Date: Fri, 16 Oct 92 05:02:03 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V15 #319 To: Space Digest Readers Precedence: bulk Space Digest Fri, 16 Oct 92 Volume 15 : Issue 319 Today's Topics: Arbitration in Action on the Extropians List Bootstrap hardware for LunaBase Dyson sphere Galileo's antenna (was Re: Gallileo's antenna) Galileo Update - 10/15/92 HRMS/SETI Answers Math progs with arbitrary precicion, for UNIX... Query Re: pluto direct/ o sub Juan Carlos Vazquez Thickness of a reflector Too thin for light pressure? (was Re: Diesen sphere or Strungen Sphere) Ulysses Update - 10/15/92 Uploaders' fate 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: 15 Oct 92 23:31:10 GMT From: Bill Higgins-- Beam Jockey Subject: Newsgroups: sci.space,sci.astro In article <1992Oct15.132708.14377@tpl68k0.tplrd.tpl.oz.au>, keithh@tplrd.tpl.oz.au (Keith Harwood) writes: [continuing a discussion on sci.space about engineering at the Moon's poles] > > In article <1992Oct13.001407.1@fnala.fnal.gov>, higgins@fnala.fnal.gov (Bill Higgins-- Beam Jockey) writes: > . . . Put manufacturing plant at the Lunar north pole. > . . . >> mirrors on a tall tower can give you power 28 days around the clock >> there, too.) > > I was under the impression that the moon's axis had much > the same obliquity to the ecliptic as the Earth's, so either > you have very tall towers or six month's light and six > month's dark. No, the Moon's axis is tilted only 1.5 degrees to the ecliptic, so at its poles a little elevation will put you in perpetual sunlight. > (If the moon's axis was normal to the ecliptic > we would get about 28 degrees of north-south libration and > I'm sure it's only about five degrees.) I can't yet answer this paradox. While I am scribbling little diagrams here, can anybody else explain it? Bill Higgins | If we can put a man on the Moon, why can't Fermilab | we put a man on the Moon? -- Bill Engfer higgins@fnal.fnal.gov | If we can put a man on the Moon, why can't higgins@fnal.Bitnet | we put a woman on the Moon? -- Bill Higgins ------------------------------ Date: Thu, 15 Oct 92 18:51:48 EDT From: Tom <18084TM@msu.edu> Subject: Arbitration in Action on the Extropians List >This is a private mailing list. It isn't run by a government -- its >run by The Extropy Institute (aka ExI), which has set up private rules >and regulations regarding its use. Part of its rules call for people >to behave in a civilized way, and provide for mechanisms, all private, ^^^^^^^^^ >to deal with people who don't behave that way. The way in which self Is it even possible to behave in an uncivilized way, while typing on a highly complex electronic machine, communicating (if you want to call it that) with others in a common language, sometimes over vast distances? I mean, we can't hit each other over the computer, right? -Tommy Mac ------------------------------=========================================== Tom McWilliams | Those who beleive ' are the ". | 18084tm@ibm.cl.msu.edu | in the , . . ones .*' . | (517) 355-2178 -or- 353-2986 | Balance '. ' . . that , don't | a scrub Astronomy undergrad | of , + get | at Michigan State University | Nature '. , .' eaten | ------------------------------=========================================== ------------------------------ Date: 15 Oct 92 21:53:34 GMT From: "Edward V. Wright" Subject: Bootstrap hardware for LunaBase Newsgroups: sci.space In <1992Oct15.130455.9862@techbook.com> szabo@techbook.com (Nick Szabo) writes: >>You snub comm sats in favor of mining the asteroids. >Huh? Not at all. I promote them both. Nonsense. You can't promote both: that violates Nick Szabo's Law. Anyone who wants to do anything *more* than launching comm sats is "snubbing" them. You've accused other people of that over and over again, letting only yourself off the hook, by special dispensation. >Furthermore, I think that >asteroid mining missions (and the volatile extraction missions that >will likely precede them) should use the same launchers as comsats, >instead of demanding their own special-purpose hardware. Instead of designing specialized launchers for different tasks, let's try to make one vehicle