Space elevator update

[nexium]

After several years of silence ISR again has a web site about space elevators. There is not much info, but a few items are significant: They are thinking 5 tons payload for the first elevator. Last I heard Dr Edwards was thinking a twenty ton payload. My guess is scaling up to 30 tons payload may prove close to impossible even if CNT = carbon nano tubes meet the more optimistic projections.<br /> ie An average cross sectional area of one centimeter at density = 1.5 means 1.5 grams per cm 150 grams per meter 150 kilograms per kilometer, 15,000 metric tons for a length of 100,000 kilometers. To build it with technology likely available before 2010 limits us to perhaps 150 tons starting thread with a cross sectional area of one square millimeter. This may not be strong enough for the 970 kilogram (gross weight) climber planned by Dr Edwards. ISR may be thinking a pay load of 150 kilograms for the early climber. At 150 kilograms, almost 100,000 climbers would need to assend to pull the total to 15,000 metric tones. That is one billion dollars if the climbers and payload cost $10,000 each (likely lots more costly) Actually the number is less as the stronger ribbon can tolerate larger climbers that carry pay loads of several tons when the ribbon is near completion. They will, however, be thinking bigger safety factor as the toal investment gets bigger.<br /> Last I heard Dr. Edwards was thinking a ribbon one meter wide and perhaps 1/10th millimeter thick to carry a payload of 20 tons. That is a cross sectional area of 100 square millimeters = one square centimeter. It was proposed that the ribbon would roll into a tube about 33 centimeters in diameter to reduce the micro meteor impacts by about half. <br /> I'm skeptical that the thousands of climbers can each unroll 100,000 kilometers of ribbon at 500 kilometers per hour without doing considerable damage to the ribbon. An average speed of 500 kilometers per hour means it takes 200 hours to reach the far end. If another cli

 

[teije]

Do you have a link to their site?<br /><br />thx<br />Teije

 

[nexium]

Try www.isr.us/SEHome.asp?m=1

 

[nexium]

That link worked for me and I found some 2002 details at that website.<br /> The Space Elevator /> FAQs Science<br /><br /> /> Science<br />Business, Economics, and Politics<br /> Engineering <br /><br />Please note that a number of issues are addressed in the Phase I NIAC paper. <br /><br />1. What about conservation of angular momentum?<br /><br />2. What if it breaks? <br /><br />3. Will high winds pose a problem?<br /><br />4. What if lightning strikes the ribbon? <br /><br />5. Won't the ribbon "short out" the atmosphere?<br /><br />6. Will the ribbon produce an electrical current?<br /><br />7. Will an oscillation bring the ribbon down? <br /><br />8. Will radiation degrade the components? <br /><br />9. Will the ribbon effect bird/other species migration? <br /><br />10. What about things hitting the ribbon?<br /><br />11. The Leonids and the Space Elevator <br /><br />12. What about alternatives?<br /> <br />What about conservation of angular momentum?<br /><br />When an elevator ascends the ribbon, it must be accelerated eastward because the Earth's rotation represents a larger eastward velocity the higher you go. The required eastward force on the ascending elevator would have to be provided by a corresponding westward force on the ribbon. <br /><br />If you go through the math quantitatively, the angular momentum for the climbers requires a pound or so of force over the one-week travel time, and we do that easily with our many tons of material in the anchor and the counterweight.<br />The quantities really are tiny, but just to be complete, a climber going up pushes the entire elevator slightly to the east, causing it to lean. However, the ribbon recovers for the same reason that it stays up in the first place. Centripetal acceleration is acting on the upper two-thirds pulling it outward, and the lost angular momentum is replaced very quickly (essentially as fast as it is lost). The ribbon will never lose enough angular momentum to even deflect a single degree, let alone

 

[nexium]

My guess is 1 through 6 are good science, however some scenarios will be different. 2When a break occurs the ends separate slowly at first, so there is a fair chance of bringing the ends together by accelerating the climbers in the correct direction and firing engines that are used to manage transients. Some space tugs may be available to try to save the tether. The effort could persist for several days, while tether/ribbon wrapped slowly around the Earth, not all in the ocean.<br /> The ribbon is perhaps rarely deadly in populated areas, but the <millimeter thickness can mean cut human flesh when a vehicle hits the ribbon miles away and/or strong wind gusts whip the fallen ribbon about. The legal rule should be anyone can have fallen ribbon. Pieces of any length should be valuable, so most of it will carted away before injuries occur other than to the scavengers. Neil

 

[teije]

Thanks for the link and the extra text. <br />Teije

 

[nexium]

