Malfunctioning Gyroscope on ISS shut down

Saw this on the CNN web today:

http://www.cnn.com/2006/TECH/space/1...eut/index.html

apparently one of the 4 gyros on ISS is vibrating excessively and has
been turned off. A decision has not yet been made as to whether or not
it will be spun back up during Discovery's mission set for December,
at which time two others will need to get shut down for cable
connections to the new solar array, leaving the station with just one
running.

To the experts out there....

1) what are the effects of just one gyro running during the space
walk/docked ops?

2) Can they repair or replace the failed unit assuming it can't get
spun up again??
===[George R. Kasica]=== +1 262 677 0766
President +1 206 374 6482 FAX
Netwrx Consulting Inc. Jackson, WI USA
http://www.netwrx1.com

ICQ #12862186

George R. Kasica wrote:
To the experts out there....

1) what are the effects of just one gyro running during the space
walk/docked ops?

The remaining gyro will have to be augmented with Russian segment
attitude thruster firings to maintain the station's orientation.

2) Can they repair or replace the failed unit assuming it can't get
spun up again??

Another CMG was replaced on STS-114 last year. The only suitable flight
coming up would be ISS-13A.1 (STS-119?), but that's pretty packed. The
manifest is very tight, and gyroscopes are heavy, so flying a
replacement could push an extra logistics mission into the schedule.

The CMGs appear to be less reliable than hoped. I wonder if NASA will
fly one or two extra CMGs up on a late shuttle flight to be used as cold
spares.

--Chris

On Thu, 12 Oct 2006 16:06:57 -0500, Chris Bennetts wrote
(in article
):

The CMGs appear to be less reliable than hoped. I wonder if NASA will fly one

or two extra CMGs up on a late shuttle flight to be used as cold spares.

And that begets (*) the question: what are the specs for on-orbit cold
storage? In other words, how long may CMGs remain unpowered in a
micro-g environment and subject to temperature extremes and still be
expected to operate when called upon? And furthermore, how many spare
ORUs (**) were contracted?

(*) Note to Mary: I did NOT say "begs the question" ;-)

(**) Orbital Replaceable Units)

--
Herb Schaltegger
"You can run on for a long time . . . sooner or later, God'll cut you
down." - Johnny Cash
http://www.angryherb.net

Herb Schaltegger wrote:
[...]
And that begets (*) the question:
[...]
(*) Note to Mary: I did NOT say "begs the question" ;-)

Bene, my son!

/dps

Herb Schaltegger wrote:
And that begets (*) the question: what are the specs for on-orbit
cold storage? In other words, how long may CMGs remain unpowered in
a micro-g environment and subject to temperature extremes and still
be expected to operate when called upon?

I sure hope NASA knows.

And furthermore, how many spare ORUs (**) were contracted?

SpaceflightNow's coverage indicates that there was only one, and it's
currently in orbit. The failed one is apparently being refurbished.

--Chris

Well, if the CMG is properly designed, it should only take one.
--
Craig Fink
Courtesy E-Mail Welcome @
--
On Fri, 13 Oct 2006 07:06:57+1000, Chris Bennetts wrote:
George R. Kasica wrote:
To the experts out there....

1) what are the effects of just one gyro running during the space
walk/docked ops?

The remaining gyro will have to be augmented with Russian segment
attitude thruster firings to maintain the station's orientation.

2) Can they repair or replace the failed unit assuming it can't get
spun up again??

Another CMG was replaced on STS-114 last year. The only suitable flight
coming up would be ISS-13A.1 (STS-119?), but that's pretty packed. The
manifest is very tight, and gyroscopes are heavy, so flying a
replacement could push an extra logistics mission into the schedule.

The CMGs appear to be less reliable than hoped. I wonder if NASA will
fly one or two extra CMGs up on a late shuttle flight to be used as cold
spares.

