8 ms·

This borders on science fiction. 88,000-and 1-million satellite clusters (as claimed in your link) are hard to take seriously, especially with the possibility o

This borders on science fiction. 88,000-and 1-million satellite clusters (as claimed in your link) are hard to take seriously, especially with the possibility of Kessler Syndrome. Also: 1. How do you cool your chips? Vacuum is a thermal insulator, so radiators are required to remove heat. nVidia (or even ASICs) require much and specialised cooling. 2. How does one radiation harden a H100? 3. I'm also seeing where TCO for these are 78x their terrestrial equivalents [0]. Is that financial sustainable? And there still remain issues with power supply, regulations, and bandwidth. This feels more like a thought experiment rather than an actual serious engineering or business case. [0] https://www.abiresearch.com/blog/data-centers-in-space https://www.abiresearch.com/blog/data-centers-in-space

alephnerd 2mo ago
The projections are questionable, but this is something the US and China are experimenting with as well. 1 and 2 are still open questions, but these are not aimed to be commercial grade DCs - this is basically edge compute (think a handful of racks). 3 is not a problem for defense usecases. (EDIT: Discussion here seems to point out that data OP is using might be flawed [1]). Ignoring the fact that just about every orbital data center startup in the US is funded by IQT and China's CMF has been doing something similar is bad from a defense perspective. Based on dealflow, these aren't being targeted for consumer usecases in the short-term and whoever has been saying that is misleading. > especially with the possibility of Kessler Syndrome... India, Russia, China, and the US don't care about Kessler Syndrome - they have already launched and deployed ASATs. This also comes after India and China had a near collision in 2024 that was treated as an offensive action [0]. [0] - https://www.bloomberg.com/news/articles/2025-09-22/india-plans-bodyguard-satellites-after-risky-orbital-near-miss https://www.bloomberg.com/news/articles/2025-09-22/india-pla... [1] - https://news.ycombinator.com/item?id=49039873 https://news.ycombinator.com/item?id=49039873
- OneDonOne 2mo ago
  This reminds me of the railgun. Basic math and physics tells us that not only would the (very expensive) barrels wear out very quickly, but that it would have had to be fitted on on a nuclear-powered pocket battlecruiser. Worse, the technology for firing any meaningful payloads from an electric gun (8" Small Diameter Bomb equivalents, guided, airburst, incendiary) simply does not exist. Same as with Musk's California Vacuum Tunnel (which diverted attention from passenger rail). And his Neuralink. In the 1980s, it was nuclear pumped space-based lasers and Soviet particle beam weapons. All of the above can be debunked with 2 years undergrad physics and a Casio calculator. Yet they were still taken seriously by high-level politicians and business, some of whom were deeply connected with the military-industrial complex. People have shrugging of questions like 1 and 2, only for 3 to hit them very hard. But we will see if they can launch 600 of these satellites as they claim.
  - alephnerd 2mo ago
    As raynier and pfdietz pointed out [0], the assumptions you are using aren't necessarily correct. [0] - https://news.ycombinator.com/item?id=49039873 https://news.ycombinator.com/item?id=49039873
    - OneDonOne 2mo ago
      Ah yes. The heat pump. My response: Carnot's theorem and refridgeration cycles rear their head. Your heat pump still needs power to pump heat uphill., negating any savings from a smaller radiator. And what happens when you shrink a radiator? It becomes a high temperature radiator, meaning the GPU must operate outside its operational tmperature of about 70 degrees C. So small radiator = big pump + extra solar panels and batteries + dead GPU Also, how do you deal with the added cost and complexity for the solar tracking mechanisms for the "edge-on-to-the-Sun" radiator?
      - pfdietz 2mo ago
        Yes, that was your response. It was a terrible and obviously invalid response, as I explained. You never explained why the GPU temperature had to increase. Could you explain that now? The GPU would be on the cold side of the heat pump, not the hot side. > Also, how do you deal with the added cost and complexity for the solar tracking mechanisms for the "edge-on-to-the-Sun" radiator? We ignore that issue, because we were debunking a bad argument about "the laws of physics". The laws of physics say nothing about budgets or complexity.
  - selimthegrim 2mo ago
    Soviets definitely experimented with airborne CO2 lasers.
    - OneDonOne 2mo ago
      It just goes to show magical thinking isn't just an American thing.
- AlotOfReading 2mo ago
  3 is not a problem for defense usecases. Cost is the critical constraint for defense programs. Yes, militaries spend a shit-ton of money, but that's usually in a penny wise and pound foolish way. A dollar spent on your project is a dollar that's not spent on the innumerable things generals think are critical to their future wars like boondoggles, missiles, planes, ships, missile defense systems, etc. The exception is if you're one of those rare projects. A starlink type constellation or launch capabilities certainly could be, but it's hard to imagine generals getting excited about compute in space just for the sake of it.
  - taneq 2mo ago
