[HN Gopher] The Race to Seal Helium HDDs (2021)
       ___________________________________________________________________
        
       The Race to Seal Helium HDDs (2021)
        
       Author : Quizzical4230
       Score  : 133 points
       Date   : 2024-07-09 06:42 UTC (1 days ago)
        
 (HTM) web link (blog.westerndigital.com)
 (TXT) w3m dump (blog.westerndigital.com)
        
       | rx_tx wrote:
       | (2021)
        
       | wigster wrote:
       | if helium is better, why not use a vacuum?
        
         | exe34 wrote:
         | vacuums tend to collapse on themselves, I think it might be
         | more costly in structural elements to prevent that?
        
           | robocat wrote:
           | It is better to think of a vacuum within air to be similar to
           | a bubble underwater.
           | 
           | Air is like water in other ways too. We slightly "float" in
           | air by the weight of air we displace. e.g. 80kg person is
           | approximately 80 litres (density of a body is 1.010
           | kg/litre). Weight of displaced air is approx 0.1 gram (1.2929
           | gram/litre). So the floating effect of air reduces your
           | weight (not mass) by about 0.1%.
        
             | Someone wrote:
             | > It is better to think of a vacuum within air to be
             | similar to a bubble underwater.
             | 
             | I don't think it is vey similar. That bubble pushes against
             | the water to maintain itself; it manages to do that only
             | because its "push" increases the higher its pressure and it
             | is more compressible than water.
             | 
             | The vacuum, on the other hand, is compressible (if you want
             | to call that so), but its "push" remains zero if you do, so
             | it needs help to push against the air to maintain itself.
             | 
             | That's why the post your replied to said _"vacuums tend to
             | collapse on themselves, I think it might be more costly in
             | structural elements to prevent that?"_
        
           | dist-epoch wrote:
           | Thermoses have vacuum in the walls, and they are very thin,
           | much thinner than a hard-drive case.
        
             | exe34 wrote:
             | I think they do get designed specially for resisting the
             | vacuum collapsing the walls, but you're right, it can
             | probably be done!
        
           | ItsBob wrote:
           | What about a partial vacuum?
           | 
           | Perhaps there is a hapy medium between air resistance and
           | cushioning? Reducing the air by an amount might help.
           | 
           | Although, I'd be surprised if they hadn't thought of this
           | already :)
        
             | fsckboy wrote:
             | a partial vacuum of only helium, tightly sealed to keep in
             | the helium. The tight seals will work to make sure that
             | when there is leakage, only helium leaks in. and if there
             | is no helium component to the air outside, you'll just get
             | helium leaking out thus improving your vacuum.
        
         | askvictor wrote:
         | Maybe structural issues in trying to stop the case from
         | imploding?
        
         | tedsanders wrote:
         | A startup called L2 drive is apparently working on this:
         | https://l2drive.com/vacuum-hdds-the-next-logical-step-after-...
         | 
         | But their website looks pretty stale, and I don't see evidence
         | of traction from brief Googling.
        
         | rwmj wrote:
         | Hydrogen would also be .. interesting ...
        
           | flir wrote:
           | Oh, the huge HDD.
        
           | dreamcompiler wrote:
           | Wouldn't be a fire risk because there's no oxygen available.
           | But hydrogen is chemically reactive and over time it could
           | corrode or weaken the materials inside the HDD.
        
             | banish-m4 wrote:
             | That's not the main problem. The main problem is hydrogen
             | is fucking painful to contain.
        
               | dreamcompiler wrote:
               | Not as painful as helium. Bigger atom but it leaks more.
        
               | banish-m4 wrote:
               | Ah, truth. Brain fart.
               | 
               | ASME Boiler and Pressure Vessel Section V
               | 
               | Helium leak detection sensitivity is 3 orders of
               | magnitude higher.
               | 
               | Memory is fallible, but the code doesn't lie.
        
           | ahartmetz wrote:
           | Hydrogen even diffuses through (and into) metal - seems not
           | doable, not cheaply and without maintenance at least.
        
