Date: Thu, 10 Sep 92 05:09:52 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V15 #182 To: Space Digest Readers Precedence: bulk Space Digest Thu, 10 Sep 92 Volume 15 : Issue 182 Today's Topics: 3 booster questions Dry DNA farthest Laser signal (4 msgs) Is NASA really planning to Terraform Mars? (2 msgs) LDO shuttle and pilot readiness One Small Step for a Space Activist... Vol 3 No 9 Pluto Direct/ options QUERY Re: Pluto Direct/ options Relativity Shuttle tank for habitation; was Inflatable Space Stations Terraforming Mars (2 msgs) Terraforming needs to begin now (2 msgs) With telepresence, who needs people in Earth orbit? 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: 10 Sep 92 05:23:22 GMT From: Brett Vansteenwyk Subject: 3 booster questions Newsgroups: sci.space [1].What makes Titan so expensive? I would think that this would be a mature launch system where no one needs to masturbate the machinery before launch. Is there something inherent in its properties (such as long storage fuel tanks?) or is it in the way the system is managed? [2].Atlas still goes *boom* a lot? Is this inherent to the design of having two of the engines fall off and the difficulty in shutting off the fuel flow to these engines? [3].It seems, like it or not, that the Shuttle will be flying for at least 10 more years. Perhaps developing an LRB for the Shuttle will not be justified on its own. Perhaps developing an HLV will not be justified on its own. However, if you have an HLV whose first stage will also serve as an LRB you could amortise development costs pretty fast. Is there something wrong with this idea? For example, a single engine "Baby Saturn" based on the F1A may qualify. If modifying the External Tank design for 3 boosters instead of 2 is not difficult, and if there is no particular reason that you cannot ride the Shuttle on "top" of the stack instead of the the bottom (angle of attack considerations would force this change), then you would have a ready use for 25-30 of these vehicles per year. Why not? --Brett Van Steenwyk ------------------------------ Date: 10 Sep 92 04:09:05 GMT From: John Roberts Subject: Dry DNA Newsgroups: sci.space -From: dietz@cs.rochester.edu (Paul Dietz) -Subject: Re: Is NASA really planning to Terraform Mars? -Date: 8 Sep 92 00:43:18 GMT -The surface of Mars is extremely dry. All terrestrial life requires -liquid water to survive. Even bacterial spores are quickly rendered -nonviable in extreme dryness: experiments that place spores in air of -near-zero relative humidity at 25 C find that the DNA begins to -degrade, and the spores become nonviable within weeks (for this -reason, the bacteria that supposedly survived in the Surveyor on the -moon were likely post-recovery contaminants). I hadn't heard that one before. What about lotus seeds and water bears? I understood water bears could survive dehydration indefinitely if placed in a non-oxygen atmosphere. Lotus seeds have a mechanism that tends to make them increasingly dry over time, yet remain viable for thousands of years. A lotus seed in a sheltered spot in the Egyptian desert ought to get pretty dry over time. I believe brine shrimp eggs last quite a while when dry too. Mars tends to be drier than Earth, but also colder. I understand researchers recently recovered DNA sequences from ancient bees that were trapped in amber millions of years ago. I agree with you that there's no known location on Mars where any known form of Earth life could be active. John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: Wed, 9 Sep 1992 23:48:07 GMT From: Henry Spencer Subject: farthest Laser signal Newsgroups: sci.space In article <199209041812.AA18322@leibniz.cs.arizona.edu> rcs@CS.ARIZONA.EDU ("Richard Schroeppel") writes: >Note that radar signals have been bounced off Venus, and were >actually used for some mapping... I believe JPL has done interplanetary radar work as far as Jupiter. >Assuming the purpose of your question is to consider "How feasible >are lasers for high bandwidth, semi-private, space communication?"