do all possible jobs? The same mistake NASA made with the Shuttle. Those who ignore history are condemned to repeat it. >That's one big reason why comsats and the military are so important. What? You want the military to pay your way? If anyone else said that, Nick, you'd accuse them of socialism. >I have a big problem with proposals like SSF and FLO that soak up >huge chunks of the budget in their own enclosed, built-from-scratch world, The budget that you want for your "private, free-enterprise" projects? >I've dreamed up over a dozen original concepts which I've posted here, >while you repeat ancient dogma. I've got you beat cold in the >imagination category. The issue here is the economic validity of these >plans, Yeah, you can say that again. :-) >Automated volatile extraction requires good controls and high >reliability. It does not require "AI" Right. It does not require AI because AI is not good enough. What the job does require is a self-repairing, self-adapting system with good dexterity and unparalleled pattern recognition capabilities. There is only one system that meets those requirements today -- Homo sap, Mark I, Mod 0 -- with no replacement in sight, despite your claims to the contrary. >the definition of which seems to be "the hard problems" -- as soon as >they're solved they're no longer AI. That definition was someone's *joke*, Nick. Maybe you should try taking an AI course some day and get some idea what you're talking about. ------------------------------ Date: Thu, 15 Oct 1992 16:02:58 GMT From: Stan Bischof Subject: Dyson sphere Newsgroups: sci.space In sci.space, asnd@msr.triumf.ca (Donald Arseneau) writes: >But the light bounces around to the other side and will still get absorbed >eventually. If the sphere is 80% reflective, there will be 4 x 2 = 8 >times the pressure as for a black sphere. Hmm. I'm a little late in this discussion, so please excuse me if I am not interpreting your statement incorrectly, but huh, what? Are you looking at the difference in kinetic energy transfer (i.e light pressure) between a perfectly absorbing surface (inelastic collision) and a reflecting surface (elastic collision)? If so then would you care to explain how the difference can ever be more than a factor of 2, since a perfectly elastic collision imparts exactly twice the energy as a perfectly inelastic collision? (unless you are using flubber, of course!) i.e how does %80 reflective become 4x2=8 times the pressure? Shouldn't this be more like 1.8 times the pressure? Stan Bischof HPSR ------------------------------ Date: 16 Oct 92 00:17:19 GMT From: Bill Higgins-- Beam Jockey Subject: Galileo's antenna (was Re: Gallileo's antenna) Newsgroups: sci.space In article <9210140332.AA04848@etu2.educ.ucalgary.ca>, dstevens@educ.ucalgary.ca (Douglas Stevens) writes: > Does anyone know if NASA has managed to get Gallileo's antenna > open yet? Boy, this is becoming a Frequently Asked Question in sci.space... I'll have to prepare something to add to the FAQ files. The answer is "no." They are still trying cooling turns. Below is an excerpt from a Galileo mission summary I recently wrote for science teachers. (Keep it around, and we can all mail hundreds of copies to the next person that asks this question...) It owes a lot to Jon Leech's notes from the 11 June briefing, and to the videotape that Ross Doyle of Fermilab made for me. Thanks again, guys. THE ANTENNA PROBLEM A number of "cooling turns" have been performed, where the antenna mast is pointed so it's in the shadow of the spacecraft. As it cools off, the mast shrinks a little, and the antenna ribs have to bend more. Putting a strain on the ribs like this, over and over again, may "walk" the stuck pins out of the sockets on the antenna mast. At least, that's what the computer models say. So Galileo will continue to perform cooling turns every couple of months. In December 1992 and January 1993, Galileo will be closer to the Sun than it ever will be again, and hence warmer. At this time cooling turns will have their maximum effect. Galileo engineers will combine these with "hammering" the deployment motor, turning them on and off