|MadSci Network: Astronomy|
1/ Not possible with present materials; Kevlar is at least five times too weak. Diamond fibres could do it but no-one yet knows how to produce/extrude enough of it for this job! Buckyballs material ( carbon buckmasterfullerene ) has potential. But then again manufacturing on an industrial scale is not in sight. Nanotechnology may be the route to this Artsutanov and Arthur Clarke ( Fountains of Paradise) have written of sky lifts stretching from Earth to orbit as a elevator providing cheap access to Space- but the same considerations of materials strength apply 2/Difficult to see how a ring can be centrifugally rotated along its circumference- the curved arc must invert itself as its rotates, A straight line can of course rotate along its axis. 3/Studies on O'Neill colonies suggest that 1-2 rpm for a spheroid 1 mile in circumference would provide 1 G acceptable for longterm health. Probably less than 1 g( 0.25-).5 G 0 would be adequate but this has yet to be established( perhaps on the ISS in future years?) This is quite possible with current marterials especially in Space where there is microgravity and no weather/winds etc 4/ In any colony where there is centrifugal force applied for artificial gravity there is a gravity gradient so that people can live and sleep in normal g and pursue recreations/sports etc in the zero g axial region. Here it is that human experiences will acquire- forgive me- full use of the third dimension ; flight with muscle power and light plastic wings becomes a truly angelic experience! 5/ Rail gun launchers or even simple electrostatic repulsion would well be used for launching payloads into deep space. 6/ An evacuated central tube for transportation might be helpful although again it would describe a gigantic circle around the Earth. Given the axial zero G simple flight with light electric motors would probably be simpler and less hazardous in the unlikely event of accidents 7/ Finally such a ring would probably not arise as a single one time construction, but could evolve into being out of several centuries of nodal island type space colonies; these however would have to be in much higher orbits to avoid slow atmospheric drag, and also to avoid disturbing the aesthetics of our night sky! Free Island O' Neill colonies could moreover be relocated anywhereto within 4 light days of the sun given large enough solar collectors and in later centuries would form the basis of a slow ( 0.01c) interstellar migration. All in all, a more diverse and capable route to a human future in Space in my view. Arthur C Clarke, Fountains of Paradise K Eric Drexler, Engines of Creation Gerard K O'Neill, The High Frontier Space Studies Institute, Update (Quarterly) Princeton, PO box No 82 New Jersey 08542 Michael Martin-Smith, Salto nello Spazio, Publ Italy Dec 1999 Tre Editori via Principe Umberto 35 00185 Rome -- Michael Martin-Smith
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