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 ; Fri, 5 Apr 91 01:31:54 -0500 (EST) Message-ID: Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Fri, 5 Apr 91 01:31:46 -0500 (EST) Subject: SPACE Digest V13 #358 SPACE Digest Volume 13 : Issue 358 Today's Topics: space debris and chaotic orbits Re: Commercial Space news (5 of 12) Re: How 'bout them Titans? Re: Why does every SAR have another resolution? Assorted responses Re: Mt. Venus 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: 1 Apr 91 22:46:45 GMT From: agate!bionet!uwm.edu!linac!pacific.mps.ohio-state.edu!zaphod.mps.ohio-state.edu!unix.cis.pitt.edu!pitt!nss!Paul.Blase@ucbvax.Berkeley.EDU (Paul Blase) Subject: space debris and chaotic orbits The following is part of a running conversation I've been having on the usenet sci.science echo re the probability of orbital debris striking a satellite. I repost it here for general interest. PB>>>... [edited: conversation re probability of a satellite or shuttle PB>>> running into space debris in orbit] PB>>> It's not the large stuff that you have to worry about, that PB>>> can be and is tracked by NORAD. It's the paint flecks, loose bolts, and PB>>> misc stuff that falls off everytime somebody jettisons a booster. I PB>>> believe the current estimate is that the Hubble can expect to run into PB>>> something just big enough to wreck it (about the size of a marble) PB>>> within the next 15 years. (Leslie Rohrer) LR>> I'm skeptical, but in any case, it won't be anything LR>> orbital that does it. It will have to be something NOT LR>> in orbit. PB> Found it: PB> "What Goes Around, Comes Around: What to do About Space Debris", PB> by Dr. Gay E. Canough & Dr. Lawrence P. Lehman; Analog Science PB> Fiction/ Science Fact, March 1991, pp54-67. PB> Includes bibliography of 28 recent articles on the problem of PB> space debris and its consequences. PB> Synopsis: PB> 1) "Each time a satellite or other spacecraft is launched, PB> there are items discarded from it that remain in orbit. These PB> include payload fairings, used upper rocket stages and bolts PB> that are blown off as part of pyrotechnic deployment of booms, PB> antennae, or solar panels....In addition, solid rocket motors PB> have aluminum oxides in their exhaust and these particles may PB> be a source of corrosion (by collisional pitting) to other PB> spacecraft. Many spacecraft are painted and after they are in PB> orbit for a time, the constant cycling in and out of hte sun PB> and exposure to atomic oxygen causes the paint to flake off. PB> These point flakes, traveling at 7 km/sec ... can cause PB> significant damage. The most famous example of this was a PB> space shuttle window (Challenger, 1983) which had to be PB> replaced when a 4 mm pit was formed in it by collision with a PB> 0.2 mm paint flake. PB> 2) "There are over 7,000 trackable objects in orbit", trackable PB> by NORAD using radar, over 10 cm in diameter. "MIT scientists PB> set out to get some idea of the population of smaller objects PB> in orbit. Using telescopes, they could see about 8 times the PB> number of objects tracked by radar, implying over 50,000 PB> objects larget than 1 cm." [This does not come close to PB> counting all of the paint flecks and bolts up there]. PB> 3) "In space, debris does not stay put.[!] In fact the orbital PB> location of a debris object cannot be predicted for longer than PB> a couple of weeks. After a few months, the object may be found PB> with equal probability anywhere within a volume bounded by its PB> apogee, its perigee, and the north and south latitude lines PB> equal to its inclination". Chaotic orbital dynamics again. PB> What is worse, these things thusly tend to stay in the "space PB> lanes" commonly traversed by LEO satellites and the shuttle. PB> Oh yes, the stuff inhabits geosync orbit too, although to a PB> somewhat lesser degree. PB> 4) "A hypervelocity collision of a working spacecraft with a PB> 10cm (1.4 kg for aluminum) piece of space debris will PB> completely demolish the craft.... An 80 gram piece (3.8 cm, PB> aluminum) of debris striking a satellite at 10 km/s has the PB> same energy as 1 kg of TNT." PB> 5) "....The larget the structure, the higher the probability of PB> a hit. Estimates range from 1% to 10% probability that Freedom PB> will suffer major damage sometime during its 10-year life due PB> to collision....For the Hubble space telescope, there is about PB> a 1% chance (over its 17-year life) that it will be severely PB> damaged by a collision with debris." PB> The article goes on to give further information on the dangers PB> of and probabilities of collisions with space debris, and then PB> to give suggestions as to what to do about it. --- via Silver Xpress V2.26 [NR] -- Paul Blase - via FidoNet node 1:129/104 UUCP: ...!pitt!nss!Paul.Blase INTERNET: Paul.Blase@nss.FIDONET.ORG ------------------------------ Date: 3 Apr 91 11:35:40 GMT From: eru!hagbard!sunic!mcsun!ukc!acorn!ixi!mike@bloom-beacon.mit.edu (Mike Moore) Subject: Re: Commercial Space news (5 of 12) In article <903@idacrd.UUCP> mac@idacrd.UUCP (Robert McGwier) writes: > >And if you will pardon me, WHAT THE HELL does Europe think ESA/Arianespace >Matra, Daimler-Benz (which now owns MBB), and all the other semi-private >`corporations' in Europe are but government subsidized and/or out right >ownership Can't speak of things I don't know about, but I do seem to recall something about Chrysler, Ford recieving 