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 ; Sat, 15 Jun 91 03:44:16 -0400 (EDT) Message-ID: Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Sat, 15 Jun 91 03:44:10 -0400 (EDT) Subject: SPACE Digest V13 #650 SPACE Digest Volume 13 : Issue 650 Today's Topics: Re: satellite refuelling Re: satellite refuelling Space Stamps Re: Galileo Antenna (was Re: Amputation) Re: Refueling satellites (was Re: Self-sustaining infrastructures) Re: Galileo Antenna (was Re: Amputation) Re: space news from April 8 AW&ST Private Research (was Re: Fred vs. Exploration...) Latest Scoup on Dead Fred Re: Rational next station design process 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: 30 May 91 21:52:57 GMT From: sequent!muncher.sequent.com!szabo@uunet.uu.net Subject: Re: satellite refuelling In article <1991May30.190659.23547@iti.org> aws@iti.org (Allen W. Sherzer) writes: > >>You missed another option, which is to decrease the payload mass in >>order to allow more stationkeeping fuel for the same launcher. > >That is a viable option right now. No new technology would be needed. >The fact that it isn't done indicates that it is not a good tradeoff. Huh? It is done all the time. SOP, in fact. The real fact is that it is the central planners, not the satellite builders and operators, who are pushing refueling capability. This indicates that refueling is not a good tradeoff. >>For most satellites, the cost of a refueling mission will not be >>significantly smaller than the cost of launching a new generation, more >>capable satellite. > >Depdend on the cost. If I can refuel the satellite for less than $100M >it is likely to be worth it. Assume that the statistical critical component lifetime is 50% longer than the fuel lifetime (the difference is probably much less, but what the hey). Increasing the lifetime of a $200M satellite with half the capability of a replacement by 50% is worth $50 million. Furthermore, the refueling schemes I've seen would, I suggest, cost $500M per shot, which is uneconomical by a factor of 10. A technology requiring large amounts of R&D and industry-wide change should _improve_ things by a factor of 5 or more. BTW, nobody has yet posted the specific information needed to estimate cost and market, including: * The target market: proposed orbits and satellites to be serviced * Component lifetime & failure rate vs. fuel lifetime statistics * Cost of redesigning satellites for refueling * R&D cost of refueling infrastructure, amortized over market * Cost of refueling missions Until we get this information it just sounds like more hot air from the centrally planned "infrastructure" pushers. -- 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: 31 May 91 00:29:46 GMT From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!wuarchive!rex!uflorida!mailer.cc.fsu.edu!prism!ccoprmd@ucbvax.Berkeley.EDU (Matthew DeLuca) Subject: Re: satellite refuelling In article <1991May30.215257.20590@sequent.com> szabo@sequent.com writes: >Huh? It is done all the time. SOP, in fact. The real fact is that it >is the central planners, not the satellite builders and operators, >who are pushing refueling capability. This indicates that refueling >is not a good tradeoff. That fact that satellite builders do not (you say) support refuelling projects is not in the least surprising; the current system of replacing satellites when they run out of fuel requires a constant supply of new satellites, hence a constant incoming revenue. Satellite operators, on the other hand, will likely support whatever costs less; since costs are passed on to the consumer in most cases it would make sense to do whatever costs less, from a consumer point of view. At this point in time it is fairly unlikely that we could refuel sats on a regular basis for less than the cost of new ones, but that may change later on. With some very moderate technological advances, it's not implausible to think of an automated 'refuelling drone' that could drift along the geosync belt tanking up satellites. Refuelling is not a 'central planning' issue, as you seem to imply, but a cost-benefit issue. If it costs less, do it. -- Matthew DeLuca Georgia Institute of Technology "I'd hire the Dorsai, if I knew their Office of Information Technology P.O. box." - Zebadiah Carter, Internet: ccoprmd@prism.gatech.edu _The Number of the Beast_ ------------------------------ Date: 30 May 91 21:41:36 GMT From: pro-magic.cts.com!mikeu@uunet.uu.net Subject: Space Stamps I have a plate block of one of the early walk in space missions. It shows in two stamps adjoined a space suited figure on the left stamp and the capsule on the right with the lifeline going between the stamps. This is a block of 5 joined stamps (10 stamps in all) with a face value of 5 cents each and a serial number on the top right edge. Anyone know if this is worth anything? Anyone interested in them? My dad apparently purchased them before he passed away and in going through his things I came across this block. ------------------------------<<>>---------------------------- Proline: mikeu@pro-magic Internet: crash!pnet01!mikeu@pro-magic.cts.com UUCP: (..uunet!tarpit!bilver!pro-magic!mikeu) Arpa: crash!pnet01!pro-magic!mikeu@nosc.mil Voice: 407-366-5840 | Prodigy: JSNP58A | Compuserve: 71326,31 ------------------------------ Date: 27 May 91 16:37:35 GMT From: agate!bionet!uwm.edu!zaphod.mps.ohio-state.edu!swrinde!elroy.jpl.nasa.gov!euclid.jpl.nasa.gov!pjs@ucbvax.Berkeley.EDU (Peter Scott) Subject: Re: Galileo Antenna (was Re: Amputation) In article <3728@ksr.com>, clj@ksr.com (Chris Jones) writes: > [...] As has been pointed out, though, there are