Sylvia Else wrote:
On 18/02/2011 1:30 AM, Jonathan Thornburg [remove -animal to reply] wrote:
James wrote:
So a lot of movies, TV shows, illustrations, etc., show spacecraft
generating "gravity" via rotating hull sections. In many cases, this
rotating section spins around a stationary central hull.

The question I have for those more knowledgeable in this area than I
is: What is the connection between these two sections? Obviously
there shouldn't be a physical connection between the two hull sections
(right?). But would this mean space enough between the spinnning hull
and the stationary hull for the interior atmosphere to escape? Or is
it sealed somehow?

If you have separate rotating and non-rotating sections (as in, for
example, the movie "2010"), then yes, you need a rotating air-seal
between them. This takes a bit of effort for the engineers, but is
certainly possible.


Do you have any references describing how it could be achieved? I've
looked, and I cannot find anything.

It can be done at simplest with the kind of rubber seal used in car
engines to keep the oil in, or with various other rotating seals of
greater complexity - but it doesn't usually need to be done.

For instance in a long flight, eg to Mars, you spin up the living
capsule say at one end of a tether and the landing module or whatever at
the other end, and it just stays spinning until a day or two before you
arrive.

For a space station with two sections the airlock between them (you do
want an airlock there!) either mates with the spinning section or with
the stationary section.

When moving from the rotating section the airlock opens to the RS,
people transfer into the airlock, it closes, it unmates with the RS, it
despins, then it mates with the stationary section etc.



In some scenarios the sections should not be in contact, if possible -
the main reason for having two sections is that you want microgravity in
one section and earthlike gravity in the other.

In order to have good microgravity with eg a rotating seal the center of
gravity of the rotating section must be at the center of the seal - but
this causes problems as eg people move around the rotating section. This
also puts pressure on the seal. It may be best to have no actual contact
between the sections, just a transfer airlock.



-- Peter Fairbrother