6 ms·

So what are the other things? You said he glossed over them and didn't mention a single one.

aorloff 8mo ago
Reliably and efficiently transport energy generated in space back to earth, for starters Or let me guess, its going to be profitable to mine crypto in space (thereby solving the problem of transporting the "work" back to earth)
- mkull 8mo ago
  Why would you transfer the energy to earth? The energy powers ai compute = $
  - Sparyjerry 8mo ago
    Dead on, You can transmit data to and from space and have the compute completed at potentially fractions of the cost.
    - aorloff 8mo ago
      Tell me about your cooling medium in space
      - rlt 8mo ago
        A large piece of aluminum with ammonia pumped through it?
        aorloff 8mo ago
        Nothing about this is sounding economically competitive with ground based solutions
        pyrale 8mo ago
        Where does the heat collected by amminia get evacuated?
        littlestymaar 8mo ago
        Through thermal radiation, it's called radiative cooling. But it's not trivial indeed, especially if you want good power density in your space data center.
        MPSimmons 8mo ago
        Datacenter capacity (and thus heat) grows by the cube law, but the ability to radiate heat grows by the square law, so it seems like it would be advantageous to have a bunch of smaller satellites, if you were concerned about cooling them.
        pyrale 8mo ago
        > it would be advantageous to have a bunch of smaller satellites, if you were concerned about cooling them. ...That's only relevant if you start from the position that your datacenters have to be space. You could already make smaller datacenters on earth, and still have better cooling, if you were concerned about that. We don't do that because on earth it's more efficient to have one large datacenter than many small ones.
        jacquesm 8mo ago
        Right up to the radiation limit and then you'll either have to throttle your precious GPUs or you'll be melting your satellite or at least the guts of it. You're looking at an absolutely massive radiator here, many times larger than the solar panels that collect the energy to begin with.
        DoctorOetker 8mo ago
        not really, for A_radiator / A_PV = ~3; you can keep the satellite cool to about 27 deg C (300K) check my example calculation (Ctrl-F: pyramid)
        mlyle 8mo ago
        > > absolutely massive radiator here, many times larger than the solar panels > A_radiator / A_PV = ~3; Seems like you're in agreement. There's a couple more issues here-- 1. Solar panels are typically big compared to the rest of the satellite bus. How much radiator area do you need per 700W GPU at some reasonable solar panel efficiency? 2. Getting the satellite overall to an average 27C temperature doesn't necessarily keep the GPU cool; the satellite is not isothermal. My back of the envelope estimate says you need about 2.5 square meters of radiator (perhaps more) to cool a 700W GPU and the solar panel powering the GPU. You can fit about 100 of these GPUs in a typical liquid-cooled rack, so you need about 250 square meters of radiator to match one rack. And, unfortunately, you can't easily use an inflatable structure, etc, because you need to conduct or convect heat into that radiator. This assumes that you lose no additional heat in moving heat or in power conversion. And they’re going to mass a -lot-. Not that anyone would use a pyramid— you would want panels with the side facing the sun radiating too. There are plenty of surfaces that radiate more than they absorb at reasonable temperatures in sunlight.
        DoctorOetker 8mo ago
        First of all a note on my calculations: they appear very simple, and its intentional, its not actually optimized, its intended to give programmers (who enjoyed basic high school physics but not more) the insight that cooling in space while hard, is still feasible. If you look around the thread you'll find categorical statements that cooling in space is essentially impossible etc. The most efficient design and the most theoretically convincing one are not in general the same. I intentionally veer towards a configuration that shows it's possible without requiring radiating surface with an area of a square Astronomical Unit. Minimizing the physics and mathematics prerequisites results in a suboptimal but comprehensible design. This forum is not filled with physicists and engineers in the physical sciences, most commenters are programmers. To convince them I should only add the absolute minimum and configure my design to eliminate annoying integrals (for example the heat radiated by earth on the satellite is sidestepped by simply sacrificing 2 of the triangular sides of the pyramid to be mere reflectors of emissivity ~0, this way we can ignore the presence of a nearby lukewarm earth). Another example is the choice of a pyramid: it is convex and none of the surfaces are exactly parallel to the sun rays (which would result in ambiguity or doubt, or make the configuration sensitive to the exact orientation of the satellite), a more important consequence of selecting a convex shape is that we don't have to worry about heat radiated from one part of the satellite surface, being reabsorbed by another surface of the satellite (in view of the first surface), a convex shape insures no surface patch can see another surface patch of the satellite. And yes I pretend no heat is radiated by the solar panel itself, which is entirely achievable. So I intentionally sacrifice a lot of opportunities for more optimal design to show