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, 28 Apr 90 03:22:55 -0400 (EDT) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Sat, 28 Apr 90 03:22:07 -0400 (EDT) Subject: SPACE Digest V11 #329 SPACE Digest Volume 11 : Issue 329 Today's Topics: Re: Decompression and 2001 Re: Fermi paradox Re: Rename the Earth? Re: PegBlimp (was Re: Pegasus launch from Valkyrie (or ...) Re: Space Station Distribution Frequency Re: Math/Science Education Payload Status for 04/27/90 (Forwarded) Re: Re: Rename the Earth? ---------------------------------------------------------------------- Date: 21 Apr 90 00:53:23 GMT From: news-server.csri.toronto.edu!helios.physics.utoronto.ca!physics.utoronto.ca!neufeld@rutgers.edu (Christopher Neufeld) Subject: Re: Decompression and 2001 In article <35682@ucbvax.BERKELEY.EDU> bwood@janus.Berkeley.EDU.UUCP (Blake Philip Wood) writes: > In being exposed to a vacuum >you certainly wouldn't want to simply open your mouth, because with no >air in your lungs you have only about 15 sec of consciousness. > I'd be surprised if this were the case for a person who was prepared for vacuum. Animal tests put the limit at about 15 to 30 seconds, but you can't tell a rat to hyperventilate. When I read the space rescue scene in _Earthlight_ I just had to try the described procedure myself. I had no trouble at all holding my breath for five minutes. Since I can't manage more than a minute and a half when I haven't prepared for it, surely preparation for vacuum can extend the conscious period by a factor of two or three. BTW, the "preparation" is to hyperventilate almost to the point of fainting, and Arthur C. Clarke recommends throwing one's arms back during the inhalation to increase lung filling. > Blake P. Wood - bwood@janus.Berkeley.EDU > Plasmas and Non-Linear Dynamics, U.C. Berkeley, EECS -- Christopher Neufeld....Just a graduate student | "Like most neufeld@helios.physics.utoronto.ca | intellectuals he is cneufeld@pro-generic.cts.com Ad astra! | intensely stupid." "Don't edit reality for the sake of simplicity" | Marquise de Merteuil ------------------------------ Date: 27 Apr 90 03:27:21 GMT From: crdgw1!sixhub!davidsen@uunet.uu.net (Wm E. Davidsen Jr) Subject: Re: Fermi paradox ------------------------------ Date: 27 Apr 90 01:57:11 GMT From: usc!cs.utexas.edu!mailrus!accuvax.nwu.edu!delta.eecs.nwu.edu!efstse@ucsd.edu (Serafim Efstratiadis) Subject: Re: Rename the Earth? So you wnat to rename the "Earth"? Very simple. Call it "Gea", its ancient Greek name. I can not think of a better name since you already use it, for example, in the word: geology = the study of this planet. (don't get confused with "geo-" instead of "gea-"; it's the Greek grammar!) Regards, Serafim. ------------------------------------------------------------------------------ Coming to you live from: NORTHWESTERN UNIVERSITY Once again, It's Saturday Night Live at the: Digital Image Processing Lab The Technological Institute, Evanston, IL 60208-3118, (708) 491-3039 ------------------------------------------------------------------------------- ------------------------------ Date: 25 Apr 90 15:32:02 GMT From: van-bc!rsoft!mindlink!a752@ucbvax.Berkeley.EDU (Bruce Dunn) Subject: Re: PegBlimp (was Re: Pegasus launch from Valkyrie (or ...) The velocity imparted by launching Pegasus from a moving airplane and the reduction in air drag by launching at altitude are not the only reasons for air launching. Another major cause of increased payloads is that rockets have a higher exhaust velocity in a vacuum than in air, and launching above much of the earth's atmosphere gives a substantial performance improvement to the first stage. -- Bruce Dunn Vancouver, Canada a752@mindlink.UUCP ------------------------------ Date: 27 Apr 90 09:57:02 GMT From: bfmny0!tneff@uunet.uu.net (Tom Neff) Subject: Re: Space Station Distribution Frequency I got this in mail (STRANGE indecipherable NASAmail header!) from Dave McKissock and am not sure whether he meant to reply or followup to the article, but the content looks like a followup and my attempt to reply bounced, so here goes. I apologize if it ends up being a duplication. --- forwarded message From: uunet!gemini.arc.nasa.gov!