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, 20 Feb 90 01:33:34 -0500 (EST) Message-ID: Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Tue, 20 Feb 90 01:33:12 -0500 (EST) Subject: SPACE Digest V11 #66 SPACE Digest Volume 11 : Issue 66 Today's Topics: Galileo Update - 02/16/90 maintaining L5 position Re: Recreation in Space Re: Why we would need a planet. RE: NASA Select TV & Operacio 9000 Approaching light speed in space travel Re: NSS STATEMENT Viewing shuttle launches ---------------------------------------------------------------------- Date: 20 Feb 90 04:48:00 GMT From: zaphod.mps.ohio-state.edu!usc!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov!baalke@tut.cis.ohio-state.edu (Ron Baalke) Subject: Galileo Update - 02/16/90 GALILEO MISSION STATUS REPORT FEBRUARY 16, 1990 As of noon Friday, February 16, 1990, the Galileo spacecraft is 36,987,350 miles from the Earth, 2,151,150 miles from Venus and is traveling at a Heliocentric velocity of 90,063 miles per hour. Perihelion will occur on February 25. Roundtrip light time is 6 minutes, 30 seconds. Venus flyby was successfully accomplished late on February 9, 1990. Radio tracking data indicated the delta velocity achieved by the gravity assist was as expected. The spacecraft velocity was increased by nearly 5000 mph. Spacecraft performance during the flyby was as expected and within predicted values. During the post-Venus closest approach phase, an apparent anomaly occurred involving the Solid State Imaging system (SSI). The anomaly resulted in several hundred (approximately 760) unplanned SSI shutter actuations. CDS and SSI memory readouts were performed and subsequently the SSI was powered-off and its replacement heater powered-on to assure the health and safety of the instrument. Intensive anomaly investigation was initiated. Later that day mission and spacecraft risk assessment by the Project personnel concluded it was safe to power-on the SSI again and continue with the imaging sequence planned for late February 10th. Careful review of the anomaly timing indicates there is high confidence that 14 of 16 images planned during this phase were properly executed. The SITURNS to lead the sun by about two degrees were successfully completed on February 10, 13 and 15. Part B of the EV-6 sequence memory load went active as planned on February 12. This EV-6 memory load contains the spacecraft events needed to accomplish the DMS MRO activity. It is pointed out that the DMS MRO is a special experimental technique which basically plays back the stored tape recorder data into the CDS at 7.68 kbps and then data is transmitted to Earth at 1.2 kbps consistent with the telemetry link performance. Since a single compressed image being returned contains a little over 3 x 106 bits and the imaging data is transmitted to Earth at 256 bits/sec. (imaging data portion of the 1.2 kbps), the time to retrieve a picture from the telemetry standpoint only is roughly 3.6 hours. The DMS MRO activity began as scheduled on February 13. To maximize the downlink performance, the spacecraft's S-Band ranging channel was turned off and the DSN diplexer was bypassed (station is listen-only mode) thereby improving the performance margin by about 1.8 db. The Venus-Earth 1 sequence memory load was transmitted and properly received by the spacecraft without incident on February 16. The VE-1 sequence controls spacecraft activities from February 19 through March 26. This sequence includes two major first time events such as Low Gain Antenna (LGA) LGA-2 to LGA-1 switch and downlink telemetry operation at 10 bps. The AC/DC bus imbalance measurements profile during this last week was not much different from that observed for the last three weeks. The AC measurement continued to fluctuate between about 45 and 48 volts (AC) and about 19 and 21 volts (DC). The GDS successfully supported the Venus Encounter and subsequent playback of selected data from the spacecraft tape recorder via CDS Memory Read Out (MRO). Support of MRO operations required manual reconfiguration of the Deep Space Network (DSN) telemetry system at the tracking stations for each of the frequent spacecraft data rate changes (twice every 45 minutes). The DSN NOCC and tracking station operations personnel are to be commended for excellent "heads-up" operational support that was able to accomplish the required reconfigurations with no loss of playback data. The two significant GDS problems occurring during Venus support were as follows: 1. An error in CDS sequencing memory management (generated by the SEQTRAN program) for the Venus sequence caused parameters for the SSI control Spacecraft Expanded Block (SEB) to be overwritten before CDS execution of the block was complete. 2. Playback of the selected images over the 70 meter antenna in Goldstone on Tuesday was interrupted when high winds forced stowing of the 70 meter antenna. About one-half of the first image was lost (temporarily since it will be played back later). A 34 meter antenna in Australia was called from a Pioneer pass (at rise time) to provide Galileo support in time for playback of the remaining two images. 