Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from hogtown.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, 4 Jun 91 02:50:01 -0400 (EDT) Message-ID: Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Tue, 4 Jun 91 02:49:55 -0400 (EDT) Subject: SPACE Digest V13 #595 SPACE Digest Volume 13 : Issue 595 Today's Topics: Re: 2001 and NASP SR-71 Re: Tethers (was Re: Laser launchers) Re: Saturn V and the ALS POTENTIAL MAJOR SOLAR FLARE WARNING CANCELLATION Re: Building Infrastructure Meteor Showers Re: What comes after Fred's death? Re: Request For Discussion: sci.space.moderated (questions/answers) Administrivia: Submissions to the SPACE Digest/sci.space should be mailed to space+@andrew.cmu.edu. Other mail, esp. [un]subscription requests, should be sent to space-request+@andrew.cmu.edu, or, if urgent, to tm2b+@andrew.cmu.edu ---------------------------------------------------------------------- Date: 15 May 91 13:54:25 GMT From: eru!hagbard!sunic!mcsun!ukc!icdoc!syma!nickw@bloom-beacon.mit.edu (Nick Watkins) Subject: Re: 2001 and NASP From article <1991May12.190909.17300@watdragon.waterloo.edu>, by jdnicoll@watyew.uwaterloo.ca (James Davis Nicoll): > In article <9105112003.AA19893@cwns10.INS.CWRU.Edu> ak104@cleveland.Freenet.Edu writes: >> Has anyone noticed the remarkable resemblance between >>the proposed National Aerospace Plane and the space transport >>in 2001: A Space Odyssey? > Wasn't the space plane in 2001 nuclear powered (NERVAesque, > if I recall correctly)? You do indeed. It also wasn't single stage to orbit, but had a recoverable first stage, and a launching rail (described in the book). More like Saenger than NASP or HOTOL I'd say. Nick -- Dr Nick Watkins, Space Plasma Physics, Univ. of Sussex, Brighton BN1 9QH, UK JANET: nickw@uk.ac.sussex.syma BITNET: nickw%syma.sussex.ac.uk@uk.ac ------------------------------ Date: 19 May 91 00:33:17 GMT From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!menudo.uh.edu!nuchat!lobster!n5abi!gak@tut.cis.ohio-state.edu Subject: SR-71 The June issue of Popular Mechanics includes an article on the SR-71 and mentions that NASA is putting three back in service for research. Does anyone know where they will operate from? I would guess Edwards but the article never says. ----------------------------------------------------------------------- Gene Kennedy - Ham Radio Operator, N5ABI - lobster.hou.tx.us!n5abi!gak ----------------------------------------------------------------------- ------------------------------ Date: 19 May 91 17:57:12 GMT From: news-server.csri.toronto.edu!helios.physics.utoronto.ca!aurora.physics.utoronto.ca!neufeld@rutgers.edu (Christopher Neufeld) Subject: Re: Tethers (was Re: Laser launchers) In article waltdnes@w-dnes.UUCP (Walter Dnes ) writes: >neufeld@aurora.physics.utoronto.ca (Christopher Neufeld) writes: > >> No, that's not right. If the tether is rotating, resembling the spoke >> of an invisible wheel rolling around the surface of the Earth, then the >> velocity of the tip drops to zero briefly. >> > "If the tether is rotating..." W-H-O-A !!!!!!!!!!!!!!!!!! > > [ Physics 101 analysis of an untapered rotating tether deleted ] > [ Conclusion, not surprisingly, is that an untapered tether > would break ] > Well, now do it again with the assumption that the area of the tether is a function of distance from the centre, and that the area at any point is sufficient to exert a tension equal to the total apparent weight of the tether it must support plus the payload apparent weight, plus some safety margin. You can manage a rotating tether with an area taper of between 2500 and 8000, or a radius taper of less than 100, with commonly available bulk materials like Aramide or HP-PE (don't ask me what this stands for). These figures are for a 1000 km tether, peak acceleration of about 10 gravities. It turns out that the longer the tether the better. The taper scales with the orbital velocity squared, so a longer, higher tether doesn't flare out in the middle so much. Further, the tip acceleration is smaller, so the tether can handle larger payloads. Remember that the payload of the tether is actually measured in Newtons, and the higher the peak acceleration the smaller the mass which can derive that acceleration from a fixed magnitude force. Make it a 2000 km tether and the area taper drops to about 1500 for HP-PE, with peak acceleration of about 5 gravities. 