"Maarten" no_one@nowhere wrote in message li.nl...
After browsing the internet for some time, I still haven't found an answer
to the following question.
As a novice in this area, I wonder why there is such a specific preference
for having e.g. ISS, Space Shuttle in an orbit of about 400km. (This I
make up from the testimonials from space ships' crew that all tell about the
sun coming up and going down every 1.5 hours).
So my question is, why this preference for 400 km and why isn't it an orbit
of 250km or 600km or even more ?

Maarten

I believe that the highest of those orbits would be in or near the Van
Allen belts. Lower orbits would be difficult to maintain due to
increased atmospheric drag on the spacecraft. Others more
knowledgable here will probably chime in with other possible reasons.

Hope this helps.

Bob Bernatchez