# [ExI] Chips The Size Of[interplanetary] Dust [and matrioshkabrains]

Eugen Leitl eugen at leitl.org
Mon Sep 3 04:29:18 UTC 2007

```On Sun, Sep 02, 2007 at 08:56:24PM -0700, spike wrote:

> Russell, this turns into an interesting question of autonomous manufacturing
> optimization and launching of nodes, as well as optimization of the use of

It is more interesting to see what happens during long-term operation
in a mature node cloud.

> energy from sunlight.  Going with smaller and more numerous nodes has an
> advantage that is related to an engineering textbook problem from a signals
> and systems class I took way too many years ago.
>
> Imagine you have a signal you wish to transmit distance x.  You can do it
> with one transmitter and one receiver, but you could put another receiver at
> x/2, amplify the signal and retransmit another x/2 to distance x.  This way

This is implicit in each node being a router.

> you actually have two transmitters, but each one requires only one fourth as
> much power as in the first case, so together they only require half as much
> power.  Now imagine three receivers and transmitters, each transmitting a
> distance x/3.  Each requires one ninth as much power, so together they
> require a third as much power as in the first case.  And so on.  Cool, huh?
> Perhaps you worked the same problem.
>
> As for station keeping, as the node size scales downward, gravity becomes
> less the driver and electrostatic forces ever more important.

You have to use photonic pressure for orbit control, as anything else
will cause reaction mass which is unacceptable long-term.

> My intuition tells me that building an M-brain is optimized by making the
> individual nodes as small as our technology permits.

There's synergy in having switches nearby, due to relativistic latency,
and you do need a certain sail/PV array size for orbit control.
They'll probably will be a bit larger than dust, few mm at the very least,
possibly cm^3 to m^3 computronium blocks, which would need much larger
sails.

--
Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
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