'hand-outs' of several million dollars. Not to mention equivalent funding for agriculture and, oh yes, the largest industry in the USA, the military. >of companies in competition of ours. The government and treaty granted >monopolies to INMARSAT, COMSAT, OK. They have a right to do so, so do the Japanese, so do the Europeans. >others in many areas makes me want to puke >and I can only say IT IS ABOUT TIME THE GD US Government did SOMETHING >to aid OUR companies who are trying to compete with other companies in an >international market where these companies are either owned by the government >or controlled or heavily subsidized by them. Sorry to say it but you're beginning to blither (a quaint English word meaning various politely impolite things including, but not limited to, repetition, confusion, red-faced, spittle scattering hand-waving) > >The US is becoming a third world country, Was it ever anything else? Millions of people on the poverty line, millions of people homeless. A child illiteracy population which is larger than the total number of children IN THE WHOLE OF THE UK! Millions of people routinely denied medical attention (My God! Your hospitals actually implement triage!) Political prisoners (Noriega, et al), a foreign policy lacking in maturity (Vietnam, Korea, Panama, Grenada, Cuba), and a dictatorial head of state - this guy really could commit troops to a war without needing any democratic vote. >exporting more scrap True, but perhaps trash would be more appropriate (?) IN BOTH SENSES. [ for the truly feeble minded: (1) trash - garbage, household waste, commercial waste, toxic chemicals (2) trash - shoddy workmanship, lacking originality ] >and raw >materials You export raw materials? Really? *That* must be where all those computers come from (for fuller explanation see below) >and less high tech (high value, high value added manufactured >goods) each and every day. Do I detect Japanophobia? Do I detect resentment that the Japanese are just plain willing to work harder? Has the 'land of opportunity' finally begun to realise that gold does NOT line the streets of every city and that money does NOT grow on trees? Has the 'land of the free' finally realised that freedom has a monetary value? >I can't understand how or why the US government >will not make SOME move to encourage there industries. They could start by lifting trade barriers! Did you know that the US Govt does not allow US high tech. companies to export their goods to foreign markets because of 'national security' (whatever that is). Even countries like the UK with it's 'special' relationship is not allowed to buy certain hardware or software. For pete's sake, you should have seen the hassle we had just trying to buy one, *ONE* Cray, when we wanted three the US Govt insisted on having access to all information that went through it. Well, the MOD wasn't very pleased so they built there own - UK 3 USA 0. (This story is apocryphal) > >Bob > >-- >____________________________________________________________________________ > My opinions are my own no matter | Robert W. McGwier, N4HY > who I work for! ;-) | CCR, AMSAT, etc. >---------------------------------------------------------------------------- Now, will you shut up and let's get back to some space talk OK? Mike -- --- Mike Moore mike@x.co.uk or mike@ixi-limited.co.uk Usual and obvious disclaimers... etc ------------------------------ Date: 4 Apr 91 18:19:58 GMT From: usc!samsung!think.com!linus!linus!cyclone!sokay@ucsd.edu (S. J. Okay) Subject: Re: How 'bout them Titans? In article <10902@ncar.ucar.edu> murphy@hao.hao.ucar.edu (Graham Murphy) writes: >Shortly after the Titan was destroyed, >one hears a voice in the background say, >"Is it supposed to do that?" >followed by another voice giving a very emphatic "No!" Hmmm...interesting...kind of like when people cheered when the Challenger exploded....Any idea if it was the media that made that query?. ---Steve ------------------------------ Date: 4 Apr 91 20:21:15 GMT From: agate!stew.ssl.berkeley.edu!korpela@ucbvax.Berkeley.EDU (Eric J. Korpela) Subject: Re: Why does every SAR have another resolution? In article <1923@mpirbn.mpifr-bonn.mpg.de> p515dfi@mpirbn.UUCP (Daniel Fischer) writes: >Now we all know that the Magellan in its orbit around Venus produces swaths >some 25km wide, with a resolution of approx. 120 meters. Why can the resolution >of RADARSAT's SAR be so much better, about a factor of 10? This can't be due >to a lower orbit alone, I presume. Also, why can RADARSAT have many more >pixels across the swath's width (according to this article 5000) compared to >Magellan (200)? Does that depend on their antennas or on the data processing? > >Furthermore, there are rumors that the Lacrosse satellite's SAR can resolve >features down to 1 meter in size (how official is that?). SAR works by illuminating the ground with a short radar pulse. The return echos do not form an image the way a camera does. The imaging is a bit more complicated than that. From the return echo you can only get doppler shift (relative motion of the illuminated feature and the spacecraft) and the delay time (distance from the spacecraft to the feature). Lines of constant delay time and lines of constant doppler shift form a roughly orthogonal (mathematically, not geometrically) coordinate system on the planets surface. The resolution of SAR is therefore proportional to the time resolution obtained by the reciever and the frequency