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Soyuz to be fixed at Space Station



 
 
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  #21  
Old June 30th 08, 09:44 AM posted to sci.space.station
Brian Gaff
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Default Soyuz to be fixed at Space Station

I know very little of these sort of bolts, but its certainly not beyond the
realms of design to make systems where the actual severing device is a bolt
cutter mounted on the actual craft, not in the bolt. I doubt if it were a
self sheering bolt, whether the idea would be entertained at all. Given that
its probably a guillotine or similar device, its probably fairly safe. The
thing is though, is it that the bolts do not sheer, or that the sheerer is
not man enough to sheer them?
Brian

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"Derek Lyons" wrote in message
...
"Jorge R. Frank" wrote:

Alan Erskine wrote:
"Brian Gaff" wrote in message
om...
Hmm, time was that anyone fiddling with bolts that had any pyro devices
associated with them was a no no for flight crew. Are we saying that
these
are definitely categorically safe to fiddle with?

No. It shows how desparate they are to fix it.


Stated another way, they consider the risk incurred by the cosmonauts
fiddling with the pyrobolts is less than the risk incurred by performing
the next Soyuz entry without inspecting the bolts.


Which sounds frightening as hell.

D.
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http://derekl1963.livejournal.com/

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



  #22  
Old June 30th 08, 10:53 AM posted to sci.space.station
John Doe
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Default Soyuz to be fixed at Space Station

Brian Gaff wrote:
I know very little of these sort of bolts, but its certainly not beyond the
realms of design to make systems where the actual severing device is a bolt
cutter mounted on the actual craft, not in the bolt.


If you use deja news /google on this group, you may find old posts from
an ex-NASA employee who spoke of the explosive bolts on the SRBs and on
launch pad. They were called "frangible" bolts and the bolts really did
explode from within, with some cocoon capturing the debris.

Whether this is the same on Soyuz, I am not sure, but I would suspect it
is very similar.
  #23  
Old June 30th 08, 02:23 PM posted to sci.space.station
Craig Fink
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Default Soyuz to be fixed at Space Station

JD in TX wrote:

Craig Fink wrote in
m:

...Russian experts have told NASA that the bolts at position 5
apparently failed to fire during both previous Soyuz descents.


Very interesting. I wonder if that's just a co-incidence or if there is
something else (wiring issue) responsible for the failure? Since neither
of the pair of bolts at that location fired, and the previous Soyuz
experienced the exact same problem with the bolts in the same location,
it would suggest that the problem isn't with the bolts themselves, but
possibly with the command used to fire the bolts. In other words, for
some reason, the bolts did not receive the signal to fire.


Yeah, I agree. If the first Space Tourist flight is include, that makes
three since they upgraded the Soyuz. Wiring or something else, maybe they
are firing, but something is hanging during the separation. Or, everything
is assembled correctly, but for some reason there is low current, not
enough to fire the bolts that have the longest wires. Hard to examine parts
that didn't work properly and are gone. Sounds like they are getting closer
to the problem.

Also, I wonder were the diagram in the article came from, a Russian media
handout, a Russian NASA presentation, or a leaked internal document... And,
if it shows accurately "position 5"

My feeling about NASA is that they tends to rely on simulation to the point
of paralysis. Really an over reliance of simulation, that provides lots of
warm fuzzy feelings (cost is unimportant). The Russian don't, that they
tend to get the hammer out, or ignore, or pick a scape goat for their
problems (low budget). Getting the problem down to "position 5" was
probably done with simulation of the vehicle dynamics, something they may
have done for the first time on this problem. I wonder if they simulated
the first Space Tourist flight and it didn't fit the dynamics profile, or
the didn't look that far back.

At least NASA would have simulated they dynamics sooner and had it narrowed
down to a certain position much sooner (the first time it happened). But
that doesn't necessarily mean they would have found the cause, example the
ET wire problem. NASA spent lots of time scratching their heads, working on
getting more data on the problem. When the eventual fix was something that
was a very "safe", "easy", "simple", "extremely low risk" change. Soldered
electrical connections is somewhat of a "no brainer" improvement that could
have been done immediately after the problem became apparent, without
knowing exactly what the problem cause was. I wonder how many crimp
electrical connections were replaced with more robust soldered connections?
Just the few that were found to be the problem?

