Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from beak.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests) ID ; Sat, 3 Mar 90 02:00:34 -0500 (EST) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Sat, 3 Mar 90 02:00:07 -0500 (EST) Subject: SPACE Digest V11 #104 SPACE Digest Volume 11 : Issue 104 Today's Topics: Re: Cheap DSN? [Alan Fernquist : HEI] Re: SLC-6 Re: Spacecraft on Venus Space List Re: Power Economics Re: Spacecraft on Venus Re: Spacecraft drives and fuel efficiency antimatter propulsion approaches Ariane V36: Mission lost ---------------------------------------------------------------------- Date: 28 Feb 90 16:39:17 GMT From: zaphod.mps.ohio-state.edu!usc!cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!utzoo!henry@tut.cis.ohio-state.edu (Henry Spencer) Subject: Re: Cheap DSN? In article <20022612475708@wishep.physics.wisc.edu> GOTT@wishep.physics.wisc.edu writes: >Could we build a better one using a helluva lot of generic satellite reciever >dishes, a helluva a lot of not-top-of-the-line PC's and a helluva lot >of very good software written by cheap programmers? ... In a word, no, probably not. Many little dishes are not a workable substitute for a few big ones, and the receiver technology used to get intelligible signals out of what the dishes pick up is not something you build in your basement. Software and such are secondary; just pulling in the signal from a 75-watt transmitter rounding Saturn is the hard part. For that you need a big precise dish and very-low-noise receivers. (Yes, there are techniques for using multiple dishes as if they were one still-bigger one, but if you thought the technology for *one* dish was difficult to do in your basement, multi-dish arraying is a whole new order of magnitude.) -- "The N in NFS stands for Not, | Henry Spencer at U of Toronto Zoology or Need, or perhaps Nightmare"| uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: Wed 28 Feb 90 14:47:23-PST From: Jay Glass Subject: [Alan Fernquist : HEI] Mail-System-Version: Return-Path: Received: from ptolemy.arc.nasa.gov by PLUTO.ARC.NASA.GOV via SMTP with TCP; Wed, 28 Feb 90 13:55:24-PST Received: from ohm.arc.nasa.gov by ptolemy.arc.nasa.gov (4.1/) id ; Wed, 28 Feb 90 13:50:59 PST Date: Wed, 28 Feb 90 13:50:59 PST From: Alan Fernquist Message-Id: <9002282150.AA29246@ptolemy.arc.nasa.gov> To: alanf@ptolemy.arc.nasa.gov, canfield@pluto, cantwell@pluto.arc.nasa.gov, chuang@pluto, clay@pluto.arc.nasa.gov, dorighi@ptolemy.arc.nasa.gov, doubek@pluto, emcgough@pluto, gdavis@pluto, glass@pluto.arc.nasa.gov, lhaughney@pluto, mah@pluto, mina@pluto, pmiller@pluto, robinson@pluto.arc.nasa.gov, shenk@pluto.arc.nasa.gov, steele@pluto, swab@charon, swanson@pluto, villegas@pluto Subject: HEI I thought you might be interested in a memo that came out of the National Space Council last week on the Presidential Decision on the Space Exploration Inititative: "The President has approved the following policy for the Space Exploration Inititative program: - The Initiative will include both Lunar and Mars program elements. - The early program will focus on technology development with a search for new/innovative approaches and technology. - The program will include investment in high leverage innovative technologies with potential to make a major impact on cost, schedule, and/or performance. - The program will take at least several years defining two or more significantly different human space exploration reference architectures, while developing and demonstrating technology broad enough to support all; selection of a baseline program architecture will occur after that time. - The program will perform mission, concept, and system analysis studies in parallel with technology development. - The program will include robotic science missions. - By spurring research and development in high technology fields, the space program will help promote American economic leadership. - The program will require the efforts of several agencies. NASA will be the principal implementing agency. The Dept. of Defense and the Dept. of Engergy will also have major roles