Thank you Michael! This puts some of the unknowns into perspective. I believe in turning dreams into reality and I know that there is a lot of grunt work that needs to happen between the two extremes.
Joe L. > > Joe Latrell asks about space elevators: > >> 1. How do you get it down in the first place. Upper atmosphere winds >> can move at over 150 MPH. How do you get a ribbon through that >> without it whipping so bad that it either tears itself apart or will >> be >> impossible to catch. A simple issue but one that is troubling. > > Tear itself apart in mere 150 MPH winds? This stuff is strong > enough to ... well, someone once estimated that if you had to > build a space elevator out of steel, the width at the highest- > tension point would be about 1000 miles. Carbon nanotube > fiber is nothing if not strong. > > Impossible to catch? Just weight it so it doesn't flap around > so bad. > >> 2. What about the electrical discharge from something like that >> connecting to the earth. Over that distance the static charge alone >> could blow the thing apart when it connects to the ground. No one has >> ever explained how to solve this to me in a way that amde sense. > > Carbon nanotubes are very conductive. And static charge dissipation > doesn't have to start when it touches the Earth -- it can start in the > upper atmosphere, the ionosphere. NASA study groups have > looked at the issues of lightning strikes, and claim it's manageable. > Presumably this applies to the issue of accumulated static charge > as well -- I forget, I haven't read the NASA report in a while. > (See below for link.) > >> 3. Orbital mechanics are pretty picky. Pertibations of the orbit >> alone will account for hundreds of meters of slack/tension. What do >> you do, spool it up when it goes slack? Now the anchoring system has >> to be able to wind up and down too? > > I don't know how much perturbation is expected, but remember that > the center of mass is about 23,000 miles out. At those distances, GEO > satellites carry rather small engines to correct for perturbations that > accumulate over *decades* of operation. Presumably, being a > ribbon, it also has some elasticity, and over tens of thousands of > miles, you'll probably just see some slight variations in tension. Note > that the orbital perturbations seen in GEO satellites must > be corrected, otherwise they'll drift out of range of fixed dishes. But > if you get some drift in the center of mass of a space elevator, the > next question is not "how do we correct it"? It's "so what?" > The answer depends on the application and the expected lifespan. > >> 4. This cable/ribbon will have to undergo a large amount of both >> tension and compression from multiple angles. I don't know that >> nanotubes are tested in a fabric mode that could provide for all of >> these forces. I have also heard that if the ribbon does snap, it will >> remain stationary and can be repaired. Stationary to what? Again the >> speeds involved with pertibation and wind forces, it will not remain >> stationary for very long. > > Tension, yes. Compression? Well, from climber treads, yes, but > the forces of tension will be vastly greater than shear from > treads, or from compression. > > Nanotube weave is currently Unobtainium. Everything depends > on being able to make a lot of this stuff, and on the properties > of what can be made. > > As for the ribbon "snapping" -- which is possible if debris strikes and > radiation degrade it enough -- I have not heard that the elevator > will remain stationary. Presumably, there will be multiple > ribbons for redundancy in the final configuration. > > It will be big enough to have considerable inertia, so a wind > whipping 23,000 miles below, across about .1% of its length /// > It's hard to see how this is going to cause much drift > even if all the ribbon in the atmosphere snaps. If it snaps > much further up, the elevator's center of gravity may change > enough that it starts spiraling outward. An emergency mission to > reattach a temporary counterweight at the snapping point > might be enough to correct this in time, however. > > In any case, except for the very early bootstrap stages, > the thing needs to be designed so that it will just never > snap. (Or be vanishingly unlikely to snap.) Once you have > the bootstrap tethers, it's hard to see