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: 19 Feb 90 06:51:01 GMT From: portal!portal!cup.portal.com!MJB@uunet.uu.net (Martin J Brown-Jr) Subject: maintaining L5 position I am posting the following for someone who does not have USENET access. You may post your answers, which I will relay to him, or you may email to him if you have BIX access, or you may email to me mjb@cup.portal.com and I will pass it on. ******************* . . This question comes from a non-astrophysicist. . . I have read that L5 in the Earth-Luna system is a gravity "plain", not a "well". Since L5 is defined as the point where Earth's gravity, Luna's gravity, and centrifugal force exactly balance, any perturbation from the sun will cause a space habitat to wander across the surface of the L5 "plain". . So my question is: can anyone give me any general concept of how much energy would be required to overcome the sun's perturbations and to keep an L5 habitat at or near the mathematical L5 point (Earth-Luna)? . In order not to limit anyone's answer, I haven't included details about the habitat. If it helps, you may assume the habitat's mass is 250,000 tons (small, as habitats go), and that it is a cylinder of 600' diameter. You may orient the diameter in whichever direction you prefer, and you may choose whatever length you prefer. You may assume that "stationkeeping" means anything within 100 kms of the mathematical L5 point. You may assume that the habitat is rotating at 3 rpm. . If you know about solar sails (I don't!), can you estimate how large a solar sail might you need to do this?? . ANSWERS TO WITHIN ONE ORDER OF MAGNITUDE WOULD BE FINE! . SO WOULD "INTUITIVE" ANSWERS! . Thank you, Bill Wright (BIXname = KATHWRIGHT) ******************** Thanx - MJB - USENET: mjb@cup.portal.com BIX: mbrown ------------------------------ Date: 19 Feb 90 16:35:27 GMT From: MATHOM.GANDALF.CS.CMU.EDU!lindsay@pt.cs.cmu.edu (Donald Lindsay) Subject: Re: Recreation in Space In article <1990Feb19.043102.16364@calvin.spp.cornell.edu> richard@calvin.spp.cornell.edu (Richard Brittain) writes: >A few months ago a rather good spoof of a NASA technical report on the subject >appeared in alt.sex. I'm still waiting for the NASA SUTRA. -- Don D.C.Lindsay Carnegie Mellon Computer Science ------------------------------ Date: 20 Feb 90 03:48:04 GMT From: voder!dtg.nsc.com!andrew@ucbvax.Berkeley.EDU (Lord Snooty @ The Giant Poisoned Electric Head ) Subject: Re: Why we would need a planet. In article <21039@watdragon.waterloo.edu>, jdnicoll@watyew.waterloo.edu (Brian or James) writes: >How likely is it that space living Islamics would consent to dismantling Mecca? Dunno, but the high-tech alternative may be more attractive (as well as a lucrative income source for the aware entrepreneur): 3D-rotating prayer mats. This neatly solves the orientation problem of zooming over Mecca at over 20,000 mph while kneeling. It begs the question of the definition of local time, of course. :-) -- ........................................................................... Andrew Palfreyman andrew@dtg.nsc.com Albania before April! ------------------------------ X-Delivery-Notice: SMTP MAIL FROM does not correspond to sender. Date: Mon, 19 Feb 90 14:29 GMT From: RITA HAYWORTH Subject: RE: NASA Select TV & Operacio 9000 From : di4007@ebccuab1.bitnet Date : Feb/19/1990 Sorry, it was a missprint. Of course it is 9000 hours (375 days) jordi Iparraguirre CS Student at U.A.B. di4007@ebccuab1.bitnet ------------------------------ Date: Mon, 19 Feb 90 23:55 EST From: Subject: Approaching light speed in space travel Scott (scott@xcf.berkeley.edu) writes: >There is yet another major problem ... with the relativistic time dialation, > piloting a vessel safely at such speeds will become quite a pain. Not only > will the computer become enormously slow at reacting to potential dangers, > but these objects will be very difficult to detect due to high speed, large > blueshift, and relativistic "tunnel vision". It is hard to see what you mean here. The computer will not slow down at all - at least not for those on the ship. However, one does have to worry about light travel time. For example, consider a ship travelling at 0.5c. It sends out a radar signal that reflects off of an asteroid that is 1 ly in front of the ship the instant the signal is sent out. By the time that the ship receives the reflection, 2/3 of a ly will have been travelled already by the ship. There is some time to react, but not overly much. At higher speeds, the available reaction time goes down even more. Travelling at the speed of light means that the ship hits the asteroid before the occupants are even aware of its existence. Makes one wonder how a starship can effectively maneuver at warp speeds. :-) >Who knows what would be considered a "dangerous" object when the ship is >travelling > so fast. Maybe even a thin interstellar gas/dust cloud would wear on the > hull over years of travel (millions of years if you're talking other galaxies > here)! Not everything out there is ionized or has a magnetic field, so you > can't just put up an electro-magnetic shield. Larry Niven covers stuff like