Re: [geo] Atmospheric CO2 to carbon fibers?
Dear David, I don't know the details of the technique, it is nice to see all the research done on this. $1000 per ton C would correspond to $270 per ton CO2 extracted, in line with what other claims for direct capture, but these numbers should be taken with a pinch of salt. The fact that C nanofibers sell a high price is certainly interesting, but I guess the market is small. Do we really need 500 Gt of C nanofibers? I would think the only mass market for C captured from the air is fuel. Regards, Olivier Stuart Licht at George Washington University apparently spoke at the American Chemical Society meeting today on a technique for extracting CO2 from the air and converting it into carbon nanofibers. Some highlights from the AAAS press release (linked below): * Licht says, We calculate that with a physical area less than 10 percent the size of the Sahara Desert, our process could remove enough CO2 to decrease atmospheric levels to those of the pre-industrial revolution within 10 years. * Energy costs are estimated to be about $1,000 per ton of carbon nanofibers. Carbon nanofibers currently sell for much more than that. * Because of its efficiency, this low-energy process can be run using only a few volts of electricity, sunlight and a whole lot of carbon dioxide. At its root, the system uses electrolytic syntheses to make the nanofibers. CO2 is broken down in a high-temperature electrolytic bath of molten carbonates at 1,380 degrees F (750 degrees C)To power the syntheses, heat and electricity are produced through a hybrid and extremely efficient concentrating solar-energy system. The system focuses the sun's rays on a photovoltaic solar cell to generate electricity and on a second system to generate heat and thermal energy, which raises the temperature of the electrolytic cell. http://www.eurekalert.org/pub_releases/2015-08/acs-ft071615.php Does anyone know more about this? It certainly sounds too good to be true. -- You received this message because you are subscribed to the Google Groups geoengineering group. To unsubscribe from this group and stop receiving emails from it, send an email to geoengineering+unsubscr...@googlegroups.com mailto:geoengineering+unsubscr...@googlegroups.com. To post to this group, send email to geoengineering@googlegroups.com mailto:geoengineering@googlegroups.com. Visit this group at http://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups geoengineering group. To unsubscribe from this group and stop receiving emails from it, send an email to geoengineering+unsubscr...@googlegroups.com. To post to this group, send email to geoengineering@googlegroups.com. Visit this group at http://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout.
Re: [geo] Tricky question - SRM / carbon credits
How many carbon credits is a tonne of SRM worth? Seriously? This is precisely what geoengineering proponents promised that it won't be used for - as a substitute in any way, shape or form to carbon emission mitigation. To get acceptance for the idea of even funding research into SRM or other geoengineering schemes in response to global warming, the repeated promise was that it is not meant to replace emission reductions, only a backup to buy us some time... Using SRM to generate carbon credits is EXACTLY to generate EXTRA carbon emissions allowances - even though all SRM could do, at best, is masking the true impact of the current GHG levels on warming while the spraying is ongoing, without ever removing a single atom of carbon from the atmosphere for which it's to claim carbon credit. In short, SRM will lead to even MORE emissions, not less, and due to the masking and the lack of public awareness that it's the masking that's keeping the temperatures from shooting up even higher even quicker, it just helps keeping business-as-usual longer, on top of ocean acidification, acid rain, potential disruption of regional climate patterns, etc etc. Maggie Zhou, PhDhttps://www.facebook.com/maggie.zhou.543 On Thursday, August 20, 2015 4:15 AM, Andrew Lockley andrew.lock...@gmail.com wrote: How many carbon credits is a tonne of SRM worth? We could work this out as watts cooling or weight sulphur for weight carbon. Doesn't really matter. Thanks Andrew -- You received this message because you are subscribed to the Google Groups geoengineering group. To unsubscribe from this group and stop receiving emails from it, send an email to geoengineering+unsubscr...@googlegroups.com. To post to this group, send email to geoengineering@googlegroups.com. Visit this group at http://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups geoengineering group. To unsubscribe from this group and stop receiving emails from it, send an email to geoengineering+unsubscr...@googlegroups.com. To post to this group, send email to geoengineering@googlegroups.com. Visit this group at http://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout.
