-Z- (Z@Gundam.Com)
Fri, 26 May 2000 19:00:32 -0700


At 07:13 5/26/2000, you wrote:
>At 18:23 05/24/2000 -0700, -Z- wrote:
>>Yes, but it'll also let the ocean in. Lots of steam will probably be
>>produced during the first hour or so, until enough sea water fills the
>>crater to seal off the breach, turning it into an undersea
>>volcano. Thereafter, the crust may "heal" or not -- I can see it going
>>either way.
>
> From what we saw of the crater in 0083, it probably healed --
>nothing similar to the underwater volcanoes of Hawaii.

Given the depth of the crater, it's doubtful that any undersea vulcanism
would be apparent at the surface. Well, the rise is temperature might make
the water a deeper blue and, of course, an entirely different ecosystem
would form in the warmer water, but I think you'd have to dive quite a way
before the volcanic activity became apparent.

Which raises the question of the Zeon submarine....

>>The mass and velocity will play a more important role than the shape. The
>>shaQnpf the colony would affect the shape of the crater, as would its
>>angle of impact, but I don't think it would affect the size of the crater.
>
> Won't the shape of the colony slow it down as it enters the
>atmo45re, depending how it hits the atmosphere, as well as making it
tumble?

No, at that speed, presenting a greater surface area to the atmosphere will
only result in a faster breakup and hotter burning. It would be different
if it were a solid mass of, say, nickel iron, but it's a tube of concrete
with titanium and steel reinforcement, the walls of which are at most a
dozen or so meters thick along the three longitudinal "ground"
sections. The windows are at most three meters thick.

Tumbling would be the worst thing that could happen to it. The greatest
concentrations of mass are the docking bay and industrial blocks at either
end. If it tumbles, the colony will be subjected to longitudinal strain as
the blocks are thrown apart by the centripetal force. The stress will be
greatest at the equator, which is the weakest region of all.

Coming in "nose first" presents the least surface area to friction. Any
other attitude increases the friction proportionally. Friction translates
into both heat and drag and the drag induces torque as well as linear
stress. That's why falling satellites break up even before they begin to
burn up.

Ever see the movie footage of the Hindenberg? That's what your re-entering
colony is likely to look like if it starts to tumble.

> Interesting thought. Shoot a colony at an angle such that it will
>not bounce off the atmosphere, but mighe just be possible that the colony
>will skip when landing. The carnage could be a heck lot more, especially if
>you aim it at a population center, but the crater might not be so obvious as
>the Sydney crater that we see in 0083.

A spinning colony coming in nose-on has the best chance. Not only does it
reduce the friction and drag as much as is possible, but the spinning helps
distribute the heat more evenly and keeps the structure in a more stable
attitude.

If you want a skipping stone effect, you need a skipping stone shape. A
Stanford torus might have the right geometry, but an O'Neill cylinder doesn't.

-Z-

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