             | credit_guy wrote:
             | Helium atoms are actually smaller than hydrogen atoms, and
             | much smaller than hydrogen mollecules.
        
               | adrian_b wrote:
               | While that is true, there are metals through which
               | hydrogen can diffuse faster than helium, because the
               | hydrogen molecules dissociate and ionize when entering
               | the metal and the hydrogen ions diffuse through the metal
               | individually.
        
           | aaron695 wrote:
           | > Hydrogen would also be .. interesting ...
           | 
           | Why?
           | 
           | It's used in power station generators. Why would a hard disk
           | be interesting?
           | 
           | https://en.wikipedia.org/wiki/Hydrogen-
           | cooled_turbo_generato...
        
             | dtx1 wrote:
             | Cause exploding hard drives are metal AF
        
               | mitthrowaway2 wrote:
               | It won't explode until it's mixed with oxygen.
        
               | AnimalMuppet wrote:
               | Hold my beer.
        
               | HankB99 wrote:
               | The small amount contained in the HDD would a minimal
               | risk.
               | 
               | Larger amounts handled in the manufacturing process,
               | OTOH...
               | 
               | I'm curious how the shaft seals for generators manage to
               | seal the hydrogen. Perhaps the hydrogen is contained
               | within the the generator and not exposed to the seals,
               | though I thought one of the reasons for its use (along
               | with cooling) was reduced windage losses.
        
         | Panzer04 wrote:
         | Is heat a concern in HDDs? Vacuum would probably make it
         | extremely difficult to cool if it's necessary.
        
           | jfjdkfnjrhr wrote:
           | No friction ... No heat
        
             | toenail wrote:
             | Sounds like an SSD..
        
               | piva00 wrote:
               | SSDs can get pretty hot though.
        
               | SirMaster wrote:
               | SSDs have lots of moving parts and friction, all the
               | electrons are zipping around the circuits with friction.
               | This creates heat :)
        
           | dist-epoch wrote:
           | Heat can still circulate through the metal parts. Which is a
           | better heat transfer medium than air anyway.
        
         | akira2501 wrote:
         | A gas provides a "bearing" for the heads to ride on as the disk
         | spins below it.
        
           | rob74 wrote:
           | Right you are, forgot about that completely! IIRC this is
           | important to prevent a headcrash if the drive is jolted while
           | in operation (of course within certain limits).
        
             | Brian_K_White wrote:
             | It's required to work at all, not just as some kind of
             | guard rail. It's like the oil in a normal bearing, the oil
             | isn't just to prevent a crankshaft crash in case the car is
             | jolted while in operation, the oil is a part of the way the
             | thing functions at all in the first place.
        
           | ahartmetz wrote:
           | Maybe magnetism could work. HDD platters take very strong
           | fields to change magnetization these days, so erasing the
           | data with the positioning magnet(s) seems avoidable.
        
             | amelius wrote:
             | So write too many zeros to your drive, the disk becomes
             | demagnetized, and the head will crash?
        
               | Faaak wrote:
               | With another encoding like Manchester, it wouldn't;-)
        
               | frud wrote:
               | The raw words written to the drive are actually re-
               | encoded into slightly larger codewords with nice
               | properties like not having too many zero or one bits in a
               | row, and error detection/correction.
               | 
               | Plus I think that the 0/1 bits are not encoded as "no
               | magnetism"/"some magnetism", but instead as "north
               | magnetism"/"south magnetism" since magnetic fields have a
               | direction.
               | 
               | And I don't think the magnetic fields on the platters
               | have any appreciable effect on the head besides the
               | electromagnetic effects at the sensor.
        
               | Cerium wrote:
               | Essentially the same problem as with fiber optics. The
               | data can't be recovered unless there are frequent bit
               | transitions. In that case the data is transformed to
               | ensure illegal patterns cannot occur.
        