4000 km tethers bring the area taper down to about 600, accn about 2 gravities. Note that in these figures the 500 m/s velocity of the surface of the Earth is included. > This is one half of the tether. Newton's 3rd law implies that >the other portion has identical force *IN THE OTHER DIRECTION*. >Also 5 times the earth-surface weight of the tether. > Whoa there! Back to your 101 notes. The tension force is not multiplied by two for the two arms of the tether! A rope under one Newton of tension applies that force in both directions, by Newton's third law. What that really means is that it doesn't matter whether there's another arm on the tether or it's nailed to an asteroid, the tension at the centre (or the surface of the asteroid) is that required to hold up one arm of the tether. Think of it this way: I have a rope running over a pulley with a 10N weight on each end of the rope. What is the tension in the rope? It's 10 Newtons. Now, I cut the rope at the pulley and tie the cut ends to the ceiling. What's the tension in each rope? It's 10 Newtons. >Walter Dnes >waltdnes@w-dnes.UUCP waltdnes%w-dnes@torag.UUCP -- Christopher Neufeld....Just a graduate student | There no place like $FC58 neufeld@aurora.physics.utoronto.ca Ad astra! | They're $FF69-ing my cneufeld@{pnet91,pro-cco}.cts.com | every word! Send for a "Don't edit reality for the sake of simplicity" | free $A56E. ------------------------------ Date: 19 May 91 00:45:58 GMT From: usc!samsung!umich!ox.com!hela!aws@apple.com (Allen W. Sherzer) Subject: Re: Saturn V and the ALS In article <1991May19.001349.13970@agate.berkeley.edu> fcrary@lightning.Berkeley.EDU (Frank Crary) writes: >If returning a broken satellite to Earth for repairs "lost money" why >are insurance companies willing to PAY NASA to do this? Simple: NASA charges the insurance company a highly subsidized rate. Suppose you have a sattellite which can be fixed up and sold for $100M. NASA says they will recover it for $75 million so you say 'fine, do it'. NASA spends upwards of a billion dollars doing the actual work. The insurance company makes money and the taxpayers absorbe the loss. That's what I mean by 'lost money'. >As for repairing a satellite on orbit, what sort of "dry dock" are you >thinking of. Standards exist for putting field replaceable units in some satellites (like Solar Max). Initially all it would be is a pressurized facility to replace these units and do minor repair. Eventually as the market grows it will make sense to add capability. Eventually they will do integration with parts sent from Earth and made on the moon. >Building and operating a station of this size, as well as building and >operating the Orbital Manuvering Vehicle could easily cost FAR more than >just throwing the satillites away when they fail. Of course it will. Just like the government lost lots getting the airline industry started with the Kelly Act. What it does do is to reduce the incrimental costs so that individual enterprises can be profitable. Eventually, the maintenance of the infrastructure can be handed off to the private sector. Also remember that a station like this would be involved in lots of other activites. Any one of these if saddled with everything would fail. >>Even as we speak the DoE is doing work using a Soviet military reactor. >The DoE has bought a soviet "Topaz 2" space nuclear reactor. They did NOT >buy it for use. Correct. The original poster was claiming that it would be impossible to buy ANY space hardware. I agree it would be a bigger step to buy a Soyuz to acutally use but it could be done. >How will the experiment module get to the station? Unless you have an >OMV (Which is worth having, but not trivial to build, fly and operate) As I said, with a portion of the second or third years savings from the Shuttle we could build an OMV. >Also, from where will the module get power during the time it is >in transit to the station? This will take at least a few hours and many >payloads CANNOT be turned of in filght. This would be a problem. I guess you are correct we would need to send them up using the HLV; a Titan wouldn't do. Fortunatly, we built two with about a third of the first years savings. >>>Sure. You're going to ask people who were put on hold for close to 3 years >>>post-Challenger to go back to the drawing board. >>In some cases, yep. >If NASA made a commitment to fly someone's experiment on the Shuttle, they >have a responsibility not to jerk him around I agree that these issues would need to be addresses in the transition. I don't know how we would do that. However, anybody who works with NASA on the Shuttle has already been jerked around so it should be nothing new :-) >(e.g. by forcing him to re- >design his experiment or constantly changing the launch data.) No, NASA would never do that! :-) Allen -- +---------------------------------------------------------------------------+ |Allen W. Sherzer | Allen's tactics are too tricky to deal with | | aws@iti.org | -- Harel Barzilai | +---------------------------------------------------------------------------+ ------------------------------ Date: Sun, 19 May 91 13:53:03 MDT From: oler <@BITNET.CC.CMU.EDU:oler@HG.ULeth.CA> (CARY OLER) Subject: POTENTIAL MAJOR SOLAR FLARE WARNING CANCELLATION X-St-Vmsmail-To: st%"space+@andrew.cmu.edu" /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ POTENTIAL MAJOR FLARE WARNING WARNING CANCELLATION /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ May 19, 1991 ATTENTION: Region 6619 has now rotated beyond the western solar limb. Major flaring is not expected from the regions currently visible. Flaring will remain confined to low-level C-class events with a chance for an isolated M-class flare. The Potential Major Flare Warning has been terminated. /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ ------------------------------ Date: 20 May 91 06:05:14 GMT