Date: Mon, 1 Mar 93 05:47:59 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V16 #244 To: Space Digest Readers Precedence: bulk Space Digest Mon, 1 Mar 93 Volume 16 : Issue 244 Today's Topics: Apollo Moon Missions ? Battery help needed! Beamed power transmission on Mars? Easy Replumbing for Fred? Getting people into S Hopkins Leaks (was Re: Blimps) HST daily reports available Nobody cares about Fred? Optical interferometry and coherence length payload return from Fred SOLAR gravity assist? NOPE. Spaceflight for under $1,000? SSF Resupply (Was Re: Nobody cares about Fred?) (2 msgs) SSTO vs. Shuttle promises (was Re: Refueling in orbit) Stupid Centaur Tricks The Future of Fred 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: 26 Feb 93 16:19:30 GMT From: 00acearl@leo.bsuvc.bsu.edu Subject: Apollo Moon Missions ? Newsgroups: sci.space In article <1mh72oINNdu8@elroy.jpl.nasa.gov>, tjt@Jpl.Nasa.Gov (Tim Thompson) writes: > I am ignorant, I admit it. My memory has failed. Can someone refresh my > tired brain cells, and tell me (us) which Apollo mission to the Moon was the > last one? There couldn't have been too many. > > Mille Mercis It was Apollo 17. I'm a bit fuzzy myself on the details, but I think that was launched in December of 1972. The crew was Eugene Cernan, Harrison Scmidt and (I'm REALLY guessing this last one) Jack Lousma. aaron christopher ------------------------------ Date: 26 Feb 1993 16:29 EST From: Pat Loyselle Subject: Battery help needed! Newsgroups: sci.space,sci.electronics,sci.aeronautics,sci.chem,sci.engr In article <1993Feb25.214437.28051@cbfsb.cb.att.com>, rizzo@cbnewsf.cb.att.com (anthony.r.rizzo) writes... > >> >You might consider using a fuel cell. NASA already uses a bunch >of them on the shuttle. So safety should be less of a problem. >A fuel cell also might have the appropriate energy density. >All you'd have to do is provide the fuel cell with the appropriate >supplies of O2 and H2, in the correct ratio of coarse. The output >will be H2O + e. > >Tony Rizzo Fuel cells are great but the problem is, if this experiment is a get-a-way special there might be volume constraints and with the tankage for the H2 and O2 you might exceed the volume allowed. You'd have to do a trade-off analysis based on the requirements to see if you'd come out ahead by using fuel cells instead of batteries Pat ---------- Patricia Loyselle seloy@mars.lerc.nasa.gov NASA Lewis Research Center (216) 433-2180 Cleveland, Ohio 44135 ------------------------------ Date: Fri, 26 Feb 1993 19:47:29 GMT From: Gary Coffman Subject: Beamed power transmission on Mars? Newsgroups: sci.space In article <0bcV02bN38DY01@JUTS.ccc.amdahl.com> haw30@macaw.ccc.amdahl.com (Henry A Worth) writes: >In article <1993Feb25.153515.18754@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes: >> In article haw30@macaw.ccc.amdahl.com (Henry A Worth) writes: >> > >> > It's really a shame certain parties rejected beamed power on Earth as >> >unsafe without any real study or basis in fact, simply on the basis of >> >technophobia, while at the same time turning a blind eye toward the very >> >significant, and quite possibly greater, negative impacts of existing >> >power sources (better the devil you know then the angel you don't?). >> >> Hidden, or not so hidden, technophobia is the reason certain back to >> the dark ages tree huggers hate SPS systems. But there are reasons >> for technophiles to disparage the systems as well. Their net efficiency >> is low, their dependence on untried complex space technologies is high, >> and their projected costs are astronomical. Doing things because they >> are neat technical exercises just isn't good enough when the object is >> as important as bulk power supply for a nation. >> >> Gary >> > > An SPS does not need high efficiency to be effective, just as long as >the losses don't heat the atomoshere more than the systems they replace. That's only part of the equation, the ground side. The primary reason efficiency is important is the way it impacts on orbit costs. The lower the system efficiency, the larger the spaceborne component has to be. All that mass, and much of it is complex semiconductor mass, that