[meteorite-list] OT: Asteroidal and Lunar Materials
From: Gerald Flaherty <grf2_at_meteoritecentral.com>
Date: Sun May 22 19:25:03 2005 Message-ID: <004f01c55f25$766757c0$2f01a8c0_at_Dell> Gotcha Marc! ----- Original Message ----- From: "Marc Fries" <m.fries_at_gl.ciw.edu> To: "Meteorite List" <meteorite-list_at_meteoritecentral.com> Sent: Sunday, May 22, 2005 1:08 PM Subject: Re: [meteorite-list] OT: Asteroidal and Lunar Materials > Howdy > > Interesting, but it needs work. First off, where do you get the > nitrogen? Asteroids are devoid of the stuff, which means hauling large > amounts of liquid nitrogen from the Earth's gravity well ($$$$!). > Second, you've got big metallurgy problems. Fe-Ni is not "stainless > steel", as anyone who has watched their iron meteorite rust can attest > to. Stainless steel is an iron-chromium alloy. Also, asteroidal metal > contains large amounts of sulfides, which acts to embrittle metals. As > a cautionary tale in that regard, it was discovered (far too late) that > the iron used to build the Titanic was very sulfide-rich and the > resulting embrittlement was a likely cause of its' sinking: > > http://dwb.unl.edu/Teacher/NSF/C10/C10Links/chemistry.about.com/library/weekly/aa022800a.htm > > In addition to sulfides, there will be silicates and minor refractory > components which will basically rip the bubbles as they form: > > http://epubl.ltu.se/1402-1617/2002/344/index-en.html > > As a macro-scale example look at Coke cans, which have to be made from > an aluminum alloy that is even more pure than aircraft aluminum to keep > from ripping open under extreme plastic deformation when the can is > made. Finally, dropping a kms-long rod of material, no matter how > light, through the Earth's atmosphere at many km/s will break or deform > the surviving pieces considerably. Perhaps this would be better off as > a building material that is not intended to land on a planetary body > (space stations?). > > I hate to keep playing the spoil-sport in these emails, but I hope > y'all will look at this as a critical evaluation of the problems > involved and not just a "told-you-so-a-thon". If we understand the > problems then someone can work to overcome them. > > Cheers, > MDF > > >>> Hi, >>> >>> A while back there was a mini-thread about the cost of returning >>> lunar materials to Earth and the effect of economies of scale on that >>> cost. These cost concerns are similar to a much more analyzed topic: >>> returning asteroidal materials to Earth. See John Lewis' book "Mining >>> The Sky." >>> Even so, to date these discussions have been about materials that >>> could be obtained on Earth (except for Helium-3). The chief point to >>> remember about economies is that they change when the material commodity >>> is both required and can not be obtained elsewhere. >>> >>> Here's an example: Imagine you want to build a bridge out of iron >>> across a 100 foot chasm. The simplest way is to take a 100 foot long >>> slab of iron (or steel), twenty feet wide and 10 feet thick, and flop it >>> down. Inelegant, but a solution. >>> More elegant is to take a very thin slab of iron and attach a >>> variety of iron trusses underneath it, designed to support the stresses >>> of the bridge. You use much less iron and get a bridge just as strong >>> or stronger. A more elegant solution. >>> Even more elegant is build the above example of a bridge very >>> lightly indeed and support it with iron cables from towers. Now we're >>> up to Golden Gate elegant, less material, more strength, all gotten by >>> subdividing the structural shape into smaller and smaller internally >>> braced "voids." >>> In older aircraft and race car design, we can see engineers drilling >>> rows of big holes in beams and such like to create a more favorable >>> strength/weight ratio. You engineers out there know all about this, of >>> course. >>> The next logical step would be to carry the principle down to the >>> micro scale, where what appear to be solid structural members are >>> themselves smaller and smaller internally braced voids. But both micro- >>> and nano- fabrication is too fantastically expensive to contemplate. >>> >>> Hey, where do the asteroids (and the Moon) come into this?! >>> >>> Here it is. You've got all this iron (or natural stainless steel) >>> in free orbit, zero gee, or at least, micro-gee. Melt it in a >>> cylindrical