We looked in detail at the feasibilty of towers for SRM in our 2012 paper "Lifting options for stratospheric aerosol geoengineering: advantages of tethered balloon systems" Peter Davidson, Chris Burgoyne, Hugh Hunt, Matt Causier http://rsta.royalsocietypublishing.org/content/370/1974/4263
The ‘cheapest’ tower we deduced is a shaped cylindrical tower in CFRP (Carbon Fibre Reinforced Plastic), at about $500 billion each with 250 million tonnes of CFRP needed. There would be major supply issues for carbon fibre; current world production is of the order of 50 000 tonnes p.a. Of course new materials may become available, but nothing much is on the horizon that is substantially better than CFRP. The foundations would need careful consideration, as would the tower’s susceptibility to earthquake and even possibly local effects of applying a very high point load to the Earth’s crust. The ThothX Tower, we're told, will be an inflatable, freestanding structure complete with an electrical elevator and will reach 20km. We considered inflatable towers in our 2012 paper. The ThothX tower appears not to have considered sideways loads because of even moderate winds, to say nothing of jet streams, and a cursory analysis shows such a proposition is impracticable with any currently known construction materials. In addition, there is an error in the basic concept, which assumes that the prestress from the internal pressure counteracts the structure’s own weight, thereby preventing buckling, which is then ignored. But the prestress is part of a set of purely internal, self-equilibrating, forces, and although they might prevent local buckling of the skin they cannot prevent global buckling. Inflatable towers would be subject to exactly the same buckling conditions as any ordinary tower. There is a direct analogy (although in reverse) with a bicycle brake cable; no matter how hard the cyclist applies the brake, the cable does not buckle because the compression in the cable sheath is equilibrated by an equal and opposite tension in the brake cable. As for ThothX being used to launch astronauts into orbit, 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. On Monday, 17 August 2015 18:56:39 UTC+1, Olivier Boucher wrote: > > Hello, > this is relevant to SRM by stratospheric particles > > http://www.independent.co.uk/news/science/a-canadian-company-is-planning-to-build-a-tower-thats-20km-high-and-could-making-flying-to-space-like-taking-a-passenger-jet-10459058.html > > http://thothx.com/news-2/ > although I don't know how realistic and advanced the plans are... > Regards, > Olivier > > -- 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 [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/d/optout.