has to be placed in orbit, assembled, and operated is what drives SPS costs. The ground side costs are fairly insignificant. At current system efficiencies, to get 1000 MWe to the transmission grid on the ground we need a SPS that's a square 113 km on a side. And that's just to replace one medium sized terrestrial power plant. >I'm not saying that SPS is the ultimate answer to Earth's energy problem. >just that it was unfortunate it, and other alternatives, have been rejected >with as little study as they have. It's not like we have to build one today >(that's the root of the problem, our society never plans, it just reacts to >crisis), some low level on-going research may have addressed some of the >problems and have more fully quantified the risks and benefits, so that >a rational, informed decision could have been made. It's not like existing >systems are without significant negative impacts (can you name a power >system that dumps significant amounts of radioactive isoptopes into the >atmosphere in the course of normal operations, resulting in a number of >lung cancers deaths in the general population every year, and BTW its not >nuclear), many of the costs related with existing systems are not directly >reflected at the gas pump or in your monthly power bill, many will end >up being paid by our children and their children. Yes I know that coal fired plants are damaging. Their routine radioactive release is much higher than that of nuclear plants, plus all the other chemical pollution they produce, and the CO2 they produce. However, there are terrestrial alternatives to fossil fueled plants whose economics are much closer to reality than SPS. Nuclear and hydro are already significant players. IMHO the most promising undeveloped power source is deep dry geothermal power. Anywhere you dig deep enough there is heat energy waiting to be tapped. Plus there is ocean thermal, and to a lesser extent direct solar and wind. The latter two are still looking for adequate storage methods to make them suitable for baseload needs. Gary -- Gary Coffman KE4ZV | You make it, | gatech!wa4mei!ke4zv!gary Destructive Testing Systems | we break it. | uunet!rsiatl!ke4zv!gary 534 Shannon Way | Guaranteed! | emory!kd4nc!ke4zv!gary Lawrenceville, GA 30244 | | ------------------------------ Date: Fri, 26 Feb 1993 20:30:14 GMT From: Gary Coffman Subject: Easy Replumbing for Fred? Newsgroups: sci.space In article <1993Feb26.135714.13574@cs.ucf.edu> clarke@acme.ucf.edu (Thomas Clarke) writes: >In article <1993Feb25.134448.17484@ke4zv.uucp> gary@ke4zv.uucp (Gary Coffman) >writes: >> ... Shuttle offloads it's >> excess water and Freedom electrolyzes it with solar cell excess power >> and stores it for stationkeeping burns. *That* was clever, but had too >> high an upfront cost for Congress to swallow. The thruster development >> had to be funded, on orbit electrolyzers had to be developed, and water >> transfer systems designed. Nothing earthshaking, but impossible without > ^^^^^^^^^^ >> the upfront funding assured. > >In article <1993Feb25.145255.18392@ke4zv.uucp> gary@ke4zv.uucp (Gary Coffman) >writes: >> ... it would be a simple matter to *add* valving >> and fittings to a replacement pack to allow on orbit fueling at >> any time. We aren't locked in to module replacement for the entire > ^^^^^^^^ >> 30 year life of the station. If the Shuttle replacement can't >> convienently recycle thrusters, we can easily modify them not to >> require recycling. > >Me thinks I detect a contradiction. One type of plumbing modification >seems to require a large up-front investment, another is done easily >at any time. The former requires developing H2/O2 thrusters, on orbit electrolyzers, and water transfer systems. None of that has been done. The latter only requires a couple of couplings, some valving, and a pump or pressure driven transfer system built into the refueling tankage. All of this, aside from the actual connections to the thruster module, has already been flown on flight 41-G. Gary -- Gary Coffman KE4ZV | You make it, | gatech!wa4mei!ke4zv!gary Destructive Testing Systems | we break it. | uunet!rsiatl!ke4zv!gary 534 Shannon Way | Guaranteed! | emory!kd4nc!ke4zv!gary Lawrenceville, GA 30244 | | ------------------------------ Date: 26 Feb 93 09:55:00 GMT From: Roland Dobbins Subject: Getting people into S Newsgroups: sci.space JL>Could that be the vehicle commonly called the flying Bumble Bee, wh JL>clai to fame in the ordinary world is the vehicle that opened the s JL>and each episode of the six million dollar man. If I recall correct JL>was aeronautically considered to be unflyable, but flew anyway and JL>for a while touted as a great instrument for flight to and from low JL>orbit. It finally crashed on descent when it touched down and did a JL>up unfortunately a Helo was in the way and the two collided as the JL>goes. I think That its prototypes and other s are still on display JL>the yearly aeronautical show at Edwards airforce base. As I recall, that particular lifting body was called the HL-10, and it was most certainly _not_ designed *not* to fly . . . . --- . Orator V1.13 . [Windows Qwk Reader Unregistered Evaluation Copy] ------------------------------ Date: Fri, 26 Feb 1993 23:56:12 GMT From: "Phil G. Fraering" Subject: Hopkins Leaks (was Re: Blimps) Newsgroups: sci.space higgins@fnalf.fnal.gov (Bill Higgins-- Beam Jockey) writes: >If we're becoming *completely* pedantic, a "zeppelin" is a rigid >dirigible airship built by the Count's method; there are other >possible structures. Nearly all the rigid airships ever built were >zeppelins (130 of them? Or was it 130 German ones and three American >ones?) The British R100 and R101 are examples of non-zeppelin rigid >airships. I'm not sure in what way, but two of the rigids built in the US, the Akron and Macon, were built differently from the standard German design, and were judged to be better except for that little modification the FAA insisted had to be made to the tail design (which was ultimately responsible for the loss of both craft, one with heavy loss of life, and the other with only light loss of life). >For the following paragraph we have the headline "Hopkins Leaks News >of Balloon Project." (Or maybe it's just a trial balloon?) >> Lighter than air vehicles do indeed have lots of potential for Mars, though the >> difficulties can't be ignored. It is however _far_ easier than floating a >> balloon on Jupiter, something Bill Higgins and I have been puttering around >> with. >Not much lately, though-- haven't had the time. Most weekends I can't >even *get* to Jupiter... Doesn't your mom and pop live there? >Oh, by the way (though this quest failed on sci.aeronautics last >fall): We're looking for a textbook that details balloon design! >Anybody know a good one? I don't know, but _Sky Ship: The Akron Era_ was a good book on airships. I know you'll just _love_ the ZMC-1... >Moira Higgins on astronomy: Bill Higgins >"I can always find Orion. Fermi National Accelerator Laboratory >Besides that the Moon Internet: HIGGINS@FNAL.FNAL.GOV >is my only other specialty." Bitnet: HIGGINS@FNAL.BITNET I'm doing better than her then, I can even find the sun. Although it has to come out first. I hear it might if the weather keeps improving. -- Phil Fraering |"...drag them, kicking and screaming, pgf@srl02.cacs.usl.edu|into the Century of the Fruitbat." - Terry Pratchett, _Reaper Man_ ------------------------------ Date: Sat, 27 Feb 1993 01:07:22 GMT From: gawne@stsci.edu Subject: HST daily reports available Newsgroups: sci.space Just read Ken Jenks' offer to post the MSFC morning reports, and thought that I'd mention that the HST daily activity reports are available in the newsgroup sci.astro.hubble. It's a moderated newsgroup BTW. We discussed the possibility of crossposting it to sci.space.news here at the STScI a while back, but there didn't seem to be much need for that. If there's anyone out there who would like to see these daily reports of HST activity but can not get the sci.astro. hubble newsgroup at your site, please let me know. The HST reports consist of a listing of the day's science activity followed by the day's engineering activity. They're likely to be fairly uninteresting for non-astronomers. -Bill Gawne, Space Telescope Science Institute "Forgive him, he is a barbarian, who thinks the customs of his