Space walk?

Have they busted something else, I tell you when these devices are out of
warranty you can never get them serviced economically....
Brian

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In article ,
says...

Have they busted something else, I tell you when these devices are out of
warranty you can never get them serviced economically....

Electronics fail from time to time, which is why spares are already
prepositioned on ISS.

Jeff
--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer

I was b being sarcastic for humourous purposes. Of course tthey do but i do
wonder if they make the right guesses about which bits fail.

How are the rotary race rings and bearings doing these days?

Brian

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"Jeff Findley" wrote in message
...
In article ,
says...

Have they busted something else, I tell you when these devices are out of
warranty you can never get them serviced economically....

Electronics fail from time to time, which is why spares are already
prepositioned on ISS.

Jeff
--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer

In article , says...

I was b being sarcastic for humourous purposes. Of course tthey do but i do
wonder if they make the right guesses about which bits fail.

For this sort of thing, you can estimate a mean time between failure
(which might be wildly off for purpose built aerospace hardware, but you
do the best you can). Plus you can ask the question "how critical is
this unit?" to come up with a ranking of "most important" to "least
important" equipment. Combine that, and other, data and you can come up
with a "wish list" of spares you'd like to have on board ISS. Since up-
mass to ISS is limited, some things lower down on the wish list have
fewer spares. For non-critical equipment (i.e. an experiment), there
may be no spares on ISS.

Some equipment may be too expensive, large, and etc. to make spares in
the first place. Things like the hulls of the pressurized modules would
fall into this category. Get a hole in something like an MPLM and
you've either got to patch it, or shut all the hatches to it and figure
out where to go from there.

How are the rotary race rings and bearings doing these days?

No idea. I've seen nothing about them in the on-line "space media"
since the EVA to clean and lube them.

Jeff
--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer

On Thursday, April 17, 2014 3:10:14 PM UTC-4, JF Mezei wrote:
They speak of a backup *computer*. Why would a backup computer be
outdoors ? I can understand a failed power controller, but the use of
the term "computer" puzzles me.


This item is properly referred to as a "multiplexer/de-multiplexer" which is just a fancy way of saying coverts from a multipurpose data stream to a single purpose data stream. But it can be thought of in terms of a special-purpose computer, not a general purpose one like a PC but more like a dedicated device controller, like the computer in your car for example. It has been designed from the get-go to withstand the rigors of the space environment it is in.
That is not to say of course that it will never fail. According to the writeup in NASASpaceFlight.com this particular unit is 13 years old having been brought up with the S0 Truss on STS-110 in April 2002.

A fairly detailed explanation can be found he

http://www.nasaspaceflight.com/2014/...m-failure-iss/

Dave



It is also disapointing that the canadian contribution DEXTRE was
designed to be able to swap electronic cards when they failed outdoors
in order to reduce the number of EVAs. Was DEXTRE ever used for actual
work, or is it just an ugly statue at top of the station that is just
used as a toy ?

Or is this more of a case of astronauts itching for any opportunity to
go outdoors for a breath of fresh air and some exercise and to get to
see the view ?

Is this unit located in a place that is inaccessible to DEXTRE?

Dave

On Friday, April 18, 2014 12:53:57 PM UTC-4, David Spain wrote:
That is not to say of course that it will never fail. According to the writeup in NASASpaceFlight.com this particular unit is 13 years old having been brought up with the S0 Truss on STS-110 in April 2002.


Also given the nature of the failure, that power consumption dropped from a nominal 55W to 33W, I'm willing to speculate a voltage rail has gone down, possibly from a Point-Of-Load regulator failure. I've seen my share of these go bad in the day....

Dave

Yes, often its the packaging of the regulator that shrinks a bit around the
legs, and then thermal cycling eventually breaks the internal contact now
that movement is possible. I even had some ordinary Silicon diodes go
intermittent due to this some years ago when I could see.
Dis similar materials and heat cycling are not the best bedfellows.
Brian

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From the Sofa of Brian Gaff Reply address is active
"David Spain" wrote in message
...
On Friday, April 18, 2014 12:53:57 PM UTC-4, David Spain wrote:
That is not to say of course that it will never fail. According to the
writeup in NASASpaceFlight.com this particular unit is 13 years old
having been brought up with the S0 Truss on STS-110 in April 2002.


Also given the nature of the failure, that power consumption dropped from
a nominal 55W to 33W, I'm willing to speculate a voltage rail has gone
down, possibly from a Point-Of-Load regulator failure. I've seen my share
of these go bad in the day....

Dave