... Feasible. There is intense interest in the idea, and some in-space experiments will fly in this decade. (It's just possible that secret military systems might be operational already -- laser communications systems would have very tight beams that would be very difficult to eavesdrop on.) -- There is nothing wrong with making | Henry Spencer @ U of Toronto Zoology mistakes, but... make *new* ones. -D.Sim| henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 10 Sep 92 02:13:09 GMT From: "Michael V. Kent" Subject: farthest Laser signal Newsgroups: sci.space In article henry@zoo.toronto.edu (Henry Spencer) writes: >In article <199209041812.AA18322@leibniz.cs.arizona.edu> rcs@CS.ARIZONA.EDU ("Richard Schroeppel") writes: >>Assuming the purpose of your question is to consider "How feasible >>are lasers for high bandwidth, semi-private, space communication?"... > >Feasible. There is intense interest in the idea, and some in-space >experiments will fly in this decade. Forgive my not knowing the basic vocabulary, but is this what's known as a lidar (laser radar?)? If so, the Lidar In-Space Technology Experiment is scheduled for a 1994 launch. >It's just possible that secret >military systems might be operational already -- laser communications >systems would have very tight beams that would be very difficult to >eavesdrop on.) I know work is active in this area, but has anything flown yet? Mike -- Michael Kent kentm@rpi.edu McDonnell Douglas Rensselaer Polytechnic Institute All facts in this post are based on publicly available information. All opinions expressed are solely those of the author. Apple II Forever !! ------------------------------ Date: 10 Sep 92 10:07:50 GMT From: Ron Baalke Subject: farthest Laser signal Newsgroups: sci.space In article , henry@zoo.toronto.edu (Henry Spencer) writes... >In article <199209041812.AA18322@leibniz.cs.arizona.edu> rcs@CS.ARIZONA.EDU ("Richard Schroeppel") writes: >>Note that radar signals have been bounced off Venus, and were >>actually used for some mapping... > >I believe JPL has done interplanetary radar work as far as Jupiter. Try a little further out, like Saturn. Radar has been bounced off of Titan using the high power transmitter on the 70 meter antenna at Goldstone. ___ _____ ___ /_ /| /____/ \ /_ /| Ron Baalke | baalke@kelvin.jpl.nasa.gov | | | | __ \ /| | | | Jet Propulsion Lab | ___| | | | |__) |/ | | |__ M/S 525-3684 Telos | Anything is impossible if /___| | | | ___/ | |/__ /| Pasadena, CA 91109 | you don't attempt it. |_____|/ |_|/ |_____|/ | ------------------------------ Date: 10 Sep 92 02:20:40 GMT From: Josh 'K' Hopkins Subject: farthest Laser signal Newsgroups: sci.space henry@zoo.toronto.edu (Henry Spencer) writes: >In article <199209041812.AA18322@leibniz.cs.arizona.edu> rcs@CS.ARIZONA.EDU ("Richard Schroeppel") writes: >>Note that radar signals have been bounced off Venus, and were >>actually used for some mapping... >I believe JPL has done interplanetary radar work as far as Jupiter. As a matter of fact, I think someone has gone so far as to bounce radar off Titan in an attempt to guess what the surface was. However, unless we're using different definitions, radar and laser are acronyms for two different things. >>Assuming the purpose of your question is to consider "How feasible >>are lasers for high bandwidth, semi-private, space communication?"... >Feasible. There is intense interest in the idea, and some in-space >experiments will fly in this decade. (It's just possible that secret >military systems might be operational already -- laser communications >systems would have very tight beams that would be very difficult to >eavesdrop on.) There is a proposed experiment to be launched by the Japanese which would try to talk to a European sattelite. However, like almost all the payloads Japan is planning, its rocket is still under development. -- Josh Hopkins "If you are sitting in an exit row and you cannot read this card or cannot see well enough to follow these instructions, please tell a crew member." j-hopkins@uiuc.edu -United Airlines safety instructions ------------------------------ Date: 10 Sep 92 01:15:39 GMT From: Joe Cain Subject: Is NASA really planning to Terraform Mars? Newsgroups: sci.space,sci.astro,sci.geo.geology There is an article of non-fiction in the October "Analog" (=old ASF) by Martyn J. Fogg regarding the futility of now attempting to terraform Mars. One of