Date: Thu, 10 Sep 92 05:06:08 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V15 #181 To: Space Digest Readers Precedence: bulk Space Digest Thu, 10 Sep 92 Volume 15 : Issue 181 Today's Topics: Climate cycles from Earth's orbital geometry Is NASA really planning to Terraform Mars? (4 msgs) Landsat Pictures? LDO shuttle and pilot readiness Magellan Update - 09/09/92 mission badges for Apollo and STS One Small Step for a Space Activist... Vol 3 No 9 Pluto Direct/ options (4 msgs) Relativity Single Stage to Orbit - How does it work? SPS Terraforming needs to begin now use of external tanks 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, 9 Sep 92 20:13:14 GMT From: Joe Cain Subject: Climate cycles from Earth's orbital geometry Newsgroups: sci.space,sci.astro,sci.geo.geology,sci.geo.meteorology Thanks to the people who answered the question in regard to references. The ones that give a good toehold are: Fisher A. G. and D. J. Bottjer, Orbital forcing and sedimentary sequences, J. of Sedimentary Petrology, Vol. 61, No. 7, December, 1991. This whole issue is devoted to the subject of "orbital cyclostratigraphy." Imbrie, J. and K. Imbrie, Ice Ages: solving the mystery, Short Hills NJ, Harvard U. Press, 1976. and such classic articles as: Hays, J. D., J. Imbrie, and N. J. Shackelton, Variations in the Earth's orbit: pacemaker of the ice ages, Science, V. 194, p 1121-1132, 1976. I noted a number of other tomes in this area, one interesting one was written by the cosmologist who originated the continuous creation theory (not creationist!), Fred Hoyle! The one item that did not emerge was a lower level article. I did hear someone remembering that there was a TV science program of some sort that discussed Quaternary climate changes in some detail, but no specific reference. Joseph Cain cain@geomag.gly.fsu.edu cain@fsu.bitnet scri::cain ------------------------------ Date: Wed, 9 Sep 1992 21:13:07 GMT From: David Knapp Subject: Is NASA really planning to Terraform Mars? Newsgroups: sci.space In article rick@trystro.uucp (Richard Nickle) writes: >In article tomk@netcom.com (Thomas H. Kunich) writes: >>Without references it is difficult to remember, but isn't there >>water, water vapor and possible liquid water along the interface of >>the Martian north pole? >> >>If so, shouldn't this represent a possible seeding area for life forms? >> >>I also seem to remember that the upper atmosphere of Venus was >>mostly water vapor even though the bulk of the atmosphere was >>sulphuric acid. >> >>Perhaps I didn't make myself clear enough. I don't believe that >>Venus could ever be made earthlike. I see the chance, however, >>of seeding life there and letting it make it's own way. >> >>The same with Mars. All of the grandiose plans aside I can't see >>the bulk of the necessary machinery being transported to Mars to >>terraform it and then the project continued for thousands of years. >I never understood this machinery bit though...my understanding of >Martian terraforming was that the timescale would be large, but the >steps taken would be rather simplistic: slamming large ice blocks ^^^^^^^^^^^^^^^^^^ >from the belt or Saturn's rings (though why anybody would want to >throw away all that nice water, I don't know...maybe they could just >send the low-grade ore towards mars), using orbiting mirrors to melt >the poles, or covering the poles with dark matter to assist in raising >the surface temperature. I think you and I have different ideas of what is 'simplistic' > Once you begin to raise atmospheric pressure >and water vapor content, you can begin seeding microbes.... > >But all of these steps, no matter how gartantuan the time scale, are >pretty passive. How are you calling going to Saturn and bringing back chunks of ring big enough to supply an atmosphere *passive*? > You just build the stuff and leave it operating autonomously, >and fiddle with it every decade or so. No massive focus of manpower, >just one hell of a long view would be necessary. Do you understand how many 'mirrors' would be required to raise the polar caps one degree centigrade? -- David Knapp University of Colorado, Boulder Perpetual Student knapp@spot.colorado.edu ------------------------------ Date: 9 Sep 92 19:26:43 GMT From: Gary Coffman Subject: Is NASA really planning to Terraform Mars? Newsgroups: sci.space In article samw@bucket.rain.com (Sam Warden) writes: >Were Venus ever to cool off, I would expect ferocious amounts of >oxidation/carbonation weathering to occur, for example. Remember that chemical reactions like oxidation proceed at a rate proportional to temperature. For most reactions, the rate doubles for every 10 degree temperature rise. On hot Venus, the reactions *are* going on at a furious rate. If it cooled the reactions would slow dramatically. The Venusian atmosphere is apparently mostly CO2 and H2SO4 now. Way too much oxygen, carbon, and sulfur, not enough nitrogen or hydrogen. The hydrogen is the critical part since you want to lock most of the oxygen