programmers (who are not trained in mathematical analysis, and not trained with physics textbook theorem-proof-theorem-proof-definition-theorem-proof-...) that physically it is not in the real of the impossible and doesn't result in absurdly high radiator/solar panel area ratios. To convince a skeptic you 1) make pessimistic suboptimal estimates with a lot of room for improvement and 2) make sure those estimates require as little math and physics as possible, just the bare minimum to qualitatively and quantitatively understand the thermodynamics of a simple example. You are asking the right questions :) Given the considerations just discussed I feel OK forwarding you to the example mini cluster in the following section: https://news.ycombinator.com/item?id=46867402 https://news.ycombinator.com/item?id=46867402 It describes a 230 kW system that can pretrain a 405B parameter model in ~17 days and is composed of 16x DGX B200 nodes, each node carrying 8x B200 GPUs. The naive but simple to understand pyramid satellite would require a square base (solar PV) side length of 30 m. This means the tip of the pyramid is ~90m away from the center of the solar panel square. This gives a general idea of a machine capable of training a 405B parameter model in 17 days. We can naively scale down from 230 kW to 700 W and conclude the square base PV side length can then be 1.66 m; and the tip being 5 m "higher". For 100 such 700 W GPU's we just multiply by 10: 16.6 m side length and the tip of the pyramid being 50 m out of the plane of the square solar panel base.
  - rlt 8mo ago
    Not sure why this is downvoted. Much cheaper to transfer data than energy.
- brd529 8mo ago
  Overview energy has done interesting work in this area.
  - _fizz_buzz_ 8mo ago
    Beaming energy always sucks. Without some very fundamental discoveries in physics nobody will every make this work economically. This isn't just an engineering problem, it's a physics problem.
    - mlyle 8mo ago
      Beaming energy does suck, but it might be something to do before we launch thousands of terawatts of GPUs to space.
- mlindner 8mo ago
  It's always better to generate electricity on the ground than attempt to beam it to the ground from space. The efficiency loss of beamed power is huge.
  - amluto 8mo ago
    The efficiency loss of nighttime is approximately 100% if we’re talking about solar energy. At least at a most basic level, it’s not totally absurd to stick some kind of power beaming contraption in space where it is mostly not shadowed by the Earth and beam power to a ground station.
    - hdjrudni 8mo ago
      Is that more or less absurd than making deals with our neighbours to share their electricity? Build some solar farms around the planet and then distribute it over wire. I honestly don't know the answer. I know there's some efficiency loss running over long wires too but I don't know what's more realistic.
      - queenkjuul 8mo ago
        There is absolutely nothing realistic about power transmission from space to earth, wired or wireless.
      - mike_hearn 8mo ago
        In theory you can do HVDC over long distances. In practice that doesn't help much. Power would normally want to run north to south (not gonna do HVDC across the oceans anytime soon), and so the terminator hits you at the same time everywhere. It's got to be batteries if you want PV at scale. The practical difficulties aren't really long distance transmission though. They're political and engineering. Spain had a massive blackout recently because a PV farm in the south west developed a timing glitch and they couldn't control the grid frequency - that nearly took out all of Europe and the power wasn't even being transmitted long distance! The level of trust you need to build a giant integrated continent-wide power grid is off the charts and it's not clear it's sustainable over the long run. E.g. the EU threatened to cut Britain's electricity supplies during Brexit as a negotiating tactic and that wasn't even war.
SergeAx 8mo ago
If we (as in "civilization") were able to produce that many solar panels, we should cover all the deserts with them. It will also shift the local climate balance towards a more habitable ecosystem, enabling first vegetation and then slowly growing the rest of the food chain.
- DoctorOetker 8mo ago
  for solar panels that are say 25% efficient, that means 75% of optical energy is turned into heat, whereas the sand had a relatively high albedo, its going to significantly heat up the local environment!
  - jacquesm 8mo ago
    That is not what 25% efficiency means for solar panels.
    - DoctorOetker 8mo ago
      care to expand on your comment? or are is this just remarking that some light was reflected?
      - jacquesm 8mo ago
        No. It is enough for me to see such a single ridiculous statement of such magnitude to discount the rest of your voluminous contributions to this thread.
        DoctorOetker 8mo ago
        I'm dumbfounded, most light incident on a solar panel is not reflected, so logically photons were absorbed, some generated useful electron hole pairs pushing current around the load loop, others recombined and produced heat. Its an entirely reasonable position in solar panel discussions to say that a 20% solar panel will heat as if 80% of the optical energy incident on the panel was turned into heat. Conservation of energy dictates that the input energy must equal the sum of the output work (useful energy) and output heat. Not sure what you are driving at here, and just calling a statement ridiculous does not explain your position.