Re: [geo] Tricky question - SRM / carbon credits
Maggie (and list), Thanks for your response. However, there are a couple of problems with the stance you take. Firstly, I'm simply looking to answer a physics / earth science question. The answer will be true whether we want it to be, or not. The world deals with many other distasteful comparisons, such as how much is a life worth in cost-benefit analyses. Secondly, even if we engage with the political angle you discuss, your logic doesn't necessarily bear scrutiny. People may choose to offset only the components of their emissions they have no control over, eg agriculture, government sector, etc. I'd suggest that those buying carbon credits are probably more prone to taking mitigation action than demographically matched controls. I'd welcome further dialogue. Thanks Andrew Lockley On 20 Aug 2015 23:49, Maggie Zhou mzhou...@yahoo.com wrote: How many carbon credits is a tonne of SRM worth? Seriously? This is precisely what geoengineering proponents promised that it won't be used for - as a substitute in any way, shape or form to carbon emission mitigation. To get acceptance for the idea of even funding research into SRM or other geoengineering schemes in response to global warming, the repeated promise was that it is not meant to replace emission reductions, only a backup to buy us some time... Using SRM to generate carbon credits is EXACTLY to generate EXTRA carbon emissions allowances - even though all SRM could do, at best, is masking the true impact of the current GHG levels on warming while the spraying is ongoing, without ever removing a single atom of carbon from the atmosphere for which it's to claim carbon credit. In short, SRM will lead to even MORE emissions, not less, and due to the masking and the lack of public awareness that it's the masking that's keeping the temperatures from shooting up even higher even quicker, it just helps keeping business-as-usual longer, on top of ocean acidification, acid rain, potential disruption of regional climate patterns, etc etc. Maggie Zhou, PhD https://www.facebook.com/maggie.zhou.543 On Thursday, August 20, 2015 4:15 AM, Andrew Lockley andrew.lock...@gmail.com wrote: How many carbon credits is a tonne of SRM worth? We could work this out as watts cooling or weight sulphur for weight carbon. Doesn't really matter. Thanks Andrew -- You received this message because you are subscribed to the Google Groups geoengineering group. To unsubscribe from this group and stop receiving emails from it, send an email to geoengineering+unsubscr...@googlegroups.com. To post to this group, send email to geoengineering@googlegroups.com. Visit this group at http://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups geoengineering group. To unsubscribe from this group and stop receiving emails from it, send an email to geoengineering+unsubscr...@googlegroups.com. To post to this group, send email to geoengineering@googlegroups.com. Visit this group at http://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout.
Re: [geo] space elevator
Hi all, Thanks to everyone for your extremely helpful responses. I have included quite a few of them into my article. http://www.techinsider.io/thoth-12-mile-space-tower-elevator-astronauts-travel-major-flaws-2015-8 Take a gander, and please let me know if you see any glaring errors or issues! Hope you enjoy it. Thanks again for everyone's help. My best, Julia Calderone On Wed, Aug 19, 2015 at 12:30 PM, David Appell david.app...@gmail.com wrote: Greg Rau wrote: Anyway, couple of thoughts. If the tether is made of carbon, that's more than a few dollars worth of carbon sequestration... Except the mass of a space elevator is only ~10^5 kg. David -- David Appell, freelance science writer e: david.app...@gmail.com w: http://www.davidappell.com b: http://davidappell.blogspot.com t: @davidappell m: Salem, OR -- You received this message because you are subscribed to the Google Groups geoengineering group. To unsubscribe from this group and stop receiving emails from it, send an email to geoengineering+unsubscr...@googlegroups.com. To post to this group, send email to geoengineering@googlegroups.com. Visit this group at http://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout. -- Julia Calderone Science Writer Cell: (818) 209-0926 Email: juliacalder...@gmail.com Web: www.juliacalderone.com Twitter: @juliacalderone -- You received this message because you are subscribed to the Google Groups geoengineering group. To unsubscribe from this group and stop receiving emails from it, send an email to geoengineering+unsubscr...@googlegroups.com. To post to this group, send email to geoengineering@googlegroups.com. Visit this group at http://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout.
