NASA Relies on Thrusters to Steer Station

NASA Relies on Thrusters to Steer Station

NASA Relies on Russian-Made Thrusters to Steer International Space
Station Following Malfunction

The Associated Press


CAPE CANAVERAL, Fla. Dec. 5 — NASA is relying on Russian-made
thrusters to steer the international space station following a new
malfunction with the U.S. motion-control system, officials said
Friday.

Flight controllers detected spikes in current and vibration in one of
the station's three operating gyroscopes on Nov. 8. Last week, when
the gyroscopes were used again to shift the position of the orbiting
outpost, all three worked fine.

To prevent further trouble and give engineers time to evaluate
everything, the gyroscopes will not be used for at least the next
month and the Russian thrusters will assume control, said flight
director Joel Montalbano. The station must be periodically moved into
a new position to prevent the exterior from getting too hot from the
sun.

The main drawback is the use of thruster fuel. For now, the two-man
station has more than enough fuel to spare, said program manager Bill
Gerstenmaier.

A fourth gyroscope broke in 2002. Only two good gyroscopes are needed
at any given time to control the space station.

"It's not where we want to be and we definitely don't want to get
there, but we have much backup capability ... and we're not in any
kind of real crisis," Gerstenmaier said.

Gyroscopes are too big to fit into a Russian supply ship, so NASA
cannot send up a spare until the shuttles are flying again. The
shuttle fleet has been grounded since Columbia broke apart during
re-entry in February.

http://abcnews.go.com/wire/US/ap20031205_1639.html

Rusty B wrote:
NASA Relies on Thrusters to Steer Station

Last time I saw the numbers for required upmass it was pretty tight
conserning especialy water. Without gyros and back to RCS the station would
spend a lot more fuel (IIRC it was a new feature of Mir). Is there someone
here that has an idea of the problems this might lead to?

Sincerely
Bjørn Ove

Flight controllers detected spikes in current and vibration in one of
the station's three operating gyroscopes on Nov. 8. Last week, when
the gyroscopes were used again to shift the position of the orbiting
outpost, all three worked fine.

They are talking about the CMG's.

I'm not thrilled about the use of the word "gyroscope" as a gyroscope
is generally a sensor rather than an actuator (hence the "scope" part
of "gyroscope").

On different web sites I saw CMG expanded as "Control Moment
Gyroscopes" or "Control Moment Gyros".

The Russian term "gyrodynes" does seem like a logical one when
considered in that light.

Anyway, enough discussion of terminology. Let's hope that they can
keep the CMG's limping until they can replace some of them. The
replacement of at least one of them is on the return to flight shuttle
mission according to
http://spaceflight.nasa.gov/shuttle/future/index.html

Re below, it shows the prudence of having two different techniques for
attitude control though, in my view. Good bit of design sense there in the
original design.

anyway, exactly how big are these gyros? Could one be sent via some kind of
expendable launcher and a cobbled together manoeuvring system?

Brian

--
Brian Gaff....
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________
__________________________________


"Jim Kingdon" wrote in message
news | Flight controllers detected spikes in current and vibration in one of
| the station's three operating gyroscopes on Nov. 8. Last week, when
| the gyroscopes were used again to shift the position of the orbiting
| outpost, all three worked fine.
|
| They are talking about the CMG's.
|
| I'm not thrilled about the use of the word "gyroscope" as a gyroscope
| is generally a sensor rather than an actuator (hence the "scope" part
| of "gyroscope").
|
| On different web sites I saw CMG expanded as "Control Moment
| Gyroscopes" or "Control Moment Gyros".
|
| The Russian term "gyrodynes" does seem like a logical one when
| considered in that light.
|
| Anyway, enough discussion of terminology. Let's hope that they can
| keep the CMG's limping until they can replace some of them. The
| replacement of at least one of them is on the return to flight shuttle
| mission according to
| http://spaceflight.nasa.gov/shuttle/future/index.html


---
Outgoing mail is certified Virus Free, so there!
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.547 / Virus Database: 340 - Release Date: 02/12/03

Jim Kingdon wrote:

Flight controllers detected spikes in current and vibration in one of
the station's three operating gyroscopes on Nov. 8. Last week, when
the gyroscopes were used again to shift the position of the orbiting
outpost, all three worked fine.

They are talking about the CMG's.

I'm not thrilled about the use of the word "gyroscope" as a gyroscope
is generally a sensor rather than an actuator (hence the "scope" part
of "gyroscope").

On different web sites I saw CMG expanded as "Control Moment
Gyroscopes" or "Control Moment Gyros".

The Russian term "gyrodynes" does seem like a logical one when
considered in that light.

I agree, gyrodyne is a better term to describe the gyro's function.

Anyway, enough discussion of terminology. Let's hope that they can
keep the CMG's limping until they can replace some of them. The
replacement of at least one of them is on the return to flight shuttle
mission according to
http://spaceflight.nasa.gov/shuttle/future/index.html


Space Station, gyrodyne problems. Hubble, gyrodyne problems, most critical
item that limits the time between service missions. Any other NASA
spacecraft with gyrodyne problems?

