Date: Sat, 27 Mar 93 05:52:02 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V16 #377 To: Space Digest Readers Precedence: bulk Space Digest Sat, 27 Mar 93 Volume 16 : Issue 377 Today's Topics: 25 kg. to Venus, how much would it cost? (2 msgs) Alumnium was available in Elizabethan times? Flight time comparison: Voyager vs. Gallileo Gravity waves, was: Predicting gravity wave quantization & Cosmic Noise Idle Question Magellan Update - 03/22/93 Space Calendar - 03/27/93 Space Posters, and where to get them? (2 msgs) Uplink/downlink rates (2 msgs) Why use AC at 20kHz for SSF Power? 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: Sat, 27 Mar 1993 04:51:18 GMT From: Henry Spencer Subject: 25 kg. to Venus, how much would it cost? Newsgroups: sci.space In article <1993Mar26.170552.21750@ucsu.Colorado.EDU> fcrary@ucsu.Colorado.EDU (Frank Crary) writes: >... So, adding it all up, a 25 kg >package to Venus would require about 600 kg IMLEO. The cheap >way to launch that would be either Pegasus or a Scout. With a >Scout, you would be well under the vehicle's capacity: You'd be >more efficient if you sent a larger (~50kg) package, or sent two... Uh, Frank, what Scout specs are you reading? No Scout has ever been able to carry 600kg into orbit; the Scout performance charts stop at 270kg. Pegasus carries *more* payload than Scout, not less; you can get about 350kg into a very low orbit with a block-1 Pegasus. (My somewhat-old Pegasus manual predicts 8-20% improvement for block 2 Pegasus and a further modest improvement for a stretched model, which I think is the XL they recently committed to building.) -- All work is one man's work. | Henry Spencer @ U of Toronto Zoology - Kipling | henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Sat, 27 Mar 1993 05:03:22 GMT From: Henry Spencer Subject: 25 kg. to Venus, how much would it cost? Newsgroups: sci.space In article <1993Mar26.171913.19764@aio.jsc.nasa.gov> mancus@sweetpea.jsc.nasa.gov (Keith Mancus) writes: > Sounds to me like there is a LOT of room for cost improvement on the >low-mass end, unless the $20M figure is really a loss to the Russians >and they just don't know it (quite possible)... It's very hard to say what a "fair price" for a Russian launcher is (all the more so because Arianespace and the Russian Space Agency would have different definitions of "fair"!). I have heard it claimed, at Making Orbit '93 as I recall, that Russian prices would probably undercut Western ones by at least a factor of 3 even with honest accounting and Western salaries -- they just need so much less manpower to build and launch the things, and they have so much larger production runs for the hardware. > It seems to me that a cost of < $1M per launch would have a great effect >on the viability of this type of mission. Granted, there are some benefits >to scale here, but I don't believe that decreases cost by a factor of 10. You could be surprised. So much of this business -- in the West -- builds hardware at very low rates that are very uneconomical. If (admittedly dim) memory serves, Rockwell offered to build NASA a dozen shuttle orbiters for the same price as four, if NASA would make a firm commitment that would allow some investment in streamlined production setups. When there was talk, some years ago, of a government market guarantee at $500/lb to low orbit, several of the more innovative companies were pretty sure that they could make a *bundle* at that rate... which is 5-10 times lower than current prices. Even the traditional launcher manufacturers will admit that they could cut costs by a factor of 2-3 if volume picked up enough to permit volume orders of subassemblies. The problem is that those low costs aren't going to appear unless someone first commits to buying a whole bunch of them. -- All work is one man's work. | Henry Spencer @ U of Toronto Zoology - Kipling | henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 26 Mar 93 22:43:21 -0600 From: Bill Higgins-- Beam Jockey Subject: Newsgroups: sci.space In article <1993Mar26.223438.19777@news.arc.nasa.gov>, yee@atlas.arc.nasa.gov (Peter Yee) writes: > EXPLORATION EFFORT SHIFTED TO OFFICE OF SPACE SCIENCE > > NASA Administrator Daniel S. Goldin today announced that the activities > of the Office of Exploration will be absorbed by the Office of Space Science, > effective immediately. Well, so much for THAT little empire. It was fun while it lasted. Bill Higgins | "I shop at the Bob and Ray Fermi National Accelerator Laboratory | Giant Overstocked Surplus Bitnet: HIGGINS@FNAL.BITNET | Warehouse in one convenient Internet: HIGGINS@FNAL.FNAL.GOV | location and save money besides SPAN/Hepnet: 43011::HIGGINS | being open every evening until 9." ------------------------------ Date: 26 Mar 93 19:17:42 GMT From: Paul Campbell Subject: Alumnium was available in Elizabethan times? Newsgroups: sci.space,sci.materials In article <1993Mar21.184053.27365@sfu.ca> Leigh Palmer writes: >According to my Rubber Bible, 63rd ed., Aluminum was first isolated in >1827 by Wohler. "Aluminium" is available in Elizabethan (II) times, and >perhaps "alumnium", whatever that is, was available in "elizabethan" >times, but aluminum was not available in Elizabethan times any more than >Macintoshes were. Ahem .... "Aluminum" is the name used by people in the US, "Aluminium" is the proper chemical name and the name used (and pronounced) by everyone else in the world. Aluminum is just one of those quaint things about the US (like inches and writing the date backwards). Paul -- Paul Campbell UUCP: ..!mtxinu!taniwha!paul AppleLink: CAMPBELL.P "Finally after much thought he tied a dollar bill to the top of the tree, it seemed to fit - after all it was the premier capitalist holiday, besides after the 'fall' of communism a star didn't seem appropriate anymore ..." ------------------------------ Date: Sat, 27 Mar 93 00:44:49 GMT From: "Lowell O Specht Jr." Subject: Flight time comparison: Voyager vs. Gallileo Newsgroups: sci.space vento@mars.lerc.nasa.gov (Dan Vento) writes: >In article <1993Mar18.000618.1023@ke4zv.uucp>, gary@ke4zv.uucp (Gary >Coffman) wrote: >> >> In article <1o822uINNf90@elroy.jpl.nasa.gov> tjt@scn1.Jpl.Nasa.Gov writes: >> >the moment, I don't think the U.S. has anything that will launch anything of >> >Voyager size from earth. >> >> Voyagers went up on Titan-Centaurs. >> >The current Titan IV-Centaur could probably handle a Voyager type (1800 >Lbs) spacecraft. It really depnds upon where you want to go and on how fast >you want to get there. It is a fact that the Titan IV-Centaur is designed to loft a 10,000 lb payload to low earth orbit. However, to date, a Titan IV-Centaur has yet to be launched. The space shuttle could also launch a Voyager-type payload depending on the upperstage used, currently Centaur's are not approved for use with the shuttle. -- Regards, Lowell ****************************************************************************** * Lowell Specht * * * Marietta, GA USA * * * home: specht@dixie.com * Go Big Orange! * * work: g584741@loads1.lasc.lockheed.com * * ****************************************************************************** * My comments are my own and not my employer's. * ****************************************************************************** ------------------------------ Date: Sat, 27 Mar 1993 04:45:58 GMT From: Tom Van Flandern Subject: Gravity waves, was: Predicting gravity wave quantization & Cosmic Noise Newsgroups: sci.space,sci.astro,sci.physics,alt.sci.planetary nickh@CS.CMU.EDU (Nick Haines) writes: > curvature is actually a property of the surface itself. Let's go back to > the balloon example. Imagine you're an ant on the balloon. How can you > tell that you're on a curved surface and not a flat one? Simple: you > measure the area or circumference of a circle. ... if the ratio of the > circumference to the diameter is pi, the surface is flat. If these are > less than pi, the surface is positively curved (like a sphere) ... These are properties of a surface that is curved in another spacial dimension