thousands of times. This will increase the force on the stuck ribs, and gives the best hope of success in nudging them loose. If the HGA still fails to open by next March, planners will begin to follow a plan to complete the mission without it. WHAT HAPPENS IF IT DOESN'T OPEN? The High-Gain Antenna can transmit from Jupiter and Earth at rates up to 110,000 bits per second. The Low-Gain Antenna is designed to transmit at only 10 bits per second. If Galileo has to get along without the HGA, its operators will have to get very clever. Here are the steps planned: --Improvements in ground antennas: The Deep Space Network will install better amplifiers at the Canberra, Australia station, better receivers at all stations, and will combine several dishes together to support a bit rate of up to 100 bits/second through the LGA. --Data compression: Galileo has multiple computers aboard. "Stealing" the spare attitude control computer, JPL can program it to process image data and "squeeze" it so that a picture can be represented by 5 to 10 percent of the usual number of bits. Tricky algorithms allow them to do this without serious loss of image quality. Data compression is a hot topic in computer science on Earth today-- for instance Compuserve's Graphical Interchange Format (GIF) makes use of it. --Error-correcting codes: Software will be installed aboard the spacecraft to encode data in better formats that are resistant to errors or noise. This will enable Galileo to transmit at a higher data rate where errors are more likely. (The modem on your computer probably uses error-detecting or error-correcting codes.) --Flyby vs. coasting: It has always been planned that Galileo will spend short periods doing close flybys of the Galilean moons, followed by long, slow loops (typically one or two months, sometimes longer) around Jupiter before the next flyby. If data are crammed into the tape recorder during a week or so during a satellite encounter, Galileo can take several weeks to process and transmit the results to the ground. It will be possible to get nearly as much science done as with the original mission, where the satellites are concerned. But some other aspects will not do as well. The first major Galileo mission objective is direct measurement of pressures, temperatures, chemistry, and other properties of Jupiter's atmosphere when the probe parachutes into the giant planet. This will happen on Day One of the orbiter's Jovian orbit-- 7 December 1995. The probe will transmit its findings to the orbiter during its 75-minute lifetime. The orbiter can manage to store all this information on its recorder and play it back using only the Low-Gain Antenna, so this part of the mission can be accomplished despite the handicap. The major sacrifice will be frequent coverage of Jupiter itself-- atmospheric scientists were hoping to make detailed and extensive movies of the planet's weather, wind circulation, color changes, and so forth. Since the total number of pictures will be reduced, these studies will suffer. The majority of Galileo's instruments produce a fairly modest stream of bits, compared to the cameras. So data that are not pictures, such as magnetic and particle measurements or ultraviolet spectra, should be fairly manageable, and most of the original objectives of these experiments should be met. The Galileo science team estimates that despite the loss of the HGA, about 70% of the scientific objectives of the mission could still be met-- given hard work by many people on planet Earth over the next few years. And who knows? The antenna might open after all. Keep an eye on the news. O~~* /_) ' / / /_/ ' , , ' ,_ _ \|/ - ~ -~~~~~~~~~~~/_) / / / / / / (_) (_) / / / _\~~~~~~~~~~~zap! / \ (_) (_) / | \ | | Bill Higgins Fermi National Accelerator Laboratory \ / Bitnet: HIGGINS@FNAL.BITNET - - Internet: HIGGINS@FNAL.FNAL.GOV ~ SPAN/Hepnet: 43011::HIGGINS ------------------------------ Date: 16 Oct 92 08:31:51 GMT From: Ron Baalke Subject: Galileo Update - 10/15/92 Newsgroups: sci.space,sci.astro,alt.sci.planetary Forwarded from Neal Ausman, Galileo Mission Director GALILEO MISSION DIRECTOR STATUS REPORT POST-LAUNCH October 9 - 15, 1992 SPACECRAFT 1. On October 9, the Energetic Particle Detector (EPD) motor maintenance exercise was performed which stepped the motor through its eight operating positions and then returned it to Sector O which is the predicted least contamination position in preparation for the execution of TCM-15 (Trajectory Correction Maneuver #15). The motor maintenance exercise was successfully verified by Memory Readout (MRO) commands. Additionally, the EPD was returned to Sector 4 at the completion of the maneuver. 