7 ms·
if helium is better, why not use a vacuum?
by wigster 2y ago
if helium is better, why not use a vacuum?
- deleted 2y ago[deleted]
- exe34 2y agovacuums tend to collapse on themselves, I think it might be more costly in structural elements to prevent that?
- robocat 2y agoIt 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 2y ago> 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 2y agoThermoses have vacuum in the walls, and they are very thin, much thinner than a hard-drive case.
- exe34 2y agoI think they do get designed specially for resisting the vacuum collapsing the walls, but you're right, it can probably be done!
- ItsBob 2y agoWhat 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 2y agoa 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 2y agoMaybe structural issues in trying to stop the case from imploding?
- tedsanders 2y agoA startup called L2 drive is apparently working on this: https://l2drive.com/vacuum-hdds-the-next-logical-step-after-helium/ 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 2y agoHydrogen would also be .. interesting ...
- flir 2y agoOh, the huge HDD.
- dreamcompiler 2y agoWouldn'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 2y agoThat's not the main problem. The main problem is hydrogen is fucking painful to contain.
- dreamcompiler 2y agoNot as painful as helium. Bigger atom but it leaks more.
- banish-m4 2y agoAh, 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 2y agoHydrogen even diffuses through (and into) metal - seems not doable, not cheaply and without maintenance at least.
- credit_guy 2y agoHelium atoms are actually smaller than hydrogen atoms, and much smaller than hydrogen mollecules.
- Panzer04 2y agoIs heat a concern in HDDs? Vacuum would probably make it extremely difficult to cool if it's necessary.
- jfjdkfnjrhr 2y agoNo friction ... No heat
- dist-epoch 2y agoHeat can still circulate through the metal parts. Which is a better heat transfer medium than air anyway.
- akira2501 2y agoA gas provides a "bearing" for the heads to ride on as the disk spins below it.
- rob74 2y agoRight 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 2y agoIt'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 2y agoMaybe 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 2y agoSo write too many zeros to your drive, the disk becomes demagnetized, and the head will crash?
- Faaak 2y agoWith another encoding like Manchester, it wouldn't;-)
- frud 2y agoThe 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.
- rasz 2y agoHeads ride on cushion of gas, would instantly friction weld into platters in vacuum.
- hughesjj 2y agoFriction or cold/vacuum welding at that point?
- deleted 2y ago[deleted]
- j16sdiz 2y agoMetal sticks to each other in vacuum https://en.m.wikipedia.org/wiki/Cold_welding https://en.m.wikipedia.org/wiki/Cold_welding