resolution of the reciever. You can increase resolution by increasing either or both of these. /\ korpela@ssl.berkeley.edu Internet /__\ rioch BKYAST::KORPELA 42215::KORPELA DecNet / \ of Chaos korpela%bkyast@ucbjade Bitnet (_____________________ ------------------------------ Date: Thu, 4 Apr 91 22:39 GMT From: AMON Subject: Assorted responses BETAMAX: There is a lot of this going around today as well. Software companies are trying to lock up their interfaces which will have a similar effect. He who publishes his interface instead of keeping it proprietary will be build the market base and dominate the market. HUGHES SUIT: It is about TIME someone sued the pants of NASA for breech of contract. They deserve to learn, just like anyone else, that when you sign a contract, you deliver. One of the reasons I would not deal with the US government (or any other) is the unreliability. When dealing with REAL business entities, the contract has "liquidated damages" clauses, "nonperformance penalty" clauses. And naturally, since there are some circumstances that warrant it, clauses that allow for contract termination under certain circumstances. When contracts are grossly out of line with reality and would put a company out of business, as might have happened with Westinghouse over it's nuclear fuel fiasco, the results can sometimes be arbitrated. But the customer still gets some satisfaction. As far as I'm concerned, NASA signed contracts and was bound to perform or pay. I agree that NASA should not have been in the business to start with, and that they should certainly have taken no new contracts after Challenger. But a professional would have realized that terminating existing contracts means you give the customer satisfaction for losses you cause him by reneging. I think it is just fine for them to be taught a good solid whacking EXPENSIVE lesson about business law. NUCLEAR ROCKETS: It's about %#@%%$# time! The only thing I can say is that this is one case when I wish it had stayed very deep black for a few more years, at least until they had the thing tested and the production line churning them out. Letting the anti-nuclear FAScists get started on this before testing is big trouble. Now we'll be hearing from the Cristic Institute and god knows who else. I also fear what will happen if NASA gets its hands on the project. It will be competing with higher-pressure pumps and advanced solid rocket engines and other miniscule improvements to the status quo. I really don't think it will be welcome. Unless there is a strong pressure behind the scenes, NASA will quitely bury it rather than take the enviro-nut heat; rather than change streams from their current LO2/LH2 development path; and rather than fight for another project when they can't even deliver on what they've got. If anyone has a long enough memory, I was flaming back in the early 80's that we'd be lucky to see a space station by the year 2000 because of the way NASA/contractors/congress work. We now have a promise of a 4 man station that will be fully time manned about 1999, CLOSE TO 20 YEARS AFTER INCEPTION!!! What a joke. Give NASA the nuclear rocket and kiss it goodbye, ladies and gentleman. Dale Amon Back on the Network Again... ------------------------------ Date: 5 Apr 91 03:41:41 GMT From: usc!rpi!news-server.csri.toronto.edu!helios.physics.utoronto.ca!aurora.physics.utoronto.ca!neufeld@ucsd.edu (Christopher Neufeld) Subject: Re: Mt. Venus In article <1991Apr3.123509.1@happy.colorado.edu> gapickrell@happy.colorado.edu writes: > >The show mentioned that Venus had a >mountain that was 30,000ft tall (1.5 times as tall as Mt. Everest). Now at >this hight, both the temperature and pressure would be drastically reduced. I >was wondering by how much. Here are some simple calculations. > >Now I know that Denver is roughly at 6,000ft and has 18% less O2 than sea >level. Rounding this up to 20% to make the math easier. Since Venus has >roughly the same gravitational force as Earth, I'll assume that it loses 20% of >its atmospheric pressure for every 6,000ft. Here is a table of height and >atmosphere pressure. > >Height in ft Pressure >0 90 >6,000 72 >12,000 58 >18,000 46 >24,000 37 >30,000 30 > >Since I have no idea how to make the temperature calculations I will assume that >since the pressure went down to 1/3 it original value, the temperature will do >the same. One third of 900F is 300F. > Aaaargh. You can't take "1/3" of any temperature unless it's on an absolute scale. Consider zero degrees celcius. Twice zero is still zero, but twice 32 degrees Farenheit is 64 degrees. So, putting my hand to these equations, using the adiabatic model for atmosphes, as recommended in an undergraduate course I once took, I get, using P0 = 9E+6 Pa, T0 = 800K, g = 8.87 m/s^2, molecular weight = 44, gamma = 7/5: P(h=914m) = 85 atm T(h=914m) = 787K Something looks funny about this, but the equation does say that the atmosphere ought essentially to disappear at 50km altitude, and that doesn't seem completely unreasonable. Maybe somebody could check my numbers, just to be on the safe side. -- Christopher Neufeld....Just a graduate student | Flash: morning star seen neufeld@aurora.physics.utoronto.ca Ad astra! | in evening! Baffled cneufeld@{pnet91,pro-cco}.cts.com | astronomers: "could mean "Don't edit reality for the sake of simplicity" | second coming of Elvis!" ------------------------------ End of SPACE Digest V13 #358 *******************