Date: Fri, 2 Apr 93 06:03:41 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V16 #409 To: Space Digest Readers Precedence: bulk Space Digest Fri, 2 Apr 93 Volume 16 : Issue 409 Today's Topics: Abyss: breathing fluids Another Kuiper Object Found? Atlas rocket question Help! Deep Space Communications: info needed. Info on Probe Computers lie low netters! UFO's want you! nuclear waste Small Astronaut (was: Budget Astronaut) Space FAQ 04/15 - Calculations the call to space (was Re: Clueless Szaboisms ) Why is Venus so bad? 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: 1 Apr 93 18:09:35 GMT From: Pat Subject: Abyss: breathing fluids Newsgroups: sci.space In article <1993Mar31.221757.28648@mksol.dseg.ti.com> mccall@mksol.dseg.ti.com (fred j mccall 575-3539) writes: |In <1pcjmt$iiv@access.digex.com> prb@access.digex.com (Pat) writes: | |>|But, I've heard reports that's a similar emulsion has been approved for | ^^^^^^^^^^^^^^^^^^^^^ |>|use in neonates who are experiencing lung problems due to underdeveloped | ^^^ |>Of course, by the Time the FDA approves it for wide spread use, ^^^^^^^^^^^^^^^^ |>the EPA will have finished Banning CFC's, so it will be back to ||the drawing board. Of course, it may make a pretty good non-dairy |>dessert topping. | |You're not paying attention, Pat. See underlined above. | |Already been approved. Is in widespread use. No, you can't go down |to the local 7/11 and buy a few hundred gallons, but then you can't do |that with most drugs. | Somehow I always thought there was a significant difference between Something being approved for a rather special care need and for widespread use. Note the underlining. So can I order this stuff from my Local hospital supply store because my mother has emphysema? Or can I get it for testing dive gear? >[I just happened to know someone who worked for the company the >developed it.] > Did they try it out as a Dessert topping? >Hey, I'd think you would approve of the FDA's attitude. It so matches >your own with regard to programs looking into innovations like 20kHz >power, after all. ;-) > Actually I do like the FDA approach. Test rigorously, Show safety and efficacy. Issue waivers in critical cases (AIDS, Cancer). Develope a good population and then broaden approved use. ------------------------------ Date: 2 Apr 93 00:10:00 GMT From: Ron Baalke Subject: Another Kuiper Object Found? Newsgroups: sci.space,sci.astro According to IAU Circular #5730, Luu and Jewitt, using the 2.2 meter telescope at the University of Hawaii, have discovered a faint object that may be another Kuiper object. The object is designated 1993 FW and is similar in motion and brightness to 1992 QB. Computations done by Brian Marsden indicates that 1993 FW is currently between 38 to 56 AU from the Earth. ___ _____ ___ /_ /| /____/ \ /_ /| Ron Baalke | baalke@kelvin.jpl.nasa.gov | | | | __ \ /| | | | Jet Propulsion Lab | ___| | | | |__) |/ | | |__ M/S 525-3684 Telos | Being cynical never helps /___| | | | ___/ | |/__ /| Pasadena, CA 91109 | to correct the situation |_____|/ |_|/ |_____|/ | and causes more aggravation | instead. ------------------------------ Date: 1 Apr 93 18:25:28 GMT From: Mark Taylor Subject: Atlas rocket question Newsgroups: sci.space The Atlas ICBM was designed as a stage an a half missile. It has an extremely light weight structure. This is achieved by making the tanks (RP-1 and LOX) the external skin. This skin is so thin that while the vehicle is empty the tanks must be presurized to prevent booster from collapseing of its own weight. After launch, as propellants are consumed, acceleration increases. There is no way to throttle the three engines so at a certain point two of the three engines are dropped. The middle, or sustainer engine continues to burn until the proper velocity is achieved. Remember, Atlas was originally planed to lob a nuclear warhead 9000 miles and this sudden switching off was a bit crude so the vierniers (sp?) continue to fire as a triming maneuver to regulate the speed and adjust the attitude. The three main engines could only gimble (swivel) on one axis the other two were taken care of by the vierniers (sp?). Atlas was a truely remarkable booster. ------------------------------ Date: 3 Apr 93 02:26:26 GMT From: rsm1@waikato.ac.nz Subject: Help! Deep Space Communications: info needed. Newsgroups: sci.space Hi, For a communications course I'm taking this year, I have been landed with the job of doing a (fortunately not very long) introductory talk on 'Deep Space Communications'. Unfortunately I am having a _very_ hard time finding any info on this topic at all. There are screeds of papers dealing with satellite comms, but very little on deep space vehicles (such as the Pioneer & Voyager probes). If anyone can point me towards anything that might help I would be _most_ grateful. Specifically I would be interested in - problems involved in communicating with deep space vehicles. eg distance, time delay, noise, tracking etc. - coding, compression & error correction techniques used. and any general background info on the subject. Nothing too heavy and technical please (I'm only an undergraduate! :-) ). Anything online would be great - the library here at Waikato is not what you would call enormous and we don't get a lot of the relevant journals. Thanks in advance to anyone who can help. Sorry if this isn't the appropriate group for this sort of thing - we obviously don't get comp.dcom.deepspace in New Zealand ;-) Cheers, Scott. -------------------------------------------------------------------- Scott Mitchell, University of Waikato, Hamilton, New Zealand (rsm1@waikato.ac.nz) ------------------------------ Date: 2 Apr 93 02:04:27 GMT From: Seth the Lesser Subject: Info on Probe Computers Newsgroups: sci.space,alt.folklore.computers simon@otago.ac.nz (The Arch-Deviant) writes: > >I'm after _detailed_ technical information on the on-board computers used in >early probes (Ranger, Mariner, Pioneer, Voyager) - system architecture, >programming model, command codes, basically everything needed to write a >true-to-life simulator of the probe as seen by programmers/flight engineers. If anyone has a pointer for this, please post it publicly--I'm sure there are even more people who would like to see such data. Seth L. Blumberg \ "The whole thing was an accident. No saboteur slb22@columbia.edu (play) \ could have been so wildly optimistic as to think sethb@ctr.columbia.edu (work) \ he could destroy an airplane this way." > No one I know shares my opinions, least of all Columbia University. < ------------------------------ Date: Thu, 1 Apr 1993 18:23:35 GMT From: Martin Connors Subject: lie low netters! UFO's want you! Newsgroups: sci.space,sci.astro This from todays Global Mail (Canada's 'national newspaper'): === Toronto - The Canadian Research Association for Cosmic Knowledge of Phenomena, Observations, and Technology is investigating UFO abductions connected with use of a global computer network. Banesh Swura, research director, claims that monitoring computer networks allows aliens to target individuals with knowledge or talents which interest them. These people may become targets for abductions and possible reprogramming. By reading the flow of information on computer discussion groups about astronomy and space exploration, Swura has found cases of people who stop participating for a period of time and then return. In many cases, he claims, there is no valid reason for this and an abduction is suspected. "In one case earlier this year, an asteroid researcher at the University of Hawaii disappeared and later came back with excuses that his connection to the world computer network had failed", he said. Investigation showed that the connection had not failed during that period. Another case involved local space enthusiast Henry Spenser, who disappeared at about the same time. "There is a clear pattern of mysterious disappearances of people widely known as space experts who use computer systems. The only consistent explanation is UFO abductions, especially given the global extent of the problem", Swura claims in a press release today. "Hopefully the current documentary film Fire in the Sky will stimulate research in this area." Mr. Spenser could not be reached for comment. === This news leaves me shaking at my keyboard. I have been having strange dreams recently. Has anyone noticed if my posts were unexplainedly interrupted for a while? -- Martin Connors | Space Research | martin@space.ualberta.ca (403) 492-2526 University of Alberta | ------------------------------ Date: 1 Apr 93 20:46:57 GMT From: fred j mccall 575-3539 Subject: nuclear waste Newsgroups: sci.space In <1993Apr1.031337.14673@cs.rochester.edu> dietz@cs.rochester.edu (Paul Dietz) writes: >In article <1993Mar31.190728.8937@mksol.dseg.ti.com> mccall@mksol.dseg.ti.com (fred j mccall 575-3539) writes: >> >>> It has been proposed that by using