[HN Gopher] NASA confirms space station cracking a "highest" ris...
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NASA confirms space station cracking a "highest" risk and
consequence problem
Author : addaon
Score : 70 points
Date : 2024-09-27 15:55 UTC (7 hours ago)
(HTM) web link (arstechnica.com)
(TXT) w3m dump (arstechnica.com)
| addaon wrote:
| The joys of HN is finding experts in just about anything, so...
|
| Assuming that NASA is correct about this leak being associated
| with an interior or exterior weld, what can we learn from the
| rate of growth of the leak? I assume (with no domain knowledge,
| seeking enlightenment!) that a leak like this is big enough to
| reflect a fracture in the weld, and not merely air sneaking past
| a tiny flaw; and I assume its growth means that the fracture
| itself is growing, under the combination of load (atmospheric
| pressure on one side) and cycling (thermal, etc). Is a fracture
| like this likely to continue to grow in a linear-ish domain, or
| is there a point where propagation goes non-linear assuming the
| loads stay constant-ish? Is this even a sane question to ask?
| bt1a wrote:
| Non-expert, pure speculator here: I cannot help but think of
| the Titan submersible and its minor flaw in the hull that
| slowly became more and more of an issue with each dive and
| pressurization cycle. I wonder if the 'untenable' leak rate
| that isn't agreed upon is the rate at which an accelerated and
| catastrophic runaway event occurs?
| themaninthedark wrote:
| There was no "minor flaw" in the Titan submersible.
|
| It was a very bad design[1], using substandard material[2] in
| new and untested ways[3] with poor assembly practices[4]. It
| was fatally flawed from the start.
|
| 1 - Asked about the carbon composite used in Titan's
| experimental design, Cameron said, "It's completely
| inappropriate for a vessel that sees external pressure." He
| went on to say that carbon fiber is very helpful when used
| for applications subject to internal pressure, like scuba
| tanks. But, he said, "for something that's seeing external
| pressure, all of the advantages of composite material go away
| and all the disadvantages come into play."
|
| 2 - Another possible "shortcut":
| https://www.latestly.com/world/titan-submersibles-hull-
| was-a...
|
| "Expired" bare carbon fiber might be ok; expired prepreg is
| likely not ok. And I still can't get my head around the
| apparent mixing of prepreg and wet winding resins in the same
| laminates.
|
| That article says Boeing has no record of ever selling
| oceangate composite material. So either he got it for free
| (Dumpster diving?) or it came from someone else. Maybe some
| guy in a parking lot: My boss told me to deliver this stuff
| to Boeing but they wouldn't take it because its expired, I'll
| sell it to you cheap.
|
| 3 - "Thickness, he says, was estimated using micromechanics,
| and then verified with finite element analysis (FEA).".
| >Wonderful. That sort of maybe can work for tension stresses,
| but can be highly unreliable for compression loading
|
| 4 - https://www.youtube.com/watch?v=4PUTbK5AqY8 : >For such a
| critical joint I see some questionable prep work >in the
| video. >-Bare hands touching the bond surface. >-Solvent
| wiping used instead of caustic degreasers. >-Poor wiping
| technique >-no surface profile/grit blast immediately prior
| to fixing.
|
| All sources are from commenters on: https://www.eng-
| tips.com/viewthread.cfm?qid=508005
| dotnet00 wrote:
| It's important to remember that the pressures involved are
| very different. The ISS pressure vessels only have to hold
| 1atm in, and not several atmospheres out.
| bebop wrote:
| To reinforce this point, it is around 375 atmospheres at
| the titanic. The deep sea is a crazy place.
| jcranmer wrote:
| Equally important is that the ISS is under tensile load
| (the cylinder is trying to explode), while a submersible is
| under compressive load (the cylinder is trying to implode).
| rbanffy wrote:
| It's just 1 atm. You can't even say it's trying
| seriously.
| jandrese wrote:
| Obviously it can't be linear forever, if you assume the crack
| is along a circumference then eventually there will only be a
| tiny piece of metal still intact between the two halves, and
| one would expect it to fail far before then.
|
| These kinds of failures tend to be linear until they are not,
| and the failure mode is catastrophic. If I were in charge I
| would have already shut off that module on the risk/benefit
| analysis of catastrophic loss of the station vs. not being able
| to evacuate as quickly in a less catastrophic emergency. Maybe
| they are worried they won't be able to get the hatch open again
| if they can't equalize the pressure again?
|
| For historical reference, consider Aloha Airlines Flight
| 243[1].