many > possibilities, and JPL seems to be taking a very cautious approach to resolving > the problem (as well they might, since they do have time, and don't want to > make things worse by hasty action). Quite. Latest gossip is that unless they positively figure out how to fix it by Gaspra, they'll leave it the way it is until Earth II. The problem is likely due to heat warping, and they'll want it warmed up again before they try anything, so when they get back to Earth they'll turn it to toast it good. I wondered whether the 200-mile flyby might shake it up a little, but the people I was talking with didn't know. There is atomic oxygen at that height, but at 15 mps, it's not going to have time to rust :-) If they decide to wait, the biggest problem will be cold-welding in the meantime. There are many unusual ideas floating around. Apparently the best guide to how the antenna has actually deployed is the radiation pattern, and there is this lobe that some people are talking about being able to use for burst transmissions... (Disclaimer: I don't know anyone on the Tiger Team; this is all nth-hand.) -- This is news. This is your | Peter Scott, NASA/JPL/Caltech brain on news. Any questions? | (pjs@euclid.jpl.nasa.gov) ------------------------------ Date: 27 May 91 16:46:25 GMT From: news-server.csri.toronto.edu!utzoo!henry@uunet.uu.net (Henry Spencer) Subject: Re: Refueling satellites (was Re: Self-sustaining infrastructures) In article <1991May27.034705.14725@helios.physics.utoronto.ca> neufeld@aurora.physics.utoronto.ca (Christopher Neufeld) writes: > On the subject of refueling satellites, can anybody tell us whether >the fuel tank is usually kept in the spun or despun section of a >satellite with both? Spin-stabilized comsats typically put everything in the spinning section except the main antennas and support for them. Scientific satellites vary, but the general "spin everything possible" approach is fairly constant. Anything moved from spun to de-spun section reduces the attitude stability provided by spin. Another consideration is that you can get by with fewer thrusters if they are mounted on the spinning section, because to thrust in direction X, you just wait until the spin carries the thruster around to point in that direction. >Some tanks are equipped with a forcing membrane to >feed the fuel. Are any fed centrifugally, possibly with a gas injector >to maintain a constant pressure? I *think* the spin-stabilized birds generally use centrifugal feed. I could be wrong, as there might be some difficulty with getting gas in the lines before spin was started. In any case, Chris makes a good point here: refuelling a spin-stabilized satellite is going to be tricky, perhaps impossible. The general trend is towards three-axis-stabilized birds, but spinners are still in use and in production. -- "We're thinking about upgrading from | Henry Spencer @ U of Toronto Zoology SunOS 4.1.1 to SunOS 3.5." | henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: 27 May 91 16:59:37 GMT From: spot.Colorado.EDU!alvin@boulder.colorado.edu (ALVIN KENNETH F) Subject: Re: Galileo Antenna (was Re: Amputation) In article <3728@ksr.com> clj@ksr.com (Chris Jones) writes: > >This particular design is the same as is >used for TDRS satellites, I recall. It wasn't changed between the >Shuttle-Centaur direct flight plan and the Shuttle-IUS VEEGA flight plan, save >for the addition of the sun shield and the delay in deploying it. The unusual >aspect of Galileo's mission is the length of time the antenna is kept >undeployed, and I'm sure there is concern that this caused or contributed to >the deployment problem. As has been pointed out, though, there are many >possibilities, and JPL seems to be taking a very cautious approach to resolving >the problem (as well they might, since they do have time, and don't want to >make things worse by hasty action). The antenna's design used TDRSS as a baseline, but the unique characteristics of the mission eventually led to some major redesigns. I believe the antenna was designed and built in the 1980-1982 time frame. I used to work in the engineering group at Harris responsible for the design and fabrication of that system (and the TDRSS antennae); I recall seeing a picture of the full spacecraft with antenna deployed on the cover of Aviation Week about 4 years ago (the system was delivered to JPL before I started at Harris in '83), and the mesh and cords near the outside diameter of the dish appeared quite damaged. There was a lot of speculation at home about what might have happened to it (definitely not the condition it was in when delivered); does anyone know whether that was the actual spacecraft in that cover photo (as opposed to a structural test model), and, if so, was the antenna launched in that same condition? >Chris Jones clj@ksr.com {uunet,harvard,world}!ksr!clj Ken Alvin alvin@spot.colorado.edu ------------------------------ Date: 28 May 91 13:32:29 GMT From: pilchuck!seahcx!phred!petej@uunet.uu.net (Peter Jarvis) Subject: Re: space news from April 8 AW&ST In article <1991May24.041512.7497@zoo.toronto.edu> henry@zoo.toronto.edu (Henry Spencer) writes: > >.... [Hmm, I wonder if they've thought about the problems >of nuclear clustering? One has to beware of interactions between reactors, >since they are unshielded and right beside each other.] > They are in the business of thinking about such problems. >NASA is interested in Timberwind but is wary of public outcry and suspects >that commitment to a specific advanced reactor design is premature. [They >would prefer to spend half a decade studying it first, as usual.]