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A Serious Conversation about the Future in Space

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Re: A Serious Conversation about the Future in Space

#61

Post by visarga »

david-given wrote: post #32
frank-weindel wrote: post #14

Earlier quoted context omitted.

Looks like someone has lost all hope for humanity and at that we should just accept our "inevitable" self-destruction. Even if the dream of colonizing mars is farfetched beyond fixing all of the problems we currently have on earth, it doesn't mean its not worth striving for. Goals like this drive people to do their best work and come up with creative solutions to problems that would otherwise never have been thought…

!Mars != !Space. Mars is a dusty, barren deathtrap of a rock that's at the bottom of a very deep hole. The only thing to do on Mars is to _be_ on Mars. It's not (plausibly) terraformable, sustaining life there will obvious continuous and hugely expensive technical input, there are no resources there worth going there for, and once you've gone there, to get back you have to climb out of a hugely deep hole. Meanwhile t…

> sustaining life there will obvious continuous and hugely expensive technical input

Not if we send first our 3D printers and deep learning based robots that we are going to build soon. We just need to build a replicator and send it there to terraform for us.

Re: A Serious Conversation about the Future in Space

#62

Post by visarga »

AndrewKemendo wrote: post #45
benihana wrote: post #39

Earlier quoted context omitted.

https://www.youtube.com/watch?v=zc4HL_-VT2Y We (complex life) couldn't recover from something like that. Maybe simple life could hide deep in the earth and emerge when it's safe thousands of years later.

Makes my point. After that event you now have an earth that is about as habitable as Mars is today. That is also the absolute worst case scenario that is theoretically possible, literally a one in a billion year event. That is something we can plan for and build for now with: Anti-Asteroid technology, "Fallout" shelters/biodomes etc... Or hell, a fucking Dyson sphere (or series of them) is a million times easier/bett…

Why bother with planets when we could live in space. There are lots of asteroids filled with materials floating around. If we make it economically feasible to do asteroid mining, we could expand population 1000 times. Think of what would a constellation of self-sufficient asteroid colonies and ships do for human freedom.

Re: A Serious Conversation about the Future in Space

#63

Post by yellowapple »

lisper wrote: post #58
yellowapple wrote: post #54

Earlier quoted context omitted.

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.

> 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.

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.

Re: A Serious Conversation about the Future in Space

#64

Post by lisper »

yellowapple wrote: post #63
lisper wrote: post #58

Earlier quoted context omitted.

> 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.

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 set…

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.

Re: A Serious Conversation about the Future in Space

#65

Post by mixmastamyk »

AndrewKemendo wrote: post #60
mixmastamyk wrote: post #49

Earlier quoted context omitted.

A red-giant Sol might be.

In which case no place in our Solar system is safe.

The outer planets will be safer longer. It is not known if Earth would be engulfed or not, but presumably Mars will be safer longer and might possibly survive.

Re: A Serious Conversation about the Future in Space

#66

Post by yellowapple »

lisper wrote: post #64
yellowapple wrote: post #63

Earlier quoted context omitted.

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 set…

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.

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.

Re: A Serious Conversation about the Future in Space

#67

Post by lisper »

yellowapple wrote: post #66
lisper wrote: post #64

Earlier quoted context omitted.

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.

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 di…

> 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

for an example of what has to be done to keep an infrared telescope cool for a long mission.

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