Re: Solar Shell
- From: Willie.Mookie@xxxxxxxxx
- Date: 26 Jan 2007 21:56:38 -0800
Really? Well I guess you're right... but the sun has more material.
http://en.wikipedia.org/wiki/Asteroids
3.6e21 kg is the total mass of all asteroids in the main belt.
http://en.wikipedia.org/wiki/Sun
The sun is 2.0e30 kg
The metals of the sun - the same materials the asteroids are made of,
amount to 3.4e28 kg - some 10 million times the mass of all the
asteroids in the main belt.
http://en.wikipedia.org/wiki/Bernal_sphere
http://en.wikipedia.org/wiki/Space_colonization
http://www.nas.nasa.gov/About/Education/SpaceSettlement/CoEvolutionBook/APPENDIX.HTML
The Stanford Torus masses about 500,000 kg and covers 1 km2 - So, the
total area that 3.6e21 kg could conceivably cover (assuming its
perfectly suited for building colonies, which it probably isn't!) is
7.2e15 km2.
This is 14.3 million Earth areas. - which is 45x the area of the sphere
described here.
So, you're right.
In reality, the asteroids are not that efficient. Say, that resource
limitations limit us to 10% of this - which is still 4.5x the area of
the sphere here.
But that's only because I've designed the sphere to be so damned thick!
Using the same space colony technology described here, we could make 10
million times the number of space colonies as we could make asteroids.
Does the sun have enough energy to light all these colonies?
The Earth is a sphere is 4x the area of a disk the same size. So, a
sphere 300 million km in radius would be illuminated the same on
average as the Earth. The area of this sphere is 2 billion times
larger than Earth. This is 140x the area possible with asteroids
(assuming the exact mix of materials occur) and 1/70th the area
possible with the materials within the sun.
The solar output will last about 5.5 billion more years. Reducing the
output of the sun to 0.08% of today's output - longevity increases to
10 trillion years or more - and surface area of 300,000x that of Earth
is built - very quickly - and with sufficient mass to resolve issues
with radiation hazards and mechanical longevity.
In addition to the length of time the sun lasts, there is the length of
time the artificial planet lasts.
Thin pressure vessels age, and may not last for millions or even
thousands of years. So over the course of billions or trillions of
years, pressure vessels will be reproceswsed thousand millions or even
billions of times.
For anyone who thinks its possible for pressure vessels to last for
centuries without being replaced consider how pressurized aircraft age.
They don't even last through decades of service.
We're talking about building something that will last for as long as
planets last. And since recycling is not 100% efficient, not all
material will be available for building materials - some will be in
process, some will not be available for recycling and lost. So, once
all the materials are processed into pressure vessels - the length of
service and efficiency of pressure vessel recycling will determine how
long humanity can live off world this way.
Even if pressure vessel recycling is 99.99% efficient, and each vessel
lasts 10,000 years, longer than the pyramids, over 5.5 billion years
will be reprocessed 550,000 times. Which means less than 3 grams of
the asteroid belt will be available for recycling at the end of the 5.5
billion year period.
A single shell like the one proposed that lasts 10 trillion years due
to its extraordinary size and thickness, with the sun modified to burn
10 trillion years supporting 300,000x the surface area of Earth with
5,000,000x the mass of the asteroid belt available for industrial use
to support interstellar transport over this same period - provides the
most bang for the buck - and is generally exportable to the rest of the
cosmos.
This doesn't mean the asteroids won't form an epoch of development of
humanity. But that depends on the history of technical development and
once solar materials are easily available - the asteroids will fall in
importance. Using our figures of 99.99% efficiency, and longevity of
10,000 years - asteroidal material will be reduced to 10% of its
original mass in 230 million years.
..
On Jan 26, 1:16 pm, "Mike Combs"
<mikeco...@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
<Willie.Moo...@xxxxxxxxx> wrote in messagenews:1169830326.167621.136020@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
We'll modify the sun in either case by building a substantial shell. Aabout the same amount of land area. And that without using any technology
shell only 1% populated with the reflective interior surface, would
hardly cause any change whatever - but still contain over 3,300 earth
areas!Yeah, but the asteroid belt converted into O'Neill habitats would provide
significantly advanced over what's currently available.
--
Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn
.
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