SDI designed particle accelerators >>>that most of the waste could be tranmutated to more useable forms. Why not >>>build a few proccessing plants to do this? >> >>'It has been proposed' by *who*? Sounds like someone need s a science >>lesson or three if they think that is feasible -- or does having the >>magic initials in it (SDI) somehow make it workable contrary to >>physical constraints? >> >>[Hint: Think energy requirements.] >Hint: don't talk about things on which you are ignorant. Hint: Now think 'out of the lab'. [descriptions of implementations deleted] >This system would produce enough energy to drive the accelerator, >perhaps with some left over. A very high power (100's of MW CW or >quasi CW), very sharp proton beam would be required, but this appears >achievable using a linear accelerator. The biggest question mark >would be the lead target chemistry and the on-line processing of all >the elements being incinerated. Paul, quite frankly I'll believe that this is really going to work on the typical trash one needs to process when I see them put a couple tons in one end and get (relatively) clean material out the other end, plus be able to run it off its own residual power. Sounds almost like perpetual motion, doesn't it? After all, there are a number of fusion power schemes that 'ought to be able to' be net power producers; I'll believe we can seriously propose practical nuclear fusion power sources when someone builds a power plant out of them. [Actually, even getting *close* to break-even energy might be enough to make such a scheme practical, from a societal point of view. Just what quantities per time do you see such a system handling, and how much would it cost? Do you really think they can get even close to actually having it power itself, or will they 'waste' that power in the name of other 'efficiencies'? Yes, the decay process can be sped up with particle beams, but do you really think this is going to be a feasible process from an industrial standpoint?] -- "Insisting on perfect safety is for people who don't have the balls to live in the real world." -- Mary Shafer, NASA Ames Dryden ------------------------------------------------------------------------------ Fred.McCall@dseg.ti.com - I don't speak for others and they don't speak for me. ------------------------------ Date: Thu, 1 Apr 1993 18:33:30 GMT From: Josh Hopkins Subject: Small Astronaut (was: Budget Astronaut) Newsgroups: sci.space sasbck@spain.unx.sas.com (Brenda Kalt) writes: >In article <1993Mar30.054935.19478@ucsu.Colorado.EDU>, fcrary@ucsu.Colorado.EDU (Frank Crary) writes: >|> Definitely possible: George is 6'2" and insists that any project >|> he works on be large enough to, in theory, fit himself. You could >|> probably cut the mass of his manned Pegasus capsule by 5% to 10%, >|> just by insisting on a 5'0" astronaut... >|> >I've wondered about this for a long time. For space missions lasting >months or years, wouldn't it be more efficient to use small astronauts? >The beds and other equipment can be smaller or, in the case of >off-the-shelf equipment, the astronauts would get less claustrophobic. >Food requirements would be less (somebody help me out on this). I've been wondering about this too. Hiring women (or short men) as astronauts would seem to be beneficial for future long term spaceflight. Lower mass means less fuel. Smaller size means smaller quarters for less mass (and Frank Lloyd Wright would approve). A lower caloric intake means the food facities can be smaller. All of these factors are, of course, lost in the noise when we fly huge gigabuck space ships. However, the economics might start showing up if one postulates that longer term spaceflights might become much more common, such as in an asteroid mining society. This isn't entirely irrelevant to the present, however. I've been told that one of the concerns about using Soyuz as the return vehicle for Freedom is that it's just a tad small. There are a couple of taller astronauts who are quite concerned about whether they would be eligible for station duty, and a number of women who are quite happy about the whole thing. -- Josh Hopkins jbh55289@uxa.cso.uiuc.edu "Tout ce qu'un homme est capable d'imaginer, d'autres hommes seront capable de la realiser" -Jules Verne ------------------------------ Date: 1 Apr 1993 14:56:14 -0500 From: Jon Leech Subject: Space FAQ 04/15 - Calculations Newsgroups: sci.astro,sci.space,sci.answers,news.answers