3 ms·

> Existence of supposedly cheap land somewhere (with not much infrastructure usually) doesn't help as you put your computer nodes into a datacenter building wit

by ben_w 6mo ago

> Existence of supposedly cheap land somewhere (with not much infrastructure usually) doesn't help as you put your computer nodes into a datacenter building with all the required infrastructure which cost more than the SV land on a sq foot basis. This is a terrible argument, given that space has zero infrastructure. Once you can break a data centre into a million sub-units and spread them over a sun-synchronous orbit or ten and cool them radiatively, you can also spread those sub-units on desert land with no water or electricity and cool them radiatively. The units on the ground would look about 6x larger because ground experiences night and even deserts have clouds, but their PV also lasts 30+ years rather than burning up every 5 years or so, which means the factory making the PV to supply them is the same size. The main thing you save on is batteries. Tesla already supplies enough batteries that it can manage a "mere" one million 25kW compute modules. > And that is without consideration of how powerful a weapon is the energy generated by a humongous field of solar panels in space. Remember Reagan's Star Wars? Nuclear explosions as a source of power for the direct energy weapons like lasers, etc. Well, you wouldn't need the nukes anymore. Just redirect a bit of power from your compute nodes. And as i already wrote, the large transnational companies will have to take care about their own defense themselves https://news.ycombinator.com/item?id=47981423 https://news.ycombinator.com/item?id=47981423 - one more "feudal" aspect of the coming techno-feudalism. While true, attacking up is easier than attacking down. Anything on the ground has a massive heat-sink all around it, the stuff in space does not. Right now, an attack up is already only limited by the supply of adaptive optics to get through atmospheric distortion.

trhway 6mo ago
>you can also spread those sub-units on desert land with no water or electricity and cool them radiatively. no, you can't. >attacking up is easier than attacking down. no.
- ben_w 6mo ago
  Asserting the contrary is not an argument. Nothing prevents SpaceX or anyone else from buying up the right to put these things on cheap desert land. They don't even need to own the land, just the right to wheel these things out on a trailer or a helicopter and leave them there. A desert is significantly less harsh than space. If your radiator is sized for space, it's overkill in an atmosphere. And for your edit: https://www.youtube.com/watch?v=xNmbvaUzC8Q https://www.youtube.com/watch?v=xNmbvaUzC8Q
  - trhway 6mo ago
    >If your radiator is sized for space, it's overkill in an atmosphere. no. Again totally wrong. The 20-40C air surrounding the radiator radiates at the radiator too. This is why a human immediately gets stone cold in space while not in the atmosphere - our body radiates away about 900W and receives 800W+ back from the atmosphere - our internal heat 'generation has to cover only the difference - less than 100W usually. You probably meant forced convection cooling. That requires additional machinery. And that additional machinery is a significant part why ground based datacenters such expensive to build and operate. To the comment below: >The planet underneath anything in low orbit also does this, making this argument irrelevant. no. Again, totally wrong. You've just stated that a human in LEO wouldn't get immediately cold when exposed to space. Just think about it for a second. And after that plug the numbers in thermodynamic calculator. You'll see your error. >Likewise, the fact that convection exists even without the adjective "forced". no. Again, wrong. Non-forced convection is pretty small. Use the calculator. And you'll understand why datacenters use forced convection.
    - ben_w 6mo ago
      The planet underneath anything in low orbit also does this, making this argument irrelevant. There's even cheap paints specifically made to be most emissive in the wavelength window the atmosphere is mostly transparent to rather than itself emitting at. As does the fact that humans are only slightly warmer than their surroundings. A human-sized object at the operating temperature of a GPU would have a net radiative loss in Earth's atmosphere of around 0.9-1.3 kW. Likewise, the fact that convection exists even without the adjective "forced". Again, replace a human with an identically shaped android at maximum GPU operating temperatures of 80-100 °C, normal (non-forced) convection goes from ~117 W (human) to 0.9-1.3 kW (80 °C) to 1.2-2 kW (100 °C).
    - ben_w 6mo ago
      > > The planet underneath anything in low orbit also does this, making this argument irrelevant. > no. Again, totally wrong. You've just stated that a human in LEO wouldn't get immediately cold when exposed to space. Just think about it for a second. And after that plug the numbers in thermodynamic calculator. You'll see your error. I already did before previous comment. I was also considering adding "don't forget evaporative cooling for human bodily fluids" to previous comment, but it seemed an irrelevant tangent to discussing data centres. Now, if you plug the mass of a human and the specific heat capacity of water into a thermodynamic calculator, tell me how long it would take for a human to cool one degree? https://www.wolframalpha.com/input?i=%2870+Kg+*+%28specific+heat+water%29%29+%2F+1000+W https://www.wolframalpha.com/input?i=%2870+Kg+*+%28specific+... And that's with the 1 kW radiative losses from being in shadow far enough from Earth to not get meaningful thermal radiation from the planet itself. Even at 500 km, thermal radiation from Earth will still add 200 W/m^2. This is comparable to the thermal paint previously mentioned, whose peak emissivity (and by extension absorption) is chosen to be a different wavelength than the thermal emission of air temperature. > >Likewise, the fact that convection exists even without the adjective "forced". > no. Again, wrong. Non-forced convection is pretty small. Use the calculator. I did, for both humans and GPUs, you saw the results. Humans are the wrong reference class. In your own words, "Just think about it for a second": a human in humid 40°C air is in immediate danger because then all the sources of cooling have been blocked off. Radiation becomes balanced, I said humid to block off evaporation. Conduction and convection there have the same problem there as radiation. A GPU wouldn't have a problem with 40°C ambient, because it will still be radiating heat, conducting heat, and by conducting heat to the air specifically also convecting it away.