2. On October 9, the Trajectory Correction Maneuver (TCM-15) was performed on the spacecraft. The maneuver used the spacecraft's axial (z) thrusters and lateral thrusters to impart a predicted total delta velocity of 0.72 m/s. This maneuver was executed at 1200 bps with the spacecraft pointed approximately 16 degrees off the Earth. The spacecraft's performance throughout the activity was normal. All RPM (Retro-Propulsion Module) pressures and temperatures and attitude control indicators were near predicted levels. After the axial and lateral burn segments, the sequence planned spin corrections and pointing corrections were not needed. Preliminary radio tracking data indicates a 0.5 percent overburn for the axial segment and a 1.2 percent overburn for the lateral segment. 3. On October 10, the Dual Drive Actuator (DDA-4) memory sequence load was uplinked to the spacecraft without incident. This sequence load covers spacecraft activities from October 12 to October 16 (see Special Topic No. 2). 4. On October 10, Delayed Action Commands (DACs) were sent to the spacecraft to switch from 40 bps uncoded telemetry to 1200 bps coded telemetry on October 12 just prior to initiation of the DDA-4 sequence memory load. 5. On October 12, real-time commands were sent to change the System Fault Protection (SFP) AACS-INIT (Attitude and Articulation Control Subsystem) pointing slot from the Earth to the Sun prior to the Dual Drive Actuator (DDA-4) pulse activities. This change will allow the spacecraft to return to a sun-pointed attitude if an AACS Power on Reset (POR) occurs during the DDA-4 pulse activities (see Special Topic No. 2). 6. On October 12, cruise science Memory Readouts (MROs) were performed for the Extreme Ultraviolet Spectrometer (EUV). Preliminary analysis indicates the data was received properly. 7. On October 12, the DDA-4 memory sequence load went active. The warming turn to a 45-degree off-sun attitude started at approximately 2313 UTC and completed 28 minutes later at 2341 UTC (see Special Topic No. 2). 8. On October 14, Delayed Action Commands (DACs) were sent to turn off the Plasma Detector supplemental heater after the sun acquisition to eliminate a 30-degree thermal cycle on the instrument. 9. On October 14, after approximately 46 hours at the warming attitude, real time commands were sent to enable the High Gain Antenna (HGA) Dual Drive Actuator (DDA) motor primary relays, pulse the motors 10 times with an on time of 0.267 seconds followed by an off time of 0.534 seconds, and then safe the primary relays and reset the command loss timer. The DDA motor temperature was approximately plus 23.5 degrees C at turn on. DDA motor current data analysis is in progress. Preliminary analysis indicates the motor current during the 10 pulses was less than the stall current of 970 milliamps, indicating some ballscrew rotation took place. Additionally, the spacecraft under stored sequence control was commanded back to a 5 degree off-sun attitude at approximately 2345 UTC. After the sun acquisition, sun gate data was collected to determine if an antenna rib is still obscuring the sun gate signal. Preliminary data analysis indicates that the sun gate field of view is still obscured, indicating no ribs released; analysis is continuing. Also, preliminary doppler tracking data collaborates the sun gate data results. 10. On October 15, as part of the Dual Drive Actuator (DDA) No. 4 pulse activities, real-time commands were sent to checkout the star scanner. This activity was performed as a precaution to protect the star scanner from "seeing" bright particles which could release if an HGA rib released (see Special Topic No. 2). 