the references he quotes implies that he was the editor of the Journal of the British Interplanetary Society (at least in 1991). I would like to see some critiques or comments by those who have looked seriously into this subject regarding his article. (pp. 60-77) To a novice like myself his arguments appear reasonable. I particularly would like to understand the "carbonate-silicate" cycle he ascribes to a James Walker et al from the University of Michigan ca. 1981 but otherwise for which no reference is given. (He does refer to the December 1989 and April 1991 issues of the BIS, which is not easily obtainable here, plus a couple of other books I have not had time to check: S. K. Atreya et al (editors) Origin and evolution of planetary and satellite atmospheres, U. of Arizona Press (1989) and Mallove, E., and G. Matloff, The starflight handbook, Wiley , 1989.) Joseph Cain cain@geomag.gly.fsu.edu cain@fsu.bitnet scri::cain ------------------------------ Date: 10 Sep 92 05:04:35 GMT From: Frank Crary Subject: Is NASA really planning to Terraform Mars? Newsgroups: sci.space In article <1992Sep9.212810.18022@ucsu.Colorado.EDU> knapp@spot.Colorado.EDU (David Knapp) writes: >If you want to make your backyard unlivable, go ahead, but the second you are >doing things that make *everyone's* backyard unlivable, you should expect >a response. I'd have to disagree on two points: I don't think there is any evdence we are making the Earth "unlivable." In some respects, we may have made it a less pleasent place to live, but that is a very different thing from uninhabitable. I hope you aren't suggesting absolute prefection with respect to the Earth's environment should be a pre-requsite to extra-planetary ventures. Second, since there is no live on Mars, nor anywhere else in the Solar System, excatly who's backyard is Mars, if not our own? Frank Crary CU Boulder ------------------------------ Date: 10 Sep 92 02:06:59 GMT From: "Michael V. Kent" Subject: LDO shuttle and pilot readiness Newsgroups: sci.space In article henry@zoo.toronto.edu (Henry Spencer) writes: >In article <1992Sep4.145946.13209@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes: >>... It may be that Shuttle pilots *can't* >>function sufficiently well to land the Shuttle manually after two >>months on orbit. In that case, Autoland is being developed to handle >>the problem. > >Well, "developed" is a bit inaccurate. The shuttle has theoretically >had full autoland capability from day one. In principle, the only >things that require manual action are deploying the pitot probes and >lowering the landing gear, both of which are manual-only because they >are irreversible and could be fatal if done too early. What is being >worked on now is not development of autoland, but convincing the crews >to actually *test* it. All shuttle landings to date have been manual. Yes, but isn't Autoland scheduled for test on STS-53 in November? I remember a blurb about it in AvWeek this summer and another in the Shuttle status reports about a month ago. Speaking of STS-53, is this mission classified? STS-38 was launched two years ago with much fanfare over its being the last classified Shuttle mission. Then it STS-38 made an unscheduled landing in Florida (the first in the post-51L era), and STS-53 was very quietly added to the manifest. What's the deal? Mike -- Michael Kent kentm@rpi.edu McDonnell Douglas Rensselaer Polytechnic Institute All facts in this post are based on publicly available information. All opinions expressed are solely those of the author. Apple II Forever !! ------------------------------ Date: 10 Sep 92 03:27:53 GMT From: "Michael V. Kent" Subject: One Small Step for a Space Activist... Vol 3 No 9 Newsgroups: talk.politics.space,sci.space In article <1992Sep9.193128.20635@iti.org> aws@iti.org (Allen W. Sherzer) writes: >On the plus side, station supply will mean placing a lot of >mass into LEO, and this could make the market for launch >services a LOT bigger, which could help reduce launch >costs. But the way things currently are, NASA intends to use >only the Shuttle (with its high cost) for resupply. Not only NASA intends to use only the Shuttle for resupply ONLY until something better comes along. Also, one of