3 ms·

The pressure difference between 1 atm and the moon is exactly 1 atm. It's less than the difference between the inside and outside of most car tires. The pressu

by kijin 9y ago

The pressure difference between 1 atm and the moon is exactly 1 atm. It's less than the difference between the inside and outside of most car tires. The pressure difference between 1 atm and the bottom of the ocean is hundreds of atm, and the deepest spots can go over 1000 atm. Put this way, it's easy to see why the ocean is so much tougher. Luckily, the ocean is much closer than the moon, and the same gravity that is responsible for the tyranny of the rocket equation actually helps you get to the bottom. We've been to both places: the moon with Apollo landers, and the bottom of the Mariana Trench with bathyscaphes. I hope we'll keep returning to learn more about both. Of course, this will be much easier with robots that don't need to stay at 1 atm.

noir_lord 9y ago
Not sure the robots help that much (apart from not dying when things go wrong). As you said in some parts pressure is 1000atm, if we can pressurise the robots to 50atm that still leaves 950atm to deal with, I'm curious what happens to electronics at 100atm, 500atm and 1000atm. I'd imagine some components wouldn't handle that very well. Of course robots have other huge advantages, duration (no messy waste problems, no need for oxygen/carbon dioxide handling systems, no need for (as much) heating) I guess.
- sp332 9y ago
  It's a lot cheaper to keep a robot than a human operating at that pressure.
- IndrekR 9y ago
  It is much easier to keep electronics working down there when empty space is filled with liquid instead of pressurised gas (usually nitrogen). It is not the pressure, but pressure difference, that matters and liquids are not as compressible as gas is. Edit: just adding a note that I have worked with submarine electronics[1] for a while and can say we even do not know much about what is happening near the shore, not to even talk about the unexploredness of oceans. Quite a lot of HW/SW in use by scientists is far from modern. We need more initiatives like the Ocean Discovery XPRIZE[2] to bring attention to the field. [1] http://www.flydogmarine.com http://www.flydogmarine.com [2] https://oceandiscovery.xprize.org https://oceandiscovery.xprize.org
- cr1895 9y ago
  >I'm curious what happens to electronics at 100atm, 500atm and 1000atm. On ROVs and the like, electronics modules are frequently immersed in mineral oil.
Cacti 9y ago
As you implied, getting to the bottom of the ocean is about as difficult as getting to the moon, and involves many of the same challenges.
craftyguy 9y ago
> It's less than the difference between the inside and outside of most car tires There are tires that are inflated with < 1 atm?
- kijin 9y ago
  It's easy to build a solid container with < 1 atm inside. But I don't think such a container will fit the definition of a pneumatic tire. Any flexible container with < 1 atm inside will collapse until the pressure inside reaches equilibrium with the air outside. It will collapse further if there's a heavy load on top of it, or maybe less if it's a run-flat tire with rigid structures inside. Perhaps if you were on top of a very tall mountain or, even better, another planet, you could get away with filling your tires with less than < 1 atm and still have them functional.
  - Dylan16807 9y ago
    The prompt was talking about pressure between the inside and outside of the tire. If that's slightly under 1atm you have a perfectly normal but overly soft tire. People actually use pressures that low for rock crawling. (For reference a typical car tire is just over 2atm relative, 3atm absolute)
amorphid 9y ago
> The pressure difference between 1 atm and the moon is exactly 1 atm. It's less than the difference between the inside and outside of most car tires. I forget the moon has a hint of an atmosphere. [1] The pressure is 3×10^−15. I wonder when, if ever, you'd need to take that into account. [1] https://en.m.wikipedia.org/wiki/Atmosphere_of_the_Moon https://en.m.wikipedia.org/wiki/Atmosphere_of_the_Moon

by kijin 9y ago

noir_lord 9y ago

Not sure the robots help that much (apart from not dying when things go wrong). As you said in some parts pressure is 1000atm, if we can pressurise the robots to 50atm that still leaves 950atm to deal with, I'm curious what happens to electronics at 100atm, 500atm and 1000atm. I'd imagine some components wouldn't handle that very well. Of course robots have other huge advantages, duration (no messy waste problems, no need for oxygen/carbon dioxide handling systems, no need for (as much) heating) I guess.

sp332 9y ago
It's a lot cheaper to keep a robot than a human operating at that pressure.
IndrekR 9y ago
It is much easier to keep electronics working down there when empty space is filled with liquid instead of pressurised gas (usually nitrogen). It is not the pressure, but pressure difference, that matters and liquids are not as compressible as gas is. Edit: just adding a note that I have worked with submarine electronics[1] for a while and can say we even do not know much about what is happening near the shore, not to even talk about the unexploredness of oceans. Quite a lot of HW/SW in use by scientists is far from modern. We need more initiatives like the Ocean Discovery XPRIZE[2] to bring attention to the field. [1] http://www.flydogmarine.com http://www.flydogmarine.com [2] https://oceandiscovery.xprize.org https://oceandiscovery.xprize.org
cr1895 9y ago
>I'm curious what happens to electronics at 100atm, 500atm and 1000atm. On ROVs and the like, electronics modules are frequently immersed in mineral oil.

Cacti 9y ago

As you implied, getting to the bottom of the ocean is about as difficult as getting to the moon, and involves many of the same challenges.

craftyguy 9y ago

> It's less than the difference between the inside and outside of most car tires There are tires that are inflated with < 1 atm?

kijin 9y ago
It's easy to build a solid container with < 1 atm inside. But I don't think such a container will fit the definition of a pneumatic tire. Any flexible container with < 1 atm inside will collapse until the pressure inside reaches equilibrium with the air outside. It will collapse further if there's a heavy load on top of it, or maybe less if it's a run-flat tire with rigid structures inside. Perhaps if you were on top of a very tall mountain or, even better, another planet, you could get away with filling your tires with less than < 1 atm and still have them functional.
- Dylan16807 9y ago
  The prompt was talking about pressure between the inside and outside of the tire. If that's slightly under 1atm you have a perfectly normal but overly soft tire. People actually use pressures that low for rock crawling. (For reference a typical car tire is just over 2atm relative, 3atm absolute)

amorphid 9y ago

> The pressure difference between 1 atm and the moon is exactly 1 atm. It's less than the difference between the inside and outside of most car tires. I forget the moon has a hint of an atmosphere. [1] The pressure is 3×10^−15. I wonder when, if ever, you'd need to take that into account. [1] https://en.m.wikipedia.org/wiki/Atmosphere_of_the_Moon https://en.m.wikipedia.org/wiki/Atmosphere_of_the_Moon