11. The AC/DC bus imbalance measurements exhibited some change. The AC measurement has ranged from 12DN to 18DN and now reads 18 DN (4.1 volts). The DC measurement has ranged from 117 DN (13.6 volts) to 141 DN (16.6 volts) and now reads 129 DN (15.1 volts). These measurement variations are consistent with the model developed by the AC/DC special anomaly team. 12. The Spacecraft status as of October 15, 1992, is as follows: a) System Power Margin - 56 watts b) Spin Configuration - Dual-Spin c) Spin Rate/Sensor - 3.15 rpm/Acquisition Sensor d) Spacecraft Attitude is approximately 5 degrees off-sun (leading) and 19 degrees off-earth (lagging) e) Downlink telemetry rate/antenna-1200 bps (coded)/LGA-1 f) General Thermal Control - all temperatures within acceptable range g) RPM Tank Pressures - all within acceptable range h) Orbiter Science- UVS, EUV, DDS, MAG, EPD, and HIC are powered on i) Probe/RRH - powered off, temperatures within acceptable range j) CMD Loss Timer Setting - 264 hours Time To Initiation - 263 hours GDS (Ground Data Systems): 1. Galileo Earth 2 Ground Data System (GDS) testing was conducted on October 6 and October 13, 1992 with the Galileo D1.0 ground system utilizing the MCCC (Mission Control and Computer Center) real-time systems and the DSN (Deep Space Network) Canberra Signal Processing Center (SPC 40). Test objectives were to validate the successful integration of the Galileo D1.0 ground system with the DSN and MCCC system that will be used to support the Earth 2 activities. Real-time analysis indicated all objectives were successfully met, however some post-test analysis of data is on-going in the MTS and PFOE areas. TRAJECTORY As of noon Thursday, October 15, 1992, the Galileo Spacecraft trajectory status was as follows: Distance from Earth 31,353,400 miles (.34 AU) Distance from Sun 121,071,200 miles (1.30 AU) Heliocentric Speed 63,400 miles per hour Distance from Jupiter 611,760,500 miles Round Trip Light Time 5 minutes, 42 seconds SPECIAL TOPIC 1. As of October 15, 1992, a total of 8324 real-time commands have been transmitted to Galileo since Launch. Of these, 3367 were initiated in the sequence design process and 4957 initiated in the real-time command process. In the past week, 87 real time commands were transmitted: 79 were initiated in the sequence design process and 8 initiated in the real time command process. In addition, 5911 mini-sequence commands have been transmitted since March 1991; 3753 were pre-planned and 2158 were not. In the past week, 234 mini-sequence commands were transmitted. Major command activities this week included commands to reconfigure the telemetry rate, update system fault protection parameters, turn off the PLS supplemental heater, pulse the DDA motors, and checkout the star scanner. 2. The Dual Drive Actuator (DDA) pulse mini-sequence No. 4 covers spacecraft activities from October 12 to October 16. The warming turn to a 45-degree off-sun attitude occurred on October 12. The spacecraft remained at the warming attitude for approximately 48 hours. The DDA 10-pulse hammer test occurred after approximately 46 hours at the warming attitude. The sun acquisition back to approximately a 5 degree off-sun attitude occurred on October 14. Sun Gate data was collected on October 15. The star scanner checkout along with the collection of wobble data is scheduled for October 16. ___ _____ ___ /_ /| /____/ \ /_ /| Ron Baalke | baalke@kelvin.jpl.nasa.gov | | | | __ \ /| | | | Jet Propulsion Lab | ___| | | | |__) |/ | | |__ M/S 525-3684 Telos | If God had wanted us to /___| | | | ___/ | |/__ /| Pasadena, CA 91109 | have elections, he would of |_____|/ |_|/ |_____|/ | given us candidates. ------------------------------ Date: 15 Oct 92 19:31:27 GMT From: Michael Rivero Subject: HRMS/SETI Answers Newsgroups: sci.space,sci.astro In article , nickh@CS.CMU.EDU (Nick Haines) writes: |> In article <1992Oct14.161418.5759@rcvie.co.at> se_taylo@rcvie.co.at (Ian Taylor) writes: |> |> Why can't HRMS detect a current earth-like technology leakage at |> interstellar distances? Isn't this the most likely case? |> |> Why is this the most likely case? We can't assign any probabilities to |> levels of technology or power use by ETs. If we just look at human |> history, we've been putting out _any_ signals for less than 100 years |> and current levels for only a few decades. Any guesses on what powers |> we'll be putting out (and at what frequencies) in 2092? 