why this is so > hard. > >> I really want to believe in the space elevator but so far, these >> questions are unanswered and untested. Anyone have ideas or am I just >> being a wet blanket? > > There is a NASA study group that looked at a wide variety > of objections, and emerged with the claim that all of the > problems people have come up with appear to be manageable. > This isn't just some half-baked idea kicking around mailing > lists. People have looked at it pretty hard. > > http://flightprojects.msfc.nasa.gov/pdf_files/elevator.pdf > > The tire-kicking will -- and should -- go on. In general, however, > it's better to do some background research before lapsing into > severe doubt. At this point, the real problems will come from > very unexpected directions. > > -michael turner > [EMAIL PROTECTED] > > >> Joe L. >> >> On Wed, 2003-11-19 at 21:53, Michael Turner wrote: >> > My take on this: the right kind of space elevator need not compete >> > for orbital space with an Earth-Moon tether. A space elevator >> > moving in the equatorial plane of the Moon could be an enabling >> > technology for > building >> > the Earth-Moon tether, since it's probably the cheapest per pound >> > way to > get >> > both to Earth-Moon L1 and to the surface of the Moon. It makes >> > sense to think more in terms of how they might be complementary than >> > competing. >> > >> > Designs I've seen so far for space elevators assume they are >> > tethered to > the >> > Earth, and have an equatorial orbit for their center of mass. >> > However, geosynchronous orbits don't have to be equatorial orbits. >> > The Earth is tilted with respect to the Earth-Moon orbital plane, so >> > a space elevator tethered to the Earth would either have to >> > pendulum, or the tip of it > would >> > have to travel north and south through the atmosphere, making a >> > round > trip >> > every 24 hours. >> > >> > A space elevator "ground floor" that travels thousands of miles a >> > day is still moving slowly enough for a jet plane, and maybe a >> > helicopter, to r > each >> > it, a small added cost. A pendulum approach might not work -- >> > anchoring > it >> > might be too hard, and might introduce angles that conflict with an >> > Earth-Moon tether. I don't this means we shouldn't do an anchored > elevator, >> > starting with equatorial orbit. Just that it should be designed so >> > that > it >> > can be unhooked and moved to an Earth-Moon orbital plane later with >> > relatively little trouble. >> > >> > Having a space elevator in the Earth-Moon equatorial plane is the >> > first approximation to reducing the chance of an Earth-Moon tether >> > and the > space >> > elevator ribbon crossing. aking the elevator "ground floor" mobile > rather >> > than fixed further reduces the intersection space. >> > >> > A second approximation might be to attach the Moon end of the >> > Earth-Moon tether to one of the Moon's poles. This introduces a >> > small angle. >> > >> > Finally, there's the issue of whether the Earth-Moon tether can be > attached >> > to the Earth, or whether it should just dangle outside the >> > atmosphere. > If >> > the tip of the Earth-Moon tether is near the equator, there's a >> > relative speed of about 1000 miles per hour. Consider, however, >> > that once you're > in >> > an aerodynamic regime of any kind, all the rules change. As you get > further >> > into the atmosphere, you can use relative speed for aerodynamic >> > lift, > and >> > rudders can steer the tether away from the equator, moving the tip >> > into higher latitudes where the relative speed is much slower. The >> > problems > of >> > attachment appear at the poles -- a relative tether-tip/atmosphere > velocity >> > that might become sub-aerodynamic. However, near those speeds, > conventional >> > aircraft could rendezvous with the tip, an attachment to the Earth >> > would > be >> > unnecessary. One could imagine a standard cargo freight plane >> > hovering > over >> > a landing pad at near stall speeds, then just touching down -- you > wouldn't >> > need something like an aircraft carrier dangling out there. >> > >> > The Earth-Moon's Earthside tether tip problems are further favored >> > by > being >> > in an aerodynamic regime, because, unlike the space elevator's >> > center of mass, the distance to the Moon is variable. The >> > Earth-Moon