up as water to reduce atmospheric pressure and establish a hydrological temperature control. Most of the primeval hydrogen has been driven off into space by the hot atmosphere pushing the light molecules to escape velocity. The problem of terraforming the atmosphere requires separating out the sulfur, reducing the CO2, and combining the resulting free oxygen with the non-existant hydrogen. And even if you could do that, you still have a 100 times too much atmosphere. The surface chemistry must be a hell of battery acid and acidic complexes. Nearly every member of the metal group is bound to be fully oxidized. Venus is a natural toxic waste dump. Gary Gary ------------------------------ Date: 9 Sep 92 22:08:51 GMT From: "Thomas H. Kunich" Subject: Is NASA really planning to Terraform Mars? Newsgroups: sci.space In article <1992Sep9.144121.18503@techbook.com> szabo@techbook.com (Nick Szabo) writes: > >>Of course it would be unethical to interfere with any life >>there may be already there. > >"Of course?" Has our civilization changed so much that this notion >is not only accepted, it is taken for granted? NASA has taken very great pains to exclude any contamination another planet with earth biology. Whether it is just because it might screw up the tests or because of the ethics of the matter I don't know. But I think that, yes, we have progressed at least that much. ------------------------------ Date: 9 Sep 92 21:28:10 GMT From: David Knapp Subject: Is NASA really planning to Terraform Mars? Newsgroups: sci.space In article <1992Sep9.151236.18969@techbook.com> szabo@techbook.com (Nick Szabo) writes: >In article samw@bucket.rain.com (Sam Warden) writes: > >>As for the morality of this sort of thing, I don't share the >>comfortable expectation that we as a civilization _have_ >>future centuries at our disposal for a conservative planetary >>exploration. The spread of terrestrial life to other >>now lifeless environments seems _very_ moral to me, even a >>moral imperative, given a possibly limited window of ability >>to do so. My opinion; others of course are free to differ. ;-) > >Even while perhaps disagreeing about the size of that window, I wholeheartedly >agree that this is a moral imperative, not "pollution" or "ruining the planet" >as the politically correct would have us believe. I'd appreciate if you would not lump me into a PC pigeon hole because I prefer to maintain my life support system. If we are to travel to and colonize the terrestrial planets and moons, we should do it without our thumbs up our collective ass which is how we've approached global terrestrial issues. I do not trust well-meaning armchair scientists endorsing orbiting space mirrors to solve chemical imbalances in our upper atmosphere caused by industrial overzealousness. I see that all too often though. 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. If you think that this behavior is limited to vogue PC yuppies, you are quite mistaken. -- David Knapp University of Colorado, Boulder Perpetual Student knapp@spot.colorado.edu ------------------------------ Date: 9 Sep 92 19:37:20 GMT From: John McDonald Subject: Landsat Pictures? Newsgroups: sci.space,sci.astro,sci.geo.geology Years ago, i had information on obtaining Landsat photos based on long-lat information. I seem to recall the address being in Colorado somewhere... Could anyone send me information on getting Landsat photos nowadays? Please e-mail... Thanks! Johnny. begin 664 signature.uu M:F]H;E\M7U\M7U\M7U\M7U\M7U\M7U\M7U\M7U\M7U\M7VUC9&]N86QD"@E! M7-I8W,* ------------------------------ Date: 9 Sep 92 21:45:19 GMT From: Henry Spencer Subject: LDO shuttle and pilot readiness Newsgroups: sci.space In article <1992Sep4.145946.13209@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes: >... Though they undoubtedly use >the Mark I eyeball out the window during landing, Shuttle pilots >are supposed to be landing IFR *today*. Thus the ground simulator's >movies aren't strictly necessary. They are considered valuable, though, to the point where the pilots have experimented with taking along videotapes of training-aircraft landings, to be screened using the little monitors on the video cameras! >... 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. -- 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: Thu, 10 Sep 1992 02:45:59 GMT From: Ron Baalke Subject: Magellan Update - 09/09/92 Newsgroups: sci.space,sci.astro Forwarded from: PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011 MAGELLAN STATUS REPORT September 9, 1992 Magellan continued successful radar mapping of the surface of Venus this week. The goal of the current mapping period is to fill the largest remaining gap in the map of Venus which will bring total coverage to 99 percent. The spacecraft had mapped 97.5 percent of the planet with its imaging radar during its first two 243-day cycles. Controllers are planning an orbit trim maneuver next Monday, September 14, to lower periapsis from its current altitude of 261 kilometers (162 miles) to 182 kilometers (113 miles) for the gravity mapping cycle beginning the next day. _____ ___ _____ ___ /_ /| /____/ \ /_ /| 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: Wed, 09 Sep 92 21:37:16 GMT From: George Hastings Subject: mission badges for Apollo and STS Newsgroups: sci.space,sci.space.shuttle Try writing to: Space Patch Collector's Club P.O.Box 17310 Pittsburg, PA 15235-0310 -- ------------------------------ Date: 9 Sep 92 19:31:28 GMT From: "Allen W. Sherzer" Subject: One Small Step for a Space Activist... Vol 3 No 9 Newsgroups: talk.politics.space,sci.space One Small Step for a Space Activist... By Allen Sherzer & Tim Kyger There is an old saying in Mexico: What cannot be remedied must be endured. With the July House appropriations vote and with the retirement of Rep. Traxler (D-MI) it looks like Space Station Freedom is out of remedy mode and into endure mode. With all its flaws and costs it looks like Freedom WILL be built (in some form anyway). At the same time, Freedom's huge costs will consume the funds needed to go back to the Moon and on to Mars. How can we endure this? 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 will this deny the advantages of a larger market but it will add huge costs to the Station life cycle. 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. 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). A heavy lift vehicle would be one way to meet requirement one. such an HLV would lift 100,000 pounds to Freedom orbit and would carry a reusable logistics module. The logistics module would have an aerodynamic shape (perhaps like DC-Y or an Apollo capsule) and be capable of returning 20,000 pounds to Earth. 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). The reusable Logistics Module is harder to cost out since it doesn't exist yet. However similar efforts have costed out around $3 billion for development; we'll toss in an extra $100M per flight for recurring costs. At four flights per year and amortizing development over ten years we get a cost of about $200M per flight (including interest). 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 which hasn't been done is integration of Soyuz on a US launcher but since launcher/payload interfaces haven't been standardized this should pose no serious problems. In quantity, Atlas launches can be had for about $60 million plus 20 million each for Soyuz. Observant readers will also note that this eliminates the ACRV problem. 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. This gives us the following costs for each year: 1. Atlas Soyuz launches (8 @ 80M each): $640M 2. Logistics modules (4 @ 200M each) : $800M 3. Heavy Lift Vehicles (4 @ 200M each) : $800M 4. Orbital Transfer Vehicle (1 @ 300M) : $300M All this adds up to $2,540 million per year, which is about half the cost of maintaining Shuttle. Using this approach would therefore save us all about $2,500 million per year. In addition, since it uses multiple launch vehicles with backups for every launcher, it could be even more reliable than Shuttle. So where does the money to develop all this come from? The answer lies with the public sector. Many of the components needed are available today. Contractors have already offered to build the HLVs themselves if the government will agree to buy them. All we need do is allow Freedom to provide the market and they will come. Legislative Roundup SSTO/SSRT Sources say that Senator Pete Domenenici (R-NM) has recently been briefed on SSRT and emerged an enthusiastic supporter. The Senator is on the Appropriations Committee and is the ranking Republican on the Budget Committee. He could be a powerful ally. The next vote is the Senate Appropriations Committee's Defense Subcommittee currently expected for September 14. We need to get letters to every Senator before then. Commercial Space The full House has voted on and passed the Omnibus Commercial Space Act. However action by the Senate is looking less and less likely. NSS Petition Drive NSS has endorsed Dr. Zubrin's petition calling on the next president to devote serious effort to SEI. Watch this space for progress reports. -- +---------------------------------------------------------------------------+ | 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?" | +----------------------227 DAYS TO FIRST FLIGHT OF DCX----------------------+ ------------------------------ Date: Wed, 9 Sep 1992 18:57:00 GMT From: "Horowitz, Irwin Kenneth" Subject: Pluto Direct/ options Newsgroups: sci.space In article <1992Sep9.025730.29227@cbfsb.cb.att.com>, wa2ise@cbnewsb.cb.att.com (robert.f.