2992? 11992? There's aother aspect. Already we are seeing mass communication moving from carrier wave systems to cable based delivery. In light of studies which suggest links between long term exposure to radio waves and certain health problems in people living next to high powered transmitters, we may see a trend of actual reduction of total planetary radio wave output from Earth. That means that we might be searching for civilizations which are operating in the narrow time perod between discovery of the radio spectrum and the move to discreet cable communications, when their radio "noise" would vanish from the heavens. <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> | Michael Rivero rivero@mdcbbs.com "Middle-aged Mutant Ninja Animator" | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | "The great masses of people. . .will more easily fall | | victims to a big lie than to a small one." | | --Adolf Hitler | | | | "All men are potential rapists, and that's _all_ they are!" | | -- Susan Brownmiller | <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> ------------------------------ Date: 15 Oct 92 19:33:32 GMT From: FRANK NEY Subject: Math progs with arbitrary precicion, for UNIX... Newsgroups: sci.space Where can I get a DOS or OS/2 version of Mathematica? Keep in mind that I do not have FTP. -- The Next Challenge - Public Access Unix in Northern Va. - Washington D.C. 703-803-0391 To log in for trial and account info. ------------------------------ Date: 15 Oct 92 22:20:51 GMT From: Henry Spencer Subject: Query Re: pluto direct/ o Newsgroups: sci.space In article <1992Oct15.162950.21583@eng.umd.edu> sysmgr@king.eng.umd.edu writes: >Couldn't you use a chemical first stage, then deploy a solar sail to add on >some speed... Getting useful acceleration from a sail, even in the inner solar system, requires dedicating a substantial fraction of the total spacecraft mass to the sail, and accepting a lot of hassles with deployment and control. Light pressure is not strong enough for a little add-on sail to be a practical propulsion system. -- MS-DOS is the OS/360 of the 1980s. | Henry Spencer @ U of Toronto Zoology -Hal W. Hardenbergh (1985)| henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Thu, 15 Oct 1992 15:52:46 -0600 From: al192191@next00.mty.itesm.mx Subject: sub Juan Carlos Vazquez SUB Juan Carlos Vazquez ------------------------------ Date: 15 Oct 92 23:35:19 GMT From: John Roberts Subject: Thickness of a reflector Newsgroups: sci.space -From: higgins@fnalc.fnal.gov (Bill Higgins-- Beam Jockey) -Subject: Too thin for light pressure? (was Re: Diesen sphere...) -Message-ID: <1992Oct14.013809.1@fnalc.fnal.gov> -Date: 14 Oct 92 07:38:09 GMT -I doubt whether 3 microns is enough to be reasonably opaque, let alone -a nearly perfect reflector (which you want when building a solar -sail.) I don't have a handbook handy, but I think you need dozens of -microns of aluminum to make a good reflector. Eric Drexler ran into the -transparency problem when he was trying to design the most lightweight -possible sail (in his previous life, before he achieved fame as Mr. -Dinky). ............. -From: dietz@cs.rochester.edu (Paul Dietz) -Message-ID: <1992Oct14.105230.10629@cs.rochester.edu> -Date: 14 Oct 92 10:52:30 GMT -I believe the skin depth of aluminum at optical wavelengths is in -the tens of nanometers. You can reduce the mass still further by -drilling holes << 1 wavelength in diameter. ............. -From: higgins@fnala.fnal.gov (Bill Higgins-- Beam Jockey) -Message-ID: <1992Oct14.170759.1@fnala.fnal.gov> -Date: 14 Oct 92 11:07:59 GMT -In article , henry@zoo.toronto.edu (Henry Spencer) writes: -> Bill has lost three orders of magnitude here... Drexler made 50nm (I think -> it was) aluminum that was an excellent