Newsgroups: sci.space.shuttle
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Re: inclination of space station
Date: Tue, 6 Feb 1996 16:17:24 GMT

In article <4f5lpj$ih9@info-server.surrey.ac.uk> eex1je@kira.isl.com (Ed) writes:
>This is the second post I've seen talking about short launch windows to ISSA.
>I don't see how the inclination can make that much difference to it (not to 
>the order of an hour, anyway).

If the station is at an inclination equal to, or only slightly greater than,
KSC's latitude, then its orbit slowly approaches KSC's latitude, lingers in
that vicinity for a while moving almost straight east, and then gradually
departs southward again.  If the inclination is much higher, than the orbit
crosses KSC's latitude at a fairly sharp angle twice (once northward and
once southward), and never lingers in the neighborhood for any length of
time.  This is the difference between one relatively long launch window
and a pair of quite short ones.

>I believe that one of the constraints for docking to Mir is that the docking
>occurs when Mir is in comms range of Russia, hence the 5-7 minute launch
>windows we typically see for that.

No, the Russians have relaxed the communications requirement somewhat.
The launch windows remain narrow due to the inclination.

This isn't necessarily a disaster.  The shuttle's overall on-time performance
has not been particularly good, but it looks much better if you examine only
the launches where time really was critical.  (It's hardly surprising that
nobody gets too excited about staying on time for payloads which don't care
about exact timing.)  It would be better if the windows were longer, but the
problem looks manageable.
-- 
Space will not be opened by always                 |       Henry Spencer
leaving it to another generation.   --Bill Gaubatz |   henry@zoo.toronto.edu