From: sequent!muncher.sequent.com!szabo@uunet.uu.net Subject: Re: Building Infrastructure In article <1991May20.043006.10451@agate.berkeley.edu> fcrary@lightning.Berkeley.EDU (Frank Crary) writes: >[garunteed purchase] >The payloads should be what the government needs, in the >orbits they need them, say in support of a major program (Lunar base?) This begs the question: why does the government need a lunar base? The government has two major needs in space that cannot be directly met privately -- defense and exploration. The purchase of launch et. al. services to meet those needs should be determined by the Pentagon and space explorers respectively, not by "space infrastructure" planners who are not motivated to meet anybody's needs. -- Nick Szabo szabo@sequent.com "If you understand something the first time you see it, you probably knew it already. The more bewildered you are, the more successful the mission was." -- Ed Stone, Voyager space explorer ------------------------------ Date: 20 May 91 08:02:48 GMT From: sequent!muncher.sequent.com!szabo@uunet.uu.net Subject: Meteor Showers Here is some info on meteor showers, and also a a couple of questions: * What are the best theories and observations regarding the distribution of mass in these orbits (from the comet itself to Tungaska-sized fragments to dust). Does the distribution come close to the "same mass in each size range" rule of thumb for asteroids? * What is the percentage of water ice in each sized fragment? I understand that dust particles contain no water, and comets themselves contain mostly water. How about fragments of intermediate size -- for example, what was the percentage of water ice in the Tungaska fragment? some meteor showers and their parent bodies ------------------------------------------- _caveat_: due to informal scholarship, the perihilion figures are +/- 2 months, at best. From various sources, but primarily from _Cambridge Encyclopedia of Astronomy_. next shower max range ZHR parent period peri ------ --- ----- --- ------ ------ ---- Quadrantids Ja4 Ja1-5 100 ? ? ? v Pi-Puppids Ap24 Ap21-26 60 Griggs-Skje 5.2 Au 92 Oc 97 d Beta Taurids Jn29 Jn23 - Jl5 20 Encke 3.3 ? f Alpha Capricornids Au1 Jl15 - Au25 10 Honda-Mrkos-Pjd 5.28 Ja 92 My97 Perseids Au12 Jl25 - Au18 70 Tuttle 2 ? ? v Draconids Oc8 Oc7-10 "high" Giac.-Zinner 6.52 Fe 91 Oc 97 Orionids Oc21 Oc6-27 35 Haley 73 2069 Taurids No1 Oc10 - De5 12 Encke 3.3 ? v Leonids No17 No14-20 1,000 Tempel-Tuttle 33.3 Oc99 Geminids De13 De8-16 60 3200 Phaeton ? ? Ursids De21 De17-25 5 Tuttle 13.6 Jn 94 ZHR = Zenith Hourly Rate v = variable, ZHR for perihilion d = daytime f = fireballs -- Nick Szabo szabo@sequent.com "If you understand something the first time you see it, you probably knew it already. The more bewildered you are, the more successful the mission was." -- Ed Stone, Voyager space explorer ------------------------------ Date: 20 May 91 18:53:28 GMT From: swrinde!sdd.hp.com!caen!ox.com!hela!aws@ucsd.edu (Allen W. Sherzer) Subject: Re: What comes after Fred's death? In article <1991May20.174837.15589@cfa250.harvard.edu> willner@cfa.harvard.edu (Steve Willner) writes: >Hasn't it occurred to anyone that life sciences research (keeping a >couple of astronauts in orbit for a year or so) can be done without a >space station? All that should be needed are another couple of >shuttle orbiters, extended duration modifications (up to 30 days is >already planned), and rendezvous capability. I don't think it would work. First of all, you would need to arrange schedules so that the desired orbits of all the missions are compatable. That may or may not be a problem. Even if this problem was solved, you still couldn't launch Shuttles fast enough. Current plans for eight flights a year which would keep over a third of the year unoccupied. >[Thanks, Allen, for keeping us up to date.] My pleasure. Allen -- +---------------------------------------------------------------------------+ |Allen W. Sherzer | Allen's tactics are too tricky to deal with | | aws@iti.org | -- Harel Barzilai | +---------------------------------------------------------------------------+ ------------------------------ Date: 20 May 91 17:48:03 GMT From: munnari.oz.au!metro!cluster!ray@uunet.uu.net (Raymond Lister) Subject: Re: Request For Discussion: sci.space.moderated (questions/answers) > From: tarl@sw.stratus.com (Tarl Neustaedter) > > ... > > Reasons for asking for a moderated group: > 1) ... > 2) There are frequently *many* answers to a single question. > A moderator can reduce that down to the few most concise answers, > and reduce the number of repeated postings. There is a simple non-moderator solution to this problem. Postings requesting information should end with something like ... "Do not post the answer. Mail it directly to me. I shall post a summary." This works reasonably well in other groups. Unfortunately, I doubt that sci.space has the *collective* intelligence to make it work. Like most people, I'd love to see sci.space moderated. But, like most people, I don't want to be the moderator. ------------------------------ End of SPACE Digest V13 #595 *******************