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Tuesday, June 09, 2009


7 metre tower
Temporary tower put up over a century ago

A giant inflatable tower could carry people to the edge of space without the need for a rocket... If built from a suitable mountain top it could reach an altitude of around 20 kilometres, where it could be used for atmospheric research, tourism, telecoms or launching spacecraft.

Pneumatic modules already used in some spacecraft could be assembled into a 15-kilometre-high tower

The team envisages assembling the structure from a series of modules constructed from Kevlar-polyethylene composite tubes made rigid by inflating them with a lightweight gas such as helium. To test the idea, they built a 7-metre scale model made up of six modules. Each module was built out of three laminated polyethylene tubes 8 centimetres in diameter, mounted around circular spacers and inflated with air.

To stay upright and withstand winds, full-scale structures would require gyroscopes and active stabilisation systems in each module. The team modelled a 15-kilometre tower made up of 100 modules, each one 150 metres tall and 230 metres in diameter, built from inflatable tubes 2 metres across. Quine estimates it would weigh about 800,000 tonnes when pressurised - around twice the weight of the world's largest supertanker.

"Twenty kilometres up is about as dark as outer space. You can see about 600 kilometres in any direction," Quine says. Tourists could get a view almost like that from space, but without the difficulties of coping with zero gravity. He calculates the tower could be extended up to low Earth orbit at 200 kilometres.

I have previously written about building a space elevator - a tether that reaches all the 36,000 km from geosynchronous orbit to Earth. That is a nicer idea than this with the minor disadvantage that we don't have materials that could do it so it is currently impossible. This, on the other hand, while state of the art, is possible. We could start building it now. We should.

Now lets fairly admit this alone will not get us into orbit. It is possible to orbit at 200km because there is no air but to stay up you have to be going about 14,000mph (actually orbit is free fall - what you are doing is falling as much as you move forward so that when you have fallen as far down as the Earth you have also moved that far forward as the radius of the orbit so you are still at the same distance from the surface). If you aren't at orbital speed when you leave the tower you will simply fall. However be the penultimate tourist trip (perhaps ultimate since it will be more comfortable than Virgin Galactic or if you lijke parachuting), will be invaluable for scientific experimentation, as a communications centre & possibly for vacuum manufacturing.

It has been said that the engineering achievement of the Eiffel Tower helped restore French self confidence & prestige after the Franco-Prussian war & this is a tower which could be seen not merely from every window in Paris but from different countries.

I can think of 2 technical ways it could be used to get to orbit;

1 - Launching a rocket from it - since it is already up there & beyond the atmosphere it would be much easier but I suspect it would be impractical to build a rocket at the top of this structure.
2 - A Skyhook Sky Hook is a satellite with two huge spokes that 'rolls' along the equator. Tie something to a spoke when it touches earth and up-it-goes. . This is part way to a full elevator but much shorter & can therefore be built with current technology but still requires us to have space industry. To do this would also require great flexibility & control of the "hook" at the end of the spokes so that when it came down close to the top of the tower it could be steered there. A Skyhook has been proposed for lifting things directly from Earth, or a high flying aircraft, but to do that the tethers have to be continuously moving through air which causes frictional losses.

I think the way to finance this is with a series of prizes for achieving particular building heights. Whether this would make a direct financial profit or not (the Eiffel Tower was not intended to do so but did) I think it would push the science, technology & human spirit in a way beyond money.

Hat tip to Al Fin for reporting this today

UPDATE - Jerry Pournelle has mentioned this as, the following day, did somebody else - they don't anticipate it as near term or as a direct way into space.


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