Re:

[T.L.G.vanderLinden@student.utwente.nl (Timothy van der Linden)]

>> How do you shove a few kilometres of clouds? Especially during acceleration
>> and deceleration a lot of cloud-rebuilding will be needed.
>
>Ion cannon.  Since the dust is light, it would take little power to throw it
>that far ahead.  The parts that fall back on the ship can be reused, the rest
>would need to be replaced.  Since you spend most of the mission coasting its
>not a big problem.

OK

>> One may not need a complete ring. Just a habitation "cube" at the two ends
>> of a long "bar". Then just turn this bar around, thus the ends making a
>> common circle. It is in fact just a the torus mentioned above only with a
>> lot of segments left out.
>
>True but you still have to have the same cross size, and you can't always use
>a bar.  (Most of my designs have a channel runing through the center of the
>ship.)

Indeed the cross size doesn't change, but it would be several times less work. 
You could make a small circle in the middle and attach the bar on that.
That circle could move around the middle-hull.


 __            _            __
|  |          / \          |  |
|H |=========| X |=========| H|       Where H are habitation "cubes"
|__|          \_/          |__|       Where X is the ship-axis
             

Tim