...... > You don't just slap something like this together and launch it. Peter Jarvis............ ------------------------------ Date: 30 May 91 01:42:10 GMT From: rochester!yamauchi@cu-arpa.cs.cornell.edu (Brian Yamauchi) Subject: Private Research (was Re: Fred vs. Exploration...) In article <0094952E.96558B80@KING.ENG.UMD.EDU> sysmgr@KING.ENG.UMD.EDU (Doug Mohney) writes: >In article <12884@mentor.cc.purdue.edu>, hrubin@pop.stat.purdue.edu (Herman Rubin) writes: >>Almost all of the pure research done in this country before WWII, the great >>bulk of it privately funded, went into the public domain. >So? WWII was 50 years ago. The times, they are a changin'. Currently, the >makers of AZT are being sued for their patent rights to that drug. Why? Much of >the research and testing was done in NIH labs without renumeration. Not in >the private sector. > >Companies will hold close to their wallets any information which will make them >a buck. This is the capitalist way. Companies will want to hold on to rights to their specific product designs (whether AZT should fall into this category is a separate issue), but that doesn't mean that they won't distribute their research results (both basic and applied). A quick flip through this year's IEEE Robotics & Automation Conference proceedings reveals papers from researchers at IBM, Hughes, Phillips, Siemens, Mitsubishi, Canon, Lockheed, Rockwell, Martin-Marietta, and IntelliCorp. >>In article <00949476.E09CC7C0@KING.ENG.UMD.EDU>, sysmgr@KING.ENG.UMD.EDU (Doug Mohney) writes: >> >>> I can't >>> see any private set of individuals gathering up $1 billion for two >>> Voyager-class probes, nor maintaining infrastructure for 15+ years to collect >>> all the data. I do agree with you here. It's unlikely that private companies will fund expensive science missions with no near- or medium-term benefits for the company, and it's unlikely that private non-profits will have the resources to fund billion dollar missions. Personally, I think all three types of organizations can produce valuable R&D: venturesome private firms can develop new technologies with possible immediate commercial benefits (OSC's Pegasus, AMROC's hybrid boosters), non-profits can develop low-cost/high-risk systems with possible long-term science/engineering benefits (SSI's lunar prospector, WSF's solar sail race, PlanSoc's Mars snake), and (well-run) government agencies/contractors (JPL) can run the larger, more expensive space exploration missions (Galileo, CRAF, Cassini, Mars rover). -- _______________________________________________________________________________ Brian Yamauchi University of Rochester yamauchi@cs.rochester.edu Department of Computer Science _______________________________________________________________________________ ------------------------------ Date: Thu, 30 May 91 00:25:29 PDT From: jim@pnet01.cts.com (Jim Bowery) To: crash!space+@andrew.cmu.edu Subject: Latest Scoup on Dead Fred The latest inside scoup on the space station fight: Today, in a members-only meeting of the Science, Space and Technology Committee, the has-beens concocted a strategy to save Space Station Fred. Next week, during the House floor fight, a prominent has-been, probably George Brown, will introduce a floor amendement to the VA, HUD and Independent Agencies appropriation bill. This amendment will slash 3% off the budget of ALL non-veterans programs, and give the resulting $1.5 billion dollars to NASA to save Fred. When the amended appropriations bill goes to conference with the Senate, Senate members of the conference committee will insist that NASA stay within its funding cap. At this point, the House will compromise with the Senate and give back $1.5 billion dollars from NASA's budget. Here is where it gets cute: They'll take the $1.5 billion from space science instead of Fred. By acting in conference, they can do it by fiat and off the record so no one can see who did what to who. ----------------------------------------------------------------------------- Jim Bowery 619/295-3164 The Coalition for PO Box 1981 Science and La Jolla, CA 92038 Commerce ----------------------------------------------------------------------------- ------------------------------ Date: 29 May 91 03:28:01 GMT From: van-bc!rsoft!mindlink!a684@ucbvax.Berkeley.EDU (Nick Janow) Subject: Re: Rational next station design process dave@fps.com (Dave Smith) writes: > How is space engineering going to get any better unless we do some? Computer > simulation is not enough, we all know this. Neither is building small > unmanned probes. Have you any proposals for doing space engineering without > building a station? Certainly. I propose that governments fund basic research in robotics, AI and automation (including teleoperation). They should also fund basic research into materials science, materials and mechanical engineering (welding, preventing vacuum welding, etc). This will require microgravity services (transportation, power, communications, etc). This will provide a stable return on investment in launch technologies and orbital facilities (microgravity modules, etc) which will encourage private R&D. The improvements gained from this work will improve the technologies and decrease the cost. This positive feedback should lead to even more R&D and experience in space engineering. Eventually, the expertise and infrastructure will be there to build a manned station at a reasonable cost. Before you embark on a major engineering project, it's wise to spend some time and effort building the tools you'll need to do the job efficiently. ------------------------------ End of SPACE Digest V13 #650 *******************