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 problem with Galileo was that it required a Venus flyby to get enough energy to go to Jupiter. This necessitated folding up the main antenna so that it wouldn't be damaged by the close approach to the sun. The Pluto direct mission does not need to worry about this, since they will be flying directly out from Earth to the outer solar system. The antenna will be fully opened when placed into the payload fairing of the Titan rocket (there was an article in yesterday's NY Times on this mission by John Noble Wilford, and I recommend reading this for anyone interested in this mission). Actually, Rob Staehle has an overhead transparency showing what the entire payload would look like in its fairing (including the two solid upper stage motors), and its miniscule size is really quite funny. ------------------------------------------------------------------------------- Irwin Horowitz | Astronomy Department |"Whoever heard of a female astronomer?" California Institute of Technology |--Charlene Sinclair, "Dinosaurs" irwin@iago.caltech.edu | ih@deimos.caltech.edu | ------------------------------------------------------------------------------- ------------------------------ Date: 9 Sep 92 23:03:23 GMT From: Henry Spencer Subject: Pluto Direct/ options Newsgroups: sci.space In article <1992Sep7.173253.1837@access.digex.com> prb@access.digex.com (Pat) writes: >Did they consider using energia? most of the charts I remember >were using titan or delta class launchers? Any use of Energia entails the sort of political complications that I imagine JPL would rather avoid... I mean complications *within the US*, not the negotiations with the Russians, which ought to be straightforward as long as you bring money. (That was how things worked *before* the breakup of the USSR, and I imagine it's even more so now...) -- 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: 9 Sep 92 23:14:15 GMT From: Henry Spencer Subject: Pluto Direct/ options Newsgroups: sci.space In article <1992Sep9.025730.29227@cbfsb.cb.att.com> wa2ise@cbnewsb.cb.att.com (robert.f.casey) writes: >I suppose that someone has figured out what design to change, or do better, >to avoid "stuck antenna" problems? It's really very simple: don't use a folding antenna. Or if you must use one, launch the mission on a shuttle (heresy! heresy! :-)) and unfold the antenna before upper-stage ignition, so there's somebody around to *fix* it if it doesn't work. The antenna on Compton stuck too -- although in a somewhat different way -- and the shuttle crew went out and fixed it. -- 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: 9 Sep 92 23:19:30 GMT From: Henry Spencer Subject: Pluto Direct/ options Newsgroups: sci.space In article <9SEP199210572154@iago.caltech.edu> irwin@iago.caltech.edu (Horowitz, Irwin Kenneth) writes: >The problem with Galileo was that it required a Venus flyby to get enough >energy to go to Jupiter. This necessitated folding up the main antenna so >that it wouldn't be damaged by the close approach to the sun... Actually, no, the problem with Galileo was that the combination of data rate, transmitter power, and size constraints made a rigid antenna impossible. The Voyager design had the biggest rigid antenna that would fit in a Centaur payload shroud; nothing in the US inventory could carry a Galileo-size antenna unless it was folded. The effect of the Venus flyby was to require that the antenna *stay* folded for the first year or so in space. This may or may not have contributed to the problem. The back-and-forth shipping needed to make those modifications quite possibly contributed to the problem. -- 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: 9 Sep 92 22:49:13 GMT From: "Alan M. Carroll" Subject: Relativity Newsgroups: sci.space In article <14902@mindlink.bc.ca>, Alan_Barclay@mindlink.bc.ca (Alan Barclay) writes: > A recent SF book used relativistic mass to produce black holes. > i.e. accelerate a spaceship until it's massive enough to collapse > into a singularity. Something seems missing in this equation. > Could it happen? No. Are you sure this was in a book? I remember seeing this in the "Probability Zero" column of Analog magazine a few years back. It was a short story that used this effect and was intended as a parody of bad science fiction writing. -- Alan M. Carroll "Weren't there yams involved, too?" - J. Ockerbloom Epoch Development Team Urbana Il. "I hate shopping with the reality-impaired" - Susan ------------------------------ Date: 9 Sep 92 21:38:14 GMT From: Henry Spencer Subject: Single Stage to Orbit - How does it work? Newsgroups: sci.space In article kdawson@AFIT.AF.MIL (KEVIN D. DAWSON) writes: >>except that it will probably use either a "plug nozzle" (which puts the >>entire base area of the rocket to work as the nozzle) or telescoping >>nozzles that can be made longer in flight... neither >>has flown, although both look workable... > >I Take it the Telescoping nozzle on the Peacekeepers upper stage doesn't >count because it only telescopes for storage? Correct. There are quite a number of nozzle designs that telescope for storage but are fully deployed before ignition. They are common for applications where nozzle length is a major issue: submarine-launched missiles (where a fixed missile-tube volume must be used as efficiently as possible), treaty-limited missiles (same