To change or not to change, which is more dangerous?


  #24  
Old June 30th 08, 04:09 PM posted to sci.space.station
Derek Lyons
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Default Soyuz to be fixed at Space Station

Craig Fink wrote:

At least NASA would have simulated they dynamics sooner and had it narrowed
down to a certain position much sooner (the first time it happened). But
that doesn't necessarily mean they would have found the cause, example the
ET wire problem. NASA spent lots of time scratching their heads, working on
getting more data on the problem.


They spent a lot of time scratching their heads mostly because the
problem was intermittent. Anyone with actual technichal experience
knows that intermittents are stone cold bitch to troubleshoot under
the best of conditions - and filling an ET in order to attempt to
induce the fault is just about as far from the best of conditions as
one can get.

When the eventual fix was something that was a very "safe", "easy", "simple",
"extremely low risk" change. Soldered electrical connections is somewhat of a
"no brainer" improvement that could have been done immediately after the
problem became apparent, without knowing exactly what the problem cause was.


In the real world, when you don't know the cause of a problem, you
don't go changing things just because. You also don't have 20/20
hindsight.

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

http://derekl1963.livejournal.com/

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL
  #25  
Old July 1st 08, 12:02 AM posted to sci.space.station
Trekker
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Posts: 2
Default Soyuz to be fixed at Space Station

On Mon, 30 Jun 2008 15:09:28 +0000, Derek Lyons wrote:

They spent a lot of time scratching their heads mostly because the
problem was intermittent. Anyone with actual technichal experience
knows that intermittents are stone cold bitch to troubleshoot under the
best of conditions - and filling an ET in order to attempt to induce the
fault is just about as far from the best of conditions as one can get.


I have to wonder how much time and effort was spent on this problem
(prior to the last time of actually finding and fixing it.)

Sure, intermittent problems are probably the most difficult to
troubleshoot but what circuitry was involved in the tank itself? Was it
just some sensors and wiring going out to the connector on the tank? If
that's all that was involved, I think they should have found the cause
earlier. Connections would be the first thing I would check with an
intermittent problem, especially one where a great degree of temperature
changes are involved.

That's why I don't think a whole lot of effort was put into figuring this
issue out until it finally because more than a nuisance and started
causing flight delays. Someone finally said "Enough is enough" and
actually troubleshot the problem instead of shrugging it off.

  #26  
Old July 1st 08, 04:01 AM posted to sci.space.station
Jorge R. Frank
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Posts: 2,089
Default Soyuz to be fixed at Space Station

Trekker wrote:
On Mon, 30 Jun 2008 15:09:28 +0000, Derek Lyons wrote:

They spent a lot of time scratching their heads mostly because the
problem was intermittent. Anyone with actual technichal experience
knows that intermittents are stone cold bitch to troubleshoot under the
best of conditions - and filling an ET in order to attempt to induce the
fault is just about as far from the best of conditions as one can get.


I have to wonder how much time and effort was spent on this problem
(prior to the last time of actually finding and fixing it.)


Quite a bit.

Sure, intermittent problems are probably the most difficult to
troubleshoot but what circuitry was involved in the tank itself? Was it
just some sensors and wiring going out to the connector on the tank? If
that's all that was involved, I think they should have found the cause
earlier. Connections would be the first thing I would check with an
intermittent problem, especially one where a great degree of temperature
changes are involved.


The problem is that in order to induce that temperature change, you have
to put the tank through a fill/drain cycle. You get one of those "for
free" every time you launch, but for troubleshooting, you'd want to
insert instrumentation into the loop - instrumentation you most likely
can't launch with. That means a dedicated tanking test, which is a lot
of money and puts an additional thermal cycle on the tank, which makes
the tank more vulnerable to foam shedding when you finally do launch it.

That's why I don't think a whole lot of effort was put into figuring this
issue out until it finally because more than a nuisance and started
causing flight delays. Someone finally said "Enough is enough" and
actually troubleshot the problem instead of shrugging it off.


No, it was causing flight delays as far back as STS-114 and people were
saying enough is enough back then. The problem is that there were really
two separate root causes. Last time around, they discovered a batch of
faulty sensors. Which was a real problem, but it wasn't the *whole* problem.
 




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