tether tip > would >> > spiral upward in latitude, and when the Moon was closer, the slack >> > would > be >> > taken up by drag forces within the atmosphere. >> > >> > How about the problem of pulling the Moon into the Earth? Well, >> > maybe > over >> > a very long time. However, a counterbalancing tether, hanging >> > outward > from >> > the Moon on its far side, would seem to take care of that problem. >> > >> > An Earth-Moon tether would be vastly more massive than a terrestrial > space >> > elevator. For one thing, the distance is much greater. For >> > another, > over >> > much of that distance (past L1 toward the Earth), the forces of >> > gravity won't be significantly counterbalanced by sub-orbital >> > centrifugal > forces. A >> > space elevator's strongest point has to be at its center of mass in >> > GEO. The Earth-Moon tether's problem, not long after the growth of >> > it has > touched >> > down on the surface of the Moon, is in anchoring it strongly enough >> > to > the >> > Moon. >> > >> > -michael turner >> > [EMAIL PROTECTED] >> > >> > >> > ----- Original Message ----- >> > From: "Mark Schnitzius" <[EMAIL PROTECTED]> >> > To: <[EMAIL PROTECTED]> >> > Sent: Thursday, November 20, 2003 11:23 AM >> > Subject: RE: Nanotube cable will connect Earth and Luna >> > >> > >> > >> > Obligatory quote from It's a Wonderful Life: >> > >> > George Bailey: What do you want, Mary? Do you >> > want the moon? If you want it, I'll throw a >> > lasso around it and pull it down for you. Hey! >> > That's a pretty good idea! I'll give you the >> > moon, Mary. >> > Mary: I'll take it! Then what? >> > George Bailey: Well, then you can swallow it, and >> > it'll all dissolve see, and the moonbeams would >> > shoot out of your fingers and your toes and the >> > ends of your hair... am I talking too much? >> > >> > Seriously, you could put a terminal at the Earth- >> > moon L1 Lagrange point, but that's closer to the moon >> > than it is to Earth. The pole idea might work. >> > It wouldn't come close to crossing paths with any >> > space-elevators that way too. I'm sure this crazy >> > idea will fizzle for some other practical reason, >> > though. To be replaced by something even crazier, >> > no doubt. >> > >> > >> > --Mark >> > >> > --- [EMAIL PROTECTED] wrote: >> > > Has anyone heard of this idea before? How would it >> > > work? The Moon doesn't >> > > revolve around the Earth at the same rate the Earth >> > > rotates, so how could >> > > such a cable be attached? (Through some sort of >> > > swiveling mechanism at the >> > > north or south poles, perhaps?) Would there be a >> > > danger of this cable >> > > getting tangled up with some Space Elevator cables >> > > that may have previously >> > > been built between the Earth's Equator and >> > > synchronous orbit? If the cables >> > > got tangled, could they pull the Earth and Moon into >> > > each other? :-) >> > > >> > > >> > > >> > > John Sheff >> > > Cambridge, MA 02139 >> > > [EMAIL PROTECTED] >> > > >> > > -----Original Message----- >> > > From: [EMAIL PROTECTED] >> > > [mailto:[EMAIL PROTECTED] Behalf Of LARRY >> > > KLAES >> > > Sent: Tuesday, November 18, 2003 9:59 AM >> > > To: setipublic >> > > Cc: BioAstro; europa >> > > Subject: Nanotube cable will connect Earth and Luna >> > > >> > > "NANOTUBE CABLE WILL CONNECT THE EARTH AND THE MOON" >> > > >> > > Andrew Yee <[EMAIL PROTECTED]> >> > > >> > > InformNauka (Informscience) Agency >> > > Moscow, Russia >> > > >> > > Contact: >> > > >> > > A.N. Redkin >> > > or >> > > L.V. Maliarevich >> > > Institute of Problems of Microelectronics Technology >> > > and >> > > Extra Pure Materials >> > > Russian Academy of Sciences >> > > Chernogolovka, Moscow Region >> > > + 7 (095)962-80-74, + 7 (095)962-80-47 >> > > [EMAIL PROTECTED] >> > > >> > > 14.11.2003 >> > > >> > > THE NANOTUBE CABLE WILL CONNECT THE EARTH AND THE >> > > MOON >> > > >> > > Researchers from the Institute of Problems of >> > > Microelectronics Technology >> > > and >> > > Extra Pure Materials (Russian Academy of Sciences) >> > > have designed and tested >> > > a >> > > new device for production of a new promising >> > > material -- nanotubes. The >> > > researchers believe that it is exactly the material >> > > a transport cable can be >> > > produced of to connect the Moon and the Earth. >> > > >> > > Back at the beginning