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From: Alastair Reynolds <areynold@estsa2.estec.esa.nl>
Subject: Re: (whorl) vampires make bootstrap lift off
Date: Wed, 06 Sep 2000 09:19:46 +0200

Michael Andre-Driussi wrote:

> (Then again, wombat: don't wings and lifting bodies have an atmospheric
> limit?  That is, they have no value in a vacuum, and as the object comes
> into the gravity well it picks up some speed before the atmosphere is
> sufficiently thick enough to provide the lift?  I guess I'm saying there's
> enough atmosphere for re-entry friction, but not enough for lift, until the
> object gets to a certain critical level which is relatively deep into the
> gravity well: but I'm just wondering around.)
> =mantis=

No; you're right, Mantis - if the inhumi "fall" from the lagrange point
Green and Blue, then they're essentially going to hit Blue's atmosphere
with speed on the order of escape velocity. The only thing they can
assuming they don't have a way to slow down in vaccum (stolen PM modules
from the Trivigaunti fliers?) is their angle at which they brush the 
atmosphere. And even with the optimum approach angle (not too steep so
that they burn up, or too shallow so that they bounce off), there'll
still be an enormous amount of friction. Somehow or other the kinetic
energy they've accumulated during their fall has to be converted to
heat, and the only variable is whether this happens slowly, in a
way (like a space shuttle re-entry) or in a quick burn-up. Barbecued
inhumi, anyone?

Re: the orbital mechanics of Green/Blue - wasn't the best explanation,
as worked out by someone here, that they're analogous to our moon and
its small satellite partner Cruithne? It was pointed out that this
had been written up (in Nature I think) early enough for Wolfe
to have incorporated it into the series. Or was there some
fatal flaw in that idea?


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