this in his various Known Space stories, especially World of Ptavvs. Basically, use a Bussard ramjet with a lightyear size magnetic scoop and fusion heating up the gas/dust in front of the ship. This would ionize anything, and then the magnetic fields can contain it. Of course, E.E. Smith just uses the interstellar gas/dust as a friction source to keep his inertialess ships from hitting infinite speeds. :-) -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- | Arnold Gill | | Queen's University at Kingston | | BITNET: gill@qucdnast | | INTERNET: gill@bill.phy.queensu.ca | -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- ------------------------------ Date: 19 Feb 90 09:54:37 GMT From: agate!usenet@ucbvax.Berkeley.EDU (William Baxter) Subject: Re: NSS STATEMENT In article <4955@itivax.iti.org>, aws@vax3 (Allen W. Sherzer) writes: >Official Notice from the National Space Society, February 14. >The so-called "space activist alert" in regards to Mr. Scott Pace >which has appeared on this bulletin board (as well as others) is >not a National Space Society action. Individuals who have >initiated this alert are acting in their own right and not on the >behalf of the National Space Society. True. >Furthermore, NSS considers this action to be completely >unjustified and detrimental to the creation of a spacefaring >civilization. Scott Pace served as the Executive Vice President >of NSS and Chairman of the NSS Legislative Committee for the past >two years. In this capacity Scott was responsible for >championing support for space in Congress including commercial >space programs. HR 2674, the Commercial Space Transportation Act >was reviewed by the committee during this time and was supported >by NSS through written testimony to the House subcommittee on >Space Science and Applications. True. Careful wording avoids the statement that Scott Pace actually supported HR2674 in his capacity as NSS Legislative Committee chairman, which would be false. >Mr. Pace has recently resigned from his posts within the National >Space Society because he has taken a position within the federal >government. In his new position, Scott is working to promote >space commerce. It is counter-productive to the National Space >Society's efforts to support commercial space to pursue Mr. >Pace's transfer or detachment from this position or to otherwise >harass him. In other words, although he has resigned his positions at the NSS, he maintains close ties with the organization. The NSS views are Scott Pace's views, even now. The point is this: Those of us working to remove Mr. Pace from his new position are doing so precisely because it will interfere with "the National Space Society's efforts to support commercial space," a euphemism for preventing the development of commercial space industries for the forseeble future. If we succeed, the remaining NSS leaders will find it difficult to use the NSS as a stepping stone to positions of administrative power as Mr. Pace has tried to do. And since many of the people who have supported HR2674 over NSS resistance are also working to remove Scott Pace from his new position, their fears are well justified. Help remove Scott Pace from a position of influence. Write your letters to the Secretary of Commerce today: Robert A. Mosbacher Secretary of Commerce 14th Street at Constitution Ave. Washington, DC 20230 ---- William Baxter ARPA: web@{garnet,brahms,math}.Berkeley.EDU UUCP: {sun,dual,decwrl,decvax,hplabs,...}!ucbvax!garnet!web ------------------------------ Date: Mon, 19 Feb 90 09:50:39 EDT From: Jerry Davis Subject: Viewing shuttle launches This may be of interest to those of you who wish to attend future shuttle launches. It was taken from the 18feb90 edition of _The Atlanta Journal and Constitution_ with excerps form _The Hartford Courant_, authored by Steve Silk (paraphrased by me). The next launch is scheduled for late February; another for late April. For a complete list of liftoffs, write NASA, BOC-155, Kennedy Space Center Fla. 32899. Those who plan well in advance can write for a special pass permitting them onto Space Center grounds for the closest view of a launch (~seven miles from the pad). About 2,000 passes are issued free for each launch date. They are parceled out on a first come first served basis. For reservations or more information, write: NASA Vehicle Passes PA-PAS Kennedy Space Center, Fla. 32899 For information about visiting the Space Coast area of Florida, write: Brevard County Tourist Development Council P.O. Box 1969 Cocoa, Fla. 32923 or call 800-872-1969 Local officials allow people to park on Route 1 in Titusville. Binoculars are a must as it is 15 miles away. You may park there 24 hrs. before a launch. Additionally, the article points out that many viewers prefer to watch the SRB's drop off. This can be seen from spots along ~20 miles of beachfront. The preferred spot is Jetty Park in Port Canaveral. I've never been there, I'm just passing along information. Eugene you may want to add this to your list :). Apologies to the author for any botches. Jerry ------------------------------ End of SPACE Digest V11 #66 *******************