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http://www.iflscience.com/space/nasa-wants-establish-floating-cloud-city-study-venus http://www.iflscience.com/space/nasa-wants-establish-floatin...

lisper 11y ago
We're talking about colonization here, not exploration. That's not even a practical plan to make more living space here on earth, let alone on Venus.
- yellowapple 11y ago
  It's actually not all that impractical. Venus' atmosphere is much more dense than Earth's; floating in it should be quite a bit easier.
  - lisper 11y ago
    > Venus' atmosphere is much more dense than Earth's Won't help: "The ships would float 50 kilometers (31 miles) above the planet’s surface. Here, there would be only one atmosphere of pressure, and the temperature would be a reasonable 75"C." 75 C is 160 F. Granted that's cool enough to keep water from boiling, but unless you're a tubeworm you're probably not going to be happy living there without air conditioning.
    - yellowapple 11y ago
      Considering the temperature fluctuations faced routinely even in Earth's own orbit, 75 degrees Celsius is actually very reasonable. It's certainly no less comfortable than Mars' rather frigid climate. If anything, the greater hazard would be the toxic and corrosive clouds of sulfuric acid that blanket the Venusian surface. The density, however, more has to do with whether or not it's feasible to build a permanent settlement in Venus' atmosphere. It turns out that it's very feasible; Venus' carbon-dioxide-based atmosphere would be thick enough even at those altitudes to keep a "balloon" filled with an Earth-like atmosphere (nitrogen, oxygen, trace CO2) afloat with little effort. This means that such a ship or city wouldn't need separate balloon and living spaces; the living space itself would be buoyant.
      - lisper 11y ago
        You can handle extreme temperature fluctuations in Earth orbit because you can dump excess heat into space with radiators. That won't work inside a hot, dense CO2 atmosphere. Maybe there's some other solution to the cooling problem that I have overlooked, but I don't see any way to keep from turning into a sous-vide.
        yellowapple 11y ago
        One such approach would be to use Sterling coolers, which (IIRC) is one of the suggested approaches for surface activities on Venus. Standard refrigeration techniques should also work reasonably well. Also, why wouldn't standard heat-dumping work well in a CO2 atmosphere? If anything, it should work better; the vacuum of space is the best insulator known to man, so literally anything else would be better for heat dissipation.
        lisper 11y ago
        > Sterling coolers Doesn't matter what technology you use, you are still bound by the second law of thermodynamics. The excess heat has to go somewhere, and so unless you have a cold sink, you have to add energy. And if you're going to colonize rather than just explore then you have to add energy all the time forever. If the power fails, you die, she dies, everybody dies. > why wouldn't standard heat-dumping work well in a CO2 atmosphere That depends on what you mean by "standard heat dumping". In space, you can radiate heat into the cosmic background radiation, which is the ultimate cold sink. It's about 3K, which is almost always colder than you want to be [1], so in space you get cooling for free. If you're inside a dense atmosphere, radiative cooling doesn't work. (There's a reason they're called "greenhouse gasses"). You have to dump the heat into the environment, which is hotter than the temperature you want to maintain, so you're fighting the second law, so you have to add energy. At the altitudes we're talking about here, you're maintaining a gradient of 30-40C. That's huge. It's not impossible (the artificial ski slope in Dubai maintains a similar gradient) but it takes a tremendous amount of energy. Where are you going to get it? --- [1] There are some cases where you need active cooling in space, for example, if you're running an infrared sensor on a telescope. Those have to be actively cooled, usually with a supply of liquid helium that is launched with the spacecraft. But see: http://jwst.nasa.gov/sunshield.html http://jwst.nasa.gov/sunshield.html for an example of what has to be done to keep an infrared telescope cool for a long mission.

lisper 11y ago

We're talking about colonization here, not exploration. That's not even a practical plan to make more living space here on earth, let alone on Venus.

yellowapple 11y ago
It's actually not all that impractical. Venus' atmosphere is much more dense than Earth's; floating in it should be quite a bit easier.
- lisper 11y ago
  > Venus' atmosphere is much more dense than Earth's Won't help: "The ships would float 50 kilometers (31 miles) above the planet’s surface. Here, there would be only one atmosphere of pressure, and the temperature would be a reasonable 75"C." 75 C is 160 F. Granted that's cool enough to keep water from boiling, but unless you're a tubeworm you're probably not going to be happy living there without air conditioning.
  - yellowapple 11y ago
    Considering the temperature fluctuations faced routinely even in Earth's own orbit, 75 degrees Celsius is actually very reasonable. It's certainly no less comfortable than Mars' rather frigid climate. If anything, the greater hazard would be the toxic and corrosive clouds of sulfuric acid that blanket the Venusian surface. The density, however, more has to do with whether or not it's feasible to build a permanent settlement in Venus' atmosphere. It turns out that it's very feasible; Venus' carbon-dioxide-based atmosphere would be thick enough even at those altitudes to keep a "balloon" filled with an Earth-like atmosphere (nitrogen, oxygen, trace CO2) afloat with little effort. This means that such a ship or city wouldn't need separate balloon and living spaces; the living space itself would be buoyant.
    - lisper 11y ago
      You can handle extreme temperature fluctuations in Earth orbit because you can dump excess heat into space with radiators. That won't work inside a hot, dense CO2 atmosphere. Maybe there's some other solution to the cooling problem that I have overlooked, but I don't see any way to keep from turning into a sous-vide.
      - yellowapple 11y ago
        One such approach would be to use Sterling coolers, which (IIRC) is one of the suggested approaches for surface activities on Venus. Standard refrigeration techniques should also work reasonably well. Also, why wouldn't standard heat-dumping work well in a CO2 atmosphere? If anything, it should work better; the vacuum of space is the best insulator known to man, so literally anything else would be better for heat dissipation.
        lisper 11y ago
        > Sterling coolers Doesn't matter what technology you use, you are still bound by the second law of thermodynamics. The excess heat has to go somewhere, and so unless you have a cold sink, you have to add energy. And if you're going to colonize rather than just explore then you have to add energy all the time forever. If the power fails, you die, she dies, everybody dies. > why wouldn't standard heat-dumping work well in a CO2 atmosphere That depends on what you mean by "standard heat dumping". In space, you can radiate heat into the cosmic background radiation, which is the ultimate cold sink. It's about 3K, which is almost always colder than you want to be [1], so in space you get cooling for free. If you're inside a dense atmosphere, radiative cooling doesn't work. (There's a reason they're called "greenhouse gasses"). You have to dump the heat into the environment, which is hotter than the temperature you want to maintain, so you're fighting the second law, so you have to add energy. At the altitudes we're talking about here, you're maintaining a gradient of 30-40C. That's huge. It's not impossible (the artificial ski slope in Dubai maintains a similar gradient) but it takes a tremendous amount of energy. Where are you going to get it? --- [1] There are some cases where you need active cooling in space, for example, if you're running an infrared sensor on a telescope. Those have to be actively cooled, usually with a supply of liquid helium that is launched with the spacecraft. But see: http://jwst.nasa.gov/sunshield.html http://jwst.nasa.gov/sunshield.html for an example of what has to be done to keep an infrared telescope cool for a long mission.