in the conduct of technology development and concept definition. The National Space Council will coordinate the development of an implementation strategy for the Exploration initiative by the three agencies. To facilitate coordination, the Dept. of Energy will be added as a formal member of the National Space Council." ------- ------- ------------------------------ Date: 1 Mar 90 23:44:24 GMT From: serre@boulder.colorado.edu (SERRE GLENN) Subject: Re: SLC-6 SLC-4E and SLC-4W are Titan launch pads. SLC-6 will probably be turned into a Titan IV launch pad. The Air Force machinery for this has apparently started to turn. --Glenn Serre serre@tramp.colorado.edu ------------------------------ Date: 1 Mar 90 16:52:06 GMT From: mailrus!b-tech!kitenet!russ@tut.cis.ohio-state.edu (Russ Cage) Subject: Re: Spacecraft on Venus In article <1702@v7fs1.UUCP> mvp@v7fs1.UUCP (Mike Van Pelt) writes: >Better, you could build a probe designed to operate at Venus surface >temperature. (At 800 degrees? Right. It would probably be easier to >build the heat pump.) Semiconductors are out.... I would not be so certain. I'm aware of at least one silicon technology with an operating temp limit of 300 C (CMOS underlain with ion-implanted glass), and GaAs runs pretty warm too. What I hear about silicon carbide is that it can run extremely hot. Not sure about 800 F, but maybe it can be pushed that far. If your probe operates at ambient, you're set (then you need POWER). -- I am paid to write all of RSI's opinions. Want me to write some for you? (313) 662-4147 Forewarned is half an octopus. Russ Cage, Robust Software Inc. russ@m-net.ann-arbor.mi.us ------------------------------ Date: Fri, 2 Mar 1990 9:13:58 EST From: KLUDGE@AGCB8.LARC.NASA.GOV Subject: Space List X-Vmsmail-To: SMTP%"space@andrew.cmu.edu" Please add me to the Space mailing list. Thanks. --scott ------------------------------ Date: 2 Mar 90 02:33:39 GMT From: mailrus!b-tech!kitenet!russ@tut.cis.ohio-state.edu (Russ Cage) Subject: Re: Power Economics (I should mention here that I have been using Ann Arbor as my reference point for insolation in Michigan. Most of Michigan is worse off in winter. None of the surrounding states is even 50% better off, though.) In article <338@altos86.Altos.COM> robk@altos86.UUCP (Rob Kleinschmidt) writes: [on cogeneration and heat/electricity needs] >Well they sync fairly nicely by season, with the generator running >only in mid winter months. [much deleted] That's one house. What about thousands of houses, plus factories and offices? I am thinking a little bigger than you are, I believe. I think domestic cogeneration is a great idea, if the generators are very cheap, safe and reliable. If they aren't, if they cost too much, have dangerous failure modes or break down very often, the average person won't want one. Storing heat is not very practical; the Luz solar-steam plants in the Mojave don't even try. Storing electricity is costly too. If you don't need heat at the same instant you need juice, or vice versa, you are talking storage. (I would love to see someone try Lofstrom loops for energy storage, they might change the whole equation. But the failure modes... If Keith Lofstrom is still on the net, maybe he'll give us an update.) >Out of curiousity, I would like to ask about: > >1) What are the general dimensions of the collector and ground based >antenna for a delivered kwh of electricity? Even assuming only a >fraction of a meter per capita (probably not enough to match peak >demand ??), this sounds like a fair amount of stuff in orbit. >Interesting disposal problems also when end of lifetime is reached. 1a.) Numbers: Our US population is about 2.5e8, US generating capacity is about 6.5e11 watts. This works out to 2.6 KW per capita. If microwave conversion, transmission and rectification are 50% efficient, solar cells on the SPS are 10% efficient, and incident sunlight is 1360 W/m^2, then you need 38 m^2 of orbital collector per capita. (6.5e11 W figure from the 1/'90 _Audubon_, p. 65. I believe that includes peaking generators. Base load is much less.) I've calculated the necessary satellite size, it's doable. Power density to the rectenna is around 150-200 W/m^2 avg. The rectenna is mostly holes, sun shines right through. The area beneath would be perfectly suited for farming. Rectennas would come in about 5x7 mile ellipsoids, and could be sited anywhere. This includes lakes & oceans. 