# [ExI] mbrains again: request

spike spike66 at att.net
Wed Sep 28 15:52:58 UTC 2011

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-----Original Message-----
From: extropy-chat-bounces at lists.extropy.org
[mailto:extropy-chat-bounces at lists.extropy.org] On Behalf Of Eugen Leitl
Subject: Re: [ExI] mbrains again: request

On Wed, Sep 28, 2011 at 07:45:30AM -0700, spike wrote:

>>... Hmmm, the adjacent rings have very low relative velocity...

>...Where did the one meter spacing come from?...

It was just an example design.  I had disk-shaped nodes of one gram and 100
cm^2, so it would had the thickness of household aluminum foil and be the
diameter of a CD or DVD.

>... There's an obvious advantage of using a closest packing of
computational cells to minimize signalling distance and maximize
performance, which is then only limited to maximum dissipable volumetric
power density. As a hunch, that volume would be cubic meters, not cubic mm.
Depending on the power, that would be km^2 of PV/sail/radiator surface, with
according elbow room to spare for sail maneuvres, and such -- that would be
some 1-10 km spacing at least. That much space is not a problem
relativistically, as high-order processes would be slow anyway...

This will be an interesting exercise to have several of us propose MBrain
designs and try to calculate orbits and temperatures.

>...At that size the speed delta would be enough to wreck the sail. Loss of
orbit control would bring nodes from nonadjacent layers to collision...

Agreed, which is why I went with a ring of nodes about 120 mm spaced at 1
meter.  The next ring outboard would have an orbit radius of 1 meter greater
and the next ring inboard a radius of 1 meter less.  The innermost ring I
arbitrarily chose as orbiting at one AU, the orbit we know so very well.
This was chosen just to give us a little intuitive feel for how things go.

If so, imagine yourself as a node, not the innermost ring, but somewhere
inboard-ish.  You would see stationary nodes to your east and west (assume
the sunward direction I down and the other way is up.)  Twice a year you
would see a node coming toward you from either the south or the north at
about 6 cm/sec (assuming I did the previous BOTEC right) in the ring inboard
and the one outboard.  It wouldn't be the same node each time, because the
nodes in the outboard ring orbit slightly slower and the one inboard
slightly faster.

>> few cm per second.  Wait, I might be able to do that to a single digit
> in my head: a microradian at I AU is about 150 km and it has three
> months to

>...I see no reason to go to down to Mercury orbit for the inner layer, or
shortly above.

Not Mercury, I meant orbiting at 1 AU, your corresponding node in the
adjacent ring would appear to pass you at 6 cm/sec, wander north 150 km and
take three months to get there.  Then it would turn around and come back and
arrive three months after that, but that particular node would be a few
meters west this time.  A different node would pass by at 1 meter.

Eugen, this verbal salad is surely confusing, apologies.  I need to come up
with some graphics.  Do you guys have PowerPoint?

I encourage a specific design with hard numbers.  Then we can derive the
general formulae.

>...I'm not sure random orbit corrections balance themselves out so that you
can fire at will most of the time. The emergent behaviour strikes me as
potentially extremely hirsute.

Cool, hirsute, I learn a new word this day.  What has hairy to do with an

> >... My spreadsheets for equilibrium temperatures are not as solidly
grounded as my orbit mechanics.  {8-[

>...It would be interesting to model as a swarm, with each agent given
behaviour constraints to conserve. -- Eugen* Leitl

Regarding difficulty in modeling, I do encourage you to pick numbers and
imagine how stability and control can be achieved.  My design has a mostly
reflective surface with some PVs, 120 mm diameter discs with mass of one
gram, three LCD patches spaced at 120 degrees of about 1 cm^2 area each.
These three patches can be switched to either dark or reflective to create a
three legged stool of sorts, to turn and maintain any orientation with
respect to the sun.  Once I get hard numbers on that, I will be willing to
analyze other designs.

spike

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