The entire tether can fall with a serious management error such as moving 1% of the far end ballast toward Earth or having an excessive number of out bound climbers. Excessive ballest at the far end can break the ribbon unless out bound climbers are slowed or revese direction. Transients can break the ribbon, if the corrective action is the revese.<br /> As far as I know no one (other than me) has considered how climbers can pass each other. Can each climber squeeze about 49% of the ribbon width allowing them to pass cautiously? Neil

 

[nexium]

items 4 and 6: The indiviual fibers of CNT are 'good' electrical conductors. I can only guess weather that means better than copper or better than cast iron.<br /> Either resistivity means perhaps 0.1 ohms per meter = 100 ohms per kilometer. If 100 amps flows, that is one million watts per kilometer of heating. My guess is that is near the maximum safe temperature in the vacuum of space where heat loss is by radiation of infrared photons = No conduction and no convection. The ribbon will also be heated by the sun, by the rolers of climbers and by stray photons from the laser beam that powers the climbers. My guess is we want to increase rather than decrease my guestimated 100 ohms per kilometer. The epoxy binder can increase the resistance. A reduction in current flow could signal that damage to the ribbon has occured. Neil

 

[teije]

Oh I love this... <br /><br />Their FAQ section on Business, economics, and politics:<br /><br /><font color="orange"> Q: How will the elevator be funded? <br />A: The elevator can be funded privately, publicly, or with a combination of the two.</font><br /><br />This is marketing speak for: We haven't got a dime! Wanna fund us?<br /><br /><font color="orange"> Q: Don't projects of this scope tend to run over-budget? <br />A: As a matter of fact, no, they don't. While there is precedent for space projects running over-budget, we are working to be as honest as possible with our costing and place contingency costing on items that are uncertain. As we continue our development, we will have a much better handle on the costs and the budget will change accordingly. The current budget may not match the end result, but once engineering studies are done there is no good reason why the final budget should not be a firm and realistic one. The other thing to remember is that cost overruns are often the result of poor planning or greed. We will do our best to avoid both. </font><br /><br />Again marketingspeak for: Yes they do! But we won't, we are smart, all the others were not.<br /><br />Yeah right. Like I would believe that if I were an investor...<br /><br />From their concept page:<br /><br /><font color="orange"> Recent analysis also finds that the first space elevator could be built for $7 to $10 billion total, including launch costs, and a second elevator would cost a small fraction of the first. The first elevators could be financially self-supporting (including recovering the initial construction costs and the cost of borrowing this money) within the first 10 years of operation on the commercial satellite market. The recurring costs are: 1) climbers, 2) power beaming system operation, 3) low-Earth object tracking system operation, and 4) anchor operations. For the initial space elevator, these recurring costs combined with repaying the initial capital investment wou</font>

 

[nexium]

Hi teije: It is depressing when the arithmetic doesn't check. The 7 to 10 billion is likely optimistic. At $100 per kilogram for the ribbon = $1.5 billion. The large number of climbers could easily cost several billion. Climbers will occasionally move in the non- profit direction to keep trancients under control and to facilitate repairs which will likely be needed due to micro meteorites meaning tomarrow's launch must be skipped. Neil

 

[yevaud]

Nexium:<br /><br />Hi. Just curious, as I have followed the progress of this somewhat, since proposed by Clarke. I was to the understanding that as of now, no carbon nano-tube more than a very tiny size could be produced. Clearly, you have better sources than I do. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[douglas_clark]

Yevaud,<br /><br />Doubt he has, but it is a fascinating idea, is it not? At this moment in time it would seem worth spending billions, if that is what it takes, to get sufficiently long tubes.<br /><br />douglas

 

[nexium]

The last I heard (year ago)many labs were making 1 to 2 centimeter tubes, but one French lab annouced they could make them kilometers long. Likely that was a fib.<br /> I understand that very long tubes are essential as the tubes are slippery, making both cohession and adhession poor. Neil

 

[douglas_clark]

nexium,<br /><br />Probably already out of date:<br /><br /><font color="yellow">Extra-long carbon nanotubes set new record<br />20 September 2004<br /><br />Researchers at Los Alamos National Laboratory and Duke University, both in the US, have created, at four centimetres long, what they believe is the world's longest single-walled carbon nanotube. The team hopes it may ultimately be able to grow nanotubes continuously.<br /><br />"Although this discovery is really only a beginning, the continued development of longer length carbon nanotubes could result in nearly endless applications," said Yuntian Zhu of Los Alamos. "Actually, the potential uses for long carbon nanotubes are probably limited only by our imagination." <br /><br />According to the researchers, applications for long single-walled carbon nanotubes could include electronic devices, microelectromechanical systems, biosensors, scaffolding for the growth of neurones, robotics, space exploration, personal armour and sporting goods. <br /><br />To grow the nanotubes, Zhu and colleagues used the iron-catalysed decomposition of ethanol vapour, creating the tubes on a silicon substrate. Both metallic and semiconducting nanotubes formed, lying flat on the substrate. The growth rate was extremely high - around 11 µm per second - and Raman spectroscopy indicated that the nanotubes were of a high structural quality. <br /><br />The scientists believe that ethanol was critical for the growth of the ultralong nanotubes, "probably because it does not tend to form amorphous carbon on dissociation". The team reckons the long nanotubes formed by a tip-growth mechanism, with the catalytic iron particles moving as the nanotube tip grew. All the tubes had a diameter between 1.31 and 2.25 nm, suggesting that the size of the catalyst particles was important. <br /><br />The researchers expect that optimizing the carrier gas flow rate and composition, the growth temperature and the initial concentration of catalyst solution (which would affec</font>