1b.) Yes, it's a fair amount of stuff in orbit. You'd build it from material already in orbit (the moon, for example). This is far more energy- and cost-efficient than launching everything from the ground, but takes a bit more R&D. 1c.) Disposal problems? What disposal problems? The space in geosync is at a premium, any obsolete powersat would be scavenged for raw materials in short order (like junk cars). The level of space activity needed to construct and maintain large numbers of SPSs would have no trouble disposing of one. >2) How well does the rate of delivery match to real demand. A pretty >fair amount of human activity does track daylight. If you deliver >equal amounts of power at 3 am. what do you do with it? Try recharging electric-car batteries, at 30+ KWH apiece overnight. (Ground-based solar cannot do this without adding a second set of battery losses.) Or electrolyzing hydrogen to make ammonia for fertilizer (replacing natural gas). In summer, freezing ice for daylight air-conditioning or desalinating salt water (replacing eco-problem aqueducts). For ocean-based collectors, electrically pulling carbonates out of solution to get CO2 for fuel synthesis (or just to pipe to the ocean floor). I'm sure we can think of more uses. I expect that cheap, abundant baseload power will cause changes in the way we use energy (like loading things on at night). And if overnight battery charging for electric vehicles is cheap, there will be more incentive to use them. Ground-based solar is not suited for powering base loads in the absence of cheap storage. >Seems like the delivery problems inherent here are the flip side of >those found in the ground based array. Exactly! Which is why we have two types of electric generating plants, base-load and peaking. The former are capital-intensive and use cheap fuel, the latter are cheaper and use more expensive fuels. Ground-based solar can handle many peaking requirements, but not the base load or new nighttime loads (like charging car batteries). SPS can handle base loads without needing storage. SPS is perfectly suited to replacing nuclear and coal-fired baseload capacity, which ground-based solar is not. Since coal is the major culprit behind acid rain and greenhouse-gas emissions and nobody likes nukes, SPS is worth a great deal of attention and investment. -- I am paid to write all of RSI's opinions. Want me to write some for you? (313) 662-4147 Forewarned is half an octopus. Russ Cage, Robust Software Inc. russ@m-net.ann-arbor.mi.us ------------------------------ Date: 2 Mar 90 06:42:19 GMT From: cdaf@iuvax.cs.indiana.edu (Charles Daffinger) Subject: Re: Spacecraft on Venus In article <1990Mar1.165206.12176@kitenet.uucp> russ@m-net.ann-arbor.mi.us (Russ Cage) writes: o In article <1702@v7fs1.UUCP> mvp@v7fs1.UUCP (Mike Van Pelt) writes: o >Better, you could build a probe designed to operate at Venus surface o >temperature. (At 800 degrees? Right. It would probably be easier to o >build the heat pump.) Semiconductors are out.... o o I would not be so certain. I'm aware of at least one silicon o technology with an operating temp limit of 300 C (CMOS underlain o with ion-implanted glass), and GaAs runs pretty warm too. What As to typical Si. process temperatures: Boron diffusion may be done at between 300 and 900 deg C, Phosphor diffusions at about 900-1400 deg. C, and Antimony diffusions at approx 600-650 deg C. Oxidation is done at anywhere from 800 to 1400 deg C. This tells me that if you want to use Si based semiconductors, you probably will want to cool them. Otherwise they won't be semiconductors for long. I don't know about GaAs or any of the more esoteric semiconductors, but I doubt they will be useful at such temperatures for long. -charles -- Charles Daffinger >Take me to the river, Drop