[geo] Mimicking biochar-albedo feedback in complex Mediterranean agricultural landscapes - IOPscience
http://iopscience.iop.org/1748-9326/10/8/084014/article imicking biochar-albedo feedback in complex Mediterranean agricultural landscapes OPEN ACCESS E Bozzi, L Genesio, P Toscano, M Pieri and F Miglietta E Bozzi et al 2015 Environ. Res. Lett. 10 084014 doi:10.1088/1748-9326/10/8/084014 13 August 2015 Abstract Incorporation of charcoal produced by biomass pyrolysis (biochar) in agricultural soils is a potentially sustainable strategy for climate change mitigation. However, some side effects of large-scale biochar application need to be investigated. In particular a massive use of a low-reflecting material on large cropland areas may impact the climate via changes in surface albedo. Twelve years of MODIS-derived albedo data were analysed for three pairs of selected agricultural sites in central Italy. In each pair bright and dark coloured soil were identified, mimicking the effect of biochar application on the land surface albedo of complex agricultural landscapes. Over this period vegetation canopies never completely masked differences in background soil colour. This soil signal, expressed as an albedo difference, induced a local instantaneous radiative forcing of up to 4.7 W m−2 during periods of high solar irradiance. Biochar mitigation potential might therefore be reduced up to ~30%. This study proves the importance of accounting for crop phenology and crop management when assessing biochar mitigation potential and provides more insights into the analysis of its environmental feedback. -- You received this message because you are subscribed to the Google Groups geoengineering group. To unsubscribe from this group and stop receiving emails from it, send an email to geoengineering+unsubscr...@googlegroups.com. To post to this group, send email to geoengineering@googlegroups.com. Visit this group at http://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout.
Re: [geo] space elevator
If the idea is to launch from a higher altitude and use inflatables for a building as part of the process, why not just build a blimp or dirigible that would lift the vehicle to altitude and then let it fly from the elevated position of the blimp? Why build a permanent structure for this? With blimp or dirigible, one could launch from nearly anywhere on Earth so get a good range of orbits, etc. Yes, I guess one needs to have a way to get up to a bit of speed for stability, but I don¹t see the value of a structure given all the complications. Mike On 8/20/15, 3:40 PM, Andrew Lockley andrew.lock...@gmail.com wrote: He's partially right about the fuel savings. In fact, he fails to discuss that almost all of the drag losses are incurred in early stage flight, so there's a bonus for him. What he's ignoring is that you can't approximate a launch from a standing start at 20km with a vehicle that's been accelerating at 13g for 20km. Speed matters! The foundations are nothing really to do with resisting torque, as it doesn't only happen at the end. If it's a straight tower subjected to wind shear, the bending moment in the bottom km of the tower is going to be insane, and it doesn't have to buckle at the footings - anywhere will do. This is a feat not dissimilar to balancing a hair on its end. All the stiff footings you'd care to build won't get rid of that buckling risk, and I'd be very surprised if it the tower structure came anywhere near to resisting it. Far easier to use tethers (just like a TV mast), but you'd struggle to mount these at the top, due to the free breaking length of the cables. Even mounting them half way up likely won't solve the problem, as you'd still have a 10km tower wobbling away like Jell-O on top. Active damping is great at removing vibrational distortion. But all the active damping in the world won't solve the problem of a steady bending load. I think the wind will huff and puff and blow the tower down. A On 20 Aug 2015 20:18, Julia Calderone juliacalder...@nasw.org wrote: Hi all, Brendan Quine, the inventor of the space tower, has followed up with some responses to a few of your thoughts (his responses are bolded below). I have included his statements in an updated version of the story: http://www.techinsider.io/thoth-12-mile-space-tower-elevator-astronauts-trave l-major-flaws-2015-8 If anyone has any thoughts or responses to his comments, please feel free to shoot me a response here. Thanks again. Best, Julia *External forces* would be an issue: ³This is a big fat tower, and it's under *compression*. The graphics don't show any tethers or taper, and the sides are not obviously wind permeable. This means the torque [twisting force] at the base will be enormous. It's just not clear how it will actually stay up.² We agree that the tower will require very substantial foundation however this requirement is similar to that of existing massive steel and concrete construction structures. The patent describes a harmonic control strategy and actively guided structure concept where the attitude of the building is constantly monitored and its vibration modes controlled (see FIG. 4 a schematic diagram showing active stabilization control of the elevator core structure, US9085897). ³Thunderstorms and icing would be a big problem. Construct[ing] a tower to take wind gusts and turbulence arising from deep tropical convection looks very problematic to me.