I wonder how many different "improved" versions of gyrodynes the Hubble has
had without successfully fixing the problem?

Craig Fink

On Sat, 6 Dec 2003 11:15:31 -0000, "Brian Gaff"
wrote:

Re below, it shows the prudence of having two different techniques for
attitude control though, in my view. Good bit of design sense there in the
original design.

anyway, exactly how big are these gyros?

Apparently somewhere in between the size that will pass through a Progress
docking port and that which will pass through a Shuttle docking port.

Could one be sent via some kind of expendable launcher and a cobbled
together manoeuvring system?

I can't imagine they'd send something "cobbled together" anywhere near
the station for a rendevous. Seems to me it would need to be grappled,
and also have an adapter allowing it to be docked to a Shuttle port. They
couldn't just pluck the gyro out of it's cargo hold and stick it in an
airlock, could they? So, you're kinda talking about developing a new
cargo ship, cobbled together or not. And doing it before the Shuttle's
return to flight.

I think the sensible course is to do what they're doing. They still have
3 functioning gyros (2 are required). Giving them a break by utilizing the
Russian thrusters for a while might keep both systems available until a
Shuttle can bring replacement gyros. This doesn't strike me as being a
dire emergency quite yet.

Dale

Space Station, gyrodyne problems. Hubble, gyrodyne problems, most critical
item that limits the time between service missions. Any other NASA
spacecraft with gyrodyne problems?

As far as I know, Hubble's reaction wheels and magnetotorquers are
working fine (it doesn't have gyrodynes).
(reaction wheel - spin slower or faster, for rotation along a single
axis per wheel
magnetotorquer - work against the Earth's magnetic field
gyrodyne - a wheel whose axis is turned, analogous to the high school
physics bicycle wheel demo
)

What has been a problem on Hubble is the gyroscopes (i.e. sensors).
Other spacecraft too. The irony here of course is that there are
replacements with no moving parts (e.g. fiber optic gyros), but said
replacements aren't yet as good as the traditional moving gyroscope.
Someone is working on one which could replace the moving gyroscopes
for spacecraft - if memory serves it was some kind of vibrating
gyroscope shaped a bit like a wine glass.
Here's a gyroscope taxonomy: http://www.spp.co.jp/sssj/sindoue.html

Apparently somewhere in between the size that will pass through a
Progress docking port and that which will pass through a Shuttle
docking port.

I don't actually know whether it is size or mass which prevents use of
Progress (possibly both). The CMG itself is over 220 kg and the
following article also refers "to the weight and volume of equipment
needed to carry the CMG into orbit":

http://www.space.com/missionlaunches...te_020608.html

That's because a CMG package - the gyro and necessary
sub-assemblies - weighs some 1,100 pounds [500 kg] at launch and
must be mounted on a special carrier beam in the shuttle's cargo
bay. http://spaceflightnow.com/station/sts111/020608cmg/

On the shuttle they don't use the docking ports - they are shipped in
the cargo bay and installed by arm and/or EVA.
(search for "CMG" at
http://www.space.com/missionlaunches...journal-2.html ).

Could one be sent via some kind of expendable launcher and a cobbled
together manoeuvring system?

I can't imagine they'd send something "cobbled together" anywhere near
the station for a rendevous.

Well, in addition to the obvious questions about reliability,
rendezvous is hard enough that you'd probably not succeed with a
cobbled together system.

Perhaps ATV or HTV could do it; I don't know.

Jim Kingdon wrote:

Space Station, gyrodyne problems. Hubble, gyrodyne problems, most
critical item that limits the time between service missions. Any other
NASA spacecraft with gyrodyne problems?

As far as I know, Hubble's reaction wheels and magnetotorquers are
working fine (it doesn't have gyrodynes).
(reaction wheel - spin slower or faster, for rotation along a single
axis per wheel
magnetotorquer - work against the Earth's magnetic field
gyrodyne - a wheel whose axis is turned, analogous to the high school
physics bicycle wheel demo
)

What has been a problem on Hubble is the gyroscopes (i.e. sensors).
Other spacecraft too. The irony here of course is that there are
replacements with no moving parts (e.g. fiber optic gyros), but said
replacements aren't yet as good as the traditional moving gyroscope.
Someone is working on one which could replace the moving gyroscopes
for spacecraft - if memory serves it was some kind of vibrating
gyroscope shaped a bit like a wine glass.
Here's a gyroscope taxonomy: http://www.spp.co.jp/sssj/sindoue.html


Thanks for correcting me. Your right there are a lot of ways to get
attitude without the traditional gyroscopes. As you said fiber optic gyros,
or couple of star trackers. When the Hubble is pointed at a
star, pitch and yaw can come from the target image. All that is needed are
a couple of cameras perpendicular to get roll. I wouldn't think there is
anything more accurate than using the stars.

Craig Fink

Jim Kingdon wrote in message ...


Perhaps ATV or HTV could do it; I don't know.


If NASA is required to wait for the HTV to be available to bring new
CMGs, it will be a long wait indeed. HTV, over the last few years, has
been postponed by about 1.2 years for every year of actual elapsed
time.