by ben_w 6mo ago

trhway 6mo ago

>you can also spread those sub-units on desert land with no water or electricity and cool them radiatively. no, you can't. >attacking up is easier than attacking down. no.

ben_w 6mo ago
Asserting the contrary is not an argument. Nothing prevents SpaceX or anyone else from buying up the right to put these things on cheap desert land. They don't even need to own the land, just the right to wheel these things out on a trailer or a helicopter and leave them there. A desert is significantly less harsh than space. If your radiator is sized for space, it's overkill in an atmosphere. And for your edit: https://www.youtube.com/watch?v=xNmbvaUzC8Q https://www.youtube.com/watch?v=xNmbvaUzC8Q
- trhway 6mo ago
  >If your radiator is sized for space, it's overkill in an atmosphere. no. Again totally wrong. The 20-40C air surrounding the radiator radiates at the radiator too. This is why a human immediately gets stone cold in space while not in the atmosphere - our body radiates away about 900W and receives 800W+ back from the atmosphere - our internal heat 'generation has to cover only the difference - less than 100W usually. You probably meant forced convection cooling. That requires additional machinery. And that additional machinery is a significant part why ground based datacenters such expensive to build and operate. To the comment below: >The planet underneath anything in low orbit also does this, making this argument irrelevant. no. Again, totally wrong. You've just stated that a human in LEO wouldn't get immediately cold when exposed to space. Just think about it for a second. And after that plug the numbers in thermodynamic calculator. You'll see your error. >Likewise, the fact that convection exists even without the adjective "forced". no. Again, wrong. Non-forced convection is pretty small. Use the calculator. And you'll understand why datacenters use forced convection.
  - ben_w 6mo ago
    The planet underneath anything in low orbit also does this, making this argument irrelevant. There's even cheap paints specifically made to be most emissive in the wavelength window the atmosphere is mostly transparent to rather than itself emitting at. As does the fact that humans are only slightly warmer than their surroundings. A human-sized object at the operating temperature of a GPU would have a net radiative loss in Earth's atmosphere of around 0.9-1.3 kW. Likewise, the fact that convection exists even without the adjective "forced". Again, replace a human with an identically shaped android at maximum GPU operating temperatures of 80-100 °C, normal (non-forced) convection goes from ~117 W (human) to 0.9-1.3 kW (80 °C) to 1.2-2 kW (100 °C).
  - ben_w 6mo ago
    > > The planet underneath anything in low orbit also does this, making this argument irrelevant. > no. Again, totally wrong. You've just stated that a human in LEO wouldn't get immediately cold when exposed to space. Just think about it for a second. And after that plug the numbers in thermodynamic calculator. You'll see your error. I already did before previous comment. I was also considering adding "don't forget evaporative cooling for human bodily fluids" to previous comment, but it seemed an irrelevant tangent to discussing data centres. Now, if you plug the mass of a human and the specific heat capacity of water into a thermodynamic calculator, tell me how long it would take for a human to cool one degree? https://www.wolframalpha.com/input?i=%2870+Kg+*+%28specific+heat+water%29%29+%2F+1000+W https://www.wolframalpha.com/input?i=%2870+Kg+*+%28specific+... And that's with the 1 kW radiative losses from being in shadow far enough from Earth to not get meaningful thermal radiation from the planet itself. Even at 500 km, thermal radiation from Earth will still add 200 W/m^2. This is comparable to the thermal paint previously mentioned, whose peak emissivity (and by extension absorption) is chosen to be a different wavelength than the thermal emission of air temperature. > >Likewise, the fact that convection exists even without the adjective "forced". > no. Again, wrong. Non-forced convection is pretty small. Use the calculator. I did, for both humans and GPUs, you saw the results. Humans are the wrong reference class. In your own words, "Just think about it for a second": a human in humid 40°C air is in immediate danger because then all the sources of cooling have been blocked off. Radiation becomes balanced, I said humid to block off evaporation. Conduction and convection there have the same problem there as radiation. A GPU wouldn't have a problem with 40°C ambient, because it will still be radiating heat, conducting heat, and by conducting heat to the air specifically also convecting it away.