Reliably and efficiently transport energy generated in space back to earth, for starters Or let me guess, its going to be profitable to mine crypto in space (thereby solving the problem of transporting the "work" back to earth)

mkull 8mo ago
Why would you transfer the energy to earth? The energy powers ai compute = $
- Sparyjerry 8mo ago
  Dead on, You can transmit data to and from space and have the compute completed at potentially fractions of the cost.
  - aorloff 8mo ago
    Tell me about your cooling medium in space
    - rlt 8mo ago
      A large piece of aluminum with ammonia pumped through it?
      - aorloff 8mo ago
        Nothing about this is sounding economically competitive with ground based solutions
      - pyrale 8mo ago
        Where does the heat collected by amminia get evacuated?
        littlestymaar 8mo ago
        Through thermal radiation, it's called radiative cooling. But it's not trivial indeed, especially if you want good power density in your space data center.
        MPSimmons 8mo ago
        Datacenter capacity (and thus heat) grows by the cube law, but the ability to radiate heat grows by the square law, so it seems like it would be advantageous to have a bunch of smaller satellites, if you were concerned about cooling them.
        pyrale 8mo ago
        > it would be advantageous to have a bunch of smaller satellites, if you were concerned about cooling them. ...That's only relevant if you start from the position that your datacenters have to be space. You could already make smaller datacenters on earth, and still have better cooling, if you were concerned about that. We don't do that because on earth it's more efficient to have one large datacenter than many small ones.
      - jacquesm 8mo ago
        Right up to the radiation limit and then you'll either have to throttle your precious GPUs or you'll be melting your satellite or at least the guts of it. You're looking at an absolutely massive radiator here, many times larger than the solar panels that collect the energy to begin with.
        DoctorOetker 8mo ago
        not really, for A_radiator / A_PV = ~3; you can keep the satellite cool to about 27 deg C (300K) check my example calculation (Ctrl-F: pyramid)
        mlyle 8mo ago
        > > absolutely massive radiator here, many times larger than the solar panels > A_radiator / A_PV = ~3; Seems like you're in agreement. There's a couple more issues here-- 1. Solar panels are typically big compared to the rest of the satellite bus. How much radiator area do you need per 700W GPU at some reasonable solar panel efficiency? 2. Getting the satellite overall to an average 27C temperature doesn't necessarily keep the GPU cool; the satellite is not isothermal. My back of the envelope estimate says you need about 2.5 square meters of radiator (perhaps more) to cool a 700W GPU and the solar panel powering the GPU. You can fit about 100 of these GPUs in a typical liquid-cooled rack, so you need about 250 square meters of radiator to match one rack. And, unfortunately, you can't easily use an inflatable structure, etc, because you need to conduct or convect heat into that radiator. This assumes that you lose no additional heat in moving heat or in power conversion. And they’re going to mass a -lot-. Not that anyone would use a pyramid— you would want panels with the side facing the sun radiating too. There are plenty of surfaces that radiate more than they absorb at reasonable temperatures in sunlight.
        DoctorOetker 8mo ago
        First of all a note on my calculations: they appear very simple, and its intentional, its not actually optimized, its intended to give programmers (who enjoyed basic high school physics but not more) the insight that cooling in space while hard, is still feasible. If you look around the thread you'll find categorical statements that cooling in space is essentially impossible etc. The most efficient design and the most theoretically convincing one are not in general the same. I intentionally veer towards a configuration that shows it's possible without requiring radiating surface with an area of a square Astronomical Unit. Minimizing the physics and mathematics prerequisites results in a suboptimal but comprehensible design. This forum is not filled with physicists and engineers in the physical sciences, most commenters are programmers. To convince them I should only add the absolute minimum and configure my design to eliminate annoying integrals (for example the heat radiated by earth on the satellite is sidestepped by simply sacrificing 2 of the triangular sides of the pyramid to be mere reflectors of emissivity ~0, this way we can ignore the presence of a nearby lukewarm earth). Another example is the choice of a pyramid: it is convex and none of the surfaces are exactly parallel to the sun rays (which would result in ambiguity or doubt, or make the configuration sensitive to the exact orientation of the satellite), a more important consequence of selecting a convex shape is that we don't have to worry about heat radiated from one part of the satellite surface, being reabsorbed by another surface of the satellite (in view of the first surface), a convex shape insures no surface patch can see another surface patch of the satellite. And yes I pretend no heat is radiated by the solar panel itself, which is entirely achievable. So I intentionally sacrifice a lot of opportunities for more optimal design to show programmers (who are not trained in mathematical analysis, and not trained with physics textbook theorem-proof-theorem-proof-definition-theorem-proof-...) that physically it is not in the real of the impossible and doesn't result in absurdly high radiator/solar panel area ratios. To convince a skeptic you 1) make pessimistic suboptimal estimates with a lot of room for improvement and 2) make sure those estimates require as little math and physics as possible, just the bare minimum to qualitatively and quantitatively understand the thermodynamics of a simple example. You are asking the right questions :) Given the considerations just discussed I feel OK forwarding you to the example mini cluster in the following section: https://news.ycombinator.com/item?id=46867402 https://news.ycombinator.com/item?id=46867402 It describes a 230 kW system that can pretrain a 405B parameter model in ~17 days and is composed of 16x DGX B200 nodes, each node carrying 8x B200 GPUs. The naive but simple to understand pyramid satellite would require a square base (solar PV) side length of 30 m. This means the tip of the pyramid is ~90m away from the center of the solar panel square. This gives a general idea of a machine capable of training a 405B parameter model in 17 days. We can naively scale down from 230 kW to 700 W and conclude the square base PV side length can then be 1.66 m; and the tip being 5 m "higher". For 100 such 700 W GPU's we just multiply by 10: 16.6 m side length and the tip of the pyramid being 50 m out of the plane of the square solar panel base.
- rlt 8mo ago
  Not sure why this is downvoted. Much cheaper to transfer data than energy.
brd529 8mo ago
Overview energy has done interesting work in this area.
- _fizz_buzz_ 8mo ago
  Beaming energy always sucks. Without some very fundamental discoveries in physics nobody will every make this work economically. This isn't just an engineering problem, it's a physics problem.
  - mlyle 8mo ago
    Beaming energy does suck, but it might be something to do before we launch thousands of terawatts of GPUs to space.
mlindner 8mo ago
It's always better to generate electricity on the ground than attempt to beam it to the ground from space. The efficiency loss of beamed power is huge.
- amluto 8mo ago
  The efficiency loss of nighttime is approximately 100% if we’re talking about solar energy. At least at a most basic level, it’s not totally absurd to stick some kind of power beaming contraption in space where it is mostly not shadowed by the Earth and beam power to a ground station.
  - hdjrudni 8mo ago
    Is that more or less absurd than making deals with our neighbours to share their electricity? Build some solar farms around the planet and then distribute it over wire. I honestly don't know the answer. I know there's some efficiency loss running over long wires too but I don't know what's more realistic.
    - queenkjuul 8mo ago
      There is absolutely nothing realistic about power transmission from space to earth, wired or wireless.
    - mike_hearn 8mo ago
      In theory you can do HVDC over long distances. In practice that doesn't help much. Power would normally want to run north to south (not gonna do HVDC across the oceans anytime soon), and so the terminator hits you at the same time everywhere. It's got to be batteries if you want PV at scale. The practical difficulties aren't really long distance transmission though. They're political and engineering. Spain had a massive blackout recently because a PV farm in the south west developed a timing glitch and they couldn't control the grid frequency - that nearly took out all of Europe and the power wasn't even being transmitted long distance! The level of trust you need to build a giant integrated continent-wide power grid is off the charts and it's not clear it's sustainable over the long run. E.g. the EU threatened to cut Britain's electricity supplies during Brexit as a negotiating tactic and that wasn't even war.

