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#60
by
Jim
on 26 Jun, 2009 00:22
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As far as the SCA option goes, the main challenge is probably getting the techs into the orbiter at the last possible moment, which should be straightforward with a cherry-picker arm. The Orbiter is pressure-tight enough (come on, it must be) that a small bank of cylinders can keep it pressurized to 18psi or so and the techs can have radio comms and breathing gear if needed.
What bank of bottles? and where are they? and how are they controlled and monitored.
This is just nonsense.
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#61
by
Jim
on 26 Jun, 2009 00:26
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The orbiter could be inert like in a regular ferry flight yet the job could be attempted by placing autonomous systems in the cockpit.
.
Autonomous power like from batteries.
Autonomous comm like radio waves going through the windows (the windows are penetrable to radio waves, no ?).
Pressure control for an extra few psi - that could be tricky. I could see a valve releasing gas from a small tank; I don't know if the pressure could be reduced by venting - if venting is needed in flight and could only be accomplished with some systems of the orbiter powered up.
What autonomous systems? The orbiter doesn't have a autonomous pressure control system. Having crew inside with comm and O2 masks doesn't do squat.
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#62
by
Lee Jay
on 26 Jun, 2009 00:31
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So that'd be a request to avoid "how about a blow torch!" posts 
C4 might be better.
Have they already tried something like dish soap? It's sort of amazing how good that stuff works at getting things unstuck by making them slip'n'slide instead of stick.
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#63
by
aaronsb
on 26 Jun, 2009 00:40
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If the knob is made out of aluminum, it will be highly susceptible to mercury amalgamation. Remove the knob by taping off the area to prevent excess mercury from escaping, then paint some on and wait for it to oxidize the aluminum away, weakening the part until it can be removed. The glass won't care one bit about having the mercury in it.
I'm sure that overall the small amount of hazmat would not be an issue to clean up.
Aaron
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#64
by
robertross
on 26 Jun, 2009 00:48
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If I can add into the flight to Palmdale (I know it's a dead issue, but simply to add): If there is physical contact of the knob against the pane now, the CHANGE in pressure during flight could create excessive stresses against the glass. The only other possibility using SCA is in-flight removal. However, if it fails, you have risk to the crew on board. Both are non-starters.
I like the mercury amalgamation idea Aaron, neat. Unfortunately the spill control for a conductive fluid in the orbiter, especially mercury which would create a serious outgassing effect on orbit, or a later SCA flight post-landing, may disqualify it with reduced cabin pressure.
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#65
by
aaronsb
on 26 Jun, 2009 00:54
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I think you could use the mercury reaction under open atmospheric conditions - the reaction is very fast. Build an impromptu fume hood to extract the mercury vapor, and pipe it out the door.
The total amount of mercury required to complete the amalgamation would be very small.
(edit)
Depending on how much it is wedged, you'd only need to dissolve one or two of the knurls on the knob, which would require a pea sized or smaller drop of the material. It's an exothermic reaction, but it would be slow enough to not be any risk to the glass at all.
If I can add into the flight to Palmdale (I know it's a dead issue, but simply to add): If there is physical contact of the knob against the pane now, the CHANGE in pressure during flight could create excessive stresses against the glass. The only other possibility using SCA is in-flight removal. However, if it fails, you have risk to the crew on board. Both are non-starters.
I like the mercury amalgamation idea Aaron, neat. Unfortunately the spill control for a conductive fluid in the orbiter, especially mercury which would create a serious outgassing effect on orbit, or a later SCA flight post-landing, may disqualify it with reduced cabin pressure.
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#66
by
DansSLK
on 26 Jun, 2009 01:51
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Yep, as Ford says, and I wrote (some people are commenting without reading the article!) you've got to be careful with the vibrations transfering to the window pane. There is one related option for cutting it, but that's lower down the list of options.
I read the article (and the presentation) mate just like always and i was left impressed, again just like always.
Jim mate this could go on for a while since i have data in front of me now, don't wan't to clutter up Chris's thread and take it OT.
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#67
by
Harleqin
on 26 Jun, 2009 06:34
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I also like the amalgamation idea, though this depends on the knob really being aluminium, and since there are likely more aluminium parts in the shuttle that you wish no harm to, the mercury would really have to be handled with great care. However, my first thought was to use aqua regia.
You would need a concentric double cannula, perhaps made from teflon. The smaller cannula in the centre would very slowly bring some aqua regia to the tip, and the outer cannula would be connected to a sufficiently high powered vacuum pump with a trap for the liquid. I'd like to dub this a "chemical saw". Some tests would be needed to find the optimum shape of the tip, especially how much the outer cannula should be longer than the inner, in order to minimize spillage.
Trace amounts of spillage could be detected in a suitable test environment through decolouring of some organic colours that are sensitive to oxidation. A critical point is when the "saw" first gets through the thickness to create a hole. I assume that the pressure will bend the disk before that, though, if a straight line is etched. The point of bending may also be critical, if it happens too violently.
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#68
by
usn_skwerl
on 26 Jun, 2009 08:59
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The orbiter could be inert like in a regular ferry flight yet the job could be attempted by placing autonomous systems in the cockpit.
.
Autonomous power like from batteries.
Autonomous comm like radio waves going through the windows (the windows are penetrable to radio waves, no ?).
Pressure control for an extra few psi - that could be tricky. I could see a valve releasing gas from a small tank; I don't know if the pressure could be reduced by venting - if venting is needed in flight and could only be accomplished with some systems of the orbiter powered up.