    It is critical to avoid a boondoggle gap.
NetMageSCW 2mo ago
Explain to the class why Kessler Syndrome isn’t possible with large LEO constellations.
- crewindream 2mo ago
  In a form of a question: does low earth orbit has big enough drag to be effectively do automatic cleanup every several years?
  - nine_k 2mo ago
    The answer is positive. LEO satellites need orbital corrections every few weeks, and some, several times a week.
- mayama 2mo ago
  In case of collision in LEO, wouldn't the debris have chance to go high altitude and cause further collisions?
  - cyberax 2mo ago
    No. It'll stay in essentially the same orbit. During collision, some of the energy will be lost, so the fragments will necessarily have a lower orbit. The only thing that can accelerate fragments into a substantially higher orbit is the energy of elastic deformation of material during the explosion.
    - lanstin 2mo ago
      Can’t two solid object with equal kinetic energy collide in such a way that most of the energy goes into one of them, giving it a velocity that boosts its orbit while the other one has lower velocity and de-orbits? Or one object explode into two fragments, equal and opposite relative velocity, again pushing the one half into a higher orbit and de-orbiting the other half? (Honest question, math major, never took orbital mechanics or played KSP much).
taneq 2mo ago
(1) seems to be the big question to me. Surely it would be much cheaper to simply stick a data centre up in the mountains somewhere, low enough to be fairly easy to reach but high enough to be nice and chilly?
Alive-in-2025 2mo ago
Yeah, there's no solution for heat dissolution at this time. You can run a few cpus in space, you are a few seconds closer to the data to figure out something basic, but you cant do that much calculation. If you do much cpu intensive stuff, you just get hot quickly and you can't dissipate the heat. I'm sure new ways to cool down will be developed, but there's not even any experimental techniques, right?
- avmich 2mo ago
  ISS collects ~250 kW solar power. All of that needs eventually to be dissipated - the energy removed by communication radiowaves is small. ISS routinely handles this thermal question for decades. There is nothing magical with cooling in space. Just a different environment - a rather well studied already, we send satellites to space for some 70 years almost. Saying there is no solution is incorrect - we have options, we have numbers, we can point to concrete questions and answers.
  - itsbczurstupid 2mo ago
    [dead]
holoduke 2mo ago
Why do you need radiation hardening? We don't need hyper deterministic systems in those setups.
- amluto 2mo ago
  You need your chip to not completely fail. Latch-up can destroy things. A complete failure of a SERDES may dramatically reduce the utility of the whole system.
LargoLasskhyfv 2mo ago
1. By using some form of liquid droplet radiator, as described in these: https://en.wikipedia.org/wiki/Liquid_droplet_radiator https://en.wikipedia.org/wiki/Liquid_droplet_radiator https://ntrs.nasa.gov/citations/19850005591 https://ntrs.nasa.gov/citations/19850005591 https://ntrs.nasa.gov/citations/19810062992 https://ntrs.nasa.gov/citations/19810062992 https://spectrum.ieee.org/orbital-data-centers-heat https://spectrum.ieee.org/orbital-data-centers-heat 2. By producing them on intel 18A, like Starfire: https://duckduckgo.com/?q=intel+foundry+18A+starfire https://duckduckgo.com/?q=intel+foundry+18A+starfire ( Or going for different substrates, like Gallium-arsenides, Gallium-nitrides, Silicon on Sapphire, by using https://en.wikipedia.org/wiki/Heterojunction_bipolar_transistor https://en.wikipedia.org/wiki/Heterojunction_bipolar_transis... on https://en.wikipedia.org/wiki/Indium_phosphide https://en.wikipedia.org/wiki/Indium_phosphide 's , enabling insane speeds & photonics. To be fabbed here, possibly: https://www.nist.gov/news-events/news/2026/06/department-commerces-chips-program-announces-letter-intent-coherent-50 https://www.nist.gov/news-events/news/2026/06/department-com... Or whichever other new metamaterial may come along. ) Now imagine the medium of these liquid droplets to directly flow through micro-capillaries in on-die cooling channels. Good Morning! Ring, Ding, Ding, Rrrrriiiinnnnng!
TeMPOraL 2mo ago
> 1. How do you cool your chips? Vacuum is a thermal insulator, so radiators are required to remove heat. This is space 101 and honestly, at this point, I consider bringing this up as disqualifying from giving criticism on the topic. > nVidia (or even ASICs) require much and specialised cooling. Whatever. They generate N kW of heat, you need to shed N kW of heat, and you need to fit that within your budget. End of worry. Pro tip: if you can slice your problem so that individual satellite needs to shed less than M kW of heat, where M corresponds to how much heat some existing, deployed satellite platform handles, you can just do your initial design around that satellite platform, replacing the "business payload" with yours. This is e.g. how the unfairly criticized recent "satellite swarm TPUs" paper from Google handled it. Everyone who brought up cooling revealed themselves as not having read the first page and not having thought about it seriously for more than 30 seconds. > 2. How does one radiation harden a H100? See that paper for some ideas and considerations, as this is part of what they focused on, after solving cooling by sizing the per-satellite payload power needs to Starlink.