             | perihelions wrote:
             | Also, you could imagine a magnetic bearing whose field
             | strength rapidly diminishes as you move away from it, due
             | to cancellation, like a Halbach array [0]. I wonder if
             | there's a simple geometric configuration for a bearing that
             | has this property, as well as the critical property of
             | _passively stable levitation_ , maybe based on diamagnetic
             | or superconducting materials [1].
             | 
             | edit: Maybe something in this direction? [2]
             | 
             | [0] https://en.wikipedia.org/wiki/Halbach_array
             | 
             | [1] https://en.wikipedia.org/wiki/Magnetic_bearing
             | 
             | [2] https://ntrs.nasa.gov/api/citations/20070006849/downloa
             | ds/20... ( _" Development and Testing of a Radial Halbach
             | Magnetic Bearing"_)
        
         | rasz wrote:
         | Heads ride on cushion of gas, would instantly friction weld
         | into platters in vacuum.
        
           | hughesjj wrote:
           | Friction or cold/vacuum welding at that point?
        
         | j16sdiz wrote:
         | Metal sticks to each other in vacuum
         | 
         | https://en.m.wikipedia.org/wiki/Cold_welding
        
       | ramchip wrote:
       | "Abundant" in the infographic is questionable... in the universe
       | yes, but on Earth not really.
        
       | formerly_proven wrote:
       | At least two roads to Rome: HGST/WD and Toshiba use laser
       | welding, Seagate uses friction-stir welding
       | (https://en.wikipedia.org/wiki/Friction_stir_welding).
       | 
       | edit: the close up in the Wikipedia article actually is from a
       | hard drive
        
       | vertnerd wrote:
       | "Helium is notoriously difficult to contain. Its atoms are some
       | of the tiniest in the universe."
       | 
       | It's a good article, and I learned a lot, but every so often it
       | reads like something an 8th grader would write the night before
       | their paper is due.
        
         | B1FF_PSUVM wrote:
         | And then it swings up and hits you with _" a way that it
         | doesn't scathe the seal"_.
         | 
         | Plenty of "unscathed" around, but I don't think I ever met the
         | "un"-free word.
         | 
         | Reminds me of the P.G.Wodehouse "far from gruntled" (
         | https://nydamprintsblackandwhite.blogspot.com/2011/05/words-...
         | )
        
           | AndrewSwift wrote:
           | [scathing remark deleted]
        
           | dmurray wrote:
           | You need to read _How I Met My Wife_!
           | 
           | https://www.newyorker.com/magazine/1994/07/25/how-i-met-
           | my-w...
        
         | amelius wrote:
         | Sometimes facts are simple.
        
         | yummypaint wrote:
         | Yeah i don't get the unnecessary vagueness. They are the
         | smallest atoms. It's like they are afraid of accidentally
         | educating the reader.
        
           | kragen wrote:
           | this terror of accidentally including a fact is one of the
           | worst of many plagues afflicting journalism today
        
             | fckgw wrote:
             | It's a company blog, not a newspaper
        
               | kragen wrote:
               | that makes it even worse, doesn't it?
        
             | neuralRiot wrote:
             | By treating people like idiots they turn them into idiots.
             | It's like "The lenght of 5 football fields" or "The weight
             | of 10 elephants" are they writing for 3rd graders?
        
         | bjoli wrote:
         | And here I was, thinking helium was the tiniest atom unless you
         | start counting cations which has it beaten by Li+ and He+
        
           | adrian_b wrote:
           | Yes, at the same number of electrons, the heavier atoms have
           | a smaller volume, i.e. they are tinier, because their greater
           | nuclear charge attracts the electrons closer to the nucleus.
           | 
           | Li+, Be++, B+++ are tinier than He, but they are ions, not
           | neutral atoms. Neutral Li, Be, B are bigger than He, because
           | they have an additional electron layer. Both neutral H and H-
           | are bigger than He, because their one or two electrons are
           | attracted less by a proton than by a He nucleus with double
           | charge. H+ is just a bare proton, so it is orders of
           | magnitude smaller than any other ion, but it is not a neutral
           | atom.
           | 
           | So He is indeed the smallest neutral atom.
        