the design missions of the Delta Clipper is station resupply. >If a way to resupply Freedom could be found which didn't >require Shuttle, the payback would be enormous. Not only >would the larger launch markets lower costs, but non-Shuttle >based resupply could mean that the entire Shuttle program >can be phased out, freeing up roughly three BILLION every year. The mistake here is thinking of the Shuttle as a launch vehicle. It is not. A second mistake is thinking its sole mission is Station resupply. That, too, is untrue. If Station resupply is offloaded to another vehicle, you still want to keep the Shuttle around for missions like EURECA, TSS, SHARE, CIRRUS, Hubble revisits, satellite repair, retrieving, and servicing, etc. These are missions which still need to be done and that the Shuttle was designed to do. Remember, the Shuttle is not a launch vehicle. It is a space transportation system (hence the acronym STS). It includes things like the OMS and RCS for multiple satellite rendezvous, the robot arm, astronauts-on-demand for contingency spacewalks, the MMU, Spacelab, the Spacelab mounting hardware (for things like Astro), the Shuttle Palette Satellite, and some things harder to quantify like the attitude control capability (essential for missions like Astro and STS-39). Your station resupply vehicle will offer few of those things. It is a valuable first step but a small one. It will not replace the Shuttle. >So what do we need to do? We need to: 1)Fly about 160,000 >pounds of supplies and experiments up and about 50,000 >pounds back down (returned cargo will need low-G return); >2)Fly four crew to and from Freedom four times a year; and >3)An Orbital Transfer Vehicle needed to transport payloads >to Freedom (this is needed since we are eliminating >Shuttle). Please note two things. NASA would like to go to a 180-day rotation about two years after PMC (instead of 90 days). Also, NASA plans to expand the station to an eight man crew (EMCC). Plan your vehicle accordingly. >Such an HLV should be a commercial procurement where the >government buys launch services only (as required by current >federal law). Two candidates are Heavy Lift Delta (see One >Small Step... Vol. 2 No 2) and Titan V (see One Small >Step... Vol. 2 No 3). Both manufacturers have already offered >to sell launch services for either vehicle for less than $200 >million per launch (including development costs). I like the heavy-lift idea, but I don't think they fill the mission well. It seems like you're adapting a mission to the vehicle and not the other way around. (You could argue NASA is doing the same with the Shuttle, but the Shuttle already exists. These vehicles do not). If you're going to build a new vehicle, build it to the mission requirements. (If I were a station manager, I'd rather have 5 flights of 20,000 lbs each than one flight of 100,000 lbs. It offers much more flexibility). >Meeting requirement 2 is easy: we can use a Russian Soyuz-TM >launched on an Atlas or Titan vehicle. All the components >exist today and have been used extensively. The only thing You want to use an Atlas? The rocket that goes "boom" a lot? (Rockets should go roooar, not boom :) ). We used to launched manned missions on the Atlas, but we didn't have much of a choice then. >Finally, we need an Orbital Transfer Vehicle (OTV) to move >payloads to Freedom. This capability is not strictly needed >and will be rarely used but will allow us to phase out >Shuttle. This vehicle has already been costed at $3 billion >to develop. I think you want the Orbital Maneuvering Vehicle (OMV). The OTV was meant to move payloads between LEO and GEO. (An OTV is nice, but we need an OMV first). Mike -- Michael Kent kentm@rpi.edu McDonnell Douglas Rensselaer Polytechnic Institute All facts in this post are based on publicly available information. All opinions expressed are solely those of the author. Apple II Forever !! ------------------------------ Date: 10 Sep 92 04:33:08 GMT From: Dave Tholen Subject: Pluto Direct/ options Newsgroups: sci.space Robert Casey writes: > If we send 2 probes to Pluto, maybe we should design them so that they > can "talk" to each other. In case one has a stuck antenna, like one > we have en route to