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 ; Tue, 24 Apr 90 01:50:56 -0400 (EDT) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Tue, 24 Apr 90 01:50:27 -0400 (EDT) Subject: SPACE Digest V11 #308 SPACE Digest Volume 11 : Issue 308 Today's Topics: Re: Radar (was Re: Drake Equation Re: Dyson spheres? NASA to brief media on Hubble Space Telescope instrument test (Forwarded) Re: Questions about the Voyagers Launch date set for Consort 3 (Forwarded) Re: Drake Equation (was Re: Interstellar travel) Re: Decompression and 2001 Re: Our galaxy ---------------------------------------------------------------------- Date: 24 Apr 90 02:21:02 GMT From: zephyr.ens.tek.com!wrgate!mrloog!dant@uunet.uu.net (Dan Tilque) Subject: Re: Radar (was Re: Drake Equation johns@calvin.spp.cornell.edu.UUCP (John Sahr) writes: >dant@mrloog.WR.TEK.COM (Dan Tilque) writes: >[] >>Now the largest military radars (as I said in an earlier post) are >>large phased array systems which watch for ICBMs. The U.S. has five of >>them (or did that last I heard). Three of these, located in Alaska, >>Greenland and England, look for missiles launched from the Soviet >>Union. The other two are located on the U.S. east and west coasts and >>look for submarine launches missiles. These last two use over the >>horizon radar (using a troposcatter effect, I think) so much or most of >>their emissions probably do not escape to space. > >OTH radars use ionospheric refraction to see "over the horizon." That's right. I was confusing radar with an over the horizon microwave comm system. >>In order to detect ICBMs, these radars would have to have ranges of >>about 2 or 3 times that of regular radars. That means that (assuming >>similar receiver sensitivity) they would use 16 to 81 times the power >>of ordinary radar (which typically run about 2-5 MW). > >Not necessarily true. For an OTH radar, the signal return is >currently limited by clutter, notably ionospheric irregularities. >Thus, increasing the transmitter power just increases the clutter. Henry Spencer has already pointed out that the ICBM detection radars are line of sight called BMEWS (for Ballistic Missile Early Warning System). I couldn't remember the acronym when I made my post (thanks, Henry). It's these guys which are the large phased array systems. There are three of them which cover a huge arc of territory from the Gulf of Alaska, across the North American Arctic and over to Europe. They have to be powerful to do that. The OTH systems were called "Pave Paws" the last I heard. That's a code word, they may have assigned an acronym to them by now. These look for submarine launched missiles. >Even for the DEW-line radars, it may be pointless to increase the >power. The DEW line radars are probably about as powerful as other USAF airplane detection radars, i.e. 2-5 MW. To get this back on the topic of aliens detecting these from out there -- most of these powerful radars (BMEWS, DEW, etc and Soviet counterparts) are primarily located in the northern hemisphere, in fact, many are well north of 50 degrees north. Thus aliens from stars in that section ofthe sky are much more likely to detect us than other aliens. >>of ordinary radar (which typically run about 2-5 MW). > >2-5 MW is a pretty boss transmitter, no matter what. 2-5 MW is what most long range Air Force search radars typically operate at. You must remember that the enemy planes are not necessarily going to have their IFF/SIF turned on. >Radio amateurs familiar with "meteor scatter" accompish hard target >scatter at hundreds of kilometer ranges with a few hundred watts of >transmitter power. Remember, radar operates under an inverse 4th power function. --- Dan Tilque -- dant@mrloog.WR.TEK.COM ------------------------------ Date: 23 Apr 90 12:54:38 GMT From: rochester!dietz@rutgers.edu (Paul Dietz) Subject: Re: Dyson spheres? In article <24257@usc.edu> robiner@oberon.usc.edu (Steve Robiner) writes: >In article <232.2631e384@iowasp.physics.uiowa.edu> dyson@iowasp.physics.uiowa.edu writes: >> the advancement of some civilizations, they would develop the >> ability to transform all of the matter of their solar system into >> a very thin layered hollow sphere centered on their star. In >> this way they could fully utilize the total stellar energy output >> as well as the maximum surface area on the interior of the sphere. > >A civilization that advanced would surely not need a star as an energy source. >In order to move that much mass around you would have to have a very advanced >energy source already. And since such a sphere would have no 'gravity' or >other centripital forces at its poles, and no 'night' anywhere on the surface, >the simple creation of another planet would be far more preferable. The energy output of a sun is more than enough to reengineer a solar system, given thousands or millions of years. It's a common misconception that Dyson was talking about a single solid sphere of material. In fact, he was talking about a large collection of objects, independently orbiting at different distances from the star, that (collectively) englobe the star. Also, the name "Dyson sphere" was coined by SF writers; Dyson himself says he got the idea from Olaf Stapledon's (sp?) SF works of the early 20th century ("Last and First Men", I think). >> Dyson recognized that an Earth-based observer would see a very >> bright infared source with no visible component. >> >If they were that advanced, they'd surely contruct the sphere out of materials >which fully absorbed all the energy from the star in *every* wavelength. We >would never see it even if they did exist. Unless they have figured out how to violate the second law of thermodynamics (in which case they don't need a sun), they have to dump waste heat somewhere. It is this waste heat Dyson was talking about. