Re: BBC's Pegasus spaceship

From: Henry Spencer (henry_at_spsystems.net)
Date: 11/23/04 

Date: Tue, 23 Nov 2004 18:13:06 GMT

In article <41a5cb34.1686997@supernews.seanet.com>,
Derek Lyons <fairwater@gmail.com> wrote:
>>Long-lived large bearings for slow rotation are routine technology, e.g.
>>assorted rotating restaurants on various tall towers.
>
>Umm... I dunno. The ones at the Space Needle are small rollers
>(think wheels, not cylinders) on which the deck of the restaurant
>rides. IIRC, they are a foot or so in diameter. They are also easily
>accessible for maintenance, and shut down completely each night, and
>shut down for extended maintenance every six months or so.
>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.

(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.) 

-- 
"Think outside the box -- the box isn't our friend."    |   Henry Spencer
                                -- George Herbert       | henry@spsystems.net

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