Megamirror or Windscoop?
I
read that some astronomers sought thermal signatures for Dyson spheres in
distant galaxies, and found none. I am not surprised, for I think that
megastructures of the Dyson/Niven/Banks form are impractical.
Any
large astroengineered structures would be heavy, fragile and expensive. They’d
also be obsolete once built. They’d need constant upkeep and central control,
but with long communication latencies due to lightspeed limits. For instance,
in one of Bank’s Orbitals, the AI in the Hub will constantly be 1.5 seconds
behind the time, yet it must busy-body in real time. And a ringworld is 16
light-minutes across. Orbitals have
awful internets, and ringworlds can have no internet at all.
Orbitals,
Ringworlds and Spheres all grab for maximum power, but must be so big that they
sacrifice communications speed. How very 20th-century of them.
Elsewhere I have discussed my “Wet Star” alternative, which matches power to
habitat rather than the other way around. Who needs a star when you have a
comet and a fusor? Also, small worlds have fast Internet. Who needs a
quadrillion watts when you have a quadrillion apps?
Dyson
originally intended a modular Sphere, made of zillions of space habitats,
orbiting independently, between them obscuring the disk of their star. I worry
about traffic control for such a mob, and the possibility of a debris cascade.
A Dyson sphere would inevitably be swarming with junk. Nuts, bolts, paint
chips, dropped tools, all flying at orbital speed. (Just like in LEO now!) This plus natural
meteorites and micro-meteorites will turn Dyson-sphere space into an
environment constantly erosive and occasionally explosive. And the larger the
structure, the bigger the risk.
Which
brings me to the question: megamirror or windscoop? Imagine two space habitats.
One powers itself by a huge mirror; let’s say 100 km^2 in area. The other
deploys a Bussard ramscoop to scoop up the solar wind, which it feeds to its
fusion reactor.
The
mega-mirror system is simpler; all it needs is the mirror and a heat engine at
the focus, whereas the windscoop system needs the windscoop and a fusion
reactor. But I think the megamirror is more vulnerable to micrometeorites. Even
if they only dull its sheen, that would reduce efficiency. Whereas a windscoop
is mostly EM fields and empty space. If a paint chip cuts a wire, then just
send the robot to repair section 17-B.
I
wonder, which has more power content? The sunlight passing through a given
km^2, or the solar wind, once put through a fusor? On the one hand, that wind’s
kind of thin; on the other hand, E = mc^2.
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