I wrote
| 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.

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

I was originally quoting Henry Spencer in this newsgroup
(article , dated 30 June 2003), when he wrote
: Making an essentially zero-leakage rotating joint is not a big problem,
: especially for slow rotation.

I don't have any specific references, but google "rotating shaft seal"
brought up about 285,000 hits just now, many of which looks relevant.
For example, each of
http://en.wikipedia.org/wiki/Rotatin...echanical_seal
http://www.azom.com/Details.asp?ArticleID=504
http://www.mt-online.com/component/c...l?directory=90
http://www.freepatentsonline.com/3088744.html
has some useful general information.

This is quite standard industrial technology. For example, every
ship has a rotating seal where its propellor shaft(s) exits the hull.
Loaded oil tankers may have their propellor shafts more than 10 meters
(33 feet) below the water level, giving an ambient water pressure of
greater than 1 atmosphere. Indeed, submarine propellor-shaft seals
must withstand up to ~50 atmospheres of pressure (= water pressure at
a depth of ~1500 ft).

ciao,

--
-- "Jonathan Thornburg [remove -animal to reply]"
Dept of Astronomy & IUCSS, Indiana University, Bloomington, Indiana, USA
"Washing one's hands of the conflict between the powerful and the
powerless means to side with the powerful, not to be neutral."
-- quote by Freire / poster by Oxfam