >I'll hold my nose until someone can put up real numbers. Let's see, we have two logistics flights but let's make it three just in case. Each delivers 80,000 pounds of cargo and let's add another 80,000 for the carrier for a total of 160,000 per cargo flight. Add to that eight Soyuz at 15,000 pounds each. This gives us: 1. Cargo (3 at 160,000 each): 480,000 2. Crew (8 at 15,000 each): 120,000 Total: 600,000 So this approach will require us to maneuver 600,000 pounds near the station every year. A fully loaded Shuttle weighs in at 200,000 pounds and you need four per year for resuply. This means the Shuttle will maneuver 800,000 pounds near the station every year. The Shuttle therefore must maneuver one third more mass and all else being equal can expect to use 1/3 more fuel to do it. You can take your fingers out of your nose now. >However, if you claim brighter teeth and fresher breath next, I'm going to >puke. If that's the best reply you can give then this must be pretty convincing. >>Polution is furthur reduced since logistic modules are teathered down >>which means both fewer burns for logistics AND fewer burns for Freedom >>stationkeeping. This also saves additional $$ since less fuel is needed. >So did you add in the money for engineering and tether development? Nyet. No I didn't. How much do you want to spend? Let's spend $4 billion on it and put off the Lunar base for a year. Allen -- +---------------------------------------------------------------------------+ | Allen W. Sherzer | "If they can put a man on the Moon, why can't they | | aws@iti.org | put a man on the Moon?" | +----------------------260 DAYS TO FIRST FLIGHT OF DCX----------------------+ ------------------------------ Date: Thu, 6 Aug 92 11:49:09 BST From: amon@elegabalus.cs.qub.ac.uk Subject: Soyuz as ACRV (Posting of previous discussion data) > Next, watch for Allen to pull some more numbers out of his hat to show > that you could actually get a fully functional moonbase from materials > bought at K-mart and have change left over for a movie..... > In other words he's a REAL engineer? Personally, I'd need to do the shopping in at least a Busy Beaver DIY store in a major american city... :-) :-) ------------------------------ Date: 6 Aug 92 08:08:48 GMT From: nicho@VNET.IBM.COM Subject: Soyuz as ACRV (Posting of previous discussion data) Newsgroups: sci.space In <1992Aug5.171345.24549@aio.jsc.nasa.gov> Mark Littlefield writes: >Next, watch for Allen to pull some more numbers out of his hat to show >that you could actually get a fully functional moonbase from materials >bought at K-mart and have change left over for a movie..... Cute, however ob-numbers, you wouldn't happen to have any to support your viewpoint would you ??? ----------------------------------------------------------------- ** Of course I don't speak for IBM ** Greg Nicholls ... nicho@vnet.ibm.com or nicho@cix.compulink.co.uk voice/fax: 44-794-516038 ------------------------------ Date: 6 Aug 92 11:03:21 GMT From: "Frederick A. Ringwald" Subject: Star Trek (anti-)realism Newsgroups: sci.space Well, my two favorite Star Trek anti-realisms are both from the old series: 1) The time when they flew back to the 20th century and picked up that pilot (etc., etc.). I distinctly remember that when flying inside the Solar system (they were rounding the Sun, to go ahead in time or whatever...), there were *stars streaming by them*! 2) No real navy would let a 35-year-old command a capital ship, no matter how good he was (unless there had just been heavy losses in a war, in which case exploration would not be a high priority). ------------------------------ Date: Wed, 5 Aug 1992 12:55:52 GMT From: "Michael K. Heney" Subject: Tether Questions Newsgroups: sci.space I have a question or two about tethers. I've heard two primary uses for thethers - one being an energy exchange with the ionosphere, which either generates/uses electricity and raises/lowers the systems orbit, and the other as a way to exchange momentum between masses on opposite ends of the tether, boosting one and lowering the other. First question - is the above correct? On the electrical generation - I'm a bit confused as to which way the tether is deployed. On the current shuttle flight, the talk is that the TSS is "lowered" on a 12.5 mile tether. Is "lowered" the correct term? I have trouble with the orbital mechanics if that's the case. It would seem to me that the TSS would have to be in the same orbit as the shuttle, trailing it by the length of the tether. Also, what mechanism is used to actually get the tether to extend, as opposed to forming a bunch of conductive spaghetti? Similarly, on the momentum transfer idea (I've seen shuttle/SSF as the pair of masses) - how would you "lower" the shuttle (since the tether isn't rigid, you can't just push against it)? Thanks for any comments/clarifications for us tether-impaired readers ... ------------------------------ Date: 6 Aug 1992 00:27:51 -0700 From: Steven Robiner Subject: Whats wrong with this CONDUCTOR (was: Tethered Satellites) Newsgroups: sci.physics,sci.space In article <77201@ut-emx.uucp> you write: >In article , srobiner@pollux.usc.edu >(Steven Robiner) writes: >|> >|>Excuse me, but isn't something missing from this "Tethered Satellite" >|>experiment? The shuttle is at one end, and the satellite is at the >|>other, right? But that's an open circuit, so where's the load >|>joining the ends of this 'generator.'? >|> [... stuff deleted ] >of electrons, it will shed them when its potential compared to the >local plasma is higher than the work function for the shuttle surfaces. >So now you have the "infused" electrons into the flux tube that contains >the shuttle. Eventually normal plasma-plasma and plasma-neutral interactions >will allow the electron to move back to its original flux tube. This however >may take some time. So the circuit is really completed in the same sense >that grounded circuits are completed, except here we don't have a good ground But in space, the plasma is not a great conductor, and in fact, electrons moving through a magnetic field should be repelled from traveling in a direction opposite from the induced current in the tether, right. I mean, just because the electrons aren't in a wire shouldn't mean that they aren't affected. So how will the current manage to travel back up to the satellite, without going through the same resistance that generated those electrons in the first place? (btw, I guess the point is moot, since the tether is stuck at the moment, but theoreticalyl, what would really happen? ) =steve= ------------------------------ End of Space Digest Volume 15 : Issue 079 ------------------------------