|
| https://en.wikipedia.org/wiki/Aloha_Airlines_Flight_243
| DSMan195276 wrote:
| > Maybe they are worried they won't be able to get the hatch
| open again if they can't equalize the pressure again?
|
| Well note that they currently keep the hatch to the docking
| port closed unless they're using it, so that presumably
| mitigates some of the risk (assuming the leak is confined to
| that location). Not using the whole Zvezda module itself
| would be more or less impossible from my understanding.
|
| If they decided to stop using that dock port at all then I
| think that complicates planning and makes everything overall
| riskier, so while it wouldn't be a disaster to do there's
| still risk you have to weigh.
| debacle wrote:
| Disclaimer: I don't know how space modules are welded or what
| forces act on a space module.
|
| Welds fail for multiple reasons - heating too fast, cooling too
| fast, material defects, human error, equipment issues,
| oxidation. The best human welder will still have some variance
| in their weld even if they lay a perfect bead.
|
| Once a weld begins to fail, under normal conditions (vibration,
| stress, etc), it will slowly get worse, but that can also mean
| deformation around the weld or even sometimes shearing right
| next to your weld. The article doesn't mention that the growth
| has been linear only that it is increasing. I expect that the
| leak is increasing over time in a non-linear fashion as force
| is applied to the weak area and metal continues to separate
| and/or shear. Still, 3.7 pounds of atmosphere a day is a very
| slow leak (relatively), a few bike tires a day.
| rbanffy wrote:
| My back of the napkin math tells me a .2 mm puncture would do
| this. This must be a very tiny crack.
|
| I'd just paint over all the welds and be happy until it
| unseals itself again.
| zardo wrote:
| > Is a fracture like this likely to continue to grow in a
| linear-ish domain, or is there a point where propagation goes
| non-linear assuming the loads stay constant-ish? Is this even a
| sane question to ask?
|
| It depends on so much that we don't know from the article.
| hedora wrote:
| From the article, it started leaking years ago, and almost
| doubled between Feb and Apr of this year, so it is definitely
| not growing linearly.
| TomMasz wrote:
| It's hard to imagine US/Russian relations improving in the coming
| years. It might be easier and safer to retire the ISS sooner
| rather than later.
| neom wrote:
| As a fun juxtaposition to your comment, here is a playlist of
| videos of them building it:
| https://www.youtube.com/playlist?list=PLYu7z3I8tdEnjgkBIBgxa...
| aaronblohowiak wrote:
| it is planned for decommission. in the interim, they are
| isolating the impacted module and not planning repair (at
| least, that's what I got from the article!)
| rbanffy wrote:
| You'll also need to have their agreement before you deorbit the
| Russian part. There is no way around that marriage (and it'd be
| better to make it work - space operations shouldn't be run by
| politicians anyway).
| aaroninsf wrote:
| When I read this I understood _cracking_ in its sense of software
| piracy aka "hacking."
|
| A mental subprocesses spawned to predict whether the cracking was
| _of_ the systems on the station--possibly inspired by that movie
| trailer I saw for the thriller about a new cold war in space
| after a nuclear war--or _from_ the space station, by bored
| occupants, either of their own systems or of some system they
| interact with on the ground.
|
| A bit deflated by the reality, tbh.
| accrual wrote:
| I wonder what kind of hardware debugging could be used to find
| the source of the leak. Could they spacewalk to the exterior of
| the tunnel and then emit some kind of detectible but inert gas
| from the interior to see where it appears outside? I suppose even
| if you found the leak there would still be some challenges in
| sealing it, especially if it's a growing leak like the data
| suggests. Would be a good experience for future space station
| maintenance though.
| cabirum wrote:
| "tunnel that connects a larger module to a docking port" -
| reads like stress-induced metal fatigue, where it leaks a bit
| from every seam. It may not be a nice round hole somewhere.
| rbanffy wrote:
| And being a docking module, I'd guess it'd be near the
| docking port structure (although all Russian modules are
| connected via docking ports, rather than berthing ones).
| potato3732842 wrote:
| Or just not an ideal design and the welded ring at the end is
| where it comes to a head because that's where the part
| connects to the next one.
|
| All aluminum stuff is gonna suffer fatigue problems
| eventually.
| bobmcnamara wrote:
| For cars I've used a smoke generator (cigarette) and waved it
| around until the smoke is sucked into the vacuum leak.
|
| I'm sure NASA has something nicer.