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ Date: 23 Apr 90 21:28:57 GMT From: trident.arc.nasa.gov!yee@ames.arc.nasa.gov (Peter E. Yee) Subject: NASA to brief media on Hubble Space Telescope instrument test (Forwarded) Paula Cleggett-Haleim Headquarters, Washington, D.C. April 23, 1990 (Phone: 202/453-1547) N90-26 Editors Note NASA TO BRIEF MEDIA ON HUBBLE SPACE TELESCOPE INSTRUMENT TEST Approximately 7 days after deployment of the Hubble Space Telescope (HST), NASA engineers will be obtaining a test image of star field NGC 3532 from the Goddard Space Flight Center (GSFC), Greenbelt, Md. Media can view this image from the HST newsroom, located in the GSFC Visitors Center. Prior to NASA's reception of this first test image, media will be briefed on how the telescope is focused and the image is captured. The exact time of the image capture cannot be determined until after deployment and a number of maneuvers have been successfully conducted. During the mission of STS-31, an update will be given on the approximate time of the engineering test briefing at a change-of- shift news briefing. The complete orbital and science verification period, which ensures that all systems and instruments are functioning properly, extends over an 8-month period. ------------------------------ Date: 23 Apr 90 17:34:35 GMT From: usc!elroy.jpl.nasa.gov!jato!mars!baalke@ucsd.edu (Ron Baalke) Subject: Re: Questions about the Voyagers In article <92233@philabs.Philips.Com> rfc@briar.philips.com.UUCP (Robert Casey) writes: >In article <1990Apr18.185031.25212@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: >> >>I don't know what the situation is right now, but in the long run, as >>projects like Magellan and Galileo demand increasing chunks of DSN's time, >>much of the (fairly boring and routine) data the Voyagers are sending will >>be lost. It won't all be lost, as there is still some value to it >> >I would have thought that the Voyagers would store the data for transmission >at scheduled times, chosen to be received at Earth when the antennas are not >needed for the newer probes. Use the on-board "video" tape that was used to >store images at planet encounters for storing the cruise data? This is what happens. However, the Voyagers are given low priority on antenna time, and since it takes over 8 hours to receive any data from Voyager, it is often the case the data will be transmitted back to deaf ears. The family portrait images sat in Voyager's tape recorders for over a month before they were allocated DSN time. DSN utilization will be at an all time high this fall when Galileo playback its Venus science data and does an Earth flyby, when Magellan will enter Venus orbit and start mapping the planet, and when Ulysses is launched. Ron Baalke | baalke@mars.jpl.nasa.gov Jet Propulsion Lab M/S 301-355 | baalke@jems.jpl.nasa.gov 4800 Oak Grove Dr. | Pasadena, CA 91109 | ------------------------------ Date: 23 Apr 90 21:22:15 GMT From: trident.arc.nasa.gov!yee@ames.arc.nasa.gov (Peter E. Yee) Subject: Launch date set for Consort 3 (Forwarded) Barbara Selby Headquarters, Washington, D.C. April 23, 1990 (Phone: 202/453-2927) Rick Mould University of Alabama-Huntsville (Phone: 205/895-6414) Walter Pennino Space Services, Inc., Houston (Phone: 703/281-2495) RELEASE: 90-58 LAUNCH DATE SET FOR CONSORT 3 The launch of Consort 3, a commercial suborbital rocket carrying 12 microgravity experiments, has been set for May 17 at 10:40 a.m. EDT, by the University of Alabama-Huntsville's (UAH) Consortium for Materials Development in Space (CMDS), a NASA Center for the Commercial Development of Space (CCDS). Consort 3 will be launched from the Naval Ordnance Missile Test Station facilities at the U.S. Army's White Sands Missile Range (WSMR), N.M., by Space Services, Inc., Houston, using its Starfire rocket. The rocket will carry the payload to an altitude of 200 miles and will provide the experiments with 7 to 8 minutes of microgravity time. The rocket and launch services are funded by a grant from NASA's Office of Commercial Programs, Wash., D.C. Commercial participants provided most of the funding for the payload. The Consort 3 mission will carry experiments from three other NASA commercial development centers. They include the Center for Advanced Materials, Battelle Columbus Laboratories, Columbus, Ohio; the Center for Cell Research, Penn State University, State College; and the Center for Bioserve Space Technologies, University of Colorado, Boulder. The UAH CMDS and the Center for Advanced Materials will perform materials science experiments, while the Penn State and