reflector. Around 30, I believe, it -> starts to become transparent. ............. And Steve Willner told me a few months ago that the reflective coating of the HST mirror is ~.001 wavelength (I would interpret that as ~0.5 nm), which seemed a little thin to me. Quite a range of numbers here. So - how to find a reasonable number? The Encyclopaedia Britannica and the American encyclopedias here use technical terms such as "thin", which are not very useful. I finally found it in the Great Soviet Encyclopedia, of which our library has a 1975 edition, thoughtfully translated into English, and (very usefully) provided with an index, because the entries are in Russian alphabetical order. >From Volume 9, page 358: "To produce a mirror with maximum reflectance, the thickness of the aluminum coating should be at least 0.12 um." (120 nm). I can believe that a 50 nm coating would still be pretty reflective. Perhaps someone who's studied crystallography or who has the atomic weight and bulk density of aluminum handy can calculate how many atoms thick that is. This brings back the question I had originally asked Steve Willner: how can you grind the mirror blank for the primary mirror for HST, coat it with something nearly 1/4 wave thick, and still have it come out figured to within 1/80 wave (or whatever the spec was) of what you want? Is the vapor deposition process so precisely controllable and uniform in its effects that it does not change the shape of the surface, or changes it in a precisely predictable manner? John Roberts roberts@cmr.ncsl.nist.gov ------------------------------ Date: 15 Oct 92 20:23:24 GMT From: Tom Knight Subject: Too thin for light pressure? (was Re: Diesen sphere or Strungen Sphere) Newsgroups: sci.astro,sci.space In article <1992Oct14.013809.1@fnalc.fnal.gov> higgins@fnalc.fnal.gov (Bill Higgins-- Beam Jockey) writes: I doubt whether 3 microns is enough to be reasonably opaque, let alone a nearly perfect reflector (which you want when building a solar sail.) 3 microns is more than sufficient to be totally opaque for a metal. Silicon is barely transparent in the far red in a thickness of 2 microns. ------------------------------ Date: 16 Oct 92 08:28:00 GMT From: Ron Baalke Subject: Ulysses Update - 10/15/92 Newsgroups: sci.space,sci.astro,alt.sci.planetary Forwarded from: PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011 ULYSSES MISSION STATUS October 15, 1992 All spacecraft and science operations are continuing normally. Routine Earth-pointing maneuvers were last conducted on Oct. 10 and Oct. 13. The next set of maneuvers will be performed on Oct. 17 and Oct. 20. A reduction in the number of ranging passes continued during this reporting period to improve the spacecraft signal at its great distance from Earth. Today Ulysses is nearly 11 degrees south of the ecliptic plane, looping back toward the sun, where it will begin its primary mission of studying the sun's poles in June 1994. The spacecraft is about 890 million kilometers (554 million miles) from Earth, traveling at a heliocentric velocity of about 32,000 kilometers per hour (20,000 miles per hour). ##### ___ _____ ___ /_ /| /____/ \ /_ /| Ron Baalke | baalke@kelvin.jpl.nasa.gov | | | | __ \ /| | | | Jet Propulsion Lab | ___| | | | |__) |/ | | |__ M/S 525-3684 Telos | If God had wanted us to /___| | | | ___/ | |/__ /| Pasadena, CA 91109 | have elections, he would of |_____|/ |_|/ |_____|/ | given us candidates. ------------------------------ Date: Thu, 15 Oct 92 18:37:39 EDT From: Tom <18084TM@msu.edu> Subject: Uploaders' fate >>When you say 'personality', do you mean that it's behavior, in all possible >>circumstances will be the same as mine, or do you mean that the experience >>of being 'it' is identical to being 'me'? >As any good physicalist philosopher will tell you, there is no way of >confirming the second apart from by the first (well, apart from brain analysis >I guess, but we have already asumed that). The 'experience of being' is known But, any good (or even bad :-) concious being will tell you there is a difference. Sure, you can't tell the difference in me, nor I in you, but if you can't tell the difference in yourself, you aren't concious. That's why the question, since your question, and the whole of the uploading fate thread seem to imply the objectification of the subject. So, if you are going to objectify the subject, you sure do need to determine the difference. If you can't, how will we know if uploading is actually successful? >in philosophical jargon as qualia, and most good physicalists (including >functionalists, who are the guys who believe in uploading most strongly) are >of the opinion that qualia are just a way of saying 'innate perception', like >a sense that is a part of your brain. 