The ISS suffered violent oscillations Jan 14 due to faulty rocket firing

so WHY DOES THIS NOT OCCUR WHEN THEY REBOOST WITH THE SHUTTLE. i'D HAVE
THOUGHT THE VARIOUS MODES AND DYNAMICS IN THAT CONFIG WOULD BE A NIGHTMARE.

bRIAN

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On Feb 4, 9:52 am, bob haller safety advocate wrote:
my question so the commander feels vibration like never before.

why didnt someone detecting the abnormal problem stop the burn?

heck it might have got worse and depressurized the station.

how many were asleep at the abort switch?

actually onboard sensors should watch automatically for out of bounds
situations and automatically stop whatever they are doing...........

to give people time to look at things........

major major screw up

As usual, you get it wrong. Always looking for the bad

The crew was never in danger and it wasn't a major screw up. The
vibrations were caused by the thrusters shutting down

Sorry, crumbs in my caps key again...
Brian

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On Feb 4, 9:52 am, bob haller safety advocate wrote:
my question so the commander feels vibration like never before.

why didnt someone detecting the abnormal problem stop the burn?

heck it might have got worse and depressurized the station.

how many were asleep at the abort switch?

actually onboard sensors should watch automatically for out of bounds
situations and automatically stop whatever they are doing...........

to give people time to look at things........

major major screw up

As usual, you get it wrong. Always looking for the bad

The crew was never in danger and it wasn't a major screw up. The
vibrations were caused by the thrusters shutting down

Brian Gaff wrote:
so WHY DOES THIS NOT OCCUR WHEN THEY REBOOST WITH THE SHUTTLE. i'D HAVE
THOUGHT THE VARIOUS MODES AND DYNAMICS IN THAT CONFIG WOULD BE A NIGHTMARE.

We don't really know just how "violent" the oscillations really were. We
just know about a sensationalistic article using such terms to grab
attention/ratings.

What is the relative thrust of the Zvezda engines compared to the RCS
used on shuttle for reboosts ?


When you start the engines, station components would flex under this new
force and remain flexed until engines would stop.

But if an engine was fired on and off, everytime the engine is fired,
station components would flex, and when it shut off, station would flex
back. You do this at the right frequency and the "flexing" would become
greater.

Is it correct to state that when the suttle does reboosts, the RCS do
not fire constantly and they do cyle on and off with some "rest" periods
to cool off between firings ?

"Brian Gaff" wrote:

so WHY DOES THIS NOT OCCUR WHEN THEY REBOOST WITH THE SHUTTLE. i'D HAVE
THOUGHT THE VARIOUS MODES AND DYNAMICS IN THAT CONFIG WOULD BE A NIGHTMARE.

Just because they are a nightmare does not mean that a normal Shuttle
reboost would be worse than a faulty Progress reboost.

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

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

Derek Lyons wrote:
"Brian Gaff" wrote:

so WHY DOES THIS NOT OCCUR WHEN THEY REBOOST WITH THE SHUTTLE. i'D HAVE
THOUGHT THE VARIOUS MODES AND DYNAMICS IN THAT CONFIG WOULD BE A NIGHTMARE.

Just because they are a nightmare does not mean that a normal Shuttle
reboost would be worse than a faulty Progress reboost.

Shuttle reboosts are analyzed months in advance and the digital
autopilot parameters are very thoroughly simulated and tested. The same
is apparently not true for a Zvezda reboost.

"Jorge R. Frank" wrote in message
...
Shuttle reboosts are analyzed months in advance and the digital autopilot
parameters are very thoroughly simulated and tested. The same is
apparently not true for a Zvezda reboost.

I'm waiting to see where the failure happened. It could very well be that
the Russians do the proper analysis, simulation, and testing. But, it
wouldn't surprise me if the Russian ground controllers had to key in values
by hand when transferring the "autopilot parameters" to their ISS modules.

That is, unless you know something about this incident that we don't...

Jeff
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"Many things that were acceptable in 1958 are no longer acceptable today.
My own standards have changed too." -- Freeman Dyson

"Jeff Findley" wrote in message
...

I'm waiting to see where the failure happened. It could very well be that
the Russians do the proper analysis, simulation, and testing. But, it
wouldn't surprise me if the Russian ground controllers had to key in
values by hand when transferring the "autopilot parameters" to their ISS
modules.

That is, unless you know something about this incident that we don't...


That is exactly what was reported at the news conference last week on NASA
TV.
Errors entering "coefficients"
The video was shown from one camera with a flexible mount, I would not have
used the term "violent"
There were vibration parameters that were exceeded, I think for the port
SARJ and one of the module couplings. These were described as not effecting
the "15 year" design criteria, but I'd say the practical life of the ISS was
reduced.

Jorge R. Frank wrote:

Shuttle reboosts are analyzed months in advance and the digital
autopilot parameters are very thoroughly simulated and tested. The same
is apparently not true for a Zvezda reboost.

Shuttle RCS are cleaned, checked and verified before every flight, and
are used very often during flight.

Zvezda's engines are fired only once in a blue moon, and haven't been
maintained in over 10 years.

We, in the peanut gallery, do not know what parts of a sensationalistic
article to believe or not. Did the engine bells change orientation all
the time or not ? If so, did the engine bells change in a coordinated
fashion between each other or were they random ?

What sort of movement do those bells have ? 1° ? 10° ? 45° ? I had been
under the impression that they had been fixed in orientation of their
output in order to ensure that their output was in a precise trajectory
that didnt burn the station down.

Or did the engines change thrust "randomly" during the event causing
uneven accelerations ?

And more importantly, from inside Zvezda, did the crew feel something
abnormal, or were was swaying eperienced only at the other end of the
station in the US segment ?

John Doe wrote:

We, in the peanut gallery, do not know what parts of a sensationalistic
article to believe or not.

Maybe those of you in the peanut gallery who read a sensationalitic
article are in that situation. Those of us who read Jim's article
while sober suffer from no such problem.

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

http://derekl1963.livejournal.com/

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

Derek Lyons wrote:

Maybe those of you in the peanut gallery who read a sensationalitic
article are in that situation. Those of us who read Jim's article
while sober suffer from no such problem.

So you feel that the choice of words such as "violent" was appropriate
in that article ?