² Ice build-up hampers proper functioning of planes and drones at such high altitudes. Unlike aircraft that can fly, a giant tower wouldn¹t be able to navigate around those regions. The structure may require de-icing in the same way that aircraft wings are sprayed with antifreeze during operation in winter. This function can be facilitated within the elevator structure however it is likely that icing will be occasional as event will be isolated and the solar radiation environment will rapidly heat and melt ice buildup during the day. It is likely that the elevators would be equipped with a de-icing capability also cleaning the outer surface as the pass up and down the core. There is some significant research developments in materials finishes that prevent ice build-up that could also be deployed in lower structural sections. It is unlikely that the mass of any ice buildup would be significant by comparison to the overall mass of the structure. The structure is designed to withstand a Category 5 hurricane with wind speed of 156 mph with significant safety margin and so the sheer and turbulent forces of a thunder storm are within this design envelope. Problem with *buckling* under it's own weight: The problem with this, assuming you could design one that you could actually build, is that it would be subject to the same problems of self-weight buckling. When one part of the internal cell starts to buckle, the volume of the gas inside does not
Re: [geo] space elevator
To address the buckling issue. There are two forms of buckling that are relevant for this tower. One is a local buckling that would cause wrinkling of the outer surface. I agree that inflated toroidal tubes can be arranged to resist this. But the more serious buckling, which the inflated tubes will not help, is global buckling. Imagine a long thin element, like a plastic ruler or a bamboo cane. If you put an axial load onto the ruler it will buckle without local wrinkling of the surface, and is what we know as Euler buckling. The material does not fail (it is purely elastic) and the cross-section is maintained. In this illustration, the load is external, but if you make a long enough and thin enough tall pole, it will buckle under its own self weight. That was the issue that we found to be the killer when considering the 20 km tower for the SPICE project, and which I addressed in an earlier post. (http://www-civ.eng.cam.ac.uk/cjb/papers/cp94.pdf) The equations there apply to the space tower: the inflation of the tube does not alter the buckling load because it is an internal self-equilibrating system. It is the same logic that stops a Bowden cable, as used in a bicycle brakes, buckling. In these systems, the central wire is under very high tension when you apply the brakes, and this is in equilibrium with a compressive force in the external coil that forms the outer tube of the cable. Ordinarily, a force of that magnitude would cause the tube to buckle, but it doesn't. The reason is that if the tube moves to the side it takes the internal cable with it. The internal cable causes a restoring force to be applied to the tube. The overall effect is that the self-equilibrating force in the internal wire has no effect on buckling capacity of the outer tube. Exactly the same logic applies to the inflated tower, although in reverse. The internal compression in the air takes the place of the internal wire in the Bowden cable. In the same way that the force in the wire does not cause the brake cable to buckle, the internal air pressure in the tube will not prevent the inflated tower from buckling. You don't need to build a 1 km tower to show that it won't work. Make a tube out of polythene (the thinner the better to show the difference, block one end, and inflate it. If its quite short, you will be able to stand it on end, but if it is long, it will buckle under its own weight. It won't matter how hard you inflate it. Chris Burgoyne On 20/08/2015 19:58, Julia Calderone wrote: Hi all, Brendan Quine, the inventor of the space tower, has followed up with some responses to a few of your thoughts (his responses are bolded below). I have included his statements in an updated version of the story: http://www.techinsider.io/thoth-12-mile-space-tower-elevator-astronauts-travel-major-flaws-2015-8 If anyone has any thoughts or responses to his comments, please feel free to shoot me a response here. Thanks again. Best, Julia *External forces* would be an issue: “This is a big fat tower, and it's under *compression*. The graphics don't show any tethers or taper, and the sides are not obviously wind permeable. This means the torque [twisting force] at the base will be enormous. It's just not clear how it will actually stay up.” *We agree that the tower will require very substantial foundation however this requirement is similar to that of existing massive steel and concrete construction structures. The patent describes a harmonic control strategy and actively guided structure concept where the attitude of the building is constantly monitored and its vibration modes controlled (see FIG. 4 a schematic diagram showing active stabilization control of the elevator core structure, US9085897).