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