What autonomous systems? The orbiter doesn't have a autonomous pressure control system. Having crew inside with comm and O2 masks doesn't do squat.
i think he means air pressure control, and that (in my mind) means taking a bottle of compressed air in the orbiter with a pressure gauge for the ambient air pressure (to monitor overpressing the cabin). You pressurize the cabin gradually-same as any pneumatic system-until the knob's either free, or ambient pressure is approaching limits.
I'd think that the engineers wearing pumpkin suits (or equivalent) with their own air supply, monitoring the air pressure in the cabin, and working to remove the knob would work. They pressure test aircraft on the ground all the time.
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#69
by
Chris Bergin
on 26 Jun, 2009 14:14
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Pressurization set for next Monday. Keep your fingers and toes crossed.
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#70
by
Danny Dot
on 26 Jun, 2009 14:49
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My uncle told me once they used liquid propane to shrink the valve seats of big propane engines so they could install them in the engine heads. They didn't bother to use a Dewar, they just poured it in a bucket. Liquid propane is probably not a good idea to use in the cockpit, but liquid nitrogen might be worth a try. I am thinking a cold liquid would have much better heat transfer than the solid dry ice. But, it might run a higher risk of cracking the window though.
Who would think such a tiny thing could give the shuttle program so much trouble. But, I guess in the world of machines, even the little pieces are important.
Danny Deger
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#71
by
Namechange User
on 26 Jun, 2009 14:51
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Already tried cooling it down to shrink it.
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#72
by
Chris Bergin
on 26 Jun, 2009 15:54
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To answer a question earlier in the thread, they do have a spare pressure pane.
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#73
by
Jim
on 26 Jun, 2009 15:59
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i think he means air pressure control, and that (in my mind) means taking a bottle of compressed air in the orbiter with a pressure gauge for the ambient air pressure (to monitor overpressing the cabin).
Which they would never do.
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#74
by
Danny Dot
on 26 Jun, 2009 16:01
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snip
The orbiter doesn't have a autonomous pressure control system. Having crew inside with comm and O2 masks doesn't do squat.
I think we have a failure to communicate. How does the orbiter control its pressure on orbit? I am pretty sure the system requires electrical power, but there might be manual back-up to dump oxygen and nitrogen into the cabin (I wasn't a system instructor); however, I think it could be characterized at autonomous.
Danny Deger
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#75
by
Danny Dot
on 26 Jun, 2009 16:07
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Already tried cooling it down to shrink it.
Try something colder. Don't stop until you have tried liquid helium. No doubt NASA can get a Dewar of this stuff from somewhere.
Good luck to the guys working this one. My stupid nozzle on the end of my garden hose has been stuck for about 6 months. This effort has motivated me to get the darn thing off. And I did not use liquid propane from my grill
Glad to hear they have a spare pane. I know the guys and gals at KSC can get it installed if they need to. From what I can tell, one of the best run shops in the world.
Danny Deger
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#76
by
Danny Dot
on 26 Jun, 2009 16:11
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If the knob is made out of aluminum, it will be highly susceptible to mercury amalgamation. Remove the knob by taping off the area to prevent excess mercury from escaping, then paint some on and wait for it to oxidize the aluminum away, weakening the part until it can be removed. The glass won't care one bit about having the mercury in it.
I'm sure that overall the small amount of hazmat would not be an issue to clean up.
Aaron
I don't know squat about metallurgy, but this doesn't sound like a bad idea. Can someone at KSC send this one up the chain at NASA?
Heck, you could just open the doors and turn off the AC. The sea breeze will eat the knob up in just a few short years. That what it does to aluminum storm doors down there.
Danny Deger
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#77
by
Spacenick
on 26 Jun, 2009 19:23
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What is the window made of? And why is it so susceptical to vibration damage, I would have thought that it might be made of Lexan which shouldn't have too much of a problem with vibrations, right?
And why exactly can't they launch with the knob where it is? Is it also due to vibration damage?
This would lead me to believe that the knob is now so dangerous for the window that the reenrty with it stuck (which they didn't know of course) was quite dangerous as well.
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#78
by
DansSLK
on 26 Jun, 2009 19:54
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What is the window made of? And why is it so susceptical to vibration damage, I would have thought that it might be made of Lexan which shouldn't have too much of a problem with vibrations, right?
And why exactly can't they launch with the knob where it is? Is it also due to vibration damage?
This would lead me to believe that the knob is now so dangerous for the window that the reenrty with it stuck (which they didn't know of course) was quite dangerous as well.
Tempered glass and it is damaged.
If they launch now and the damage is of a critical size then the pane can fail, throw in the vibration from the SRB's and even if it is not critical at this point it soon could be, if the pane fails then the feeling is the stress on the redundant pane will be too much (check out Chris's article for quotes from the presentation) and it could also fail leading to a loss of cabin pressure (thermal pane not designed to hold pressure).
I don't know if i would call the reentry dangerous because of it, i don't think they know at what point it became stuck and the stress on the window from this increased as they desended so i suspect a failure would be more likely closer to touchdown when a loss of cabin pressure is not as catastrophic, plus they should all be buttoned up in the suit.
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#79
by
Spacenick
on 26 Jun, 2009 20:10
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I see that sounds quite hard to solve, why wasn't it considered in the design that a dynamic failure of the inner pressure pane will likely make the redundant outer one fail as well, makes it sound like it isn't actually that redundant, especially since tempered glass tends to fail completely when it fails.
Why does the Shuttle use glass instead of high strength plastics? is it because of its age?