             | addaon wrote:
             | Muonic atoms are many, many times smaller, and neutral --
             | so small that the reduction in atomic radius by
             | substituting a muon for an electron can catalyze fusion.
             | Purely muon helium would be the smallest such. (Tauons
             | can't form atoms as their decay time is shorter by orders
             | of magnitude than would be needed.)
        
               | adrian_b wrote:
               | You are right, so in order to say that the helium atom is
               | the tiniest, the statement should be additionally
               | qualified, by saying that it is the tiniest among the
               | _stable_ neutral atoms, in order to exclude the muonic
               | atoms.
        
         | chasil wrote:
         | Would neon offer some degree of these benefits?
         | 
         | Is neon more plentiful than helium?
         | 
         | Edit: No.
         | 
         | "...neon is comparatively scarce on Earth... It is primarily
         | obtained through the fractional distillation of liquid air,
         | making it significantly more expensive than helium due to air
         | being its sole source."
         | 
         | https://en.wikipedia.org/wiki/Neon
        
       | Wowfunhappy wrote:
       | ...I didn't really we had the technology to seal helium at all.
       | 
       | Stupid question, but could you potentially create a helium
       | balloon that never runs out of helium (because it's sealed and
       | doesn't leak)?
        
         | ahartmetz wrote:
         | If it's made of metal foil, probably. Much more diffusion-
         | resistant than rubber. The problem with rubber balloons isn't
         | that they have macro- or mesoscopic holes. They lose gas by
         | diffusion all over.
        
           | ejdhshsuwisjsh wrote:
           | The article talks about how hard it is to contain helium.
           | 
           | Why would you assume that a basic metal foil would keep
           | helium indefinitely?
        
             | ahartmetz wrote:
             | It's right there in the article: it mentions welding of
             | aluminum foil seals - for helium.
             | 
             | I have also worked with high vacuum in lab exercises.
             | There's a leak finder apparatus using helium because helium
             | creeps through the smallest leaks - but they have to be
             | leaks! Hydrogen just diffuses through anyway, though not
             | quickly through thick metal (I have that from Wikipedia).
        
               | ejdhshsuwisjsh wrote:
               | I have to read up on this.
               | 
               | I have seen a YT on someone doing this in a lab env but I
               | always assumed that you can't contain it indefinitely
        
               | Wowfunhappy wrote:
               | ...so, uh, any idea why balloons suck?
               | 
               | I assume it would be way more expensive but if it lasted
               | for decades or more...
        
       | Towaway69 wrote:
       | > Western Digital ships about a million helium-sealed drives
       | every month.
       | 
       | I'm surprised that there was such demand for spinning disks, I
       | would have thought SDDs would have replaced them all.
       | 
       | I say ,was' as the article is from 2021.
        
         | ricardobeat wrote:
         | SSDs are still too expensive for high volume storage.
         | 
         | Enterprise purchases will be much lower, but as a consumer you
         | can buy a 12TB helium-sealed HDD for $100-$200, while solid
         | state alternatives don't even reach that capacity in a single
         | unit and cost 5-10x more.
        
           | Towaway69 wrote:
           | Thanks for the explanation, I didn't realise that was the
           | case.
        
       | throwaway81523 wrote:
       | Are HDD's a significant consumer of the world's helium, in the
       | scheme of things? I had thought helium was used only in a few
       | bleeding edge drives, and they went to normal air as the tech
       | matured.
        
         | Out_of_Characte wrote:
         | Assuming a drive contains helium at standard temparature and
         | pressure, and contains about a liter in volume. That would be
         | about 1 gram worth of helium per drive.
        
           | margalabargala wrote:
           | Hard drives are much, much smaller than one liter.
        