outside itself. The original question was about whether that additional dimension is required or not. By requiring another dimension itself, your example seems to imply that it is also required for the universe. > Now suppose your ant civilisation lives on the surface of a cone (not > near the vertex). You do this experiment. You find these numbers are > always equal to pi, and you conclude you're living on a flat surface. Curvature can only exist relative to something non-curved. In your first example, both balloon dimensions are curved, so there must exist a third spacial dimension for them to be curved in. In the cone/cylinder example, only one of the two surface dimensions is curved, so measuring circumference:diameter ratios is not a test for curvature in a third dimension. > The curvature in which we're interested is thus a property of the surface > (or space) itself, and does not require the concept of an `embedding > space.' Since we can never observe such a space, why suggest it exists? Your own examples suggest just the opposite. Since all three spacial dimensions are supposedly curved, we should be able to detect this by measuring circumference:diameter or area:diameter or volume:diameter ratios. If they all came out as expected for flat space over any scale, however large, that would prove that space was flat. If those measurements indicated curvature, that would prove the existence of another spacial dimension. > Should this go in the FAQ? Your descriptions still don't answer the original question about another spacial dimension, at least for me. Essential point: What does it mean to be "curved" unless there is some standard for "straight"? -|Tom|- -- Tom Van Flandern / Washington, DC / metares@well.sf.ca.us Meta Research was founded to foster research into ideas not otherwise supported because they conflict with mainstream theories in Astronomy. ------------------------------ Date: 26 Mar 1993 21:26:56 -0500 From: Pat Subject: Idle Question Newsgroups: sci.space How much weight would an SS-20 or a Pershing 2 lob to 120Nm from san Marco or Cape York? And could these rockets hit those altitudes without significant engineering work. pat ------------------------------ Date: 26 Mar 1993 20:43:13 -0500 From: Pat Subject: Magellan Update - 03/22/93 Newsgroups: sci.space,sci.astro,alt.sci.planetary In article <1ovckaINN2kl@rave.larc.nasa.gov> S.D.Derry@LaRC.NASA.Gov writes: >Eric H Seale (seale@possum.den.mmc.com) wrote: >: say, 60 deg C). One option that I heard being talked about is called (I >: think) bistatic radar -- Magellan transmits the radar which bounces off >: the surface and is then received at Arecibo. Even with a low circular >: orbit, I'm not sure that this buys you much, tho' ... > Wow. What kind of power levels are we talking about? The gain off arecibo must be enormous, but then this will only work on certain geometric areas. The target and arecibo need to be a equal-angle trieangle . I doubt one could see very much. THe earth's rotation would take arecibo off point pretty fast, and given arecibo is mostly a passive reflector, i doubt it can slew electronically it's pointing angle much. Now the VLA, might be able to track over much of the horizon, but the gain off VLA is lower then arecibo, i imagine. >Another alternative would be to map small selected areas of high interest >and play the data back at the current 1200bps rate. By the time that TEX Is that the engineering data downlink? What's the link speed of the Transmitters? And could some sort of data compression scheme be run, just like on Galileo? The SAR returns are essentially large analog signals, maybe if you applied ADPCM or something else, you could squeeze out a lot more. Magellan has the computing horsepower right? >and cycle 5 gravity mapping is complete, the target areas could be selected. >If they were small enough, and spaced far enough apart, then the data could >be stored onboard during mapping orbits (only mapping over a small latitude >range), and played back at slow rate after