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, 28 Jun 91 01:28:17 -0400 (EDT) Message-ID: <4cOgXcW00WBwI79k5J@andrew.cmu.edu> Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Fri, 28 Jun 91 01:28:09 -0400 (EDT) Subject: SPACE Digest V13 #729 SPACE Digest Volume 13 : Issue 729 Today's Topics: Re: Pet Projects The SPACE Digest is... Re: Beanstalk analysis reprise Re: Gold Space Digest ESA attempting to recover Olympus satellite 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: 11 Jun 91 01:30:00 GMT From: nuchat!lobster!n5abi!gak@uunet.uu.net Subject: Re: Pet Projects > >>...your pet projects are toast anyway. > > > >Amazing that after hundreds of postings from dozens of people in > >-- > >Nick Szabo szabo@sequent.com > > While all this talk of reorganization is hot, > I would like to propose one more group: > > sci.space.allen&nick > > That way, they can scream at each other all they want. (-: > > Seriously, guys, I often appreciate your comments, but I think you're > going overboard. > -- AMEN ! ------------------------------ Date: 11 Jun 91 22:04:18 GMT From: tm2b+@andrew.cmu.edu (Todd L. Masco) Subject: The SPACE Digest is... la_carle@sol.brispoly.ac.uk (Les Carleton) writes: > I'm sorry if this is a FAQ or something, but what is Space Digest > (everybody seems to talk about it, but its doesn't seem to enter the > net)? The SPACE Digest (don't ask me why SPACE is in all caps. As far as I know, it's only for historical reasons) is a version of sci.space that is available through email. Messages are gatewayed back to sci.space through the adress space+@andrew.cmu.edu -- some broken mailers interact badly with the andrew message system (AMS) and cause messages At the moment the Digest has over a thousand subscribers, is gatewayed through four listservs, and is received on (as far as I know -- forwarding may cause this to be false) every continent. Digest subscribers seem to account for about a quarter to a third of the traffic on sci.space. The Digest is lightly moderated (when I am able, I try to slow completely outrageous conversations, such as advanced bickering about Velikovsky's prediction of the face on mars) and has a companion, the SPACE magazine, which is heavily moderated -- I tend to place only factual articles into it, though the occasional interesting interchange is added. The magazine is necessary because of the absurd amount of traffic that goes through the Digest. I took the Digest over from Ted Anderson two years ago, and will soon be looking for a replacement, as I graduate in December. Requests for subscription to the SPACE Digest go to space-request@andrew.cmu.edu, while magazine requests go to space-mag-request@andrew.cmu.edu. Now, aren't you sorry you asked? :-) -- Todd Masco | tm2b@andrew.cmu.edu | "Free speech is the right to shout CMU Physics | tm2b@andrew.BITNet | 'theatre' in a crowded fire." ------------------------------ Date: Tue, 11 Jun 91 07:29:30 EDT From: markhunt@zen.cac.stratus.com (Mark Hunt) signoff space ------------------------------ Date: 10 Jun 91 22:09:26 GMT From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!rpi!news-server.csri.toronto.edu!utgpu!utzoo!utdoe!torag!w-dnes!waltdnes@ucbvax.Berkeley.EDU (Walter Dnes ) Subject: Re: Beanstalk analysis reprise wreck@fmsrl7.UUCP (Ron Carter) writes: > In , > waltdnes@w-dnes.guild.org (Walter Dnes) writes: > > >Your calculations seem to be based on an airless earth, i.e a > >good vacuum. Don't forget that we have an atmosphere. > > Beanstalks don't do work on the air, so air drag is not a > major consideration. > TV transmitters and microwave relay towers aren't *DESIGNED* to "do work on the air" (pun not intended). Yet occasional failures/collapses do happen. > > 1) You've allowed for longitudinal forces. What about > >perpendicular forces ? What happens when the beanstalk gets hit > >by a 100 km/h (60 mph) wind ? How about a 250 km/h > > If the wind continues long enough, the beanstalk assumes a > catenary curve rather than running upward in a straight line. > Changing winds excite vibrations, which may have to be damped. In the general case, you will *NOT* find wind blowing at the same direction and speed from ground level to the top of the stratosphere. Wind at 10,000 feet can be one speed and direction, another at 20,000 feet and yet another at 30,000 feet, etc. The change with elevation (vertical wind shear) can be quite abrupt. And wind speed and direction at any one level changes with passing fronts and general circulation. Expect the beanstalk to be pummeled from all sides by winds at various speed and directions. > Alternative: trifurcate the beanstalk at a point high in > the stratosphere. Attach each third to a separate anchor, > on the points of an equilateral triangle. No matter which > way the wind blows, it only moves tension from one part > to another; it does not push the beanstalk as a whole. > This will mean 3 sections subject to structural icing as discussed below. >> 2) Since a geosynchronous orbit sits on the equator, you >>won't have to worry about icing... *AT SEA LEVEL*. At higher >>elevations in the atmosphere it will be a worry in two ways. >>Heavy icing will strain the beanstalk by sheer weight alone. >>Icing will also increase the cross-section that wind loading >>works on. > >Any flex in the beanstalk, or vehicles moving up and down, >will cause it to shed ice. Also, it can be heated electrically >if icing is a difficulty. Structural