 

[douglas_clark]

nexium,<br /><br />What length would be needed? Are there sources for this?<br /><br />Thanks<br /><br />douglas

 

[nexium]

I have not seen any numbers on fiber length, but my guess is kevar and CNT makes better tethers if the fibers are as long as the tether. Fibers like wool grip each other like velcro, so even one centimeter fibers make moderately strong cloth and thread. Present thinking is epoxy as a binder for CNT fibers. I wonder if anyone is researching ceramic binders for CNT. I think CNT retains it's strength to more than 1000 degrees c, which is a big plus if the binders are still working that hot. Hot CNT needs to be protected from oxygen as it burns much like charcoal or coke. Apparently atomic oxygen degrades CNT (and lots of other substances )even below room temperature. Atomic oxygen is found in Earth's upper atmosphere and is one atom to a moelecule, while ozone is three atoms per molecule and likely also degrades CNT. Neil

 

[nacnud]

I think the possiblites of CNT get interesting once the fibers start being easily produced a around an inch long.<br /><br />Where I read this or even if I make it up I can't recall<br />

 

[spacester]

<font color="yellow">I think the possiblites of CNT get interesting once the fibers start being easily produced a around an inch long.</font><br /><br />I concur.<br /><br />A space elevator rated CNT ribbon would be made of a composite. The idea behind composites is that you combine a load-bearing material (fiber) with a load-spreading material (matrix). The CNT fibers would be embedded in an "epoxy" matrix.<br /><br />If one inch CNT fibers become readily available, the challenge shifts to the matrix material. It does not need to be as strong as the CNT, but it does need to be strong enough and ductile enough to distribute the load between adjacent fibers. The CNT fibers would of course overlap along their lengths, so in principle they don't have to be as long as one might think.<br /><br />That being said, the longer the CNT fibers the better; this would reduce the requirements on the matrix.<br /><br />Of course, the matrix has other material property requirements that add to the challenge. And it seems more than likely that a space elevator would not be the first application of this new "wonder" material. <div class="Discussion_UserSignature"> </div>

 

[nacnud]

<font color="yellow">...it seems more than likely that a space elevator would not be the first application of this new "wonder" material</font><br /><br />I agree, I think that if CNT becomes cheap that one of its major uses will be in construction. Currently most construction materials (metal, steel, glass, concrete) are very heavy and require a large amount of machinery to move them around. If cheap composites could be used instead the weight of the materials drops substantially and therefore so does the cost of the associated machinery. <br /><br />Also it’s not until some other usage drops the price of CNT that SE become realistically affordable from a materials point of view.<br />

 

[teije]

Hi nexium.<br />I agree. I was thinking about climber costs as well. Those babies won't come cheap. And they are climbers only. Not climber/descenders. So they are 1 use only. <br /><br />Along with the other facts stated above about the maturity of CNT technology and some more plausible arguments, I must come to the conclusion that space elevators are not something for the near future. <br /><br />Nice website, nice dream, but not to realistic I'm afraid.<br /><br />Teije

 

[chris_in_space]

I have always found the idea of a space elevator interesting but it couldn't convince me it would be profitable. I mean there are really a lot of numbers out there which really come from nowhere and are just set up in order to give an impression of profitability. I mean if you just take the fact that there's a launched payload (5000 kg) every day. Hey there would be many rocket companies that would be very happy if that happened to be true. Today there are 10 to 20 5000 kg satellites launched per year not 365 as supposed in the space elevator concept. So for me the really important question is: is there a sufficient market out there for the space elevator to be profitable?<br />I agree that with low launch costs the elevator could create a whole new market but still, you have to start planning from the initial market and not more than 10 times this market because I really don't see how the space elevator could find at it's begining so many new customers.<br />But still, it could be really nice if the space elevator would be built. Maybe financed by NASA and other space agencies since it couldn't be more unprofitable than the space shuttle and unlike the shuttle the costs would really go down the more you would use the elevator.

