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#11
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Oberg: "The real significance of the ISS thruster test failure"
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#12
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Oberg: "The real significance of the ISS thruster test failure"
Derek Lyons wrote:
When the thrusters were not supposed to ever be used again - and indeed were supposed (IIRC) to be permanently deactivated years ago... You're confusing Zvezda's engines with Zarya's engines. Zarya's engines were the ones that were (I believe) deactivated after docking to Zvezda. Zvezda's engines were always meant to be a backup to other boost methods, even though they weren't needed for normal operations since Zvezda docked to Zarya/Node 1 in 2000. Then something is up and/or wrong when they test them 'to see if they work'. Why is this so strange? There was no particular reason to fire the engines since Zvezda became part of the ISS complex, so they simply weren't fired in that time. More recently, somebody decided to test them out, even though there was no particular need for them. I think the reason for conducting the test was probably entirely innocent. --Chris |
#13
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Oberg: "The real significance of the ISS thruster test failure"
DA wrote:
You are being paranoid. It is a valid experiment in itself to find out if the thrusters are going to work after 6 years of non use. Does this type of engine ever go ka-boom after six years of sitting unused? It seems like this test should be conducted on an earthbound test stand before being conducted in a space laboratory. Glen Overby |
#14
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Oberg: "The real significance of the ISS thruster test failure"
Chris Bennetts wrote: [...] Why is this so strange? There was no particular reason to fire the engines since Zvezda became part of the ISS complex, so they simply weren't fired in that time. More recently, somebody decided to test them out, even though there was no particular need for them. I think that there are constraints on when these thrusters *can* be tested, since the presence of a Soyuz or a Progress at that docking position means the other craft gets contaminated (at best) during a firing. It was noted that there was a period with the docking position clear, enabling the test, and that the next opportunity will be September. And that no retest is planned for September at this time. I think the reason for conducting the test was probably entirely innocent. Maybe. /dps |
#15
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Oberg: "The real significance of the ISS thruster test failure"
Derek Lyons wrote:
When the thrusters were not supposed to ever be used again - and indeed were supposed (IIRC) to be permanently deactivated years ago... Then something is up and/or wrong when they test them 'to see if they work'. It is the thrusters on Zarya (FGB) that were de-activated when Zvezda came long with its own thrusters. Zvezda's thrusters are theoretically supposed to remain functional for the lifetime of the station. From what I recall, they are rated for a certain number of hours of operations as opposed to years in space. So using Progress engines instead of Zvezda,s lengthens the time Zvezda's thrusters remain functional. Perhaps they should be testing them are more frequent intervals. But this time, they tested them, found a problem and now we have to wait to see if they can solve the problem or not. I don't think you can fault anyone for this at this point in time. We have to wait to see how they react in the event they cannot fix the thruster. |
#17
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Oberg: "The real significance of the ISS thruster test failure"
DA wrote: Derek Lyons wrote: Are they seeing if ISS will remain stable if they throttle the Soyuz/Progress pipeline for political advantage? Are they bored and lacking adequate adult supervision? Do they know something about the system that we don't? (Potential nightmare scenarios that end with the propellants must be jettisoned/used.) You are being paranoid. It is a valid experiment in itself to find out if the thrusters are going to work after 6 years of non use. Those are hypergolicly fueled engines using N2O4 and UDMH, and they don't trust the Soyuz, whose motors use the same propellants, after six months. Pat |
#18
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Oberg: "The real significance of the ISS thruster test failure"
On Fri, 12 May 2006 07:21:27 -0500, Pat Flannery wrote:
DA wrote: You are being paranoid. It is a valid experiment in itself to find out if the thrusters are going to work after 6 years of non use. Those are hypergolicly fueled engines using N2O4 and UDMH, and they don't trust the Soyuz, whose motors use the same propellants, after six months. I thought the Soyuz' shelf life was more an issue with its batteries, not its thrusters (?)... Dale |
#19
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Oberg: "The real significance of the ISS thruster test failure"
"Pat Flannery" wrote in message ... Those are hypergolicly fueled engines using N2O4 and UDMH, and they don't trust the Soyuz, whose motors use the same propellants, after six months. I thought the issue with Soyuz limited in orbit lifetime was due it's use of hydrogen peroxide for the descent module's attitude control system. I believe that the issue there is that hydrogen peroxide degrades over time due as it slowly turns back into oxygen and water. http://www.nasa.gov/mission_pages/st...ft_detail.html Jeff -- "They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety" - B. Franklin, Bartlett's Familiar Quotations (1919) |
#20
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Oberg: "The real significance of the ISS thruster test failure"
John Doe wrote: I don't think you can fault anyone for this at this point in time. We have to wait to see how they react in the event they cannot fix the thruster. As to why they are keen to test them: http://www.hq.nasa.gov/osf/station/images/issalt.gif Without the Shuttle reboosts they are slowly but surely getting lower despite the Progress reboosts. Pat |
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