* “Thunderstorms and icing would be a big problem. Construct[ing] a tower to take wind gusts and turbulence arising from deep tropical convection looks very problematic to me.” Ice build-up hampers proper functioning of planes and drones at such high altitudes. Unlike aircraft that can fly, a giant tower wouldn’t be able to navigate around those regions. *The structure may require de-icing in the same way that aircraft wings are sprayed with antifreeze during operation in winter. This function can be facilitated within the elevator structure however it is likely that icing will be occasional as event will be isolated and the solar radiation environment will rapidly heat and melt ice buildup during the day. It is likely that the elevators would be equipped with a de-icing capability also cleaning the outer surface as the pass up and down the core. There is some significant research developments in materials finishes that prevent ice build-up that could also be deployed in lower structural sections. It is unlikely that the mass of any ice buildup would be significant by comparison to
Re: [geo] space elevator
On this issue of icing, while the situation would vary depending on what it is constructed of, the structure will be able to radiate heat away far more effectively than the air can radiate. Thus the building surface will cool with respect to the air. The air temperature at upper troposphere/lower stratosphere levels is 40 C or below, being maintained at this level by heat from convection that maintains the lapse rate through the tropsophere. I would think the building surface would cool to lower than that and so the skin temperature would be well below the temperature at which one would expect water vapor to be freezing out. This doesn¹t happen on an airplane because its interior is kept warm and this must make the plane¹s exterior pretty warm compared to what could happen to a building that just sits there. So, given the different IR emmissivities of the building surface and the air mass, I¹d be quite careful of the analysis. True that there is not much water vapor in air near highest altitudes, but the analysis would need to be done at each level, etc. Mike On 8/20/15, 2:58 PM, Julia Calderone juliacalder...@nasw.org wrote: Hi all, Brendan Quine, the inventor of the space tower, has followed up with some responses to a few of your thoughts (his responses are bolded below). I have included his statements in an updated version of the story: http://www.techinsider.io/thoth-12-mile-space-tower-elevator-astronauts-travel -major-flaws-2015-8 If anyone has any thoughts or responses to his comments, please feel free to shoot me a response here. Thanks again. Best, Julia *External forces* would be an issue: ³This is a big fat tower, and it's under *compression*. The graphics don't show any tethers or taper, and the sides are not obviously wind permeable. This means the torque [twisting force] at the base will be enormous. It's just not clear how it will actually stay up.² We agree that the tower will require very substantial foundation however this requirement is similar to that of existing massive steel and concrete construction structures. The patent describes a harmonic control strategy and actively guided structure concept where the attitude of the building is constantly monitored and its vibration modes controlled (see FIG. 4 a schematic diagram showing active stabilization control of the elevator core structure, US9085897). ³Thunderstorms and icing would be a big problem. Construct[ing] a tower to take wind gusts and turbulence arising from deep tropical convection looks very problematic to me.² Ice build-up hampers proper functioning of planes and drones at such high altitudes. Unlike aircraft that can fly, a giant tower wouldn¹t be able to navigate around those regions. The structure may require de-icing in the same way that aircraft wings are sprayed with antifreeze during operation in winter. This function can be facilitated within the elevator structure however it is likely that icing will be occasional as event will be isolated and the solar radiation environment will rapidly heat and melt ice buildup during the day. It is likely that the elevators would be equipped with a de-icing capability also cleaning the outer surface as the pass up and down the core. There is some significant research developments in materials finishes that prevent ice build-up that could also be deployed in lower structural sections. It is unlikely that the mass of any ice buildup would be significant by comparison to the overall mass of the structure. The structure is designed to withstand a Category 5 hurricane with wind speed of 156 mph with significant safety margin and so the sheer and turbulent forces of a thunder storm are within this design envelope. Problem with *buckling* under it's own weight: The problem with this, assuming you could design one that you could actually build, is that it would be subject to the same problems of self-weight buckling. When one part of the internal cell starts to buckle, the volume of the gas inside does not change, which means that it would not resist the collapsing action The problem of structural wrinkling (the onset to buckling) has been addressed by previous research (see Experimental investigation of inflatable cylindrical cantilevered beams ZH Zhu, RK Seth, BM Quine, S Okubo, K Fukui, Q Yang, T Ochi, JP Journal of Solids and Structures 2 (2), 95-110, 2008). In fact there is a volume change during the buckling event. Also the commentator may be assuming that the core is comprised of a single gass cell the diameter of the structure however the structure is comprise of many cells arrange in a torus and there is a significant volume change between the sides of the structure during buckling. The research paper lays out experimentally derived guidelines for pneumatic structures to avoid the onset of wrinkling which we have adopted in our design. *Material and cost* limitations: The