           | robocat wrote:
           | 0.05 gram Helium assuming: (1) half of drive volume is used
           | for platters, (2) at 15deg Celcius (3) at 1 atmosphere (I'm
           | guessing not pressurised since that would defeat purpose of
           | using Helium, although might be less than 1 atmosphere)..
           | 
           | 0.376 litres for total 3.5-inch HDD volume from my first
           | Google result: "Width: 101.6 mm, Height: 25.4 mm, Length: 146
           | mm". Actual volume used for platters is less than that.
           | 
           | Helium is light ~ 0.169 g/litre from "0.169 kg of Helium is
           | 0.999 m3 at 15degC":
           | https://microsites.airproducts.com/gasfacts/helium.html Note
           | that I think comment assumed one litre of normal air not
           | Helium: "The density of dry air is 1.2929 g/litre at STP".
        
           | joezydeco wrote:
           | One MRI machine uses about 2,000L of liquid He, which expands
           | to around 1:770 in gaseous form. So roughly 1,540,000L of
           | helium gas per machine.
        
             | banish-m4 wrote:
             | MRI machines borked the MEMS accelerometers in iPhone due
             | to helium contamination. I assume most smartphone sensors
             | are now helium-tolerant.
        
               | joezydeco wrote:
               | Nope. They just added a warning so it's _your_ fault if
               | you get any helium atoms in your oscillator.
               | 
               | https://support.apple.com/guide/iphone/important-safety-
               | info....
        
             | Y_Y wrote:
             | GE says over its lifetime (roughly 13 years) an MRI machine
             | will use about 1e4 litres of liquid helium. Two thousand
             | litres is a good estimate for the _capacity_ of a machine,
             | but it 's not a useful figure unless you know how often you
             | need to replenish it.
        
         | ndiddy wrote:
         | Helium drives are basically standard for enterprise hard drives
         | now. The reduced drag force allows for using thinner drive
         | platters (helium drives can hold up to 10 platters, while air-
         | filled drives can only hold up to 6 platters) which boosts
         | capacity. Helium drives also use less power, run cooler, and
         | the helium gas helps to absorb vibrations that can cause wear
         | and tear (useful in enterprise settings where you have 45 or
         | more drives in a 4U chassis).
        
         | thinkfaster wrote:
         | Helium in the atmosphere is almost two orders of magnitude more
         | common than xenon and three times as concentrated than krypton.
         | Both are extracted from air.
         | 
         | Even though He is constantly venting to space, alpha emitters
         | keep replenishing it.
         | 
         |  _Cheap_ helium from 7% CH4 wells is not going to last. But we
         | 're not going to run out of He. Just the energy to extract it.
        
         | buildsjets wrote:
         | Let me go read the article for you.
         | 
         | Yep, it says right there that a "standard" helium tank is
         | adequate to fill 10,000 hard drives. I am going to assume that
         | by "standard" they mean 220ft^3 or 250ft^3, even though my
         | "standard" for tanks is 125ft^3 because I can comfortably carry
         | one of those on my shoulder.
        
       | aaron695 wrote:
       | If anyone has a helium drive you can check it's levels -
       | S.M.A.R.T. ID 22
       | 
       | If you are bored I'd be interested to hear what level it's at on
       | old drives.
       | 
       | Like is it still 100% after a year? [edit] I assume the 100/64h
       | means 100% maybe not [1]
       | 
       | https://www.reddit.com/r/windows8/comments/11ndk0o/what_is_c...
       | 
       | https://en.wikipedia.org/wiki/Self-Monitoring,_Analysis_and_...
       | 
       | [1]
       | https://www.reddit.com/r/DataHoarder/comments/wl20q2/just_a_...
        
         | SirMaster wrote:
         | I have an 8TB WD RED that has been at 7/100 helium level
         | according to Smart 22 for over 2 years now. Still running just
         | fine in my ZFS pool 24/7.
        
         | jasomill wrote:
         | I have a pair of HGST HDN728080ALE604 drives (8TB Deskstar
         | NAS). One has SMART 22 at 100 after 43,239 power-on hours; the
         | other is offsite and online, but is the same age and had SMART
         | 22 at 100 last time I checked.
         | 
         | My other helium drives (WUH721816AL5204 -- 16TB Ultrastar DC
         | HC550) are SAS, and I don't know how to check helium levels of
         | these (smartctl reports neither SMART 22 nor anything related
         | to helium).
        