Jupiter. Then one can relay data from the other. > Or a dead high power transmitter, or a deaf receiver, and such. > > I suppose that someone has figured out what design to change, or do better, > to avoid "stuck antenna" problems? The current spacecraft design has a fixed antenna, not a deployable antenna like Galileo. Note that the data rates we're talking about with the Pluto spacecraft aren't that much higher than Galileo's data rate through the low gain antenna. It's a tradeoff of mass versus data rate. We can get the data rate up, but only by using either a larger antenna or a more powerful transmitter, which requires more electricity. Either way, the spacecraft mass goes up, so you either travel more slowly to Pluto or you use a more powerful booster, which also adds to the cost. The design tradeoffs are rather involved. ------------------------------ Date: Wed, 9 Sep 1992 23:10:23 GMT From: Henry Spencer Subject: QUERY Re: Pluto Direct/ options Newsgroups: sci.space In article tombaker@world.std.com (Tom A Baker) writes: >Could you clarify whether this craft is supposed to just flyby (a la >Voyager) or is truly a Pluto "orbiter"? ... It is extremely difficult to combine a reasonable payload and a manageably short trip time with an orbiter mission. Pluto is *a long way away*; to get there in under a decade, the probe has to be fast. Killing all that velocity is inordinately expensive in mass. You really cannot do a Pluto orbiter in a reasonable amount of time with 1960s propulsion technology, which is what all currently-planned missions use. -- There is nothing wrong with making | Henry Spencer @ U of Toronto Zoology mistakes, but... make *new* ones. -D.Sim| henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 10 Sep 92 04:20:45 GMT From: John Roberts Subject: Relativity Newsgroups: sci.space -From: Alan_Barclay@mindlink.bc.ca (Alan Barclay) -Subject: Re: Relativity -Date: 9 Sep 92 07:21:06 GMT -Organization: MIND LINK! - British Columbia, Canada -What I was trying to simplify is the following: -1) Observer starts at v=0 relative to stars A and B. He starts at Star A. -2) Observer measures distance to star B = 4 ly. -3) Observer accelerates to a high relativistic speed travelling towards -star B, turns over halfway and decelerates to v=0 relative to star B -adjacent to star b. During this time he makes no measurements except to -keep track of subjective time passed. -4) When he steps onto the surface of a planet around star B, he can look -back at star A, measure it as 4 ly away, and know it took him less than -four (subjective) years to get there. -It seems to me that it is possible to travel at greater than 1 ly per -year FROM A CERTAIN POINT OF VIEW, and that point of view is valid, -in that it would have real experiential consequences on a traveller. That's true. It's also true that if human cryogenic storage is ever perfected, the astronaut could be frozen for the entire duration of the trip on a spacecraft moving at only a tiny fraction of c. Even if the ship's chronometer indicates that 10000 years of ship time passed, from the astronaut's point of view, the trip was instantaneous, and thus the velocity was therefore infinite. John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: 10 Sep 92 05:08:08 GMT From: Frank Crary Subject: Shuttle tank for habitation; was Inflatable Space Stations Newsgroups: sci.space In article <1992Sep5.014529.26001@porthos.cc.bellcore.com> netnews@porthos.cc.bellcore.com (USENET System Software) writes: >Why not orbit the tank with solid fule trap-on boosters and >build them with an access hatch? There are two problems (neither unsolvable): There would be no internal hardware (live support, research equipment, etc...) and there would be a pressing, immediate need for station keeping rockets: Due to the low mass/cross sectional area of an external tank, one on orbit would de-orbit from atmospheric drag very soon (months I think). Frank Crary CU Boulder ------------------------------ Date: 10 Sep 92 04:11:39 GMT From: John Roberts Subject: Terraforming Mars Newsgroups: sci.space -From: tomk@netcom.com (Thomas H. Kunich) -Subject: Re: Is NASA really planning to Terraform Mars? -Date: 7 Sep 92 23:55:32 GMT -Organization: Netcom - Online Communication Services (408 241-9760 guest) -It is a simple, possibly even elementary, matter to find -various bacteria, algae, fungi, lichen etc. that can exist -in the harsh environment of Mars. Or, for that matter, the -upper reaches of the Venusian atmosphere. These life-forms -are small, light and quite capable of being transported in -rather massive quantities to these planets by presently -possessed technology. It's probably harder than you think. The main challenge on Mars is not necessarily the scarcity of water (though that is a major problem), but finding a location where they can get the energy to support life processes without being killed by the UV in the sunlight or the reducing soil that destroys organic matter. -Should there not be appropriate life -forms, our present knowledge of biotechnology should lead -us to be able to develop some in fairly short order. We should think twice before deliberately producing microorganisms that can survive some of our best sterilization techniques. Remember that in the realm of microorganisms, "recombinant DNA" isn't something that happens only with human assistance. -I suggest that we send a space vessel bearing our life -substitutes to Mars and Venus. The cost is relatively -miniscule. Thereon we can sprinkle the makings of man -himself. I suggest we make sure we understand the matter thoroughly before we try anything. This is not a good area for trial and error. (Remember Asimov's novel "Foundation and Earth".) John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: 10 Sep 92 06:58:13 GMT From: Nick Janow Subject: Terraforming Mars Newsgroups: sci.space roberts@CMR.NCSL.NIST.GOV (John Roberts) writes: > It's probably harder than you think. The main challenge on Mars is not > necessarily the scarcity of water (though that is a major problem), but > finding a location where they can get the energy to support life processes > without being killed by the UV in the sunlight or the reducing soil that > destroys organic matter. Does it destroy _all_ organic material (carbon, hydrogen, nitrogen material), or is there a molecule that can convert UV photons to chemical energy without being destroyed? Even if no organic molecule could manage that, there are other possibilities. What of a microorganism (similar to Terran types) that fills a silicone or silica bubble with inorganic chemicals that can be split to form useful chemical energy (H2 and O2, for example)? It could shove the bubbles above the sand, while the body is deep below, connected by silicone tubes. The entire organism could be underground, using silica fibres to the surface as light pipes. I think some Terran life forms use something like this (there are plants that use light pipes). Limiting your thoughts to Terran organic processes leaves out a _lot_ of possibilities. -- Nick_Janow@mindlink.bc.ca ------------------------------ Date: 10 Sep 92 02:24:46 GMT From: Josh 'K' Hopkins Subject: Terraforming needs to begin now Newsgroups: sci.space jgj@ssd.csd.harris.com (Jeff Jackson) writes: >On the wall of a nearby office is this neat picture of a planet with >large amounts of liquid water, but large portions of the land mass is >brown -- dry, relatively lifeless desert. How about some ideas on how >to terraform good old earth? Starting with the Sahara or Austrailia's >outback. >I guess the hard part is getting fresh water to these regions. Here's >my wild, uneducated, naive silly idea for all ya'll to shoot holes in. >There's tons of sand in these deserts. You can use sand to make >glass, so, use all this glass to make huge solar distillation systems. >I'm envisioning long salt-water canals running from the Med. Sea, or >Oceans running hundreds of miles inland. Covering each canal is a >greenhouse that heats the water up and makes it evaporate. At the top >of the greenhouse, the vapor is collected and cooled of, and the resulting >distilled water is then pumped out into irrigation canals runing >perpendicular to the salt-water canals. This might work, and I believe something similar but but on a smaller scale and using aquifers is being tried in Lybia. The trouble is that big projects like this are _big_ and expensive. A cheaper way to do it is Chinas "green Great Wall" approach. They are planting millions of plants in the northwest, and using sattelite imagery to pick the best spots. >Yes, I'm an idiot, but tell me why. Why won't it work? What *would* >work? >-- >============================================================================ >Jeffrey Glen Jackson _|_Satan jeered, "You're dead meat Jesus, I'm gonna >jgj@ssd.csd.harris.com | bust you up tonight." >x5120 | Jesus said, "Go ahead, make my day." > ~~~~~~~~~ -- Carman, "The Champion" >-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- > Politically, I am neither conservative nor liberal -- > I think for myself instead. -- Josh Hopkins "If you are sitting in an exit row and you cannot read this card or cannot see well enough to follow these instructions, please tell a crew member." j-hopkins@uiuc.edu -United Airlines safety instructions ------------------------------ Date: 10 Sep 92 08:32:13 GMT From: nicho@VNET.IBM.COM Subject: Terraforming needs to begin now Newsgroups: sci.space In Jeff Jackson writes: > -- description of terraforming the outback deleted for brevity -- Believe it or not, in OZ we actually think about things like this. Our problem is that the outback is dead flat. There's nothing to interrupt the moisture laden air coming off the coast. Without this, it cannot rise and precipitate. The coolest idea I know of, was to cover vast (strategically located) areas with tar/black paint etc. to create hot spots that would form artificial mountains. Do this properly and you can get a convection cycle going, that will bring moisture laden air in from the coast, and cause it to precipitate on the upwind border of your 'parking lot' ----------------------------------------------------------------- ** 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: Wed, 9 Sep 1992 23:40:35 GMT From: Henry Spencer Subject: With telepresence, who needs people in Earth orbit? Newsgroups: sci.space In article <1992Sep3.152129.22162@cs.ucf.edu> clarke@acme.ucf.edu (Thomas Clarke) writes: >> It's absurd to tie teloperation in low earth orbit to a communication >> path involving two round trips to Clark orbit. Build a necklace of >> co-orbiting microsats ... > >Easier still, use the Motorola Iridium constellation... Both of these ideas assume that the delay *around the Earth* is tolerable for teleoperation. Probably true for the simpler forms, but I've heard some very low numbers for the tolerable delay if you're using the fancier methods like force feedback. -- There is nothing wrong with making | Henry Spencer @ U of Toronto Zoology mistakes, but... make *new* ones. -D.Sim| henry@zoo.toronto.edu utzoo!henry ------------------------------ id AA01175; Wed, 9 Sep 92 21:58:48 EDT Received: from crabapple.srv.cs.cmu.edu by VACATION.VENARI.CS.CMU.EDU id aa23720; 9 Sep 92 21:49:39 EDT To: bb-sci-space@CRABAPPLE.SRV.CS.CMU.EDU Path: crabapple.srv.cs.cmu.edu!cantaloupe.srv.cs.cmu.edu!das-news.harvard.edu!ogicse!uwm.edu!cs.utexas.edu!torn!utzoo!henry From: Henry Spencer Newsgroups: sci.space Subject: Re: Is NASA really planning to Terraform Mars? Message-Id: Date: 9 Sep 92 23:45:27 GMT Article-I.D.: zoo.BuC4nt.3B3 References: <1992Sep4.143843.18127@neptune.inf.ethz.ch> Organization: U of Toronto Zoology Lines: 14 Sender: news@CRABAPPLE.SRV.CS.CMU.EDU Source-Info: Sender is really isu@VACATION.VENARI.CS.CMU.EDU In article <1992Sep4.143843.18127@neptune.inf.ethz.ch> aweder@iiic.ethz.ch (Andreas Michael Weder) writes: >I'd say, forget about that. Even a manned mission to Mars would cost >*at least* 500 billion dollars (according to a NASA researcher). According to a NASA politician, you mean. There is no technical reason why it has to cost that much. See Bob Zubrin's "Mars direct" proposal for an example of a method that ought to cost about a tenth that much, total, for the first ten missions. If enough people prod me, I'll type in my notes from his talk, although there was a good summary paper about it a year or two ago in JBIS. -- There is nothing wrong with making | Henry Spencer @ U of Toronto Zoology mistakes, but... make *new* ones. -D.Sim| henry@zoo.toronto.edu utzoo!henry ------------------------------ End of Space Digest Volume 15 : Issue 182 ------------------------------