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> That it is the Russian Zvevda module that is leaking/cracking is likely related to the fact that it is also the oldest module in the ISS. Definitely sounds l
by akiselev 6y ago
> That it is the Russian Zvevda module that is leaking/cracking is likely related to the fact that it is also the oldest module in the ISS.
Definitely sounds like it. They can't identify the leak on the inside so it doesn't sound like a micrometeoroid impact and they suspect a second leak that is so small they need a microscope to verify:
> "So far, we have found one place and suspect another, where as some kind of leak exists. We must bring a powerful microscope on a cargo spacecraft and use to examine this place. We are not totally certain so far," Solovyov said.
IANAMS but that screams microfractures. The Zvezda is made largely of an aluminum magnesium alloy [1] that has a fatigue limit so even small repetitive stress can cause it to eventually fail. I'm curious whether this is wear and tear from just being in space and getting irradiated or if its repetitive mechanical stresses like a small tidal force as it orbits the earth.
[1] https://weebau.com/iss/zvezda.htm https://weebau.com/iss/zvezda.htm
- bartread 6y agoIs it possible it could also be from constant heating and cooling cycles as it orbits?
- deleted 6y ago[deleted]
- HPsquared 6y agoThose are the cause of the stress cycles. Components don't expand/contact uniformly, resulting in deformation and therefore stress. This process goes through cycles, causing stress cycles which eventually cause the growth of cracks (fatigue).
- HenryKissinger 6y agoHave we invented a material that is resistant to these thermal cycles indefinitely, or at least within a range of temperatures of several thousand degrees? I'm never going to have my own Star Destroyer if we continue to use subpar materials.
- coryrc 6y agoSteel, below a certain loading (err, ~20% of max fatigue?) does have indefinite life.
- chaboud 6y agoClimbers and riggers should all be familiar with fatigue limits. It can be as high as 50% max tensile strength for steel, but I use 30% as my working figure when rigging, and I regularly re-inspect and age-retire gear (at least use annualized color coded markings). When I’ve rigged circus in the past I’ve taken to replacing aluminum gear I find with steel, especially if it’s going to be installed for a while. That said, I climb on aluminum. I just age out my equipment. I’d hate for my last thought to be “huh... I guess aluminum really does degrade with repeated stress.”
- lanstin 6y agoI had an aluminum bicycle where the front fork failed suddenly. Not instantly but in maybe one or two seconds (just slowly enough to let me not have a terrible fall). My next bike was chrome/steel.
- HPsquared 6y agoThis solves something I'd wondered for a while - why my aluminium bike has a steel fork.
- robryk 6y agoI was told once that the reason for that was stiffness: apparently aluminum forks are stiffer, so unsuspended ones are way less comfortable (in terms of vibrations being transmitted to the frame and handlebars) than steel unsuspended forks.
- chaboud 6y agoYears ago I totaled a mountain bike in a strange pinched-wheel-in-crack accident that bent the frame in two places but left me uninjured. When I commented to a bike designer/engineer that it was a strange failure, he said that it was intentional, at least on hardtail mountain bikes like mine. A bent frame is ruined but doesn't lead to a catastrophic loss of control. A detached wheel or twisted fork would be next to impossible to control to a stop. He looked at my frame and explained that that the two bends were in exactly the place they'd been designed to be, just behind the last butting. It's an impressive bit of forethought. My guess on road bikes with steel forks, though, is that it's a matter of aerodynamic performance calling for compactness to reduce frontal area, something that would be harder to do in aluminum, and for far less weight savings than the longer tubes on the frame. There's always titanium... The only big drawback is the cost...
- vaduz 6y agoIt completes a cycle of heating and cooling every 90 minutes as it orbits. The temperature differential between sunlit/shaded is quite large, so even though it certainly does not heat to +120C / cool down to -100 C as there is just not enough time, it would still put some stress on it.
- joe-collins 6y agoOr simple mechanical stress when the ISS raises its altitude. The thrusters cause vibration, and are not applying a uniform force across its surface.
- rtkwe 6y agoThe hull where they're able to manually inspect it shouldn't be going through quite that extreme of a temperature differential because it's wrapped in insulation and protective layers. But it's also almost 21 years old so even the smaller actual cycle is probably getting to it combined with all the other mechanical stresses from equipment and thruster firings.
- Out_of_Characte 6y agoI was curious so I checked what temparature the sun exposed parts reached and what the shadow side reaches; 121c to -157c a temparature difference of over 278 degrees. Your remark was almost spot on. https://science.nasa.gov/science-news/science-at-nasa/2001/ast21mar_1/ https://science.nasa.gov/science-news/science-at-nasa/2001/a...
- tomcam 6y agoHmm... my first encounter with "IANAMS" in the wild. Assume it means "I am not a materials scientist"? I like it.
- rcthompson 6y agoPart of the joke is that's it's NASA. (NASA stands for Not A Standard Acronym, of course.)
- geocrasher 6y agoBrings my mind to the ultimate acronym: PCMCIA People Can't Memorize Computer Industry Acronyms
- grogenaut 6y agoTLA and FLA are my favorites
- Lvl999Noob 6y agoWhat's TLA and FLA?
- atsaloli 6y agoIt's a YABA (Yet Another Bloody Acronym). :)
- toxik 6y agoThree / Four Letter Acronym, respectively.
- spopejoy 6y ago(should be) obligatory (now get off my lawngrange) http://eyebeam.com/1985/index.php?num=45 http://eyebeam.com/1985/index.php?num=45
- fastball 6y ago
- Rebelgecko 6y agoI would imagine that there's also some temperature swings on the skin of the ISS
- WalterBright 6y agoIf the leaks are that small, sounds like putting an elastic coating on it should fix it.
- jccooper 6y agoThey have put tape on suspected leak areas in Zvezda before.
- GordonS 6y agoSo bizarre to imagine a space station patched up with duct tape o_O Assuming the ISS is never going re-enter the Earth's atmosphere, how permanent a solution is tape? Presumably the fracture underneath will get worse with time.
- techdragon 6y agoOther than the growth (in terms of length across the surface in question) of a crack/fracture, tape is a pretty valid solution as long as it can hold the pressure. In fact on the “inside” that’s even more strait forward since the pressure pushes the tapes bonding surface interface into the opening, so depending on how malleable the “tape” is, it might not even need “glue” to do the job of sealing a hole sufficiently to hold in the ISS’ internal atmosphere. Effectively the major issue is “larger”width/diameter cracks/holes create greater pressures that eventually exceed the ability of simple “tape” to suffice for a workable patch. This is all ignoring any NASA engineering manuals and limits, I’m talking entirely theoretical “how long can my duct tape keep me from suffocating” type of engineering, just to be clear. What needs emphasis in the long term for more permanent structures in space is on the poorly explored topic of welded joint fatigue, with respect to joints that were welded in low earth orbit. We have welded with several techniques in space before (the Soviets did it) but it basically stopped there and not much has gone into studies of the long term fatigue of the resulting welded joints. If we want permanent space stations we need to be able to “patch them up” in a way that we can rely on and at least have some idea what the lifespan will be. It’s ok if we have to re-weld pressure hull segments every decade or two but not if the large scale structural welds on a space station hull assembled in space only hold for a few years before they start leaking.