         | dale_glass wrote:
         | I've got 3 drives at around 20K hours and all 3 are showing
         | "100" in helium level.
        
       | cainxinth wrote:
       | The solution:
       | 
       | - They moved all the casing openings to the top of the drive and
       | used a thin metal foil as a second cover.
       | 
       | - They adapted laser welding techniques from the satellite
       | industry to seal the foil to the casing without damaging
       | components with excess heat.
       | 
       | - They found an aluminum alloy used in aerospace that could
       | withstand the laser welding without cracking.
       | 
       | - To get electricity and data in and out without breaking the
       | seal, they used glass-metal feedthroughs similar to those used to
       | seal Freon in refrigerators.
       | 
       | - To get the solder to adhere when attaching the feedthroughs,
       | they used a nickel plating mask.
        
         | alright2565 wrote:
         | > used glass-metal feedthroughs
         | 
         | I wonder if this is still the case. I took a WD helium hard
         | drive apart recently and I think I saw just a PCB glued in
         | place for the electrical signals. Probably made from very
         | special materials, but it looked just like usual.
        
           | adrian_b wrote:
           | Glass-metal feedthroughs have been the standard means of
           | connecting semiconductor devices during the first decade of
           | their existence, when they were packaged in hermetic cases
           | made of either metal or glass. Their main problem is to use
           | pairs of special kinds of glasses and of metal alloys that
           | are matched in their thermal expansion coefficients.
           | 
           | After 1960, better passivating methods for the semiconductor
           | chips have been developed, so the hermetic packages have been
           | slowly replaced with plastic packages for most applications.
           | 
           | It is likely that the PCB glued in place covers the glass-
           | metal feedthroughs, which have metal pins that are inserted
           | in connectors soldered on the PCB. It is impossible for any
           | case that contains helium to have any part made of plastic in
           | any of its walls. Plastic parts like a PCB can only be
           | attached externally.
        
         | writeslowly wrote:
         | They also invented a new welding technique to control some sort
         | of aluminum micro-explosions
        
         | kragen wrote:
         | thanks, this is great!
         | 
         | to add a bit more context:
         | 
         | - laser welding has been in use since 01967 and is used not
         | only for satellites but also for auto body panels, pacemakers,
         | 3-d printing (sls/slm), batteries, etc.
         | 
         | - glass-metal feedthroughs are used in incandescent lightbulbs,
         | fluorescent tubes, neon tubes, and vacuum tubes (including crts
         | and electron microscopes), because in all cases you need a
         | vacuum-tight seal around the wires that lead into the tube.
         | special glass formulations with custom thermal expansion
         | coefficients have been available for this purpose since at
         | least the 01950s. the refrigerator guys may have the cheapest
         | ones but they didn't invent them
         | 
         | - nickel plating is the conventional way to make steel
         | solderable with electronic solders since forever. it's also
         | used, for example, to make battery tabs solderable. i think
         | this goes back to the 19th century
         | 
         | that is, the design process the article depicts is considerably
         | less daringly original than the author makes it sound. the
         | people who made it work deserve a lot of praise, but because
         | manufacturing is hard and they had to solve a lot of hard
         | problems, not because they're geniuses doing totally
         | unprecedented things with brilliant strokes of insight. the
         | author makes it sound like that presumably because she doesn't
         | know anything about the problem space
         | 
         | if you like that kind of thing, you'll probably enjoy dalibor
         | farny's youtube channel where he documents his process of
         | solving the problems of his nixie tube factory (including
         | vacuum-tight glass-metal seals) in a czech castle
         | https://www.youtube.com/@daliborfarny/videos
        
       | kbelder wrote:
       | What would happen if you had a rigid structure that helium could
       | permeate, but nothing larger could, and then filled it up with
       | helium and waited?
       | 
       | Would most of the helium exit, until it was balanced with just
       | the partial pressure of helium in the atmosphere? That would be
       | nearly a vacuum, wouldn't it?
        
