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Achieving the Space Elevator / Science & Technology / Re: Other uses for CNT
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on: August 09, 2007, 03:17:30 PM
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Note: A Lunar Space Runway is not a lunar SE although they have a lot of technology in common.
A Lunar Space Runway is a horizontal ring 192.5 km in radius that a magnetic levitation train drives around until it reaches escape velocity. The ring will probably be made out of CNT or a strong plastic like Kevlar.
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123
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Achieving the Space Elevator / Science & Technology / Re: Record SWNT array length!
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on: August 09, 2007, 08:09:47 AM
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If the clips grip with enough friction to break the thread. If you can get a CNT thread long enough to provide gripping surface.
We are now dealing with nanotubes nearly 2 centimetres long. Since thy are as long as the width of a finger you can probably hold them with your fingers. For extra grip when measuring something like paper could be placed in the bulldog clips or vice head.
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124
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Achieving the Space Elevator / Science & Technology / Re: Other uses for CNT
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on: August 08, 2007, 05:55:25 PM
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10 GPa CNT would permit construction of a 50 tonne payload lunar runway whose track/ribbon weighs 300 to 400 metric tons.
At 23 metric tons per lunar lander 400/(23-1) = 18 landings would be needed to take the ribbon to the moon. Bulldozers, solar panels, connectors to supporting towers and motors will need extra flights.
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125
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Achieving the Space Elevator / Science & Technology / Re: Record SWNT array length!
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on: August 08, 2007, 05:29:49 PM
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I thought about this for a bit. I guess the reason is, is that scientific experiments like this take time and funding to perform. There already are tensile strength experiments for smaller lengths. The other explanation is that the macrolength CNT producer doesn't want to give up the CNT.
A third option is that the material was weaker than steel and they did not want to admit it. It is not too difficult to string a CNT thread between two bull dog clips and add weights until the thread breaks.
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127
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Research / The Lifter / Re: magnetic propulsion
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on: August 08, 2007, 09:10:09 AM
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{snip}
For the proposed 90 tonne (90,000kg) vehicle the figures are just as tough as the total energy requres IS directly proportional to the MASS of the vehicle so I'll just scale my previous result by the proportional mass increase of 90,000 / 7,000 (or about 12.857), giving the required engine power of 1,215kW (or 1.215MW!) to achieve the proposed average 0.1G acceleration for 27 seconds. Remember these final engine powers are net average power over the entire acceleration time, so you would need (much) less power for the first few m/s and MUCH MORE power for the final couple of seconds IF you wanted to keep the acceleration at a constant 0.1G.
eg., To go from 26 to 27 m/s in 1 second (the final second of acceleration) for the 7,000kg vehicle this would be as follows: E = 0.5 * 7,000 * ((27 * 27) - (26 * 26)) E = 0.5 * 7,000 * (729 - 676) E = 185,500 J in 1 second, or 185.5kW For the 90 tonne vehicle this would be 2,385kW!
If you want a low power engine, you must accept the acceleration will slow down the faster you go.{snip}
So the problem is that although school boy Newtonian physics uses constant acceleration the only source of constant acceleration is gravity and then only over short distances. Man made motors can however produce constant power (energy per second). So t = E/P Where t is the time in seconds E = total energy needed in Joules P = Power in Watts (= Joule/second) or t = (m v 2) / (2 P) where m = mass in kilograms v = final velocity in metres/second Thank you.
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128
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Achieving the Space Elevator / Law & Politics / Re: Orbital debris.
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on: August 07, 2007, 04:31:27 PM
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On the notion of active satellites, the national security considerations alone might require some work on the part of anyone running the SE. Here I'm thinking of the various spy satellites employed by both the US and other governments. If they need to be in a certain orbit, and that orbit intersects the operational path of the SE, I wouldn't be surprised if a few sudden steering movements were required after a late-night call from the Pentagon.  Of course, they hate to advertise the orbits of their birds, and I think having to notify a company to move their space elevator would count as a pretty big advertisement to their thinking... A satellite crashing into the strongest material that man can make will probably be destroyed. Consequently it is very much in the interest of the military, intelligence and commercial owners of satellites to ensure that this does not happen to one of their birds. The orbital information can be forwarded to LiftPort Inc. via the encrypted cell phone allocated to the on site military liaison officer who arranges secure flights on the space elevator. LiftPort Inc. may have a need to know that Satellite XY372 will be in the vicinity on Wednesday, they do not need to know that it is the same machine as Bird ABC568 from 3 months ago or the content of Black Box Delta-Xray 953 launched by LiftPort last year. Any of LiftPort staff clever enough to work this out is also clever enough to know that they will be fired if they tell say the press. LiftPort can be encouraged to act ethically by the threat that future $5 million launches will be cancelled (or delayed for a year whilst "unexpected additional testing is performed").
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134
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Research / The Ribbon / Re: 32 GPa graphene oxide paper
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on: July 29, 2007, 07:59:26 AM
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More information http://intl.emboj.org/nature/journal/v448/n7152/full/nature06016.htmlVarious thicknesses. "... after drying, free-standing graphene oxide paper with thicknesses ranging from 1 to 30 micro-metres. This material is uniform and dark brown under transmitted white light and almost black in reflection when thicker than 5 micro-metres." "However, the work of extension to fracture for graphene oxide paper is as high as 350 kJ m-3 (approx190 J kg-1, at the material density of approx1.8 g cm-3," "The average modulus of graphene oxide paper was determined to be 32 GPa (average from 31 tested samples, with the highest being 42 plus/minus 2 GPa" Comment research may reveal ways of increasing the average strength by controlling the production process. "Samples for bending tests (approximately 2 x 20 mm^2) were cut from the same membranes as those for tensile tests." Comment if smaples can be cut to that size then the material must be longer than 2 cm and they are not trying for long lengths yet.
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