Colorado centers will conduct biotechnical experiments, each using the effects of microgravity in their investigations. This is the third commercial launch for the UAH CMDS and Space Services. Consort 1, carrying six microgravity experiments, was successfully launched on March 29, 1989. Consort 2, launched Nov. 15, 1989, was terminated 30 seconds into the flight by the WSMR range flight safety personnel. However, the undamaged payload was recovered by parachute. The Consort 3 experiment package is essentially the same payload as the aborted Consort 2 mission. An incident investigation board, chaired by Space Services, Inc., determined that the Consort 2 flight anomaly was caused by a mechanical failure in the MIDAS gyro platform that provides attitude reference input into the S19 boost guidance system. The loss of the platform caused the vehicle to cone, which lead to high structural loads and premature separation of the payload from the booster. "Management and independent experts have carefully analyzed the known and other potential failure modes," said Donald (Deke) Slayton, President of Space Services. "All possible corrective actions have been taken." - end - NOTE TO EDITORS: While this event is not open to the general public, news media representatives may attend. Requests for accreditation to attend the launch of Consort 3 should be submitted directly by May 10, 1990, to: Debbie Bingham, PAO Building 122 White Sands Missile Range, N.M. 88002-5057 Phone: 505/678-1134 Radio and television reporters planning live coverage directly from the range are required to submit their transmission frequencies to the WSMR Department of Defense Area Frequency Coordinator (505/678-5417) for approval to transmit. Requests must be received no later than May 7, 1990. ------------------------------ Date: 23 Apr 90 17:41:58 GMT From: att!cbnewsl!moss!feg@ucbvax.Berkeley.EDU (Forrest Gehrke,2C-119,7239,ATTBL) Subject: Re: Drake Equation (was Re: Interstellar travel) In article <21891@nuchat.UUCP>, steve@nuchat.UUCP (Steve Nuchia) writes: > The 10 Hz beat would be interesting. The phase relationship > probably doesn't change very much, since most grids are phase-locked > to a coordinated time base. If you think a beat could be detected any distance out beyond the earth, build yourself a low frequency receiver and listen for it right here on Terra Firma. You will be rewarded with more racket than you ever dreamed possible, but no 10 hz beat. I have read somewhere that at any moment there are several thousand lightning storms going on somewhere on earth. You will think you are hearing them all. I know that receivers that operate below the standard broadcast band are not plentiful, but if you ever have the chance to listen to one you will learn that those wavelengths are a far piece from what you hear in the FM band. A lightning bolt has to be within visible distance to hear it at these short wavelengths. As to radiation from high power transmission lines, consider for moment how much radiation you would get from an antenna array whose element current vectors at all points add up to virtually zero. Why would you expect to get any substantial far field radiation from such an antenna? Forrest Gehrke feg@dodger.ATT.COM ------------------------------ Date: 23 Apr 90 19:47:24 GMT From: convex!ewright@uunet.uu.net (Edward V. Wright) Subject: Re: Decompression and 2001 bwood@janus.Berkeley.EDU (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. The best >strategy may be to exhale and hold that. In some of his science fiction stories, when there was a sudden decompression, Jerry Pournelle had his characters scream to force as much air as possible out of there lungs. Dr. Pournelle was the head of Boeing's human factors research lab during part of the Apollo program. He should know what he's talking about and usually tries to get things right in a story. ------------------------------ Date: 23 Apr 90 15:19:06 GMT From: haven!aplcen!jhunix!gwollman@purdue.edu (Garrett A Wollman) Subject: Re: Our galaxy In article wmartin@STL-06SIMA.ARMY.MIL (Will Martin) writes: >[...] Or perhaps >a Latinized name like we use "Terra" instead of "Earth"? [Since, actually, >both of those words can be translated to "dirt", they really are not >very dignified names for the home planet. I suppose every intelligent >extraterrestrial species has a name for their home planet that means >"dirt"... Is there *any* Earth language that has a name for the planet >that is different from the word for "dirt" or "soil" or "ground"?] How about Sol-3? Of course, that's cheating. What we need is a numbering system that's not so geocentric; we should chose some other center (perhaps that hypothetical point 10 kpc away?) from which to base our system...still purely arbitrary, but it would at least free us to speak in less charged terms about our home. -GAWollman -- "All societies are based on rules to protect pregnant women and children. . . . As racial survival is the only universal morality, no other bases is possible." - Lazarus Long [RAH, _TEFL_] ---------------Hopkins doesn't *want* my opinions------------------------ ------------------------------ End of SPACE Digest V11 #308 *******************