         | BizarroLand wrote:
         | This is a good question.
         | 
         | I don't know the answer, but this does make me think of atomic
         | sieves like the ones used in oxygen concentrators.
         | 
         | This is an armchair scientist explanation of them, but they
         | "concentrate" oxygen by first having atmospheric air pumped in
         | and then pressurized. The microsieves have holes so small that
         | mostly only oxygen can fit through, the larger CO2 and Nitrogen
         | atoms simply won't fit.
         | 
         | Then, pressure is let off and fresh air brought in. The fresh
         | air scrubs out the oxygen depleted air and refreshes it with
         | standard air.
         | 
         | Then, the pressure decrease allows the oxygen to leak back out
         | of the sieves, leaving you with oxygen enriched air.
         | 
         | I don't know if there are any atomic helium sieves, but if you
         | can find one it might be a start to testing the question.
        
         | s0rce wrote:
         | It would be a vacuum I guess, but generally not in the normal
         | sense because this is the case with most metals. You don't
         | really consider the interstitial space between the atoms in the
         | crystal lattice a vacuum even though there is space for small
         | atoms (He/H) to diffuse through.
        
           | avoid3d wrote:
           | The OP is imagining a device with a "hollow core" of
           | atmospheric pressure helium surrounded by a solid and
           | continuous membrane.
           | 
           | Since this hollow core would be much larger than the
           | crystalline structures in a metal would this not therefore be
           | a very weak comparison?
        
         | jayd16 wrote:
         | Pretty sure it would simply equalize to the external pressure.
         | 
         | Consider it another way. If you have such a device with a
         | vacuum inside, would it not pull in the external helium over
         | time to reduce the vacuum?
        
           | alexey-salmin wrote:
           | > Pretty sure it would simply equalize to the external
           | pressure.
           | 
           | External _partial_ pressure of helium which is extremely low.
           | 
           | > Consider it another way. If you have such a device with a
           | vacuum inside, would it not pull in the external helium over
           | time to reduce the vacuum?
           | 
           | It would, but only until the partial pressure of helium
           | inside is equal to the partial pressure of helium outside
           | (assuming the membrane is permeable only to helium). After
           | that point the same amount of helium will traverse both ways,
           | establishing the equilibrium.
        
           | thinkfaster wrote:
           | A real material would. But thermodynamically OP is right,
           | you'd get a vacuum.
        
         | Enginerrrd wrote:
         | I don't think so.
         | 
         | Ignoring the fact that what you're describing sounds
         | suspiciously like a Maxwell's demon, I think the equilibrium
         | would be at a higher pressure because helium escaping against
         | an overall pressure gradient would be doing work.
         | 
         | In essence, at the boundary I think the rate at which helium
         | escapes would not simply be proportional to the gradient
         | created by the internal pressure and the exterior partial
         | pressure, but I think would include a term involving the whole
         | exterior pressure.
        
           | alexey-salmin wrote:
           | It's not a Maxwell daemon, it's just a device for which
           | nothing but helium exists. In the ideal gas model it would
           | indeed create almost vacuum but the second law of
           | thermodynamics is not violated since the process is
           | symmetrical. Pressure of helium outside is also almost zero.
        
           | avoid3d wrote:
           | This relates to the difference between how a real gas and how
           | an ideal gas behave in this scenario.
           | 
           | The difference in this situation will be very small in my
           | opinion, broadly because the gas molecules in the atmosphere
           | still have comparatively high mean free paths and therefore
           | won't interact with the "escaping" helium molecules.
        
         | thereisnospork wrote:
         | Internal pressure would equilibrate to the partial pressure of
         | helium in the atmosphere, presuming all other species can be
         | assumed to have zero permeability. Osmotic
         | pressure/semipermeable membranes is the analogous liquid
         | system.
        
         | huppeldepup wrote:
         | Cody's lab on youtube did a video on this, with balloons
        
         | thinkfaster wrote:
         | It would create an almost perfect vacuum. You could then
         | extract work by collapsing the vessel. The free energy for the
         | work would come from putting the trapped helium (state 1) in a
         | higher entropy state (state 2).
         | 
         | For what it's worth, this is done industrially to separate
         | gasses using porous membranes.
        