icing simply makes loading worse. It adds weight to the whole structure, and increases the cross-section area that the wind sees. Don't expect heating elements to keep the beanstalk 100% ice-free 100% of the time. If it's hot enough to do so, I'd hate to see what it does to the graphite beanstalk itself. Heavy rime icing in cloud is a lot worse than the worst freezing-rainstorm you have ever seen. It is one of the worst nightmares for a pilot. On encountering it, a pilot basically has to get out of there fast. Either dive down below the freezing level or climb up over the cloud top. An anti-icing system will hold off light icing indefinitely, assuming that the system isn't fluid-based, in which case, when your de-icing fluid runs out, your luck runs out. In the case of heavy rime icing, an anti-icing system will give a plane a few minutes grace period to get away. As for vibration knocking off all ice immediately... if that was the case, then a light prop-driven plane should have absolutely no worry whatsoever about icing ! I've been a passenger on prop planes, and I can assure you they definitely aren't smooth. Ask an experienced pilot what he does when he encounters heavy rime icing. Also, if the beanstalk flexes violently enough to do this, I'd start worrying about metal fatigue (or whatever-material-it- is-you're-using fatigue). You might also try talking to contractors who put up TV, cellular, and microwave towers on mountaintops, where the cloud base does frequently drop down to envelope the structure. Their only available reaction is to build heavy-duty structures, which could be very difficult for a beanstalk. Those towers are usually built to a 30-year worst-case load. If they fall over, communications can be disrupted until alternate channels are found. No one gets physically hurt. The financial bottom-line for the customer depends on where increased reliability is exceeded by increased building costs. A falling beanstalk can wrap around most of the equator and cause damage in lots of countries. Aside from the diplomatic fallout, if any of the (sub)contractors/builders of the failed beanstalk were American (especially based in California), it would be a guaranteed annual income for lawyers for the next decade. Electrical heating is one anti-icing system. You'd need power fed from the surface up to a height of 10 - 15 km. A couple of insulated cables power to worry about. What does this do to the weight of the whole system ? Does the whole beanstalk need to be made thicker ? How much ? Your other alternatives are to pump de-icing fluid several km uphill against gravity, or encase several km of the beanstalk in a flexible airtight sleeve (in short manageable sections) and inflate/deflate it in cycles to dislodge icing as it accumulates. Those are the three main types of anti-icing systems used on aircraft. In summary, wind and ice loading is an important real world problem that no amount of hand-waving will make go away. >A much greater difficulty will be supporting the required >weight of aircraft warning strobes and such. It may make Better to establish a "yellow zone" around the beanstalk in which stray aircraft would be warned away, and a smaller "red zone" in which they would be shot down. If anybody strays into the "red zone", assume that they are terrorists trying to destroy the beanstalk. In that case, absolutely the last thing you would want to do would be to give them a flashing strobe or a radio beacon to home in on. As far as weight is concerned, I would be much more worried about the weight of several km of heating cable wrapped around near the bottom of the beanstalk. >more sense to use a Lofstrom loop for the portion of the >structure which is in the atmosphere, because it can be >self-supporting and carry (and power) lots of accessories. >The tension-supported part could run from 80 km upward. >(This also cuts the required amount of material for the >rest of the tether by about 1/e; quite a savings!) ^^^^^^ The thread title says "Beanstalk reprise". I said in a post almost two weeks ago that while tethers may be feasible, I didn't think the same about beanstalks. If you're saying that tethers are much more feasible than beanstalks, then I think we're about to have a violent agreement ;^) >I'm disappointed that you can't come up with better objections. >Much more to the point would be "Where are you going to get 15 >million metric tons of graphite whisker?" That's a much more More to the point is... 40,000 km worth of the stuff put together as one piece. >difficult question, because we don't know how to make the stuff >in quantity yet. Beanstalks aren't possible given today's technology. I agree with you... again !! > I'm assuming that this will be done, soon, >because the market for high-strength fibers is large and >growing, and the state of the art is progressing rapidly. This may be optimistic, but never say "never". ------------------------------ Date: 11 Jun 91 21:38:10 GMT From: ogicse!sequent!muncher.sequent.com!szabo@uunet.uu.net Subject: Re: Gold In article <1991Jun11.055227.2611@nas.nasa.gov> crayfe@.nas.nasa.gov (Cray Hardware Support) writes: >Today's Washington Post reports that an asteroid has been found >orbiting the Sun at a distance of about 20 million miles from Earth >(closest point). It apparently contains 10000 tons of gold and >100000 tons of platinum, as well as 10 billion tons of iron and 1 >billion tons of nickel. Its estimated