[Server-sky] Maximum limit on server-sats in m288 set by biology
keithl at kl-ic.com
Tue Apr 14 20:42:25 UTC 2009
The m288 orbit can hold trillions of serversats without collisions.
However, it turns out that the real limit is not orbital, but
biological. A clear night sky on the equator with a full moon at
zenith produces about 1 lux of perceived light power (approximately
1mW/m2). Without a visible moon, the light level is 0.001 lux.
The worst case for server-sky is all the server-sats out of control
and tumbling. In that case, when they are lined up right, they
will reflect light to the ground. Under these conditions, a
trillion serversats will produce about 1.5 lux . The server-sats
will eventually evolve to a much lower reflection condition, and
a properly controlled array will also reflect less light, but the
worst case is not impossible.
The reason this matters is because plants and animals depend on
the deep darkness for timing. Corals are photosensitive, and spawn
during the full moon. Some plants open and close leaves, and start
and stop photosynthesis, anticipating the dawn. It can take a large
part of an hour for a leaf to open, so they start opening when they
detect pre-dawn light.
The literature I've found suggests that the lower limit of sensitivity
is well above 0.1 lux. To add a decent margin of safety, I am
assuming a maximum of 0.03 lux from an out-of-control array of
20 billion server-sats in m288 , much less than trillions, but
enough to provide decent communications and web service with
sub-100-millisecond round trip ping times.
For applications that can tolerate much larger ping times, the
L3, L4 and L5 earth-moon Lagrange points are 30x farther away,
and can support perhaps 500 times as many server-sats (10 trillion)
for the same worst-case night illumination levels. If server-sats
eventually evolve into power-sats, that region can deliver perhaps
100 terawatts of power to the earth.
For really big computations, where minutes of ping time are tolerable
compute clusters at the earth-sun Lagrange points are 12000x further
away than m288. Earth biology can tolerate about 500 quintillion
server-sats there. In that far future time, the constellation
maximum size limit will be imposed by communication interference -
Olber's paradox applied to communications. Only a small asteroid's
material would be needed to build them, though.
Keith Lofstrom keithl at keithl.com Voice (503)-520-1993
KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon"
Design Contracting in Bipolar and CMOS - Analog, Digital, and Scan ICs
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