/C=USA/ADMD=TELEMAIL/PRMD=RESTON.SSFP/O=tmis/OU=8510/S=McKissock/ Date: Fri, 27 Apr 90 06:49 PDT Message-Id: FN:David,I:B,G:1) Well, somebody actually read my posting! I'll try to answer your questions (as I said in my posting, I am an Mechanical Engineer, so I'm really winging it on some of this stuff)... "Maximize Control Response" - I believe the desire is to maximize the response of the electrical power system (EPS) to changes in loads & faults. For example, if a load on the EPS were to short out, you would not want that fault to "backup" through the entire EPS & cause damage to many EPS components. You would want an EPS box that is close to the load to recognize that a fault exists & isolate the load (i.e. turn off the power to the load). I believe, from my conversations with the EE's around here, that the higher the frequency, the quicker the EPS can respond to fault conditions. "Minimize Mass" - I'll quote some numbers from a TRW Phase B report on their Distribution Trade Study... (while were at it let's throw in cost & end-to-end efficiency) 20 kHz 400 Hz, 3 Phase 200 Vdc 440 Vdc Mass 10,076 14,263 14,708 11,347 (lbs) Delta from 20 kHz 0.0 4,187 4,632 1,271 --------------------------------------------------------------- Cost ($M) 1034 1140 1046 1070 Delta from 20 kHz 0.0 +106 +12 +36 --------------------------------------------------------------- Efficiency (%) 87.1 88.0 85.1 87.8 "Delivery of energy under fault conditions" - Again, I'll quote from the TRW study "With regard to the safety issue, 20 kHz power distribution has the advantage against competing approaches in presenting minimal half-cycle energy and higher values of let-go current" (I believe let-go current is just what it sounds like, if you grabbed an uninsulated cable, the let-go current is the most current you handle & still be able to "let-go" of the cable. So the higher the number the better. A picture in the report clarifies the issue (y-axis is let-go current, milli-Amps, top curve is dangerous current, bottom curve is let-go threshold): 80 | * | | + 60 | | | 40 | * | * | + * * 20 | + | + + | 0 ---------------------------------------------------------------- 1 10 100 1000 10000 Frequency, Hz Soo, the point of the Figure is that the higher the frequency, the higher the dangerous current values & the higher the let-go threshold, which is good. To continue with the quote from the TRW report "Half cycle energy values are 31.25 joules and 0.625 joule, respectively, in 400 Hz and 20 kHz systems while let-go current is approximately 40 mA in a high voltage dc system, 80 mA or more for a 20 kHz system and approximately 20 mA in a 400 Hz system. Another point raised by Mr. Spencer in his original posting was that there was vast experience with 400 Hz in the aircraft industry. TRW also commented on that... (my editorial comments on the report are in parenthesis like this sentence is)... "Technical Readiness. The technical status of each option was reviewed and the findings point to a more mature system technology base in dc and 400 Hz systems but from the component technology status viewpoint, 20 kHz and 400 Hz options are essentially equivalent. (So 20 kHz loses in the "system" technology area but is even in the component technology) Breadboard 20 kHz equipment has been built and tested at power levels up to 25 kW. Both switchgear and transmission lines are currently under development. There is strong 400 Hz heritage derived from military and commercial aircraft and submarine programs. System characteristics are well understood but new power equipment would have to be designed and packages for space applications. (So althouth there is lots of experience with 400 Hz in ground applications, there isn't lots of flight qualified 400 Hz equipment lying around waiting to be used. So we would have to pay the development costs of 400 Hz hardware). A high voltage breadboard dc test bed effort is under way at NASA/MSFC. Switchgear designs have been breadboarded and tested by LeRC (200 Vdc to 1200 Vdc) with power levels up to 50 kW (800 Vdc). Power processor brassboards in the range of 3 to 12 kW have been built and tested with high voltage inputs on previous ion engine development programs." In summary, I would say that 20 kHz offered several advantages over 400 Hz and dc systems. 20 kHz presents less of a safety risk for the astronauts, is roughly the same cost as the other systems (some studies, like the one quoted above showed 20 kHz to be the least expensive, other studies showed slight advantages to 400 Hz or dc), weighs less than other systems, and has faster controls for quicker responses to faults in the power system. Hope this answers your questions about 20 khz --- end of forwarded message ------------------------------ Date: 27 Apr 90 20:13:32 GMT From: skipper!bowers@ames.arc.nasa.gov (Al Bowers) Subject: Re: Math/Science Education In article DAVISM@ATSUVAX1.BITNET ("Michael N. Davis") writes: >Hold on bucko, I just finished student teaching in math and received a >math education degree in December and I was well prepared to teach, over >prepared if you ask me. For my degree I was required to take 3 courses >of Calculus, a theoretical course in Algebra (Modern Algebra), >a theoretical course in Geometry, and a course in Matrices. Sounds about like what I needed to get my degree in