of the last century, the idea >> > > was born to build a >> > > transport cable between the Earth and the Moon to >> > > deliver goods from our >> > > planet >> > > to the Moon. Until recently, there has been no >> > > material enabling to make >> > > this >> > > idea a reality. Polymers would not stand cosmic >> > > radiation, and the steel >> > > cable >> > > would have enormous weight. The most durable >> > > material as of today -- Spectra >> > > 1000 -- would allow to produce a cable of only 315 >> > > kilometers long, as the >> > > longer cable is simply unable to bear its own >> > > weight. >> > > >> > > Carbonic nanotubes would very well suit the role of >> > > a structural material >> > > for >> > > such a cable. According to the researchers' >> > > estimates, a lightweight cable >> > > of >> > > required length can be produced from this material, >> > > the cable being 50 times >> > > stronger than the current most durable materials. >> > > The problem is that the >> > > researchers have not learned yet to produce high >> > > quality nanotubes in large >> > > quantities: that is either too expensive or feasible >> > > only in the laboratory >> > > environment. Therefore, this material is still >> > > pretty exotic, its price >> > > varying >> > > from $60 through $100 per gram. >> > > >> > > The scientists from Chernogolovka have designed a >> > > device that allows to >> > > produce >> > > pretty large amounts of high quality nanotubes. The >> > > device is based on a >> > > rather >> > > simple scheme: spirit, glycerin or their mixture >> > > gets from a specially >> > > cooled >> > > chamber into the zone of graphite heater bar, where >> > > the temperature reaches >> > > 1000-2000 degrees C. That results in ultraspeed >> > > heating and substance >> > > combustion. The products precipitate on a special >> > > carbonic glass bell >> > > covering >> > > the device, or they are removed outside together >> > > with vapors and gases, thus >> > > allowing to protect the product from various >> > > unnecessary impacts. >> > > >> > > Precipitations of such kind normally contain >> > > amorphous carbon, soot and >> > > various >> > > particles covered by a shell of carbon, as well as >> > > carbon fibre and >> > > nanotubes. >> > > However, in this particular case the researchers >> > > came across a surprise: the >> > > precipitations obtained in the device turned out to >> > > contain only nanotubes >> > > and >> > > carbon fibre. No other admixtures were found. It >> > > means that a laborious >> > > procedure is not required for rectification from >> > > unnecessary compoments. The >> > > fibres are 30-150 nanometers thick, and nanotubes >> > > are 20-50 nanometers >> > > thick, >> > > their length being several micrometers. >> > > >> > > The growth of nanotubes can be accelerated with the >> > > help of catalysts -- >> > > iron, >> > > nickel, cobalt and gold. If the surface where >> > > nanotubes are to be >> > > precipitated >> > > is covered with a thin film of such catalyst in the >> > > form of some pattern, >> > > then >> > > nanotubes will precipitate only upon the pattern, >> > > the other parts remaining >> > > clean. >> > > >> > > In principle, such devices may lay the foundation >> > > for industrial production >> > > of >> > > nanotubes. Maybe, a nanotube cable will soon connect >> > > the Moon and the Earth. >> > > >> > >> > >> > __________________________________ >> > Do you Yahoo!? >> > Free Pop-Up Blocker - Get it now >> > http://companion.yahoo.com/ >> > == >> > You are subscribed to the Europa Icepick mailing list: >> > [EMAIL PROTECTED] Project information and list (un)subscribe info: >> > http://klx.com/europa/ >> > >> > >> > >> > == >> > You are subscribed to the Europa Icepick mailing list: >> > [EMAIL PROTECTED] Project information and list (un)subscribe info: >> > http://klx.com/europa/ >> >> == >> You are subscribed to the Europa Icepick mailing list: >> [EMAIL PROTECTED] Project information and list (un)subscribe info: >> http://klx.com/europa/ >> >> > > == > You are subscribed to the Europa Icepick mailing list: [EMAIL PROTECTED] > Project information and list (un)subscribe info: http://klx.com/europa/ == You are subscribed to the Europa Icepick mailing list: [EMAIL PROTECTED] Project information and list (un)subscribe info: http://klx.com/europa/
