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Monday, December 15, 2008


The picture shows the sort of Ringworld from Larry Niven's book of the same name because there aren't any for this proposal. His was a solid body built of unobtanium, though I suspect theoretical carbon structures such as in a space elevator would do.

My proposal is more modest. Simply take the O'Neil Cylinders discussed previously here & here & string them together with a beam which will be enough to prevent orbital drift pulling them together. If they are all placed in the same orbit they would tend to drift together & if they got too close would ultimately exert a miniscule gravitational attracting. However we are talking about billionths of a G so even the largest cylinders could be held in place by a small beam. Such a beam could also be used for monorail communication. Since a mag-lev system has no friction there is no wear on the beam, very high speeds & little energy use - not much use for going half way round but useful for meeting the neighbours.

All you need is to keep stringing them till they have gone right round the Sun & heh presto - a Ringworld, or perhaps more grammatically a ring of worlds.

So how long is that?
Well working with a cylinder 30 km deep & assuming the mirrors are of a similar size you would need about 60 km separation. I can think of a couple ways to cut it but space is not a problem so lets be cautious. The circumference of Earth's orbit is about 480,000,000 km. That gives us 8 million cylinders. Not quite up with the Galactic Empire of Asimov's Foundation series which had 25 million worlds but it will do for the time being. At 560 square km per cylinder we get 4480 million km (Earth is 67 million) & because it is all designed for us (no ocean, desert, icecaps or unfriendly lifeforms except where we choose) would be much more habitable.

That comes out at about 1 world for every 1,000 people now alive - 80 for all the South Ossetians, or 6 worlds reserved for the Apache & 200 for the Krajina Serbs (Krajina means borderland which fits). Or some for polar bears or tigers, even for every subspecies of tiger.

The real shocker is the timescale.

On my previous post on mass producing cylinders I said that if production only expanded 10% a year by 2096 we could be producing 64 a year. To keep expanding at this rate would probably require production to take place not just on the Moon but also in the asteroid belt & the rings of the outer planets but there is no theoretical reason why such expansion cannot continue.

So doubling every 7 years (10% annual growth) gets us up to half a million a year in 91 years (doubling 13 times) & would have exceeded the 8 million in 8 more years.

2195 AD

To stop a recession, if such things have not been abolished, they might wish to add extra rings, which would require stronger beams because the microgravitational effects would start rising to millionths of a G. More likely would be another Ringworld, say a million miles further out & on a different orbit. However I don't really think we have to go there.


When I started the Big Engineering articles in September I said I was going to do at least 30 of them. This is not the end & I will produce more in future but less regularly. However this seems to be a high water mark since I can't think of anything bigger than a ring of worlds, without developing faster than light travel & have no useful advice on how to do that. I've probably done enough of the Greening ones though some of the same principles could be used in those parts of the world I didn't touch. Looking over them there seem to be no show stoppers, certainly nobody has found any & no question that taken together, or indeed separately, they could make humanity wealthy literally beyond the dreams of previous ages. There are no limits to what humanity can do except the ones we impose on ourselves.

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