alephnerd 2mo ago

The projections are questionable, but this is something the US and China are experimenting with as well. 1 and 2 are still open questions, but these are not aimed to be commercial grade DCs - this is basically edge compute (think a handful of racks). 3 is not a problem for defense usecases. (EDIT: Discussion here seems to point out that data OP is using might be flawed [1]). Ignoring the fact that just about every orbital data center startup in the US is funded by IQT and China's CMF has been doing something similar is bad from a defense perspective. Based on dealflow, these aren't being targeted for consumer usecases in the short-term and whoever has been saying that is misleading. > especially with the possibility of Kessler Syndrome... India, Russia, China, and the US don't care about Kessler Syndrome - they have already launched and deployed ASATs. This also comes after India and China had a near collision in 2024 that was treated as an offensive action [0]. [0] - https://www.bloomberg.com/news/articles/2025-09-22/india-plans-bodyguard-satellites-after-risky-orbital-near-miss https://www.bloomberg.com/news/articles/2025-09-22/india-pla... [1] - https://news.ycombinator.com/item?id=49039873 https://news.ycombinator.com/item?id=49039873

OneDonOne 2mo ago
This reminds me of the railgun. Basic math and physics tells us that not only would the (very expensive) barrels wear out very quickly, but that it would have had to be fitted on on a nuclear-powered pocket battlecruiser. Worse, the technology for firing any meaningful payloads from an electric gun (8" Small Diameter Bomb equivalents, guided, airburst, incendiary) simply does not exist. Same as with Musk's California Vacuum Tunnel (which diverted attention from passenger rail). And his Neuralink. In the 1980s, it was nuclear pumped space-based lasers and Soviet particle beam weapons. All of the above can be debunked with 2 years undergrad physics and a Casio calculator. Yet they were still taken seriously by high-level politicians and business, some of whom were deeply connected with the military-industrial complex. People have shrugging of questions like 1 and 2, only for 3 to hit them very hard. But we will see if they can launch 600 of these satellites as they claim.
- alephnerd 2mo ago
  As raynier and pfdietz pointed out [0], the assumptions you are using aren't necessarily correct. [0] - https://news.ycombinator.com/item?id=49039873 https://news.ycombinator.com/item?id=49039873
  - OneDonOne 2mo ago
    Ah yes. The heat pump. My response: Carnot's theorem and refridgeration cycles rear their head. Your heat pump still needs power to pump heat uphill., negating any savings from a smaller radiator. And what happens when you shrink a radiator? It becomes a high temperature radiator, meaning the GPU must operate outside its operational tmperature of about 70 degrees C. So small radiator = big pump + extra solar panels and batteries + dead GPU Also, how do you deal with the added cost and complexity for the solar tracking mechanisms for the "edge-on-to-the-Sun" radiator?
    - pfdietz 2mo ago
      Yes, that was your response. It was a terrible and obviously invalid response, as I explained. You never explained why the GPU temperature had to increase. Could you explain that now? The GPU would be on the cold side of the heat pump, not the hot side. > Also, how do you deal with the added cost and complexity for the solar tracking mechanisms for the "edge-on-to-the-Sun" radiator? We ignore that issue, because we were debunking a bad argument about "the laws of physics". The laws of physics say nothing about budgets or complexity.
- selimthegrim 2mo ago
  Soviets definitely experimented with airborne CO2 lasers.
  - OneDonOne 2mo ago
    It just goes to show magical thinking isn't just an American thing.
AlotOfReading 2mo ago
3 is not a problem for defense usecases. Cost is the critical constraint for defense programs. Yes, militaries spend a shit-ton of money, but that's usually in a penny wise and pound foolish way. A dollar spent on your project is a dollar that's not spent on the innumerable things generals think are critical to their future wars like boondoggles, missiles, planes, ships, missile defense systems, etc. The exception is if you're one of those rare projects. A starlink type constellation or launch capabilities certainly could be, but it's hard to imagine generals getting excited about compute in space just for the sake of it.
- taneq 2mo ago
  It is critical to avoid a boondoggle gap.