requirement for a different reason), and shuttle payloads (the IUS uses telescoping nozzles). Nobody has yet flown a nozzle designed to be *fired* in more than one position. -- 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: 9 Sep 92 22:38:51 GMT From: Henry Spencer Subject: SPS Newsgroups: sci.space In article <9209020213.AA15023@cmr.ncsl.nist.gov> roberts@CMR.NCSL.NIST.GOV (John Roberts) writes: >-... to develop less expensive >-technologies for getting lunar material into space, such as >-electromagnetic mass drivers and powdered aluminum/oxygen rockets. > >Ah, one of my favorites! Apparently a private company actually built a >working aluminum-oxygen rocket last year... Actually, you don't have to fool around with aluminum-oxygen (which is a hassle as a rocket fuel, because both the aluminum and the aluminum oxide are solids, where you'd really like liquid and gas respectively). Jordin Kare's latest laser-launcher design, the heat-exchanger rocket, needs liquid hydrogen for launch from Earth but would work well enough on liquid oxygen for a lunar launch. You'd still have to do some of the same work on chamber/nozzle materials, I expect. >important, because I think you get the best specific impulse with an excess >of oxygen, and hot oxygen is bad for most metals. Your exhaust velocity [specific impulse is exhaust velocity in bizarre units] will go all to hell without that excess of oxygen, because the combustion products of that reaction are *solid* at any reasonable temperature. To convert heat to jet velocity, you need hot *gas*. So yes, such a system would have to run very oxygen-rich. -- 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 00:02:52 GMT From: Jeff Jackson Subject: Terraforming needs to begin now Newsgroups: sci.space 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. 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. ------------------------------ Date: 9 Sep 92 23:00:37 GMT From: Henry Spencer Subject: use of external tanks Newsgroups: sci.space In article <1992Sep3.134158.3514@access.digex.com> mheney@access.digex.com (Michael K. Heney) writes: >the current direct-ascent trajectories used on shuttle launches has the >orbiter climbing to apogee and the tank re-entering after MECO, with no >burns to alter either's trajectory... For those who didn't read the above carefully :-), note in particular that *it is no longer true* that the shuttle expends fuel just to get the tank into a disposal trajectory. Taking it into orbit, even low orbit, will cost you. To expand on Michael's general point, the tanks won't stay in orbit long because they are big and light and very vulnerable to air drag. This is especially true because, left to themselves, they will stabilize with the long axis pointing along the tank-Earth line, which puts them broadside-on to orbital motion -- the worst possible case for air drag. It is Politically Unacceptable to just let them come down anywhere. You have to be able to either keep them up or deorbit them under control, with a very high probability of success (i.e. you need redundant systems). Another significant point is that any large, light structure has to count on being punctured by space debris. The Gamma-Ray Imaging Telescope concept -- the most detailed study on ET use that I know of -- planned to wrap an outer blanket around the entire tank once on orbit, both to act as a "meteor bumper" and to contain popcorning insulation. >There *is* an access "hatch" on the bottom of the LH2 tank - 3 feet in >diameter and bolted on *very* securely... In fact there are two, although one is obstructed by some of the internal plumbing. There is also one in the top of the LH2 tank (letting you into the intertank space), one in the bottom of the LO2 tank (ditto), and a door in the side of the intertank ring (giving you access to those hatches). Getting access to any of them is going to require cutting away the spray-on insulation, by the way. >... Now, you need to somehow add on a >*real* airlock, build internal structures, add power supplies, plumbing, >windows, etc, all of which involves cutting and welding on orbit by >astronauts on EVA... Actually, you can shortcut this a lot by using the technique planned for the original "wet workshop" Skylab concept: once the hatch cover is off, insert a cylinder 3ft in diameter and the length of the tank (actually, you'd probably have to join two pieces end-to-end to get that length from something fitting the shuttle cargo bay). Bolt it down where the hatch used to be. The outside end of the cylinder contains your airlock, which can stay *outside* and hence be any convenient diameter; only the inserted part is limited to 3ft in diameter. That part is packed as solidly as you can with parts, plumbing, etc.; it becomes your utility core, while things like structure can be assembled -- by people in shirtsleeves, inside the pressurized tank -- from the parts. -- 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 181 ------------------------------