the target area has been covered. >Alternatively, portions of the data could be played back between mapping >passes, but this would make operations a bit more complex. > >-- >Steve Derry > Your right, the target areas of interest are getting smaller. From my understnading, Maxwell Montes has some black outs right across the kisser. A goof, by JPL. Shit Happens. The tape recorder was making a swap over, at just that point in orbit. Also, certain parts of the poles have not been mapped, plus the few cycles at solar conjunction. Plus a few areas could really use some stereo mapping. My take on it was 1% of the planet still needs mapping, do-able i think even at 1200 baud, and 65% of the planet still needs stereo mapping. Implausible, even if the can use coding to get up to 10KBS, but do-able for the more interesting areas, like the supposed slide zones and for doing some stereo mapping of the rift zones. So does anyone from JPL care to comment? pat ------------------------------ Date: 27 Mar 1993 07:02 UT From: Ron Baalke Subject: Space Calendar - 03/27/93 Newsgroups: sci.space,sci.astro,sci.space.shuttle,alt.sci.planetary The Space Calendar is updated monthly and the latest copy is available at ames.arc.nasa.gov in the /pub/SPACE/FAQ. Please send any updates or corrections to Ron Baalke (baalke@kelvin.jpl.nasa.gov). Note that launch dates are subject to change. The following people made contributions to this month's calendar: o Jeff Bloch - Updated ALEXIS launch date (04/22/93). o Allen Sherzer - Updated DC-X test flight date (June 1993). o Steven Pietrobon - Updated Ariane launches date for April, June & July. ========================= SPACE CALENDAR March 27, 1993 ========================= * indicates change from last month's calendar March 1993 * Mar 27 - GPS/SEDS-1 Delta II Launch Mar 31 - Commercial Experiment Trasporter (Comet) Conestoga Launch April 1993 * Apr ?? - STS-55, Columbia, Spacelab Germany (SL-D2) * Apr ?? - Astra 1C Ariane Launch Apr 06 - 20th Anniversary, Pioneer 11 Launch (Jupiter & Saturn Flyby Mission) * Apr 07 - STS-56, Discovery, Atmospheric Lab for Applications and Science (ATLAS-2) Apr 19 - Venus/Moon Occultation, Visible from North America Apr 22 - Lyrid Meteor Shower (Maximum: 03:00 UT, Solar Longitude 32.1 degrees) * Apr 22 - ALEXIS Pegasus Launch * Apr 26 - First Test Firings of the DC-X Apr 28 - STS-57, Endeavour, European Retrievable Carrier (EURECA-1R) May 1993 May ?? - Advanced Photovoltaic Electronics Experiment (APEX) Pegasus Launch May ?? - Radcal Scout Launch May ?? - GPS/PMQ Delta II Launch May 04 - Galileo Enters Asteroid Belt Again May 04 - Eta Aquarid Meteor Shower (Maximum: 21:00 UT, Solar Lon: 44.5 deg) May 20 - 15th Anniversary, Pioneer Venus Orbiter Launch May 21 - Partial Solar Eclipse, Visible from North America & Northern Europe May 25 - Magellan, Aerobraking Begins? June 1993 Jun ?? - Temisat Meteor 2 Launch Jun ?? - UHF-2 Atlas Launch Jun ?? - NOAA-I Atlas Launch * Jun ?? - First Test Flight of the DC-X (Unmanned) * Jun ?? - Hispasat 1B & Insat 2B Ariane Launch Jun 04 - Lunar Eclipse, Visible from North America Jun 14 - Sakigake, 2nd Earth Flyby (Japan) Jun 22 - 15th Anniversary of Charon Discovery (Pluto's Moon) by Christy Jun 30 - STS-51, Discovery, Advanced Communications Technology Satellite July 1993 Jul ?? - MSTI-II Scout Launch * Jul ?? - Galaxy 4 Ariane Launch Jul 01 - Soyuz Launch (Soviet) Jul 08 - Soyuz Launch (Soviet) Jul 14 - Soyuz TM-16 Landing (Soviet) Jul 21 - Soyuz TM-17 Landing (Soviet) Jul 28 - S. Delta Aquarid Meteor Shower (Maximum: 19:00 UT, Solar Longitude 125.8 degrees) Jul 29 - NASA's 35th Birthday August 1993 Aug ?? - ETS-VI (Engineering Test Satellite) H2 Launch (Japan) Aug ?? - GEOS-J Launch Aug ?? - Landsat 6 Launch Aug ?? - ORBCOM FDM Pegasus Launch Aug 09 - Mars Observer, 4th Trajectory Correction Maneuver (TCM-4) Aug 12 - N. Delta Aquarids Meteor Shower (Maximum: 07:00 UT, Solar Longitude 139.7 degrees) Aug 12 - Perseid Meteor Shower (Maximum: 15:00 UT, Solar Longitude 140.1 degrees) Aug 24 - Mars Observer, Mars Orbit Insertion (MOI) Aug 25 - STS-58, Columbia, Spacelab Life Sciences (SLS-2) Aug 28 - Galileo, Asteroid Ida Flyby September 1993 Sep ?? - SPOT-3 Ariane Launch Sep ?? - Tubsat Launch Sep ?? - Seastar Pegasus Launch October 1993 Oct ?? - Intelsat 7 F1 Ariane Launch Oct ?? - SLV-1 Pegasus Launch Oct ?? - Telstar 4 Atlas Launch Oct 01 - SeaWIFS Launch Oct 22 - Orionid Meteor Shower (Maximum: 00:00 UT, Solar Longitude 208.7 degrees) November 1993 Nov ?? - Solidaridad/MOP-3 Ariane Launch Nov 03 - 20th Anniversary, Mariner 10 Launch (Mercury & Venus Flyby Mission) Nov 03 - S. Taurid Meteor Shower Nov 04 - Galileo Exits Asteroid Belt Nov 06 - Mercury Transits Across the Sun, Visible from Asia, Australia, and the South Pacific Nov 10 - STS-60, Discovery, SPACEHAB-2 Nov 13 - Partial Solar Eclipse, Visible from Southern Hemisphere Nov 15 - Wilhelm Herschel's 255th Birthday Nov 17 - Leonids Meteor Shower (Maximum: 13:00 UT, Solar Longitude 235.3 degrees) * Nov 20 - Mars Observer, Mapping Begins Nov 28-29 - Total Lunar Eclipse, Visible from North America & South America December 1993 Dec ?? - GOES-I Atlas Launch Dec ?? - NATO 4B Delta Launch Dec ?? - TOMS Pegasus Launch Dec ?? - DirectTv 1 & Thiacom 1 Ariane Launch Dec ?? - ISTP Wind Delta-2 Launch Dec ?? - STEP-2 Pegasus Launch Dec 02 - STS-61, Endeavour, Hubble Space Telescope Repair Dec 04 - SPEKTR-R Launch (Soviet) Dec 05 - 20 Anniversary, Pioneer 10 Launch (Jupiter Flyby Mission) Dec 08 - Mars Observer, Mars Equinox Dec 14 - Geminids Meteor Shower (Maximum: 00:00 UT, Solar Longitude 262.1 degrees) Dec 20 - Mars Observer, Solar Conjunction Begins Dec 23 - Ursids Meteor Shower (Maximum: 01:00 UT, Solar Longitude 271.3 degrees) January 1994 * Jan 03 - Mars Observer, End of Solar Conjunction Jan 24 - Clementine Titan IIG Launch (Lunar Orbiter, Asteroid Flyby Mission) February 1994 Feb ?? - SFU Launch Feb ?? - GMS-5 Launch Feb 05 - 20th Anniversary, Mariner 10 Venus Flyby Feb 08 - STS-62, Columbia, U.S. Microgravity Payload (USMP-2) Feb 15 - Galileo's 430th Birthday Feb 21 - Clementine, Lunar Orbit Insertion Feb 25 - 25th Anniversary, Mariner 6 Launch (Mars Flyby Mission) March 1994 * Mar ?? - TC-2C Launch * Mar 05 - 15th Anniversary, Voyager 1 Jupiter flyby * Mar 14 - Albert Einstein's 115th Birthday * Mar 27 - 25th Anniversary, Mariner 7 Launch (Mars Flyby Mission) * Mar 29 - 20th Anniversary, Mariner 10, 1st Mercury Flyby ___ _____ ___ /_ /| /____/ \ /_ /| Ron Baalke | baalke@kelvin.jpl.nasa.gov | | | | __ \ /| | | | Jet Propulsion Lab | ___| | | | |__) |/ | | |__ M/S 525-3684 Telos | Don't ever take a fence /___| | | | ___/ | |/__ /| Pasadena, CA 91109 | down until you know the |_____|/ |_|/ |_____|/ | reason it was put up. ------------------------------ Date: Sat, 27 Mar 93 04:12:49 GMT From: Ross Borden Subject: Space Posters, and where to get them? Newsgroups: sci.space In article <1993Mar25.102746.1@aurora.alaska.edu> nsmca@aurora.alaska.edu writes: >Wiers question, where is a good place to get Space Posters??? I know that many >people seem to like posters of movie stars and such, beer (sexy girls okay), >and other such things, I was wondering if someone has any Space Posters and >where to get them? > Try Nova Graphics in Tuscon, AZ. They have some nice prints of spacescapes by artists like Kim Poor and Alan Bean. They're good quality, but a bit pricey ($30-$80) because they're all limited editions. Sorry, can't give you the address, my catalog is at home. ------------------------------------------------------------------------------- | I shot a man just to watch him die; | Ross Borden | | I'm going to Disneyland! | rborden@ra.uvic.ca | ------------------------------------------------------------------------------- ------------------------------ Date: 27 Mar 93 01:58:42 From: Jeff Moersch Subject: Space Posters, and where to get them? Newsgroups: sci.space In article <1993Mar25.102746.1@aurora.alaska.edu> nsmca@aurora.alaska.edu writes: > Wiers question, where is a good place to get Space Posters??? I