[ExI] asteroid defense

spike spike66 at att.net
Tue Mar 1 18:43:13 UTC 2011

-----Original Message-----
From: extropy-chat-bounces at lists.extropy.org
[mailto:extropy-chat-bounces at lists.extropy.org] On Behalf Of Kelly Anderson
Subject: Re: [ExI] libertarian (asteroid) defense

On Tue, Mar 1, 2011 at 4:39 AM, Anders Sandberg <anders at aleph.se> wrote:

>The Tunguska event in 1908 Siberia is supposed to have been the result of
an asteroid or comet less than 100m across...The smaller ones are harder to
find, and once all the large ones are mapped, I hope we continue to look for
smaller and smaller asteroids and comets.  -Kelly

Since the topic has drifted from libertarianism for now (thanks) I request
we keep subject lines in keeping with the subject.

As a first order approximation, one can divide the asteroids (and meteors
for that matter) into arbitrary categories and use a straight line to
describe the total mass of particles in that category.  For instance, if you
want to use a linear length scale, you can approximate the mass of asteroids
between 1 km and 10 km (using the tables) and calculate their total mass.
Then you can estimate that there are about 1000 times as many asteroids
between 100 meters and 1 km, so that their cumulative mass is about the same
as the previous.

This is a critically important means of estimating the cumulative effects of
orbital debris on sensitive and expensive space stuff, such as solar panels.
If one is hit by a counter orbiting pebble a cm across, it will likely punch
right thru and end the mission.  If it's a millimeter across, it will likely
not cause too much trouble, but the probability of such a hit is about 3
orders of magnitude greater.  The biggest problem of all for most long lived
space missions is the 10 micron to 100 micron class of debris, because it
stays around long enough to interfere, and causes gradual erosion (pitting)
of the solar panels.  Smaller than 10 microns apparently gets pushed away by
solar radiation or dragged down by traces of atmosphere.



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