NetMageSCW 2mo ago

Explain to the class why Kessler Syndrome isn’t possible with large LEO constellations.

crewindream 2mo ago
In a form of a question: does low earth orbit has big enough drag to be effectively do automatic cleanup every several years?
- nine_k 2mo ago
  The answer is positive. LEO satellites need orbital corrections every few weeks, and some, several times a week.
mayama 2mo ago
In case of collision in LEO, wouldn't the debris have chance to go high altitude and cause further collisions?
- cyberax 2mo ago
  No. It'll stay in essentially the same orbit. During collision, some of the energy will be lost, so the fragments will necessarily have a lower orbit. The only thing that can accelerate fragments into a substantially higher orbit is the energy of elastic deformation of material during the explosion.
  - lanstin 2mo ago
    Can’t two solid object with equal kinetic energy collide in such a way that most of the energy goes into one of them, giving it a velocity that boosts its orbit while the other one has lower velocity and de-orbits? Or one object explode into two fragments, equal and opposite relative velocity, again pushing the one half into a higher orbit and de-orbiting the other half? (Honest question, math major, never took orbital mechanics or played KSP much).

taneq 2mo ago

(1) seems to be the big question to me. Surely it would be much cheaper to simply stick a data centre up in the mountains somewhere, low enough to be fairly easy to reach but high enough to be nice and chilly?

Alive-in-2025 2mo ago

Yeah, there's no solution for heat dissolution at this time. You can run a few cpus in space, you are a few seconds closer to the data to figure out something basic, but you cant do that much calculation. If you do much cpu intensive stuff, you just get hot quickly and you can't dissipate the heat. I'm sure new ways to cool down will be developed, but there's not even any experimental techniques, right?

avmich 2mo ago
ISS collects ~250 kW solar power. All of that needs eventually to be dissipated - the energy removed by communication radiowaves is small. ISS routinely handles this thermal question for decades. There is nothing magical with cooling in space. Just a different environment - a rather well studied already, we send satellites to space for some 70 years almost. Saying there is no solution is incorrect - we have options, we have numbers, we can point to concrete questions and answers.
- itsbczurstupid 2mo ago
  [dead]

holoduke 2mo ago

Why do you need radiation hardening? We don't need hyper deterministic systems in those setups.

amluto 2mo ago
You need your chip to not completely fail. Latch-up can destroy things. A complete failure of a SERDES may dramatically reduce the utility of the whole system.

LargoLasskhyfv 2mo ago

1. By using some form of liquid droplet radiator, as described in these: https://en.wikipedia.org/wiki/Liquid_droplet_radiator https://en.wikipedia.org/wiki/Liquid_droplet_radiator https://ntrs.nasa.gov/citations/19850005591 https://ntrs.nasa.gov/citations/19850005591 https://ntrs.nasa.gov/citations/19810062992 https://ntrs.nasa.gov/citations/19810062992 https://spectrum.ieee.org/orbital-data-centers-heat https://spectrum.ieee.org/orbital-data-centers-heat 2. By producing them on intel 18A, like Starfire: https://duckduckgo.com/?q=intel+foundry+18A+starfire https://duckduckgo.com/?q=intel+foundry+18A+starfire ( Or going for different substrates, like Gallium-arsenides, Gallium-nitrides, Silicon on Sapphire, by using https://en.wikipedia.org/wiki/Heterojunction_bipolar_transistor https://en.wikipedia.org/wiki/Heterojunction_bipolar_transis... on https://en.wikipedia.org/wiki/Indium_phosphide https://en.wikipedia.org/wiki/Indium_phosphide 's , enabling insane speeds & photonics. To be fabbed here, possibly: https://www.nist.gov/news-events/news/2026/06/department-commerces-chips-program-announces-letter-intent-coherent-50 https://www.nist.gov/news-events/news/2026/06/department-com... Or whichever other new metamaterial may come along. ) Now imagine the medium of these liquid droplets to directly flow through micro-capillaries in on-die cooling channels. Good Morning! Ring, Ding, Ding, Rrrrriiiinnnnng!

TeMPOraL 2mo ago

> 1. How do you cool your chips? Vacuum is a thermal insulator, so radiators are required to remove heat. This is space 101 and honestly, at this point, I consider bringing this up as disqualifying from giving criticism on the topic. > nVidia (or even ASICs) require much and specialised cooling. Whatever. They generate N kW of heat, you need to shed N kW of heat, and you need to fit that within your budget. End of worry. Pro tip: if you can slice your problem so that individual satellite needs to shed less than M kW of heat, where M corresponds to how much heat some existing, deployed satellite platform handles, you can just do your initial design around that satellite platform, replacing the "business payload" with yours. This is e.g. how the unfairly criticized recent "satellite swarm TPUs" paper from Google handled it. Everyone who brought up cooling revealed themselves as not having read the first page and not having thought about it seriously for more than 30 seconds. > 2. How does one radiation harden a H100? See that paper for some ideas and considerations, as this is part of what they focused on, after solving cooling by sizing the per-satellite payload power needs to Starlink.