engineering, but then I also needed differential equations, and advanced engineering math. Then they let me do things like physics and statics and dynamics and... Well you get the idea. From what you say it sounds like you are a one in a thousand, and unfortunately you get painted with the same brush in generalizations like I do when everyone rags on NASA. The point is that we have neglected to teach our kids the basics and allow them to be motivated. >My bottom line is that it takes the effort of two people for learning to >occur, one who is willing to teach and one who is willing to learn. >If either half doesn't make the effort then learning fails to occur. That's true, but if you can't motivate them to learn then it really doesn't matter what you cram into their heads. Did they end up being better people for all the work and effort you put in? >For anyone interested, I have a 360 line journal/flame about my student >teaching experience for 10 weeks this past fall that I will send upon >request. Don't worry I won't send it to the list. It might be interesting to post a synopsis. -- Albion H. Bowers bowers@elxsi.dfrf.nasa.gov ames!elxsi.dfrf.nasa.gov!bowers `In the changing of the times, they were like autumn lightning, a thing out of season, an empty promise of rain that would fall unheeded on fields already bare.' attributed to Abe Shosaburo by Dave Lowery ------------------------------ Date: 27 Apr 90 21:19:00 GMT From: trident.arc.nasa.gov!yee@ames.arc.nasa.gov (Peter E. Yee) Subject: Payload Status for 04/27/90 (Forwarded) Daily Status/KSC Payload Management and Operations 04-27-90. - STS-31R HST (at pad-B) - Post launch GSE removal was started Thursday and will be completed today. - STS-35 ASTRO-1 (at OPF) - The payload bay doors were opened Thursday and connector safety wiring and BBXRT liquid argon servicing were completed. Today the BBXRT ivt will be performed and the hut battery will be removed. - STS-40 SLS-1 (at 0&C) - Experiment train interface testing continues. - STS-42 IML-1 (at O&C) - Module pyrell foam replacement, floor staging, and rack staging were worked Thursday and will continue today. - STS-45 (Atlas-1)- Bracket installations were worked Thursday. Today coldplates and the orthogrid will be installed. - STS-46 TSS-1 (at O&C) - EMP deintegration continues. - STS-47 Spacelab-J (at O&C) - The light weight rack handling frame fit check is scheduled for today. - STS-55 SL-D2 (at O&C) - Rack 12 staging will continue today. - HST M&R (at O&C) - ORUC interface testing continues today. ------------------------------ Date: Thu, 26 Apr 90 17:20:32 EDT From: John Roberts Disclaimer: Opinions expressed are those of the sender and do not reflect NIST policy or agreement. Subject: Re: Re: Rename the Earth? >From: cs.utexas.edu!uwm.edu!mrsvr.UUCP@tut.cis.ohio-state.edu (Russ Brown) >Subject: Re: Rename the Earth? >So instead of standardizing with latin, and having one word for mountain, sea, >etc., we should force a few hundred thousand students around the world to >learn four or five equally foreign words? No, let them learn in the vernacular (their native languages). If they need to read scientific papers in another language, they should learn the entire language. There's very little value in looking at a paper and being able to understand only the place names, except in the very limited case of reading a map to learn the place names. There's considerable value in Joe Taxpayer being able to understand that the space probe he paid for has discovered a mountain, a crater, a plain, etc. Most other fields of study use different words in different languages, and it works fine. If you want to translate, just look in one of many multilanguage dictionaries of technical terms: ENGLISH GERMAN SPANISH FRENCH POLISH ------- ------ ------- ------ ------ copper Kupfer cobre cuivre miedz hydrogen Wasserstoff hidrogeno hydrogene wodor oxygen Sauerstuff oxigeno oxygene tlen silver Silber plata argent srebo sulfur Schwefel azufre soufre siarka I had to leave out a few accent marks in this example. There was also a Russian translation, which I couldn't include because it uses the Cyrillic alphabet. By the way, how do the Soviets refer to places with Latin names? They *can't* use Latin - their alphabet won't support it. Do they use a phoneticized version with Cyrillic characters? As several people pointed out, I had the chronology wrong. I remember hearing mostly English names as a kid, and should have recalled the history of names for features on the moon. (The features on Venus, however, are all recently discovered.) John Roberts roberts@cmr.ncsl.nist.gov [PS. to match the planet names, Tellus' moon should be named Cynthia. :-) ] ------------------------------ End of SPACE Digest V11 #329 *******************