tribe are the laws of the universe." - G. J. Caesar ------------------------------ Date: Sat, 27 Feb 1993 00:36:50 GMT From: Nick Janow Subject: Nobody cares about Fred? Newsgroups: sci.space munoz@sweetpea.jsc.nasa.gov (tomas o munoz 283-4072) writes: > You can't just send stuff to orbit and leave it there. That's MSFC's > booster mentality. It seems a shame to throw away all the energy that has been invested in bringing that mass out of the gravity well. If it can't be used immediately, store it in lightweight containers (a big bag). It might have a temporary use as shielding. It also makes the station more stable. Someday, when the station is large enough to reprocess materials, that "trash" will be a valuable resource. If nothing else, you can lower the bag of trash on a tether and release it to boost the station. -- Nick_Janow@mindlink.bc.ca ------------------------------ Date: 27 Feb 93 00:12:47 GMT From: Tim Thompson Subject: Optical interferometry and coherence length Newsgroups: sci.astro,sci.space From hausner@qucis.queensu.ca (Alejo Hausner): > Ok, I understand that radio interferometry means measuring the > difference in arrival time of the same wavefront at two different > telescopes. But doesn't that mean that the wavefront is the same > wavefront at both places? I remember when in physics class when they > were talking about lasers, that light travels in photons, little > packets. An ordinary light bulb emits lots of photons, but doesn't > emit them all in phase. They leave randomly. In a laser, one photon > triggers the emission of lots of other photons, and they are all in > phase. > Starlight is like incandescent bulb light, isn't it? Its photons > are all randomly out of phase. So to do interferometry, the two > telescopes (or more than two, as you point out) must all be looking at > the same photon, mustn't they? If photons aren't very big, then you > can't space the telescopes too far from each other, otherwise they are > guaranteed to be looking at different photons. > I don't understand how those interferometers do it. No, the two different antennae are not sampling the same photon. If my understanding of QM is reasonable, it is not possible for one photon to share energy between two different antennae. After all, if the energy is quantized in photons, and each antenna gets a fraction of a photon, then a photon is really not a quantum. Yes, all of the antennae sample the same wave front, but this is strictly a classical problem, QM and photons are not required, only Maxwell's equations. Also, the sources are so far away, that the incident waves are plane waves. It is not so that sampling the same wavefront means sampling the same photon. There are books about radio/optical interferometry, but the level of sophistication is pretty high, so one must be prepared to work, to understand the details. Most books on radio astronomy, like Kraus, have chapters on interferometry as well. --- ------------------------------------------------------------ Timothy J. Thompson, Earth and Space Sciences Division, JPL. Assistant Administrator, Division Science Computing Network. Secretary, Los Angeles Astronomical Society. Member, BOD, Mount Wilson Observatory Association. INTERnet/BITnet: tjt@scn1.jpl.nasa.gov NSI/DECnet: jplsc8::tim SCREAMnet: YO!! TIM!! GPSnet: 118:10:22.85 W by 34:11:58.27 N ------------------------------ Date: 27 Feb 93 00:01:25 GMT From: "Phil G. Fraering" Subject: payload return from Fred Newsgroups: sci.space henry@zoo.toronto.edu (Henry Spencer) writes: >Why not? Most of it will be more useful up there than down here. And >a heavier station is *better*, because it reduces the frequency with >which reboost is needed; even trash is more useful as station ballast >than as return cargo. You could also reboost by dumping it into the atmosphere with a tether... But the main reason you can't just leave stuff in space: someone might start using it, and we don't want anything that crass to happen. >C++ is the best example of second-system| Henry Spencer @ U of Toronto Zoology >effect since OS/360. | henry@zoo.toronto.edu utzoo!henry -- Phil Fraering |"...drag them, kicking and screaming, pgf@srl02.cacs.usl.edu|into