--- In spacesettlers@yahoogroups.com, Al Globus wrote:
> The minimum is close to 1000 km up, to avoid deorbiting any time
soon.

Drag is less of an issue with a larger, more-massive habitat. A larger habitat also enjoys greater economies of scale and therefore can more-easily afford things like ion thrusters to continuously overcome drag. A low-altitude habitat is more attractive to traffic from Earth and so therefore should encourage earlier growth to larger sizes -- which, again, are more aerodynamically efficient.

On Jan 28, 2012, at 1:49 AM, hitssquad wrote:

> --- In spacesettlers@yahoogroups.com, Al Globus wrote:
> > The minimum is close to 1000 km up, to avoid deorbiting any time
> soon.
>
> Drag is less of an issue with a larger, more-massive habitat. A
> larger habitat also enjoys greater economies of scale and therefore
> can more-easily afford things like ion thrusters to continuously
> overcome drag. A low-altitude habitat is more attractive to traffic
> from Earth and so therefore should encourage earlier growth to
> larger sizes -- which, again, are more aerodynamically efficient.
>

That's fine if you assume everything works well and no one ever screws
up. Unfortunately, that hypothesis has been decisively shown to be
false. I'm not sure exactly what the requirement should be, but
given no inputs I would not like to see a habitat with an orbital
lifetime of under a century or two.

Still, 1000 Km (625 M) is a better orbit to be in for a number of reasons.
1000 Km puts it into lower regions of the inter Van Allen Belt' Maybe 1100
KM would be better. Either distance would be less likely for orbit
degrading. But 1000 Km is the lowest I would put it. And it would not be too safe
in the Van Allen Belt so the highest I would place one would be 1300 Km or
about 800M.

The lower Van Allen belt supposedly starts at about 1600 KM (1000 M) but
it's presence can be felt and seen as low as 320 Km (200 M)

John Wayne Smith

In a message dated 1/28/2012 4:42:30 P.M. Eastern Standard Time,
hitssquad@... writes:

--- In spacesettlers@yahoogroups.com, Al Globus wrote:
> The minimum is close to 1000 km up, to avoid deorbiting any time soon.

Drag is less of an issue with a larger, more-massive habitat. A larger
habitat also enjoys greater economies of scale and therefore can more-easily
afford things like ion thrusters to continuously overcome drag. A
low-altitude habitat is more attractive to traffic from Earth and so therefore should
encourage earlier growth to larger sizes -- which, again, are more
aerodynamically efficient