Re: BBC's Pegasus spaceship

From: Derek Lyons (fairwater_at_gmail.com)
Date: 11/23/04 

Date: Tue, 23 Nov 2004 22:26:52 GMT

henry@spsystems.net (Henry Spencer) wrote:
>In article <41a5cb34.1686997@supernews.seanet.com>,
>
>>A central bearing (howsoever slow rotating) for a large station is
>>going to be more like the shaft bearing on a ship, expected to operate
>>for years on end, without significant maintenance.
>
>Why "without significant maintenance"? It's not a difficult design
>problem to put the bearing inside the pressure seal, so you can work on it
>in shirtsleeves. And with a similar approach -- lots of wheels/rollers,
>not a single massive sleeve bearing -- you can even replace sections of it
>without a shutdown.

Assuming that the final design admits of such refinements as lots of
parts that can jacked out for maintenance... Which (in your design
above) means a rotating seal (itself needing maintenance) to maintain
that shirtsleeve environment, as well as sufficient clearance and/or
housings to work safely among the active elements. Non trivial I
suspect.

The there is the maintenance tradeoffs - One Big Bearing can go years
without anything more than ensuring an ongoing flow of lubricants and
a regular checks of that flow for metal fragments. Multiple smaller
bearings mean these systems are more complex, but the bearing itself
has redundancy.

>(This problem is different from a submarine or one of today's spacecraft
>in an important way: internal volume is essentially free. The bearing
>assembly can be *big*, providing room for internal maintenance access.)

Maintenance acess, at least for submarines, is a non issue. The big
bearings in the red gears and the thrust line nowadays typically last
the entire life of the hull with nothing more than swapping out the
(much smaller) internals of the bearing every few years. Making the
wearing parts modular is a long solved problem. There's no need to
get inside the bearing.

D. 

-- 
Touch-twice life. Eat. Drink. Laugh.
-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

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