the Century of the Fruitbat." - Terry Pratchett, _Reaper Man_ ------------------------------ Date: 27 Feb 93 03:21:29 GMT From: Bill Higgins-- Beam Jockey Subject: SOLAR gravity assist? NOPE. Newsgroups: sci.space,alt.sci.planetary In article <1mm26fINNqbn@news.aero.org>, shag@aero.org (Robert M. Unverzagt) writes: [scathing quantitative denial that the Sun helps you get to Pluto deleted] > > In the orbital mechanics world this is called a bi-elliptic > transfer with interior conjunction. > > Can the person who originally claimed a benefit for this please > explain again? Maybe I missed something, but this sure sounds > like what you were talking about. *Sigh*. Okay, I seem to have confused everybody. And I'm probably confused myself. I was responding to a suggestion that a solar gravity assist might help a Pluto mission. I found out that a "solar gravity assist," contrary to conventional wisdom, is not impossible but just barely possible. This is intriguing. Let's forget about going to Pluto, okay? The core of my question was, "How much delta-V can you pick up by skimming the surface of the Sun in a gravity-assist manuever?" Barycenter of Solar System (if you think the world revolves around you, you probably live here) | Sun v (-------------Cs-------------) . to Jupiter ---> Cs is the center of the Sun, 1 ASCII character = 47,000 km Again, we are assuming here that the solar system consists only of the Sun and Jupiter, to keep things simple. The center of the Sun describes a circle around the barycenter once every Jovian year. Therefore it moves 78.2 centimeters per second in the "solar system rest frame." The right answer, pointed out by several people, is that when a small mass "scatters" off a large one, it gains at most twice the speed of the large one. As any alleged physicist should have known. :-( So under the most favorable encounter conditions, our probe can pick up about 1.56 meters per second, jogging speed. As Jon Thaler put it in e-mail, "No significant boost is possible, unless one wants to jog to Pluto." I claim that this is consistent with intuition, which tells you that this is a ridiculous way to pick up energy and will not be useful. But I wasn't sure how to calculate it, so I posted it on the Net, hoping that it would be read by somebody who can say "bi-elliptic transfer with interior conjunction" three times real fast. Like you, Shag. Kepler: "Did you know that Tycho, | Bill Higgins, Beam Jockey my boss, had an artificial nose?" | Fermi National Accelerator Laboratory Galileo: "An artificial nose! | Bitnet: HIGGINS@FNAL.BITNET How did he smell?" | Internet: HIGGINS@FNAL.FNAL.GOV Kepler: "Terrible!" | SPAN/Hepnet: 43011::HIGGINS ------------------------------ Date: Fri, 26 Feb 1993 23:48:38 GMT From: gawne@stsci.edu Subject: Spaceflight for under $1,000? Newsgroups: sci.space In article <25FEB199314460941@elroy.uh.edu>, st1r8@elroy.uh.edu (Guillot, Burt J.) writes: > In article , henry@zoo.toronto.edu > (Henry Spencer) writes... >>Yes, but those computers and that memory will survive conditions which >>would turn your PC into a paperweight. When you can't get home without >>them, you're a bit fussier about computer quality than the MSDOS crowd >>usually is. > > So what were to happen if John Doe takes his 386 to orbit with 4 megs > of memory on board with, say, a 40 megabyte hard disk. Would it > affect the memory only or the storage of the hard disk as well? And, > what is "it"? Cosmic ray flux. Various other high speed ions zipping around. When they go flying down the crystal lattice of silicon they can do a lot of damage. The magnetic storage media, like disks and tape, are less susceptable to damage by ions but are not immune. All the VLSI chips would need to be hardened, and lots of bit checking algorythms included to guard against ionization effects. -Bill Gawne, Space Telescope Science Institute "Forgive him, he is a barbarian, who thinks the customs of his tribe are the laws of the universe." - G. J. Caesar ------------------------------ Date: 26 Feb 93 14:40:40 From: Steinn Sigurdsson Subject: SSF Resupply (Was Re: Nobody cares about Fred?) Newsgroups: sci.space In article <1993Feb26.205533.6505@iti.org> aws@iti.org (Allen W. Sherzer) writes: In article <26FEB199300340539@judy.uh.edu> wingo%cspara.decnet@Fedex.Msfc.Nasa.Gov writes: >You are also assuming a freight value charge that even trucking companies >do not use. How about an experiment to see if that is true. You claim that Shuttle shouldn't charge or account for transport costs for the engines since there will be deadhead space anyway. Now go out and buy a brick. Wrap it in paper and see if you can find a company who will ship it to me for free. If they balk, explain to them how they have deadhead space and so it doesn't matter. If you manage to do this, I'll accept your arguement. Well, Allen, I could ship you a brick FedEx (or USPO express) (COD of course ;-) - you will be rather astonished to find that the charge for shipping the brick will not be the cost of the truck+flight from here to there, rather they'll charge a marginal cost figuring that not only can they ship a few other bricks in the same direction at the same time, but the cost of salary etc for the people involved is a constant overhead and is amortised over all their activities - even FedEx is not going to fire a driver if I change my mind and don't ship the brick. Except that with automated refueling we can use $35 million Delta's instead of half a billion $$ shuttle flights for refueling. If we re-fueled automatically and left the thrusters in place we would go from ~50 shuttle flights costing $25 billion and go to ~50 Delta flights costing less than $2 billion. A savings of over $23 billion. Allen, what is the development cost of learning how to do automatic refuelling and over how many flights will you amortise it? Do you propose flying fewer shuttle flights without the resupply (in which case the marginal cost on the remaining flights increase) or should NASA redirect those flights to another purpose? Or should they simply fire 20,000 support staff - in which case what is the cost of severance (including any welfare support to the government)? You make good points, but your accounting methods are, shall we say systematically skewed. | Steinn Sigurdsson |I saw two shooting stars last night | | Lick Observatory |I wished on them but they were only satellites | | steinly@lick.ucsc.edu |Is it wrong to wish on space hardware? | | "standard disclaimer" |I wish, I wish, I wish you'd care - B.B. 1983 | ------------------------------ Date: 26 Feb 1993 19:41:18 -0500 From: Pat Subject: SSF Resupply (Was Re: Nobody cares about Fred?) Newsgroups: sci.space In article <1993Feb26.210248.7355@iti.org> aws@iti.org (Allen W. Sherzer) writes: |In article <1993Feb26.192024.991@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes: | |>I'm saying the reality of SSF upfront funding (remember the chart |>you so convienently deleted?) is so constrained that we're using |>hydrazine thrusters because development money wasn't available for |>H2/O2 thrusters. | |Who said anything about H2/O2 thrusters? Even if you wanted to use |H2, the RL-10 should be just fine. | Um. Allen. I think Gary has me confused with you. I had been talking about how ET Dregs FUel recovery would be useful for Centaur, and That SSF management was so inept, that they were using Hydrazine intead of Methane thrusters. I think he blended the two ideas together and shoved the reply at you. My point was given SSF was going to produce waste CO2, you could carry upa small supply of Hydrogen, and convery CO2 -> CH4. then with the released oxygen run thrusters. although, if the fuel cells produce water, you might crack that electrically, and then have all your feedstocks. pat. I agree with you on the concept of automated docking vehicles, it's just cheaper to make fuels in orbit with leftovers then to haul them up in tankers. I'd reserve the tankers for astronaut consumables, life support spares, experimental gear.... ------------------------------ Date: 26 Feb 93 21:31:10 -0600 From: Bill Higgins-- Beam Jockey Subject: SSTO vs. Shuttle promises (was Re: Refueling in orbit) Newsgroups: sci.space In article , steinly@topaz.ucsc.edu (Steinn Sigurdsson) writes: > SSTO fans would do well to re-read the history of some > modern