'Qualia' is also a way of saying 'me'. If you can't tell the difference, then uploading degenerates into a way of making highly complex robots, not replicas of people, which, I think, takes away most of it's value. > When you start talking about the connection between two 'I's, then you >are on much less philosophically complex territory. It is testable, we can >eventually construct a duplicate, and see if this 'connection' effect occurs. What 'connection effect'? It's a subjective experience. Can you show that my colorblindness is a reality, rather than just something I make up as a party game? >I think not. As I side note, a creature with a truly identical mind really has >to have received pretty much identical senosry impressions. 'Indentical mind' is pretty vague. The only identical thing in the world is the thing itself, so of course it would have recieved the same sense impressions. If you mean by identical 'unable to tell the difference between the two' then you mean that the difference in sense impressions is undetectable, from the impressions they left on the mind. Whatever the ratio between sense experience and changes in the mind is, I'm pretty sure that 'low error' and 'identical', in term of juding other beings experiences, from the objective evidence left over in the structure of their brains, is vastly different. This is pretty vague territory, isn't it? Am I going to see a lot of this on this list? -Tommy Mac ------------------------------=========================================== Tom McWilliams | Those who beleive ' are the ". | 18084tm@ibm.cl.msu.edu | in the , . . ones .*' . | (517) 355-2178 -or- 353-2986 | Balance '. ' . . that , don't | a scrub Astronomy undergrad | of , + get | at Michigan State University | Nature '. , .' eaten | ------------------------------=========================================== ------------------------------ Path: crabapple.srv.cs.cmu.edu!cantaloupe.srv.cs.cmu.edu!rochester!galileo.cc.rochester.edu!ub!dsinc!cs.widener.edu!eff!world!ksr!jfw From: "John F. Woods" Newsgroups: sci.astro,sci.space Subject: Re: Diesen sphere or Strungen Sphere Message-Id: <16941@ksr.com> Date: 15 Oct 92 16:32:23 GMT References: <1992Oct12.230843.19014@m.cs.uiuc.edu> <1992Oct14.001905.25147@infodev.cam.ac.uk> Sender: news@ksr.com Lines: 18 Source-Info: Sender is really news@CRABAPPLE.SRV.CS.CMU.EDU Source-Info: Sender is really isu@VACATION.VENARI.CS.CMU.EDU jbh55289@uxa.cso.uiuc.edu (Josh 'K' Hopkins) writes: >sl25@cus.cam.ac.uk (Steve Linton) writes: >>> Where is there enough stuff to build out of? >>The answer of course is that you don't build it 1km thick. Using all the >> available >>matter we get about 1m thick, which would be plenty to plate solar collectors >>on. >But here's where I pull the ace out of my sleeve. The vast majority of the >solar system isn't rock. It's hydrogen, helium and other stuff not especially >well suited to construction. If the goal is just capturing solar energy, as Dyson postulated, most of that hydrogen can be used far enough out in the solar system where it *is* rock (to catch the "leaks" around the plates closer in where real "rock" is needed). I guess you'd need a thin plate around a chunk of frozen hydrogen to prevent sublimation, but that's much less material. And as someone else pointed out, by the time a civilization is ready to try this stunt, a simple trick like bulk transmutation is hardly a stumbling block... ------------------------------ End of Space Digest Volume 15 : Issue 319 ------------------------------