know that many > people seem to like posters of movie stars and such, beer (sexy girls okay), > and other such things, I was wondering if someone has any Space Posters and > where to get them? > > == > Michael Adams, nsmca@acad3.alaska.edu -- I'm not high, just jacked If you're interested in really high-quality photographic prints of space-related things (especially planetary posters), I can recommend an outfit called "Planetary Arts and Sciences". The owner of this business is a planetary scientist here at Cornell (and also a friend of mine) who does this work on the side. He has gone back to the original digital image data from JPL probes and reprocessed everything to get color images which look *a lot* better than the usual stuff available through NASA. The lithographs available from NASA are usually press release versions that were slapped together in a hurry for post-flyby news conferences (I know - I've done a few of them!), whereas these images took several weeks to process/enhance and print. The company has a toll free number: 1-800-272-1154, and they have a little glossy catalog that shows what stock they have available. There may be a small charge for the catalog - I don't remember. They also have done special request projects (like large, wall-sized prints) in the before, so if you have an interest in that, you should ask. Jeff Moersch Astronomy and Space Sciences Cornell University P.S. Sure this is a plug, but it answers the question... Besides, it isn't my business! ------------------------------ Date: Sat, 27 Mar 1993 04:42:12 GMT From: Henry Spencer Subject: Uplink/downlink rates Newsgroups: sci.space In article <1993Mar24.164640.2385@head-cfa.harvard.edu> willner@head-cfa.harvard.edu (Steve Willner) writes: >... The DSN receivers are the best that can be built... Actually, not so. (I said the same thing a year or two ago, and the radio astronomy people corrected me!) The DSN receivers are very good, but they are no longer the absolute best. The latest radio-astronomy ones are better, although I expect DSN will be upgraded at some point (perhaps soon, given the Galileo situation). -- All work is one man's work. | Henry Spencer @ U of Toronto Zoology - Kipling | henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 27 Mar 1993 07:00 UT From: Ron Baalke Subject: Uplink/downlink rates Newsgroups: sci.space In article , henry@zoo.toronto.edu (Henry Spencer) writes... >although I expect DSN will be upgraded at some point (perhaps soon, given >the Galileo situation). The DSN upgrade is in progress and has been proceeding along for 3 or 4 years now. ___ _____ ___ /_ /| /____/ \ /_ /| Ron Baalke | baalke@kelvin.jpl.nasa.gov | | | | __ \ /| | | | Jet Propulsion Lab | ___| | | | |__) |/ | | |__ M/S 525-3684 Telos | Don't ever take a fence /___| | | | ___/ | |/__ /| Pasadena, CA 91109 | down until you know the |_____|/ |_|/ |_____|/ | reason it was put up. ------------------------------ Date: 26 Mar 1993 21:22:20 -0500 From: Pat Subject: Why use AC at 20kHz for SSF Power? Newsgroups: sci.space In article <1993Mar24.175055.27927@mksol.dseg.ti.com> mccall@mksol.dseg.ti.com (fred j mccall 575-3539) writes: >In <1odi0sINNcn4@access.digex.com> prb@access.digex.com (Pat) writes: >>rather then Fred McCall venting his spleen, a much higher level |what you most deserve. Go ahead, Pat. Try posting like an adult for |a while without all the ad hominem attacks on people and insulting | Well, Gee Fred. At that point, I had waited something around 2 weeks for someone from a NASA or SSF contractor site to pick up a defense. McKissock had popped up, thrown a few vague terms around and then dissappeared. I had wanted to see something a little more solid, and he seemed to be hiding from the debate. You may want to defend your Namesake station, but I wasn't interested in your speculation. I wanted to hear something from someone who actually works there. Your insinuations that i was making up allegations, didn't help the level of discourse. | |No, the paperwork was *not* good because