From: henry@spsystems.net
In article <4016c09f.362265@supernews.seanet.com>,
Derek Lyons wrote:
>>No, Hubble *was* meant for maintenance in space, although as usual
>>(repeating a mistake made on Skylab), they cheaped out and decided that
>>some portions of it wouldn't break and hence wouldn't need to be set up
>>for maintenance...
>
>It's not cheaping out, it's designing for the real world. It's very
>difficult to provide every component with clear access, and large
>(spacesuit operable) connectors and fasteners etc... If you had
>infinite volume available the problem becomes much simpler, but the
>designers/builders of Hubble didn't have infinite volume.
Unfortunately for this theory, some of the problems occurred in places
where there were no volume constraints (e.g., no provision for replacing
the magnetometers, which were external). People simply made assumptions,
some of which turned out to be wrong, about which things would need fixes.
On Skylab it was even worse, with major areas of the exterior lacking in
handholds because they were put only in places where somebody could
*prove* that they would be needed.
There is designing for the real world, and then there is designing for an
imaginary world in which your predictions are always right and there is no
need to take even simple precautions when the predictions say they are
unnecessary. NASA is very big on predictions, but is not consistently
attentive to the possibility that the predictions might be wrong. They do
get this right sometimes -- the ISS airlock gear includes "contingency
toolboxes", with an assortment of general-purpose gear to "provide a
generic capability to react to unforeseen situations" -- but not always.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. | henry@spsystems.net
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