MadSci Network: Astronomy

Re: Can a ring be built at low altitude that circles the earth?

Date: Thu Dec 30 07:36:36 1999
Posted By: Michael Martin-Smith, Other (pls. specify below), Family Physician, Fellow,BIS, amateur astronomer( BAA), British Interplanetary Society
Area of science: Astronomy
ID: 942905048.As

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 
 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 
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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