the requirements were bad. | Of course, people were so busy working on the paperwork, no-one ever bothered to see if the requirements were any good. Were asses kicked for this? were people taken to task for missing something as simple as a requiremnt for a testbed? No, Probably not, but if these two centers can't co-ordinate enough to make a simple test bed and test article conform, what makes you Fred McCall, think that they will get it together for one of the largest integration efforts in engineering history? |>Ah, the but the paperwork was good, the requirements document |>had been flowed down into each sub-contract and a full tracability |>matrix had been done. How could it not work. | |Bad requirements. Do you know *anything* about engineering, Pat? | Usually the lead requirement is that the system work. Do you know anything about making Products? |>How did skylab cope with the DC problems? Skylab was |>fairly big, it had several arrays, and various power demands. |>Anyone have the historical background? | |Skylab was small and underpowered compared to what SSF was supposed to |be. | Skylab also Flew. Which SSF, looks unlikely to do at any time this century, unless serious changes occur. The Tiger Team review, now has it Down to Space Station F. |>Also, despite what GD may say about DC power complexity, Somehow |>it does seem to power a large fraction of our industrial equipment, |>every vehicle in america, and numerous LARGE transportation |>systems. I would guess that the complexity of the power |>system of METRO is at least as large as that of SSF. | |Gee, and here all this time I thought my vehicle was powered by an |internal combustion engine, except for a very small electrical system. |What kind of car are *you* driving, Pat? | Last time I checked, all my cars sub-systems used 12VDC. Let me know when your car starts running on 20KHz. |>|The AC Alternative | |Well gee, Pat, you must live in a real chicken-and-egg dilemma for |your entire life. It ain't gonna show up in the catalogs until it's |being used, and you don't want to use it until it shows up in the |catalogs. Back to the caves, boys! | No, But the school of engineering I come from says, that if you can order it froma catalog, Faster, Cheaper and better then you can make it custom, you are a FOOL to try to make it custom. You seem to put the most negative connotations on to the legitimate engineering criticism I raise. I may prefer, proven somewhat crude mechanics, but I'll bet you my philosophy will get more hardware up, then your Gold Plated, Boondogle Charging let's waste money, the more the merrier philosophy ever would. |>Actually, i would imagine that 20Khz transformers would not |>be terribly efficient, the Reactance of these is proportional |>to frequency. I'd imagine the impedance losses, may make High Frequency |>Transformers actually imprcatical. DSoes anyone have the idea |>of the Inductance of a 50 KW transformer coil? assume 208/480 volts, |>three phase. | |Somehow I suspect that the people doing the studies probably looked at |this issue, and I suspect they used a better tool than "Pat's |imagination". | Then Maybe Dave McKissock, wouldn't mind posting some of these analyses. I mean, I imagine they were done? | |>| |>|AC System Frequency |>| |>|Since it is now clear that AC has many advantages and is the | |>I don't know why anyone is worrying about delivery costs, |>after all, the shuttle flies up with dead head space, and |>that's free. I mean if they have to haul up the module, |>why worry about some extra weight, i mean it's marginal |>cost is only a little hydrogen. :-) | |If this were convincing logic, we'd be hauling whatever we pleased to |orbit, since it would always fit in the "deadhead space". The point, |Pat, is that if you don't have to lift X pounds of one thing you can |lift X pounds of something else if you want to. | Fred, you must have a poor memory, or a short attention span. In another thread flame, Dennis wingo was arguing that spare mass wasted on a fueling flight