1) None if it doesn't fail, for a properly designed CMG.
2) It isn't broken yet, it's just vibrating too much. For a properly
designed CMG, it would just need a few light weight part to repair, or at
best just rebalnced.
--
Craig Fink
Courtesy E-Mail Welcome @
--
--On Thu, 12 Oct 2006 14:48:11-0500, George R. Kasica wrote:
Saw ...

http://www.cnn.com/2006/TECH/space/1...eut/index.html

apparently one of the 4 gyros on ISS is vibrating excessively and has
been turned off. A decision has not yet been made as to whether or not
it will be spun back up during Discovery's mission set for December,
at which time two others will need to get shut down for cable
connections to the new solar array, leaving the station with just one
running.

To the experts out there....

1) what are the effects of just one gyro running during the space
walk/docked ops?

2) Can they repair or replace the failed unit assuming it can't get
spun up again??
===[George R. Kasica]=== +1 262 677 0766
President +1 206 374 6482 FAX
Netwrx Consulting Inc. Jackson, WI USA
http://www.netwrx1.com

ICQ #12862186

Craig Fink wrote:
2) It isn't broken yet, it's just vibrating too much. For a properly
designed CMG, it would just need a few light weight part to repair, or at
best just rebalnced.

As it stands, the ISS will never be equipped to do such maitenance on
the CMGs. They are too big to fit in the airlock. And you can't do such
precision work in a EVA with those gloves.

In terms of the vibration: how much energy do those wheels store ? Is
there a danger that the casing would not fully contain a flywheel
breaking apart ?


Unless the USA extends the shuttle's life and adds more flights, the USA
segment is already on "self maintenance" for items such as CMGs that
fail.

So, which would be easier now ? Outfit a progress to carry a CMG and a
fake docking port ahead of it ?
Outfit ATV in a similar fashion ?

Could they just stick a CMG on a progress and have the progress station
keep close enough to be grappled by the station arm, at which point an
EVA can travel along teh arm to the progress, fetch the CMG, bring it to
Z1, and then bring the failed CMG to the progress, fasten it, and then
let Progress go away and deorbit ?

Since CMGs are expected to fail every couple of years, and NASA stops
having the ability to bring back stuff, it won't be able to refurbuish
CMGs so it shoudl start to order new ones right away.

John Doe wrote:

In terms of the vibration: how much energy do those wheels store ? Is
there a danger that the casing would not fully contain a flywheel
breaking apart ?

Possibly, if the failure was violent enough.

So, which would be easier now ? Outfit a progress to carry a CMG and a
fake docking port ahead of it ?
Outfit ATV in a similar fashion ?

I'd bet that an extra shuttle flight would be cheaper than either of
those options.

Could they just stick a CMG on a progress and have the progress station
keep close enough to be grappled by the station arm, at which point an
EVA can travel along teh arm to the progress, fetch the CMG, bring it to
Z1, and then bring the failed CMG to the progress, fasten it, and then
let Progress go away and deorbit ?

Such work would require very tight manoeuvring of the Progress via
remote control. That would be extremely difficult, with a high
probability of the Progress colliding with the station. They wouldn't
risk it.

--Chris

The CMG can't fit through the Russian segment hatches so the ATV is out.
However, the Japanese HTV is designed to mate with the CBM and its
big door -- the problem would then be to get it outside. The Progress idea
is a good
one since on occasion the Russians sent steamer-trunk sized external ORUs to
Mir
mounted in a recess in the Progress tank module (where the command module is
for
Soyuz), and retrieving/manipulating it via EVA and booms. It's a proven
design
and should not be more expensive than the standard design.

Retrieving worn-out CMGs is another problem post-shuttle, but here
I suspect inflatable down-cargo canisters will quickly step in.



"John Doe" wrote
So, which would be easier now ? Outfit a progress to carry a CMG and a
fake docking port ahead of it ?
Outfit ATV in a similar fashion ?

Could they just stick a CMG on a progress and have the progress station
keep close enough to be grappled by the station arm, at which point an
EVA can travel along teh arm to the progress, fetch the CMG, bring it to
Z1, and then bring the failed CMG to the progress, fasten it, and then
let Progress go away and deorbit ?