worth was put at around 1 >trillion dollars. There is very little chance that this supply of metals will become available during the next decade. NASA and other space agenices have never developed any sort of space mining technology, and have not shown any significant interest in researching the earth-crossing asteroids. Our knowledge and capabilities in these areas are very poor. Mining and processing in microgravity and vacuum is potentially very lucrative, but requires a large amount of experimentation, failure, and learning from mistakes before it can become economical. Safety concerns will likely prohibit all but the most high-value, low-mass metals (platinum group metals and gold) from being flown through Earth's atmosphere. The value of the asteroid is probably worth no more than a decades' worth of gold and platinum group metal production on Earth. This is in the $10's of billions, not $1 trillion. The platinum-group elements are found in concentrations greater than in the best Earth ores, but not significantly greater. Gold is less concentrated in asteroids than in Earth ores. This is from the sparse research done on asteroids to date. To make asteroid mining economical, we need to find concentrated ores, and/or we can take advantage of the plentiful solar energy, vacuum, and microgravity of space to make processing more efficient. Both of these avenues require research which has not yet been conducted. To sum up, if we want to tap these resources we need to begin exploration that could pay off in the next century. Until that happens, we need not worry about getting flooded with a gold rush from space. -- 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: 11 Jun 91 16:53:56 GMT From: mcsun!ukc!edcastle!dcl-cs!gdt!brispoly!gould2!la_carle@uunet.uu.net (Les Carleton) Subject: Space Digest I'm sorry if this is a FAQ or something, but what is Space Digest (everybody seems to talk about it, but its doesn't seem to enter the net)? ...Les... "Naiive question ... naiive person" -- +---------------------------+--------------------------------------------+ | Les Carleton | la_carle@uk.ac.bristol-poly.gould2 (JANET) | | MCI#4 Bristol Polytechnic | "My Life - My Opinions - ALL MINE!!!" | | Brissle, England | "I love children ... but I couldn't eat a | | "UNIX troubleshooter" | whole one" | | Moving soon ... redirect to les@decuk.uvo.dec.com after July 1st | +---------------------------+--------------------------------------------+ ------------------------------ Date: 9 Jun 91 01:27:38 GMT From: agate!spool.mu.edu!caen!zaphod.mps.ohio-state.edu!unix.cis.pitt.edu!pitt!nss!freed@ucbvax.Berkeley.EDU (Bev Freed) Subject: ESA attempting to recover Olympus satellite 06 June 1991 ESA RELEASE #17 ESA IS ATTEMPTING TO RECOVER THE OLYMPUS SATELLITE After the loss, early on 29 May 1991, of orbit and attitude control of the Olympus satellite, the European Space Agency (ESA) is now attempting to rescue the mission. Olympus is an advanced telecommunications satellite featuring direct TV broadcasting, distance learning, various business networks and several other experimental payloads. Since the loss of orbit and attitude control, all services are interrupted. It is now believed that the satellite is rotating with a period of about 90 seconds. It is drifting eastwards at five degrees per day. ESA continues to receive signals from the satellite at the Fucino ground station (Italy) during a portion of each revolution as the solar array receives the Sun. The Fucino ground station also continues to transmit streams of commands, designed to enable the batteries to receive again power and hence become charged. This is seen to be the key to performing a recovery. To this end, ESA has also sought assistance from the network of the US Space Command in Massachusetts. NASA has also agreed to assist with their Deep Space Network and, after having obtained the required clearances, its Robledo station near Madrid will shortly be put into operation to transmit commands at high power to Olympus. The recovery action itself, will be led by a Chief of Operations in ESA's Operations Centre, ESOC, in Darmstadt (FRG). He will work in direct conjunction with a team from British Aerospace, the company which headed the industrial consortium that developed Olympus. All teams have been set up and joint activities are now running. The first task is to confirm that Olympus is, indeed, recoverable and this should be known by next week. The second and parallel activity is to determine the detailed operational procedures which will bring the spacecraft back to normal operation, if this is at all possible. The Director General of ESA has instructed a Board under the Chairmanship of Professor Massimo Trella, Inspector General of ESA, to conduct an enquiry into the incident and to determine the technical or operational anomalies which led to the loss of spacecraft control. "One has to realize that the situation is extremely serious. There is very little chance of recovery unless we can get the crucial commands into the satellite to enable the batteries to start accumulating charge again" said Rene Collette, ESA's Director of Telecommunications Programmes. --- Opus-CBCS 1.20.16a * Origin: NSS BBS - Ad Astra! (412)366-5208 *HST* (1:129/104.0) -- Bev Freed - via FidoNet node 1:129/104 UUCP: ...!pitt!nss!freed INTERNET: freed@nss.FIDONET.ORG ------------------------------ End of SPACE Digest V13 #729 *******************