Re: Dyson shell redux

From: Robert J. Bradbury (
Date: Fri Mar 16 2001 - 11:16:31 MST

On Thu, 15 Mar 2001, Spike Jones wrote:

... a moderately detailed description of connecting orbiting nodes with an
optical waveguide...
> What say ye, Sir Robert? spike

Good question. If you think it will work then I'm willing to accept it.

The comments from Anders seem to indicate the material strength problems
are resolvable. I had devoted some thought to this when I was thinking
about the MBrain internode communication. A lot of my thinking was
driven by cross-sphere long distance laser communications (as Anders
proposed with the Dyson-Net(Web) solar sail design). In my current
calculations I only do nearest neighbor communications calculations
to avoid the photon losses due to beam spreading.

Perhaps I thought that materials requirements would be too high for
fibers and/or perhaps I thought you would need the satellites to
be "independent" to allow them to make orbital adjustments to
compensate for specific forces that would impact them (from
coronal mass ejections for example).

But I've done some work on the bandwidth of fibers for the brain-computer
uplink and current/near-future transmission & reception capabilities
and I think this idea needs serious consideration.

I can imagine that you could put the fiber on rapid spool reels
that would allow you to maintain a constant tension on the fibers
that is within their material limits (kind of like what they must
use to lay submarine cables). I think current fibers of around
100-200 microns perhaps coated in buckytube cladding would be the
way to go.

I'll have to think about the relative photon losses in the fibers
vs. free vacuum. You do have the advantage with open space comm.
that you can move up to UV-lasers. Currently you can't go there
in regular fibers. Perhaps you use free-space to carry UV signals
across the long-distance links and fiber to carry Visible and IR
across the local connections.

The real "trick" is going to be finding ways to recycle the energy
contained in the photons. You would like to be able to pick up
the photons extract the information they contain and then use then
reuse the energy in an outgoing stream. The best lasers currently
are ~63%+ efficient, and the best CCD detectors are around 99%
for some frequencies. But you pass those photons around through
millions of nodes and your losses are going to add up pretty quickly.

You also have to move to single photon transmission & reception of
the bits. With current transmission technologies, the energy
value of the circulating photons of an MBrain are a sizeable
fraction of the power output of the sun.


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