Re: [geo] space elevator
He's partially right about the fuel savings. In fact, he fails to discuss that almost all of the drag losses are incurred in early stage flight, so there's a bonus for him. What he's ignoring is that you can't approximate a launch from a standing start at 20km with a vehicle that's been accelerating at 13g for 20km. Speed matters! The foundations are nothing really to do with resisting torque, as it doesn't only happen at the end. If it's a straight tower subjected to wind shear, the bending moment in the bottom km of the tower is going to be insane, and it doesn't have to buckle at the footings - anywhere will do. This is a feat not dissimilar to balancing a hair on its end. All the stiff footings you'd care to build won't get rid of that buckling risk, and I'd be very surprised if it the tower structure came anywhere near to resisting it. Far easier to use tethers (just like a TV mast), but you'd struggle to mount these at the top, due to the free breaking length of the cables. Even mounting them half way up likely won't solve the problem, as you'd still have a 10km tower wobbling away like Jell-O on top. Active damping is great at removing vibrational distortion. But all the active damping in the world won't solve the problem of a steady bending load. I think the wind will huff and puff and blow the tower down. A On 20 Aug 2015 20:18, Julia Calderone juliacalder...@nasw.org wrote: Hi all, Brendan Quine, the inventor of the space tower, has followed up with some responses to a few of your thoughts (his responses are bolded below). I have included his statements in an updated version of the story: http://www.techinsider.io/thoth-12-mile-space-tower-elevator-astronauts-travel-major-flaws-2015-8 If anyone has any thoughts or responses to his comments, please feel free to shoot me a response here. Thanks again. Best, Julia *External forces* would be an issue: “This is a big fat tower, and it's under *compression*. The graphics don't show any tethers or taper, and the sides are not obviously wind permeable. This means the torque [twisting force] at the base will be enormous. It's just not clear how it will actually stay up.” *We agree that the tower will require very substantial foundation however this requirement is similar to that of existing massive steel and concrete construction structures. The patent describes a harmonic control strategy and actively guided structure concept where the attitude of the building is constantly monitored and its vibration modes controlled (see FIG. 4 a schematic diagram showing active stabilization control of the elevator core structure, US9085897).* “Thunderstorms and icing would be a big problem. Construct[ing] a tower to take wind gusts and turbulence arising from deep tropical convection looks very problematic to me.” Ice build-up hampers proper functioning of planes and drones at such high altitudes. Unlike aircraft that can fly, a giant tower wouldn’t be able to navigate around those regions. *The structure may require de-icing in the same way that aircraft wings are sprayed with antifreeze during operation in winter. This function can be facilitated within the elevator structure however it is likely that icing will be occasional as event will be isolated and the solar radiation environment will rapidly heat and melt ice buildup during the day. It is likely that the elevators would be equipped with a de-icing capability also cleaning the outer surface as the pass up and down the core. There is some significant research developments in materials finishes that prevent ice build-up that could also be deployed in lower structural sections. It is unlikely that the mass of any ice buildup would be significant by comparison to the overall mass of the structure.The structure is designed to withstand a Category 5 hurricane with wind speed of 156 mph with significant safety margin and so the sheer and turbulent forces of a thunder storm are within this design envelope.* Problem with *buckling* under it's own weight: The problem with this, assuming you could design one that you could actually build, is that it would be subject to the same problems of self-weight buckling. When one part of the internal cell starts to buckle, the volume of the gas inside does not change, which means that it would not resist the collapsing action *The problem of structural wrinkling (the onset to buckling) has been addressed by previous research (see Experimental investigation of inflatable cylindrical cantilevered beams ZH Zhu, RK Seth, BM Quine, S Okubo, K Fukui, Q Yang, T Ochi, JP Journal of Solids and Structures 2 (2), 95-110, 2008). In fact there is a volume change during the buckling event. Also the commentator may be assuming that the core is comprised of a single gass cell the diameter of the structure however the structure is comprise of many cells arrange in a torus and there is a significant volume change