me in the water< (812) 339-7354 cdaf@iuvax.cs.indiana.edu Home of the Whitewater mailing list: whitewater-request@iuvax.cs.indiana.edu ------------------------------ Date: 2 Mar 90 17:53:09 GMT From: samsung!aplcen!aplvax.jhuapl.edu!jwm@think.com (Jim Meritt) Subject: Re: Spacecraft drives and fuel efficiency Take off in the "torch" ships (antimatter/fusion) from at sea. Ashore, towers melt and pads may too, but water is rather easy to replace. Land there, too. We KNOW that works. Unless, of course, your exhaust is other than real, real hot. That that is is that that is. That that is not is that that is not. That that is is not that that is not. That that is not is not that that is. And that includes these opinions, which are solely mine! jwm@aplvax.jhuapl.edu - or - jwm@aplvax.uucp - or - meritt%aplvm.BITNET ------------------------------ Date: 2 Mar 90 18:57:30 GMT From: cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!utzoo!henry@tut.cis.ohio-state.edu (Henry Spencer) Subject: antimatter propulsion approaches In article <17556@boulder.Colorado.EDU> serre@boulder.Colorado.EDU (SERRE GLENN) writes: >Probably the simplest way to use antimatter to power a launch vehicle would >be to inject a very small stream of it into the combustion chamber of a rocket >and use the matter-antimatter reaction to heat propellent instead of using >a chemical reaction to do so... This would be the normal approach for use within the solar system. Getting near-100% annihilation and using the charged particles that result gives maximum exhaust velocity but relatively low thrust (for a given flow of antimatter). The exhaust velocities available are so enormous that for anything short of interstellar missions, it makes sense to trade off some velocity for the sake of higher thrust, and the way to do that is to use small amounts of antimatter to heat much larger amounts of reaction mass. -- MSDOS, abbrev: Maybe SomeDay | Henry Spencer at U of Toronto Zoology an Operating System. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu ------------------------------ Date: 27 Feb 90 14:56:49 GMT From: mcsun!hp4nl!esatst!neil@uunet.uu.net (Neil Dixon) Subject: Ariane V36: Mission lost The following is copied from ESTEC News 14 Feb 1990. ----------------------------------------------------------------------- Ariane V36: Mission lost The series of successful Ariane flights, 17 perfect launches in a row since September 1987, has unfortunately stopped on February 22 with flight V36. About 1 minute and 40 seconds after lift-off, the Ariane 4 launcher exploded In the sky above Kourou, French Guiana. The launcher, which was carrying two Japanese satellites, lifted off at 20:17 hrs, Kourou time, after a nominal countdown. The pressure in the chambers of the 4 engines of the 1st stage propulsion bay and of the 4 liquid strap-on boosters was nominal till 6.2 seconds after ignition (HO + 6.2s). At that moment, the pressure in the combustion chamber of one of the 4 engines (engine D) dropped, in half a second, from the nominal value of 58 bars down to approximately 30 bars and remained around this value until HO + 101 s. Within HO + 6 and HO + 8.5 s, the attitude control system had sent to engines A and C swivelling commands of 1,2 degrees amplitude in order to compensate for the insufficient thrust of engine D. At approximately HO+90 s, no further corrections were possible as the engines of the 1st stage propulsion bay had reached the maximum of their swivelling range. At H0+101 s, the high dynamic pressure attained created excessive stresses on the structure and triggered the explosion of the launcher at an altitude of about 9 km and 12.5 km away from the launch pad. An inquiry board is at work as of today. All Ariane flights are suspended until the causes of this accident have been fully understood and corrected. -- Neil Dixon UUCP:...!mcvax!esatst!neil, BITNET: NDIXON@ESTEC Thermal Control & Life Support Division (YC) European Space Research and Technology Centre (ESTEC), Noordwijk, The Netherlands. ------------------------------ End of SPACE Digest V11 #104 *******************