What is the best number of habitats in a cluster

Lucio,

I knew that asking these questions in this forum would get some good
feedback. I think we could put aside the problem of solar collectors and
habs being in shadow if they were in a grid, the power could come from other
places, a number of mirrors attached to the framework could collect power
and it could then be distributed to the habs.

But the problem of heat and gravity was not one I had thought of. The heat
could be used to some degree, that heat is energy and if collected could be
used (before anybody points it out, yes I do understand the 2nd law of
thermodynamics) and then pumped outside the grid to giant radiators.

The gravity problem is much harder, the first thing to jump into my mind was
getting around it by spinning the framework that could be used to counter
the inward pull of gravity. And almost as fast I realised that this would
not work, the location of down would be changing all the time. No, without
some super strong material to build your framework out of then there are
some basic limits to the size of your clusters.

I tend away from1D structures with more than a handful of habs in them,
travel time grows quickly when you get to large 1D structures. 2D frameworks
are a better idea but still keep coming back to 3D frameworks.

How about this, cylinder habitats, they do not have windows so the entire
surface can be used and light is piped in through an axial light source. A
framework in the form of a cube (each side about the same as the length of
the habitats), inside the cube is a sphere (made of ice if you want but
given it would be a permeant structure something better might be the way to
go), the sphere does not spin and is the main manufacturing facility. Each
habitat is attached to the framework, here you can decide how many habs to
use.

Six, with one per face of the cube.
Eight, with a hab at each corner of the cube.
Twenty four. Four per cube face, three per corner.

This last one holds a certain appeal to me but also is the most dangerous,
the three hab at each corner would be very near to each other and I shudder
to think what would happen if then touched.

Then of course you could mix 2D & 3D structures, consider the option with
six hab attached to a cube with a sphere in the middle and now build a dozen
of them and then attach the cubes to each other.

So many options, I can see a time when there are all of these and many other
styles are up there.

Damn, why isnt there now?? SIGH, looks like I have a looooooooong wait.

Darren, still waiting 8-{

From: Lucio de Souza Coelho
Reply-To:
Date: Wed, 30 Aug 2006 14:28:01 -0300
To:
Subject: Re: [spacesettlers] What is the best number of habitats in a
cluster

On 8/30/06, Darren >
(...)
> A couple of definitions first, I refer to a single line of habitats arranged
> in a framework as a 1D structure, to get from the habitat at one end of the
> line to the one at the other end of the line you have to go through all the
> ones in between (I am assuming a framework holding the habitats and an
> internal transport system along the framework). A 2D structure would be like
> a chess board, a framework in a grid with habitats locked in the frame. A 3D
> structure would be like a cube or some other solid shape with the habitats
> located at the junction of the grid, a 10 X 10 X 10 grid would hold 1000
> habitats.

I have also thought about 3D clusters, but I found the following problems:

- Collecting solar energy would be more difficult in such a structure.
The habitats inside the cube would be mostly in shadow, and therefore
you would have to increase - 2D-wise - the surface of solar collectors
in the outside and build power lines to supply the internal habitats.
Either that or use nukes or some other energy source.

- Even worse, there would be difficulties in heat dissipation.
Internal habitats would irradiate their heat on the surface of the
external ones. In the end you would have to put some "air
conditioning" system in the grid itself to transfer heat (probably
using some efficient mechanism like convection) from the inside to the
outside.

So if I were to design a cluster, I would stick to 2D and 1D designs.

(...)
> The question is how large can a cluster of habitats get before you would be
> better starting a second cluster? Is there an optimum size for a cluster of
> habitats after which you start to lose efficiency? Ignoring things like how
> strong the frame can be, where are you going to get the mass and assuming
> they do not need to be in direct sunlight, you have some other power source,
> could you have a cluster with a million habitats or how about a billion?
> What are the limits?
(...)

It depends on the cosmic neighborhood and geometry.

I guess 3D clusters (dismissing the energy supply and heat dissipation
problems) probably can grow to the size of dwarf planets - many
hundreds of kilometers in side - until the gravity of the structure
itself starts to put too much stress on it. And I think that the
better design for such a planet-sized cluster would be a sphere of
concentric geodesic grids, creating and following quite natural
spherical equipotential surfaces of gravity.

2D clusters are basically limited by the gravity gradient in its
orbit. So a 2D cluster in GEO probably can't grow more than a few
hundred kilometers until the gravity field of Earth and the orbital
forces starts to bend it. On the other hand, I would think that a 2D
cluster freely orbiting the Sun somewhere in the habitable zone could
grow to thousands, perhaps tens of thousands of kilometers without any
problematic bending.

As for a ring 1D cluster, its maximum length is the circumference of its
orbit.