Malfunctioning Gyroscope on ISS shut down

"Ian Stirling" wrote in message
...
If it was me, I'd be putting nearly all the crap like CMGs, inside the
pressure cabin.
If it needs vacuum, you have a vacuum line to a suitable place.
Then you do turn off the vacuum line, open the box, and fiddle with it.

If it breaks, you stick it in the trash pile in the corner.
(bolted to the trash-frame of course)

But I'm not designing these things.
(yes, this is a ET station)

Sounds good, but there are some things which really want to be outside, like
solar panels and radiators, and other things that you'd like to put outside,
like the part of the coolant loop that's filled with toxic coolant or the
batteries, which also contain rather nasty chemicals that can outgas. Once
you start sticking some of this equipment outside, you're likely to find
other equipment, like DC to AC converters or coolant pumps, that would also
be very convenient to stick outside since they need to be close to equipment
that's already outside.

When you're in a vacuum, it's hard to stick *everything* inside.

Jeff
--
"They that can give up essential liberty to obtain a
little temporary safety deserve neither liberty nor
safety"
- B. Franklin, Bartlett's Familiar Quotations (1919)

Sounds good, but there are some things which really want to be outside, like
solar panels and radiators

OK, hard to argue with that one.

other things that you'd like to put outside, like the part of the
coolant loop that's filled with toxic coolant or the batteries, which
also contain rather nasty chemicals that can outgas.

Well, at the risk of being polyannish, maybe this is an argument for
less nasty ingredients.

Once you start sticking some of this equipment outside, you're likely
to find other equipment, like DC to AC converters or coolant pumps,
that would also be very convenient to stick outside since they need to
be close to equipment that's already outside.

The whole line of thought seems to be predicated on optimizing for
factors which don't include maintenance. It seems a bit odd to marvel
at how having a crew lets you fix things which break, but then not
design things to be fixed easily.

Of course, it's easy to play armchair engineer.... Henry would get
away with it because he'd say "oh, in Gemini they had a better
solution..." or something ;-).

Jim Kingdon wrote:
The whole line of thought seems to be predicated on optimizing for
factors which don't include maintenance. It seems a bit odd to marvel
at how having a crew lets you fix things which break, but then not
design things to be fixed easily.

The ISS was designed to be fixable. But it was also designed to have a
up/down cargo functionality.

The is a "hand" that is ready to be sent to the station that is supposed
to be good enough to actually open an MDM box on the truss, pull a
circuit board card out and insert a new one in and close the box.

Stuff like CMGs were not designed for orbital repairs because of the
expectation that the USA would replace the shuttle with a more capable
vehicle (or series of vehicles giving same operational capabilities).
There was not the expectation of returning to limited capabilities of
Apollo era phone booths.

You need to think of the CMGs in the same way that you think of disk
drives. You cannot open up a disk drive at home and fix some bearings.
This needs to be done in a clean room facility. Similarly, the CMGs
cannot be opened up and fixed in vacuum. And NASA would probably argue
that since it has no manuals that document how such maintenance would be
done in 0G therefore, the conclusion is that maintaining CMGs in space
is impossible.


I suspect that if the station had been designed with knoweldge that the
USA would revert to Apollo only capabilities by 2010, the station might
have been quite different. I doubt they would have bothered with the CBM
hatches for instance. And you wouldn't have MPLMs. And racks would have
been made much smaller.

Jim Kingdon wrote:
other things that you'd like to put outside, like the part of the
coolant loop that's filled with toxic coolant or the batteries, which
also contain rather nasty chemicals that can outgas.

Well, at the risk of being polyannish, maybe this is an argument for
less nasty ingredients.

Sometimes that's possible - sometimes its not.

Once you start sticking some of this equipment outside, you're likely
to find other equipment, like DC to AC converters or coolant pumps,
that would also be very convenient to stick outside since they need to
be close to equipment that's already outside.

The whole line of thought seems to be predicated on optimizing for
factors which don't include maintenance. It seems a bit odd to marvel
at how having a crew lets you fix things which break, but then not
design things to be fixed easily.