SergeAx 8mo ago

If we (as in "civilization") were able to produce that many solar panels, we should cover all the deserts with them. It will also shift the local climate balance towards a more habitable ecosystem, enabling first vegetation and then slowly growing the rest of the food chain.

DoctorOetker 8mo ago
for solar panels that are say 25% efficient, that means 75% of optical energy is turned into heat, whereas the sand had a relatively high albedo, its going to significantly heat up the local environment!
- jacquesm 8mo ago
  That is not what 25% efficiency means for solar panels.
  - DoctorOetker 8mo ago
    care to expand on your comment? or are is this just remarking that some light was reflected?
    - jacquesm 8mo ago
      No. It is enough for me to see such a single ridiculous statement of such magnitude to discount the rest of your voluminous contributions to this thread.
      - DoctorOetker 8mo ago
        I'm dumbfounded, most light incident on a solar panel is not reflected, so logically photons were absorbed, some generated useful electron hole pairs pushing current around the load loop, others recombined and produced heat. Its an entirely reasonable position in solar panel discussions to say that a 20% solar panel will heat as if 80% of the optical energy incident on the panel was turned into heat. Conservation of energy dictates that the input energy must equal the sum of the output work (useful energy) and output heat. Not sure what you are driving at here, and just calling a statement ridiculous does not explain your position.