Archive-name: space/math Last-modified: $Date: 93/04/01 14:39:12 $ PERFORMING CALCULATIONS AND INTERPRETING DATA FORMATS COMPUTING SPACECRAFT ORBITS AND TRAJECTORIES References that have been frequently recommended on the net are: "Fundamentals of Astrodynamics" Roger Bate, Donald Mueller, Jerry White 1971, Dover Press, 455pp $8.95 (US) (paperback). ISBN 0-486-60061-0 NASA Spaceflight handbooks (dating from the 1960s) SP-33 Orbital Flight Handbook (3 parts) SP-34 Lunar Flight Handbook (3 parts) SP-35 Planetary Flight Handbook (9 parts) These might be found in university aeronautics libraries or ordered through the US Govt. Printing Office (GPO), although more information would probably be needed to order them. M. A. Minovitch, _The Determination and Characteristics of Ballistic Interplanetary Trajectories Under the Influence of Multiple Planetary Attractions_, Technical Report 32-464, Jet Propulsion Laboratory, Pasadena, Calif., Oct, 1963. The title says all. Starts of with the basics and works its way up. Very good. It has a companion article: M. Minovitch, _Utilizing Large Planetary Perubations for the Design of Deep-Space Solar-Probe and Out of Ecliptic Trajectories_, Technical Report 32-849, JPL, Pasadena, Calif., 1965. You need to read the first one first to realy understand this one. It does include a _short_ summary if you can only find the second. Contact JPL for availability of these reports. "Spacecraft Attitude Dynamics", Peter C. Hughes 1986, John Wiley and Sons. "Celestial Mechanics: a computational guide for the practitioner", Lawrence G. Taff, (Wiley-Interscience, New York, 1985). Starts with the basics (2-body problem, coordinates) and works up to orbit determinations, perturbations, and differential corrections. Taff also briefly discusses stellar dynamics including a short discussion of n-body problems. COMPUTING PLANETARY POSITIONS More net references: Van Flandern & Pullinen, _Low-Precision Formulae for Planetary Positions_, Astrophysical J. Supp Series, 41:391-411, 1979. Look in an astronomy or physics library for this; also said to be available from Willmann-Bell. Gives series to compute positions accurate to 1 arc minute for a period + or - 300 years from now. Pluto is included but stated to have an accuracy of only about 15 arc minutes. _Multiyear Interactive Computer Almanac_ (MICA), produced by the US Naval Observatory. Valid for years 1990-1999. $55 ($80 outside US). Available for IBM (order #PB93-500163HDV) or Macintosh (order #PB93-500155HDV). From the NTIS sales desk, (703)-487-4650. I believe this is intended to replace the USNO's Interactive Computer Ephemeris. _Interactive Computer Ephemeris_ (from the US Naval Observatory) distributed on IBM-PC floppy disks, $35 (Willmann-Bell). Covers dates 1800-2049. "Planetary Programs and Tables from -4000 to +2800", Bretagnon & Simon 1986, Willmann-Bell. Floppy disks available separately. "Fundamentals of Celestial Mechanics" (2nd ed), J.M.A. Danby 1988, Willmann-Bell. A good fundamental text. Includes BASIC programs; a companion set of floppy disks is available separately. "Astronomical Formulae for Calculators" (4th ed.), J. Meeus 1988, Willmann-Bell. "Astronomical Algorithms", J. Meeus 1991, Willmann-Bell. If you actively use one of the editions of "Astronomical Formulae for Calculators", you will want to replace it with "Astronomical Algorithms". This new book is more oriented towards computers than calculators and contains formulae for planetary motion based on modern work by the Jet Propulsion Laboratory, the U.S. Naval Observatory, and the Bureau des Longitudes. The previous books were all based on formulae mostly developed in the last century. Algorithms available separately on diskette. "Practical Astronomy with your Calculator" (3rd ed.), P. Duffett-Smith 1988, Cambridge University Press. "Orbits for Amateurs with a Microcomputer", D. Tattersfield 1984, Stanley Thornes, Ltd. Includes example programs in BASIC. "Orbits for Amateurs II", D. Tattersfield 1987, John Wiley & Sons. "Astronomy / Scientific Software" - catalog of shareware, public domain, and commercial software for IBM and other PCs. Astronomy software includes planetarium simulations, ephemeris generators, astronomical databases, solar system simulations, satellite tracking programs, celestial mechanics simulators, and more. Andromeda Software, Inc. P.O. Box 605 Amherst, NY 14226-0605 COMPUTING CRATER DIAMETERS FROM EARTH-IMPACTING ASTEROIDS