       | esd_g0d wrote:
       | I wanna be this guy when I grow up.
       | 
       | Seriously, how realistic is it to get a job like this guy's? Open
       | ended, no rules, just solving problems... Most days I'm fine with
       | a boring specialized engineering career, but this one got to
       | me...
        
         | striking wrote:
         | Before he was a researcher for IBM, he was a "groundbreaking
         | physicist", for which the article provides this as the
         | evidence: https://news.cornell.edu/stories/1998/03/rotating-
         | single-oxy...
         | 
         | So, be one of the best in the field, and perhaps folks will
         | trust you to do wild open-ended research forever. I think that
         | sounds like a pretty reasonable deal.
        
         | numeri wrote:
         | Any career in fundamental research is more or less like that.
         | From what I've seen personally, academics and government labs
         | are the two biggest places you can find the most open ended
         | roles. Each comes with their own caveats, of course.
        
       | buro9 wrote:
       | I received a HDD only last year where the SMART status
       | immediately reported a failure for status 22, and it led me to
       | https://www.backblaze.com/blog/smart-22-is-a-gas-gas-gas/
       | 
       | It's an immediate "return the drive" scenario, as something
       | happened between factory and the SMART test and the drive is no
       | longer within spec.
       | 
       | Thankfully an easy returns and replacement process, but an eye
       | opener too, I hadn't heard of SMART 22 prior to this.
        
       | TacticalCoder wrote:
       | Fun fact: the Rolex "deep sea" sea-dweller contains Helium and an
       | Helium valve. I'm not too sure how they keep the Helium from
       | escaping. James Cameron (who made the movie The Titanic) actually
       | strapped a Rolex sea-dweller "deep sea" to a little robot
       | submarine and sent it to 10 000 meters deep to see if Rolex was
       | full of shit or not.
       | 
       | Turns out the "veblen good" did quite well and didn't break.
       | 
       | And James Cameron got a limited edition Rolex Sea-Dweller deep
       | sea model named after him.
        
         | patclay wrote:
         | You have this backwards, the valve is to let the Helium out.
         | 
         | The watch was designed for saturation diving - people
         | essentially living at high pressure in a pressure cylinder,
         | breathing a mixed gas which includes a high helium percentage
         | (as nitrogen becomes narcotic). This saved them hours of
         | decompression every dive - just do one decompression at the end
         | of the job.
         | 
         | The problem was despite all of the seals to withstand seawater,
         | the watches would let helium in & gradually equalise the
         | internal & external pressures. All fine until they came up to
         | the surface, when the watch would blow the crystal off, as the
         | helium couldn't escape quickly enough to equalise. The Helium
         | valve is there to release this pressure on ascent.
         | 
         | The sea dweller was designed as a highly specialised tool for a
         | specialised industry, before becoming luxury item.
        
         | m463 wrote:
         | I can't help but think of deep sea divers using helium as part
         | of their mix, and talking in chipmunk high-pitched voices.
        
           | runlevel1 wrote:
           | Here's a phone call between US President Lyndon B. Johnson
           | and Sealab 2 who were doing just that:
           | 
           | https://www.youtube.com/watch?v=wusrtGfjzZg
        
       | fortran77 wrote:
       | Since it's a relatively small volume, why not hydrogen? Is it too
       | reactive?
        
         | banish-m4 wrote:
         | Even harder to contain than helium. Hydrogen notoriously
         | diffuses through many materials and ridiculously-small pores.
        
       | banish-m4 wrote:
       | Note that it's possible to (mostly) hermetically-seal non-helium,
       | air-exchanging breather holes of HDDs for use in submerged
       | mineral oil applications. It's typically done by adhering a
       | flexible membrane over the air port.
        
       | nxobject wrote:
       | An interesting side-story here is how the R&D here was sustained
       | through three corporate acquisitions - from IBM to Hitachi GST to
       | WD.
        
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