Re: [geo] space elevator
Hi all, Brendan Quine, the inventor of the space tower, has followed up with some responses to a few of your thoughts (his responses are bolded below). I have included his statements in an updated version of the story: http://www.techinsider.io/thoth-12-mile-space-tower-elevator-astronauts-travel-major-flaws-2015-8 If anyone has any thoughts or responses to his comments, please feel free to shoot me a response here. Thanks again. Best, Julia *External forces* would be an issue: “This is a big fat tower, and it's under *compression*. The graphics don't show any tethers or taper, and the sides are not obviously wind permeable. This means the torque [twisting force] at the base will be enormous. It's just not clear how it will actually stay up.” *We agree that the tower will require very substantial foundation however this requirement is similar to that of existing massive steel and concrete construction structures. The patent describes a harmonic control strategy and actively guided structure concept where the attitude of the building is constantly monitored and its vibration modes controlled (see FIG. 4 a schematic diagram showing active stabilization control of the elevator core structure, US9085897).* “Thunderstorms and icing would be a big problem. Construct[ing] a tower to take wind gusts and turbulence arising from deep tropical convection looks very problematic to me.” Ice build-up hampers proper functioning of planes and drones at such high altitudes. Unlike aircraft that can fly, a giant tower wouldn’t be able to navigate around those regions. *The structure may require de-icing in the same way that aircraft wings are sprayed with antifreeze during operation in winter. This function can be facilitated within the elevator structure however it is likely that icing will be occasional as event will be isolated and the solar radiation environment will rapidly heat and melt ice buildup during the day. It is likely that the elevators would be equipped with a de-icing capability also cleaning the outer surface as the pass up and down the core. There is some significant research developments in materials finishes that prevent ice build-up that could also be deployed in lower structural sections. It is unlikely that the mass of any ice buildup would be significant by comparison to the overall mass of the structure.The structure is designed to withstand a Category 5 hurricane with wind speed of 156 mph with significant safety margin and so the sheer and turbulent forces of a thunder storm are within this design envelope.* Problem with *buckling* under it's own weight: The problem with this, assuming you could design one that you could actually build, is that it would be subject to the same problems of self-weight buckling. When one part of the internal cell starts to buckle, the volume of the gas inside does not change, which means that it would not resist the collapsing action *The problem of structural wrinkling (the onset to buckling) has been addressed by previous research (see Experimental investigation of inflatable cylindrical cantilevered beams ZH Zhu, RK Seth, BM Quine, S Okubo, K Fukui, Q Yang, T Ochi, JP Journal of Solids and Structures 2 (2), 95-110, 2008). In fact there is a volume change during the buckling event. Also the commentator may be assuming that the core is comprised of a single gass cell the diameter of the structure however the structure is comprise of many cells arrange in a torus and there is a significant volume change between the sides of the structure during buckling. The research paper lays out experimentally derived guidelines for pneumatic structures to avoid the onset of wrinkling which we have adopted in our design.* *Material and cost* limitations: The most feasible type of tower that could reach such heights is a cylindrical tower made out of plastics reinforced with carbon fibers, called Carbon Fibre Reinforced Plastic, or CFRP, which would cost about $500 billion and need 250 million tons of the carbon material. Of course new materials may become available, but nothing much is on the horizon that is substantially better than CFRP. *Our patent proposes the use of polyethylene reinforced with Kelvar 49 (both widely available in industrial quantity). We agree that there would be a need for a significant increase in industrial manufacturing capability of these materials and consequently we are proposing the a 1.5 km demonstrator be constructed first in order to grow production capacity before embarking on the 20 km tower.* Not much fuel savings: Less than 1% of the energy required for orbit is saved by launching from a height of 20km. There doesn't seem to be much benefit. *As we describe in A free-standing space elevator structure: a practical alternative to the space tether BM Quine, RK Seth, ZH Zhu Acta Astronautica 65 (3), 365-375, 2009, rockets consume approximately 30% of their fuel during the initial ascent phase to 20