 

[nexium]

I suppose few of the great advances of humans would have occured without a bit of unjustified optimism. It appears there will be solutions to all the problems, but some of the solutions may cause cost over runs and/or delay the completion. If there are 300 launches per year for ten years averaging 8 tons, with recepts of $100 per kilogram = $100,000 per ton, that is 2.4 billion dollars. The first elevator fell short of break even by a factor of 3 or 4. but there will be licencing fees for perhaps ten more elevators which can produce a pay back in less than ten years, if there are a sufficient number of customers. I agree, not a get rich quick skeem, but the space elevator may attract investors anyway. Keep in mind that a high percentage of the launches may be to locals farther than Mars, at 1% of the likely cost by rocket. More details at www.liftport.com click on forums in the center, near the bottom of the first page of their web site. Neil

 

[torino10]

I find the idea of an earth to Geo space elevator fascinating, but wouldn't it be much more practical to have a so called flying space elavator?<br /><br /> I found a description of one in a paper on space elevators located on the NASA website here.<br />http://trs.nis.nasa.gov/archive/00000535/<br /><br />I think the flying space elevator would be much more workable and able to pay for itself in far less time.<br /><br />If it could bridge the gap between suborbital launch technologies and orbital deployments then it would generate impetus and financial backing for the numerous suborbital technologies being developed in the wake of the X prize.<br /><br />If enough of them were built you could have communication and earth monitoring equipment at the lower end replacing much of the current clutter in low earth orbit.<br /><br />One of the more beneficial aspects of the flying space elevator concept is that instead of competing with current launch technologies it could increase payload capacity of those technologies.<br /><br />the space elevator as pictured on page 8 of the previously mentioned paper and described on page 9 would seem to be a good idea for an advanced space launch infrastructure but may be too large a fist step.<br /><br />it might be better to use a LEO rotating space tether with a slightly eliptical orbit to take small unmanned payloads from suborbital launch vehicles and fling those payloads into an actual orbit <br /><br />the main reason I prefer the flying space elevator to the rotational space tether concept is that the flying space tether would be able to grow more easily and would be a more permanent structure with more possibilities for development.<br /><br />The view from the hotel at the bottom would be awsome

 

[mlorrey]

The reason there isn't a payload-a-day market is primarily because launch prices are in the thousands of dollars per lb payload. This is a simple matter of supply/demand price curves: if it only cost $10k for a person to travel to orbit, there would automatically be a backlog of millions of people wanting to get to orbit, where today with a $20 million price tag per seat, there are only a handful at most per year wanting to make the trip.<br /><br />Similarly, if it cost $50/lb to get payload to GEO, you'd have a stampede of industry to orbit and beyond, and a lunar base set up within a year shipping lunar LOX, solar cells, and structural metals back to GEO for further construction.<br /><br />It is truly a "Field of Dreams" concept: once you build it, the economic benefits and potential profits make themselves obvious, but typically the bankers, congressmen, and other people who hold the vast amounts of capital needed to make it a really do not have the vision to see and understand the potential. They can't see the players in the field, or the line of cars full of people coming in the night to watch a game they don't know they are coming to see.<br /><br />Most people have very stasis-oriented outlooks on life: they don't see how life has really changed that much due to major technological advances. Even with the railroads, the airline industry, and the computer industry, people don't see the potential until it smacks them in the face.<br /><br />The railroads are an excellent example. Technologies necessary to build railroads had existed for centuries: the principles of the steam engine were known since ancient Greece, and various mechanical engines had been developed first for pumping water out of mines long before they were applied to transportation.<br /><br />The real limitation on railroads as transcontinental trade expanders was caused by materials: a lack of the ability to produce vast quantities of steel, just as today the lack of the tether rests on the need for co

 

[nexium]

A 1000 kilometer flying space elevator has some disadvantages, one of which is they fly very fast/ about 16,000 miles per hour, so landing on the low end takes almost as much energy as getting to LEO = low Earth orbit. Then we need something equivelent to the climbers to reach the far end. We solve both problems in part, by rotating a 1000 (ten kilometers might make a proto type to test the theory) kilometer ribbon, so that the low end slows to about 12,000 miles per hour and the far end speed is about 3000 miles per hour faster than the flying elevator. Climbers are only needed to inspect and repair the ribbon as the tether/ribbon changes ends about twice per hour. The ribbon can dip a bit farther into the upper atmosphere because of the lower tip speed. A big plus is 40 pay loads per day might be practical and a semi polar orbit would give frequent acess to all the countries of the world.<br />Disadvantages are 1 Very critical timing to land on the tip 2 Tip rockets are likely essentual, to fine tune the rondevous, reduce the stress on the ribbon, and the g loading of the payload. 3 That means part of most payloads needs to be fuel for the tip rockets. 4 Unless returning space craft are using the rotating ribbon to decelerate, the tip motors also need to increase the speed of rotation and altitude of the rotating ribbon, periodically. Neil