was ir-relevant because it could be billed at the marginal cost for extra lift. He was roundly flamed for that suggestion. I was merely using it to sarcastically justify a heavier electrical system weight. | |>|there isn't a strong size and weight driver, pushing us above |>|that frequency region. If we're conserned about a manned |>|vehicle, we should probably move to at least 20 khz to get the |>|power line noise above the audio region. (That 400 Hz whine |>|in my airliner stereo head-set is really annoying if I have to |>|listen for very long). |>| |>I've worked in lots of industrial plants with louder things then |>some power noise. Seriouly, i can't believe this would ever be |>a major criteria. | |Yes, but one would like not to have all that loud racket and vibration |on a space station. Background noise *better* be a serious criteria, |since people are going to be stuck in that environment for months at a |time. | They are astronauts. They can take it. It's no worse then the constant low-level whine emitted by the Net:-) |>|But how high can we comfortably go? The answer comes from the |>|DC power processing folks. When we design DC to DC converters |>|in this power range, readily-available component technologies |>|for semiconductor switching devices, transformers, capacitors, |>|etc. limit us to a maximum frequency of about 50kHz. So if we |>|stay comfortably below that, and continue with our initial |>|thought to chose something close to 20 kHz, we can expect |>|to find a good selection of qualified power components and |>|materials, and a good body of design data, with which to |>|implement hardware designs. |>| | |>Gee, I look in a lot of electrical industry magazines, and I see |>a lot of articles on problems caused by DC power processing. |>A large number of PC's plugged into one room, generate enough |>non-linear current and harmonic noise to be destroying conductors, |>transformers and switch gear. | |Gee, your point? | The article cites the number of qualified components available to do 20KHz power work, and my literature, mostly complains about problems related to high frequency. |>Plus, i have to wonder what kind of body of design data exists at |>50 KW. | |>So how does efficiency wise a DC-DC converter stack up against |>a motor/generator pair. For large power generation i'd imagine |>it would be a lot more reliable, and able to handle transients a lot |>better. | |One would like to reduce high-inertia rotating equipment to a minimum |on a space station, Pat. Otherwise, you spend a lot of fuel |cancelling out spins imparted to the station by rotating equipment. Given the presence of the alpha-gimbels, the motor generator will quite nicely complement the torque needed by the main axis of the station. If anything, it would help reduce the load on the G&N System, providing a constant spin to these elements. |And solid state is always more reliable than anything involving moving |parts, as well as easier to repair/replace. The equipment I used to Not neccesarily. Depends on the quality of the Electronics, and the mechanicals. |work on in the Navy took the 440 3-phase from ship's supply, used a |motor generator set to get DC (what we called 'quasi-DC', actually), |then used a solid state inverter set to convert it to high-current DC. |This was then reconverted to AC elsewhere in the system as needed. >Would you consider 1/4 Megawatt as 'high power'? > Reasonably. > >>Does that mean we are looking at 50,000 dollars/watt >>costs deployed? > Did your Naval system, cost $50,000/Watt? [ Citation List deleted] > > >>Interesting, most of these papers are either NASA reports, or >>IECEC papers. Kinda a small community. > >Well, that sure invalidates everything, doesn't it, Pat? No, But it sure doesn't show the technology being used by a large community. Means you have to be your global test bed. Installed Base, is oftentimes a significant engineering criteria. ------------------------------ End of Space Digest Volume 16 : Issue 377 ------------------------------