electric induction furnace and eject it through a special >>> nozzle at one end. (The furnace is electric because the sunshine is >>> free and in constant supply.) >>> The exit nozzle's walls have a multitude of injectors that inject a >>> whoppingly large number of bubbles of nitrogen gas into the molten steel >>> as it emerges. The injector banks are computer controlled for rate, >>> pressure, pulsation pattern, and so forth. >>> As the molten asteroidal steel foam exits the furnace into vacuum, >>> it expands from the internal expansion of the nitrogen bubbles that have >>> been injected into it. The desired goal is to regulate the process so >>> that the final product contains a very large number of small voids which >>> butt up to each other forming regular and irregular polyhedra with thin >>> steel walls separating them. >>> The result is a material with a density about 1/3rd that of water, >>> twenty times lighter than a piece of steel the same size and shape, a >>> structural strength greater than the best aircraft grade aluminum, and a >>> strength / weight ratio that is an engineer's dream! >>> Because it's fabricated in zero-gee, it can be produced in virtually >>> any shape without distortion and made in gigantic sizes limited only by >>> the capacity of the furnace producing it. ("You want an I-beam how many >>> miles long?") >>> >>> If any of you out there are engineers, your mouths should be already >>> watering. If not, you're no engineer, at least not one in the mold of >>> Isabard Kingdom Brunel. >>> Do you want to build a bridge across the 29-mile Straight of >>> Gibraltar? No problem. Do you want to build a skyscraper five miles >>> high? No problem. Do you want to build a Tokyo-sized city that will >>> float on the sea? No problem. Do you want to build a...? You get the >>> idea. >>> From fabrication in zero-gee, the huge pieces of Foam Steel will be >>> spun sprayed with an ablative polymer and gently de-orbited into the >>> central Pacific Ocean, after which they will be recovered, transported >>> to the work site, cleaned of polymer, and put in use. >>> Why the Pacific? Well, you know, there are always these silly folks >>> who get unreasonably nervous about mile long pieces of steel falling out >>> of the sky too near them; it's just good public relations to use the >>> middle of the Pacific. Remember, Foam Steel will float! In fact, the >>> density of Foam Steel could be only about twice that of Balsa wood! >>> Foam Steel will float only 1/3rd submerged. No problem. Hello, Hawaii! >>> >>> The First Iron Age is over. The Second Iron Age is about to begin. >>> Here is the miracle material of which the future will be built, and it >>> must come from space because that is the only place where it can be >>> made, so the raw material is most economically obtained from asteroids >>> (or the Moon). >>> It would make no economic sense to boost Earth steel into orbit to >>> be re-fabricated as Foam Steel! It is conceivable that the demand for >>> Foam Steel could become so great that one might foresee the growth of an >>> environmental slash wilderness movement to "Save Our Asteroids!" >>> So, study those iron asteroids while you've still got them. >>> >>> >>> >>> Sterling K. Webb >>> >>> >>> ______________________________________________ >>> Meteorite-list mailing list >>> Meteorite-list_at_meteoritecentral.com >>> http://six.pairlist.net/mailman/listinfo/meteorite-list >> >> ______________________________________________ >> Meteorite-list mailing list >> Meteorite-list_at_meteoritecentral.com >> http://six.pairlist.net/mailman/listinfo/meteorite-list >> > > > -- > Marc Fries > Postdoctoral Research Associate > Carnegie Institution of Washington > Geophysical Laboratory > 5251 Broad Branch Rd. NW > Washington, DC 20015 > PH: 202 478 7970 > FAX: 202 478 8901 > ----- > I urge you to show your support to American servicemen and servicewomen > currently serving in harm's way by donating items they personally request > at: > http://www.anysoldier.com > (This is not an endorsement by the Geophysical Laboratory or the Carnegie > Institution.) > ______________________________________________ > Meteorite-list mailing list > Meteorite-list_at_meteoritecentral.com > http://six.pairlist.net/mailman/listinfo/meteorite-list Received on Sun 22 May 2005 07:24:50 PM PDT |
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