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#22
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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
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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
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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
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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
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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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