Astrogeologist Gene Shoemaker proposes the following formula, based on studies of cratering caused by nuclear tests. (1/3.4) D = S S c K W : crater diameter in km g p f n (1/6) S = (g /g ) : gravity correction factor for bodies other than g e t Earth, where g = 9.8 m/s^2 and g is the surface e t gravity of the target body. This scaling is cited for lunar craters and may hold true for other bodies. (1/3.4) S = (p / p ) : correction factor for target density p , p a t t p = 1.8 g/cm^3 for alluvium at the Jangle U a crater site, p = 2.6 g/cm^3 for average rock on the continental shields. C : crater collapse factor, 1 for craters <= 3 km in diameter, 1.3 for larger craters (on Earth). (1/3.4) K : .074 km / (kT TNT equivalent) n empirically determined from the Jangle U nuclear test crater. 3 2 19 W = pi * d * delta * V / (12 * 4.185 * 10 ) : projectile kinetic energy in kT TNT equivalent given diameter d, velocity v, and projectile density delta in CGS units. delta of around 3 g/cm^3 is fairly good for an asteroid. An RMS velocity of V = 20 km/sec may be used for Earth-crossing asteroids. Under these assumptions, the body which created the Barringer Meteor Crater in Arizona (1.13 km diameter) would have been about 40 meters in diameter. More generally, one can use (after Gehrels, 1985): Asteroid Number of objects Impact probability Impact energy diameter (km) (impacts/year) (* 5*10^20 ergs) 10 10 10^-8 10^9 1 1 000 10^-6 10^6 0.1 100 000 10^-4 10^3 assuming simple scaling laws. Note that 5*10^20 ergs = 13 000 tons TNT equivalent, or the energy released by the Hiroshima A-bomb. References: Gehrels, T. 1985 Asteroids and comets. _Physics Today_ 38, 32-41. [an excellent general overview of the subject for the layman] Shoemaker, E.M. 1983 Asteroid and comet bombardment of the earth. _Ann. Rev. Earth Planet. Sci._ 11, 461-494. [very long and fairly technical but a comprehensive examination of the subject] Shoemaker, E.M., J.G. Williams, E.F. Helin & R.F. Wolfe 1979 Earth-crossing asteroids: Orbital classes, collision rates with Earth, and origin. In _Asteroids_, T. Gehrels, ed., pp. 253-282, University of Arizona Press, Tucson. Cunningham, C.J. 1988 _Introduction to Asteroids: The Next Frontier_ (Richmond: Willman-Bell, Inc.) [covers all aspects of asteroid studies and is an excellent introduction to the subject for people of all experience levels. It also has a very extensive reference list covering essentially all of the reference material in the field.] MAP PROJECTIONS AND SPHERICAL TRIGNOMETRY Two easy-to-find sources of map projections are the "Encyclopaedia Brittanica", (particularly the older volumes) and a tutorial appearing in _Graphics Gems_ (Academic Press, 1990). The latter was written with simplicity of exposition and suitability of digital computation in mind (spherical trig formulae also appear, as do digitally-plotted examples). More than you ever cared to know about map projections is in John Snyder's USGS publication "Map Projections--A Working Manual", USGS Professional Paper 1395. This contains detailed descriptions of 32 projections, with history, features, projection formulas (for both spherical earth and ellipsoidal earth), and numerical test cases. It's a neat book, all 382 pages worth. This one's $20. You might also want the companion volume, by Snyder and Philip Voxland, "An Album of Map Projections", USGS Professional Paper 1453. This contains less detail on about 130 projections and variants. Formulas are in the back, example plots in the front. $14, 250 pages. You can order these 2 ways. The cheap, slow way is direct from USGS: Earth Science Information Center, US Geological Survey, 507 National Center, Reston, VA 22092. (800)-USA-MAPS. They can quote you a price and tell you where to send your money. Expect a 6-8 week turnaround time. A much faster way (about 1 week) is through Timely Discount Topos, (303)-469-5022, 9769 W. 119th Drive, Suite 9, Broomfield, CO 80021. Call them and tell them what you want. They'll quote a price, you send a check, and then they go to USGS Customer Service Counter and pick it up for you. Add about a $3-4 service charge, plus shipping. A (perhaps more accessible) mapping article is: R. Miller and F. Reddy, "Mapping the World in Pascal", Byte V12 #14, December 1987 Contains Turbo Pascal procedures for five common map projections. A demo program, CARTOG.PAS, and a small (6,000 point) coastline data is available on CompuServe, GEnie, and many