From: vince@offshore.ai (Vincent Cate)
Newsgroups: sci.space.tech,sci.space.science,sci.space.history
Subject: Re: Simple Atmospheric Model for Space?
References: <9186edb5.0310052108.54744457@posting.google.com> <HMCF18.Kv5@spsystems.net>
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Message-ID: <9186edb5.0310061640.2b9f4d0d@posting.google.com>

henry@spsystems.net (Henry Spencer) wrote in message news:<HMCF18.Kv5@spsystems.net>...
> And yes, this means that orbital lifetimes are also highly variable.
> Predictions of Skylab's orbital life disagreed by years, largely because
> they made different assumptions about solar activity. 

If I can get within a factor of 2 half the time I will be much better 
off than I am now.  :-)  I am thinking of my simulator as something for
learning and checking out design ideas, not trying to predict exactly 
when a particular satellite will reenter.

> The discussion in section 8.6.2 of Vallado's "Fundamentals of Astrodynamics
> and Applications", 2nd ed, is the best readily-accessible one that I'm 
> aware of.
> [...]
> Vallado gives a piecewise-exponential model that varies scale height with
> altitude (using a small table, it's not a single formula), and says it's
> suitable for general studies.  (Ah, and he says he swiped it from Wertz's
> "Spacecraft Attitude Determination and Control", so that's two books to
> look for.)

Thanks.  That is what I am looking for.  Strangely, while Vallado is 
$178.60 used on abebooks.com it is only $54.75 new on Amazon.
Wertz is $99.69 on abebooks and $152 new or $104 used on Amazon.  
I went with Vallado new.  :-)

Thanks again,

   -- Vince