launchers, including the original Shuttle concept and how > it evolved. Might make some a little less firm in their cost estimates > and a little less ready to cut other transport systems before the > SSTOs have demonstrated operational ability... in particular Allen > might be astonished to realise that some of his DC claims look > like they were cut out from a NASA report circa 1971-1974 providing > STS claims ;-) Oh, yeah, right, I'm sure Allen's never heard THAT criticism before. Bill Higgins, Beam Jockey | "Based on the antiproton Fermi National Accelerator Laboratory | decay, I would estimate the Bitnet: HIGGINS@FNAL.BITNET | incident occurred Internet: HIGGINS@FNAL.FNAL.GOV | within the last 4.3 hours." SPAN/Hepnet: 43011::HIGGINS | --Mr. Data ------------------------------ Date: 26 Feb 93 23:35:12 GMT From: "Phil G. Fraering" Subject: Stupid Centaur Tricks Newsgroups: sci.space davem@ee.ubc.ca (Dave Michelson) writes: >Centaur continues to evolve. AW&ST recently carried an item about General >Dynamics looking for funding to develop a single engine version of the >Centaur to increase both payload (marginally) and reliability. I guess >price would also decrease slightly as well since it's easier to test and >verify one engine than two. I don't understand why it's more reliable to have a single engine than two engines with a gimballing system that would allow it to function on one engine. I guess they're just into newspeak (half the engines, half the chance of failures!). Anyone else concur? -- Phil Fraering |"...drag them, kicking and screaming, pgf@srl02.cacs.usl.edu|into the Century of the Fruitbat." - Terry Pratchett, _Reaper Man_ ------------------------------ Date: 26 Feb 1993 16:43 CST From: wingo%cspara.decnet@Fedex.Msfc.Nasa.Gov Subject: The Future of Fred Newsgroups: sci.space In article <1993Feb26.141738.13904@cs.ucf.edu>, clarke@acme.ucf.edu (Thomas Clarke) writes... >wingo%cspara.decnet@Fedex.MSfc.Nasa.Gov writes: > >> the battle for the power system that pitted >> the DC power system against a 20 khz AC system. This battle was won and >> is one of the unknown things done to build a good station. > >20kHz !?! DC ?!? What is this, the year 1880. >Scientific gear works off 60Hz AC, may 400 Hz AC if it is aircraft, >or 12V DC if it is portable. > >Why would NASA pick something that requires every experimenter >to have equipment specially made? No wonder Fred is so expensive. > >I suppose the carbon-fiber equipment racks are something other >than the 19 inch standard relay rack also. > >Wait. Maybe I'm flying off the handle again. Could the 20kHz just >be an engineering convenience to be able to use small light transformers >in power distribution? Might NASA have provided state-of-the-art power >convertors to give experimenters 60Hz AC? > > Yes you are indeed flying off the handle. When NASA Lewis first was given responsiblity for the electrical power system architecture on SSF they came up with this utterly weird 20Khz AC power distribution systeem. The theory was that it was lighter and more efficient. Well NASA (lets say center b) wanted to keep the Skylab type DC power system due to its simplicty and ease of integrating experiments. Due to congresional pressure center b was overruled and development work on 20Khz went ahead. When a demonstration of the 20Khz system was developed and brownt to center b it was connected in the same room where the center b proposed 75KVA DC system was already up and operating. (Actually it had been there in one form or another since Skylab). Well when the 20Khz system was powered up all of the terminals in the room locked up! All of their computers also went south from the rich RFI environment that the system produced. Needless to say the 20Khz system soon went the way of the dodo bird. The moral of the story is keep congress out of the engineering design process. Also the SSF racks will be common with SpaceLab and SpaceHab, so yes you can go home and sleep well tonight, knowing that NASA is not completely a bunch of incompetents. Dennis, University of Alabama in Huntsville ------------------------------ End of Space Digest Volume 16 : Issue 244 ------------------------------