BBSs. Some references for spherical trignometry are: _Spherical Astronomy_, W.M. Smart, Cambridge U. Press, 1931. _A Compendium of Spherical Astronomy_, S. Newcomb, Dover, 1960. _Spherical Astronomy_, R.M. Green, Cambridge U. Press., 1985 (update of Smart). _Spherical Astronomy_, E Woolard and G.Clemence, Academic Press, 1966. PERFORMING N-BODY SIMULATIONS EFFICIENTLY "Computer Simulation Using Particles" R. W. Hockney and J. W. Eastwood (Adam Hilger; Bristol and Philadelphia; 1988) "The rapid evaluation of potential fields in particle systems", L. Greengard MIT Press, 1988. A breakthrough O(N) simulation method. Has been parallelized. L. Greengard and V. Rokhlin, "A fast algorithm for particle simulations," Journal of Computational Physics, 73:325-348, 1987. "An O(N) Algorithm for Three-dimensional N-body Simulations", MSEE thesis, Feng Zhao, MIT AILab Technical Report 995, 1987 "Galactic Dynamics" J. Binney & S. Tremaine (Princeton U. Press; Princeton; 1987) Includes an O(N^2) FORTRAN code written by Aarseth, a pioneer in the field. Hierarchical (N log N) tree methods are described in these papers: A. W. Appel, "An Efficient Program for Many-body Simulation", SIAM Journal of Scientific and Statistical Computing, Vol. 6, p. 85, 1985. Barnes & Hut, "A Hierarchical O(N log N) Force-Calculation Algorithm", Nature, V324 # 6096, 4-10 Dec 1986. L. Hernquist, "Hierarchical N-body Methods", Computer Physics Communications, Vol. 48, p. 107, 1988. INTERPRETING THE FITS IMAGE FORMAT If you just need to examine FITS images, use the ppm package (see the comp.graphics FAQ) to convert them to your preferred format. For more information on the format and other software to read and write it, see the sci.astro.fits FAQ. SKY (UNIX EPHEMERIS PROGRAM) The 6th Edition of the Unix operating system came with several software systems not distributed because of older media capacity limitations. Included were an ephmeris, a satellite track, and speech synthesis software. The ephmeris, sky(6), is available within AT&T and to sites possessing a Unix source code license. The program is regarded as Unix source code. Sky is <0.5MB. Send proof of source code license to E. Miya MS 258-5 NASA Ames Research Center Moffett Field, CA 94035-1000 eugene@orville.nas.nasa.gov THREE-DIMENSIONAL STAR/GALAXY COORDINATES To generate 3D coordinates of astronomical objects, first obtain an astronomical database which specifies right ascension, declination, and parallax for the objects. Convert parallax into distance using the formula in part 6 of the FAQ, convert RA and declination to coordinates on a unit sphere (see some of the references on planetary positions and spherical trignometry earlier in this section for details on this), and scale this by the distance. Two databases useful for this purpose are the Yale Bright Star catalog (sources listed in FAQ section 3) or "The Catalogue of Stars within 25 parsecs of the Sun" (in pub/SPACE/FAQ/stars.data and stars.doc on ames.arc.nasa.gov). NEXT: FAQ #5/15 - References on specific areas ------------------------------ Date: 2 Apr 93 04:04:07 GMT From: Henry Spencer Subject: the call to space (was Re: Clueless Szaboisms ) Newsgroups: sci.space In article <1pf7q5INNsrj@mojo.eng.umd.edu> sysmgr@king.eng.umd.edu writes: >>... But have U.S. rules apply to Canada? I hadn't >>even heard we'd annexed them yet. ;-) > >Annex? No, they're going to ask to be members of the United States, once >Quebec decides to make it on their own. Hmm, time to start keeping a sharp eye on some of our more objectionable politicians... what's obviously going on here is that the US doesn't dare try to move in uninvited, so they're going to try to wangle an invitation. (It's not hard to figure out why they're being chicken -- the last time they tried moving in uninvited, in 1812, it was the biggest military disaster in US history. A small mob of Canadian militia and a handful of our British buddies utterly destroyed a much larger US army, smashed the invasion of Canada completely, and occupied a couple of US states for a while in retaliation. Clearly an experience that the US is not anxious to repeat.) -- All work is one man's work. | Henry Spencer @ U of Toronto Zoology - Kipling | henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Thu, 1 Apr 1993 19:01:05 GMT From: Oivind Toien Subject: Why is Venus so bad? Newsgroups: sci.space,rec.scuba In article <1pchne$fir@access.digex.com> prb@access.digex.com (Pat) writes: > In