| jandrese wrote:
| It is currently a very slow leak. That said a cloud of smoke
| shouldn't dissipate much at all in zero g so it might work.
| dotnet00 wrote:
| I feel like there must be something being lost in
| communication.
|
| Since this is a docking port connector, they ought to be able
| to block it off on one side with some sort of temporary
| airtight seal and measure the direction the air within flows in
| to gradually narrow down where the leak is.
|
| I get the impression that maybe NASA is avoiding openly
| discussing the cause of the leak to be nice to roscosmos
| (because despite all the geopolitical conflict, they're still
| trying to keep the station running as is for a few more years).
| rbanffy wrote:
| They are just closing the hatch to the faulty module.
| Considering the leak is very small and that it'd be a huge
| hassle to detect it (with little that could be done to fix
| the structural problem - while you can stop the leak with
| bubble-gum, but can't redo the weld in space)
| toomuchtodo wrote:
| https://www.nasa.gov/nexis/robotic-external-leak-locator/
|
| https://ntrs.nasa.gov/api/citations/20070022572/downloads/20...
| rbanffy wrote:
| > some challenges in sealing it
|
| It's a 1 atm difference, so even adhesive tape stuck on the
| inside would do the trick. Unfortunately, I don't think there
| is much unexposed hull on the inside and I bet the crack is
| behind some equipment that isn't trivial to remove (or else
| it'd have been found years ago by some annoyed astronaut in
| their off-time).
|
| Detecting from the outside is also complicated, as you'd need
| to release (and reattach) the thermal blankets to see the
| actual surface of the module.
|
| Closing the hatch and stopping the use of that docking port
| seems to be the smart thing to do. Worst case scenario,
| repressurise, dock the Progress, unload, load it with trash,
| and close the hatch. I also don't think anyone is considering
| using this module to boost the station's altitude - I would't
| put any additional stresses on it anyway.
| schiffern wrote:
| True, but also sealing the leak is only putting a bandaid
| over the problem. The hull is still going to fail eventually.
|
| A better fix would be (believe it or not) _drilling holes in
| it_ , then sealing it over. This "stop drilling" prevents the
| crack from growing any larger.
|
| https://old.reddit.com/r/engineering/comments/6bdugb/how_doe.
| ..
| molticrystal wrote:
| Maybe several pieces of flat paper or thin foam and see what
| walls and joints it likes to stick too. Repeated often enough
| it might show some suspicious spots.
| rtkwe wrote:
| The station has so many fans for cooling equipment and
| circulation to keep the air fresh I doubt that'd show results
| fast enough that the station could be kept half shut down
| for. Anything that's air cooled up there requires circulation
| remember because convection requires gravity for density to
| drive movement.
| zikduruqe wrote:
| They could send up a few cartons of cigarettes to detect the
| cracks. /s
|
| https://www.upi.com/Archives/1988/05/27/The-recently-
| imposed...
| jjk166 wrote:
| For something like this an ultrasonic leak detector would
| likely be ideal. Much like wind blowing through an open window,
| as air flows through the leak it makes noise which is totally
| inaudible to the human ear but detectable by sensitive
| electronics. The closer you get to the leak, the louder it is.
| mmooss wrote:
| > Once the station reaches the end of its life, NASA intends to
| transition its activities in low-Earth orbit onto private space
| stations, and it has funded initial development work by Axiom
| Space, Northrop Grumman, Blue Origin, and Voyager Space.
|
| One publication I read made a couple of relevant points:
|
| NASA should be careful about privatization and subcontracting, as
| it replaces NASA top-notch engineers with contract managers and
| oversight. Most engineers aren't interested in that work, and the
| skills don't stay sharp.
|
| Also, it said that Gateway, the space station planned to orbit
| the Moon, is considered the conceptual descendent of ISS.
|
| Much more here:
| https://nap.nationalacademies.org/cart/download.cgi?record_i...
|
| IMHO NASA should focus on the cutting edge, pushing the frontiers
| of space and technology. I'm glad they stopped bothering with
| orbital launch, which they've done for over 60 years - many
| countries and many private companies can do that now. I'm not
| sure where ISS falls - LEO is obviously relatively common
| technology, but habitation in orbit? Space stations orbiting the
| Moon are the kind of thing where NASA should aim.
| bdangubic wrote:
| Hard to focus on the cutting edge, pushing the frontiers of
| space and technology with an ever-dwindling budget...
| m463 wrote:
| > Most engineers aren't interested in that work
|
| What if you worked for a nasa contractor and you got paid quite
| a bit more than working for nasa?
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