Ease of maintenance is but *one* factor to be considered.
Overoptimizing on any [one] factor is generally considered to be a Bad
Thing.

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

"Derek Lyons" wrote in message
...
Ease of maintenance is but *one* factor to be considered.
Overoptimizing on any [one] factor is generally considered to be a Bad
Thing.

I'm guessing that on a submarine, there are some pieces of equipment that
necessarily have to be exposed to the pressures outside and therefore can't
be repaired or even accessed while at sea. Any examples that aren't
classified? ;-)

Jeff
--
"They that can give up essential liberty to obtain a
little temporary safety deserve neither liberty nor
safety"
- B. Franklin, Bartlett's Familiar Quotations (1919)

"Jeff Findley" wrote:

"Derek Lyons" wrote in message
...

Ease of maintenance is but *one* factor to be considered.
Overoptimizing on any [one] factor is generally considered to be a Bad
Thing.

I'm guessing that on a submarine, there are some pieces of equipment that
necessarily have to be exposed to the pressures outside and therefore can't
be repaired or even accessed while at sea.

Generally that stuff is minimized - partly for maintenance reasons,
partly to reduce weight, and complexity, and partly for streamlining
issues.

Any examples that aren't classified? ;-)

Tons of 'em. Hatch mechanisms (both for people and missiles), torpedo
tube shutters, all the masts and antennas have at least portions
exposed to the sea (as well as their supports, guides, and bearings -
inside the sail), sonar transducers, the anchor and portions of its
operating gear, windlasses, radio and emergency buoys, portions of the
operating gear for the control surfaces, ballast tank vent valves and
certain portions of the ballasting system, the SPM (Secondary
Propulsion Motor AKA 'the outboard'), portions of the main propulsion
shaft, the propulsor (propeller or pump jet), portions of the Snorkel
system, for boats carrying a DDS - much of the DDS operating gear, and
for VLS equipped boats - the entire missile tube and contents...

In fact I can only think of two external items whose mere existence is
classified - despite their existence being widely known or suspected.
1) any cute lil' toys carried by Carter and 2) any 'landing gear'
allowing a boat to sit on the bottom.

An equally large maintenance problem is the myriad of valves, cables,
and shafts which cross a pressure boundary - whether to sea or to a
tank at sea pressure.

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

In sci.space.shuttle Jeff Findley wrote:

"Ian Stirling" wrote in message
...
If it was me, I'd be putting nearly all the crap like CMGs, inside the
pressure cabin.
snip
Sounds good, but there are some things which really want to be outside, like
solar panels and radiators, and other things that you'd like to put outside,
like the part of the coolant loop that's filled with toxic coolant or the
batteries, which also contain rather nasty chemicals that can outgas. Once
you start sticking some of this equipment outside, you're likely to find
other equipment, like DC to AC converters or coolant pumps, that would also
be very convenient to stick outside since they need to be close to equipment
that's already outside.

When you're in a vacuum, it's hard to stick *everything* inside.

Sure.
But...

Batteries for example.

The station uses NiMH batteries to get 38000 cycles.
You'd want another sealed container round the existing pressure vessel
on each cell, so you could pull an individual cell, and throw it in the
'to be deorbited' - dangerous safe.

Coolant loops.
CFCs are probably a good option.

Even water/alcohol.

My initial design has lots of little portholes all over it.
You need to hook up a solar array, you find a free 30cm port on the
correct side.

You take the stowed solar array poles - bundles of tubes 30cm in diameter
by 2m or so.
Screw them together to the required length.
Now, deploy through the hole.

Connect up.

To get rid of an undesired add-on, you spin the station, unplug any
connectors, attach a rope, put a teeny airlock over the porthole,
winch up to the correct tension, wind the accessory out till it's well
clear.
Free the winch, allow the device to free-fall, then cut the load off,
and reel in the wire.
The end of the wire has small gas thrusters in, to control the reel-in.

All devices jettisoned this way must have a low sectional density.