article oivindt@fagmed.uit.no (Oivind Toien) writes: > | > |In a previous record dive (dry) at NUTEC, Bergen, Norway to about 500 > |m they used a Heliox mixture most of the time except during the descent > |were the gas mixture contained some nitrogen. The idea was the the > |effect of N2 narcosis should reduce the effect of high pressure nerve > |syndrome. > |Several of the divers suffered serious injury. Although technology > |seems to develop infinitely, physiology sets certain limits... > | > >In a program on the Norwegian channel 2 yesterday it was said that 1 > >of 7 divers are injured (per dive...) in dive operations in the North > >Sea occuring at more than 300 m. > My understanding is that Commercial diving has some real problems > following the Navy Dive tables. Even if you rigorously follow them, > that multiple diving causes some form of Micro Nitrogen bubbles > in the nervous tissue. Long term studies of the spinal tissues > of commercial divers shows large amounts of nerve damage. > There is some movement to require deep diving bells, where the divers > can live underwater for extended periods and undergo > slow decompression. > pat They *are* of course doing saturation dives from bells where they stay pressurised for an extended period of time. I do not have any details here, but I think the 500m test dive took more than a month. Btw, the safety requirements in the Norwegian sector of the North sea are said to be some of the strictest in the world. Obviously this is'nt enough when physiology sets the limits... Oivind -- Oivind Toien Dept. of Arctic Biology, Institute of Medical Biology, University of Tromso --------------------------------------------------------------------------- 9037 Tromso, NORWAY Phone+47-83-45661 Fax+47-83-80706 ------------------------------ Date: 1 Apr 93 17:53:25 GMT From: Pat Subject: Why use AC at 20kHz for SSF Power? Newsgroups: sci.space In article <1993Mar31.194337.12043@mksol.dseg.ti.com| mccall@mksol.dseg.ti.com (fred j mccall 575-3539) writes: |In <1ovfa9$j3p@access.digex.com> prb@access.digex.com (Pat) writes: | |>In article <1993Mar24.180140.28433@mksol.dseg.ti.com> mccall@mksol.dseg.ti.com (fred j mccall 575-3539) writes: |>> |>>But not nearly as weight conscious as spacecraft have to be. In |>>addition, needs are somewhat different between an aircraft and a space | |>Yeah,fred. The difference is that aircraft have to fly. | |Oooo, he's such a clever boyo, he is! | I am going to make a prediction. Something I really dislike doing. The texas Senate race is going to be done. The shea team will come in with their new design. The congress will look at it, and say. It's 20 Billion, but it's 1/4 the station we last voted on and kill it. They may get money to work with the russians, they may get some money to do some fancy SHuttle adaptions. But I don't think we are ever going to see SSF. And it will be due to management failure. |>>station. Personally, I think 20kHz was a bad idea, but I also think |>>that this insistence of yours that if it was good enough for the |>>Wright brothers it's good enough for SSF is just a bit silly. | | |>Don't try to misrepresent my position, fred. It's intellectually |>dishonest. I am all for 20KHz power as part of a engineering |>research and developement test bed. TO make it the defined |>Prime power on an OPERATIONAL station is absolutely stupid. | |I don't have to misrepresent your position, nor did I. No one should |ever actually *use* anything until it's a catalog item -- except it |ain't gonna become a catalog item until after it's in widespread use. | Actually, most things become catalog items, after some reasonable engineering developement program. Something i've never seen SSF engage in. >>You just can't believe that someone wwants to see proven trackrecord >>before commiting a 40Billion dollar program. > >Nice to be told what I "can't believe". And here all this time I >thought that *I* would be the one to tell people that. You don't get >a 'proven trackrecord' until it's in widespread use, Pat. Except it >can never go into widespread use because it must have a 'proven >trackrecord' before anyone should use it for anything. > I guess the X-15 doesn't count for proving technology? >Where do chickens come from, Pat? > The other side of the road. >[Really? Where'd you get the egg?] > My refrigerator. ------------------------------ End of Space Digest Volume 16 : Issue 409 ------------------------------