4 ms·

Lots of funny comments here, but does anyone actually have a good argument against this idea? It seems both ridiculous and obvious.

yorick 2y ago
To passively radiate a gigawatt of heat in space at 100C, you'd need a radiator with a (visible) surface area of 1 million square meters.
- DiscourseFan 2y ago
  so you're saying its possible
  - reaperman 2y ago
    Not for “$5 million in launch costs” per 40MW compute unit. Sure, many things are possible with enough money, but their “Table 1” is a pretty bald-faced lie. Just the weight of 40MW’s worth of H100 GPU’s alone would be $200 million in launch costs on a Falcon Heavy. That’s before you even add on launch costs for solar panels or “magic” not-invented-yet radiator panels. The first question isn’t whether it’s “possible” with enough money, it’s whether it could ever be within even an order of magnitude of “profitable”. The second question is why would you trust a company who provides these kinds of estimates with no reasonable explanation for these obvious massive discrepancies?
  - atoav 2y ago
    1000000 m2 are a 1x1 km square. If we assume a 5mm copper sheet of that size it weighs 44512900 kg. A kg in a heavy falcon costs ~1500 USD. So we land at 66 billion USD in launch cost for the copper alone. I probably don't have to explain that building a radiator of that size in space isn't free either. And the stuff that gets the heat to those radiatoes is neither free nor lightweight either. Yet cooling somehow costs them zero dollars.
Veedrac 2y ago
It's one of those ‘Is a space elevator a good idea?’ vibe questions. In theory, sure, inevitably civilization does this in passing if it continues on pace for another hundred or so years, because at minimum at some point you've already tiled the Earth and automation has brought cost of remote handling down to zero. But it's also, the proposal is to build a 4km x 4km array in space, and the main reason to do this now rather than say a data center in the Sahara is permitting, skipping storage, and solar utilization. The last two are rather silly reasons when the cost of solar panels is taking a nosedive and cheap energy enables dumb storage solutions, and permitting, well, let's just take as given that it's right and permitting really is that hard. That still only gives you an advantage after you scale to the point your permits would be denied, and whereas a Falcon 1 didn't really have competition so could get away with cost inefficiency, a mini compute cluster in space is competing against a terrestrial server rack. None of the arguments seem physically implausible. Launch can get to <$5m/Starship. You can build 20km² of solar and radiation. You can hook up 5 GW of compute with remote space vehicles. It's just really shockingly hard in an Apollo sort of way. Somehow I doubt the permitting will be easy either.
- reaperman 2y ago
  > Launch can get to <$5m/Starship What are you basing this on? Just the GPU’s to utilize 40MW will weigh nearly 100 metric tons (40MW / 700W * 1.7kg). Thats an entire Starship payload just for the GPU’s and absolutely nothing else. Starship launches currently are $100 million and after adding in solar panels and radiator panels and radiation shielding you’ll need several of those Starship launches per single “40MW compute unit”. How do you get this down to “<$5 million”?
  - Veedrac 2y ago
    Starship launches are not currently any price. The stated long run goal was $2-3m, per Elon Musk, and if you put aside practicalities like limits on how big the market is, and then not having a robust heatshield design yet, it's fundamentally coherent, because of full reuse. If you're looking for more practical medium term numbers, Gwynne Shotwell suggested around the $50m mark would be an early price goal.
atoav 2y ago
Does anybody have an argument against building floating cities? You just need ballons (5m) and a city (20m). Easy, right? Now imagine me phrasing that without sarcasm and really trying to sell you on it, while still never doing the actual math. That is the problem here. The idea is one that is designed to appeal to a specific audience. It is not an idea that makes sense to anybody who runs data centers or builds satellites. Let's talk physics: In space there is no air, that means fans are useless. That means the extremely cold outside temperature is absolutely useless for cooling, because it is essentially a vacuum. The kind of vacuum used by the thermos company to keep your tea warm. Only the tea is now a data center emitting megawatts of heat. If you don't want the datacenter to melt you will need to get heat out and in space you can only do that by passive radiation, which is essentially copper radiating heat out. We have the math to calculate how big that radiator needs to be to be able to move energy out, and to no surprise it is going to habe to be significantly bigger than any active cooling solution used in a data center (just like passive coolers in PCs have to be bigger to allow the same power dissipation). Now mind they estimated the cost for cooling with 0 USD. I don't know how much copper they are going to but with 0 USD, but either they haven't the slightest clue what they are doing or they try to trick you. Keeping the temperature of satelites stable is a major challenge and if I have heard that, they know that too. Keep in mind this is just cooling, there are other significant parts they skip entirely, like communications, maintenance, RND costs, massive amounts of radiators.. A data center in space is more than taking a satellite and a data center and mashing them together. There are specific challenges to operating a data center in space, some of which may make it so uneconomic that it doesn't make sense to do it, just like a floating city. It looks cool in the drawings tho.
raverbashing 2y ago
Here's a good comparison: how did MS's idea of submerged datacenters compare? - Much easier power supply/handling - Way less problems with cooling - Much simpler hw requirements - Sub-million dollar launches And still failed

yorick 2y ago

To passively radiate a gigawatt of heat in space at 100C, you'd need a radiator with a (visible) surface area of 1 million square meters.

DiscourseFan 2y ago
so you're saying its possible
- reaperman 2y ago
  Not for “$5 million in launch costs” per 40MW compute unit. Sure, many things are possible with enough money, but their “Table 1” is a pretty bald-faced lie. Just the weight of 40MW’s worth of H100 GPU’s alone would be $200 million in launch costs on a Falcon Heavy. That’s before you even add on launch costs for solar panels or “magic” not-invented-yet radiator panels. The first question isn’t whether it’s “possible” with enough money, it’s whether it could ever be within even an order of magnitude of “profitable”. The second question is why would you trust a company who provides these kinds of estimates with no reasonable explanation for these obvious massive discrepancies?
- atoav 2y ago
  1000000 m2 are a 1x1 km square. If we assume a 5mm copper sheet of that size it weighs 44512900 kg. A kg in a heavy falcon costs ~1500 USD. So we land at 66 billion USD in launch cost for the copper alone. I probably don't have to explain that building a radiator of that size in space isn't free either. And the stuff that gets the heat to those radiatoes is neither free nor lightweight either. Yet cooling somehow costs them zero dollars.

Veedrac 2y ago

It's one of those ‘Is a space elevator a good idea?’ vibe questions. In theory, sure, inevitably civilization does this in passing if it continues on pace for another hundred or so years, because at minimum at some point you've already tiled the Earth and automation has brought cost of remote handling down to zero. But it's also, the proposal is to build a 4km x 4km array in space, and the main reason to do this now rather than say a data center in the Sahara is permitting, skipping storage, and solar utilization. The last two are rather silly reasons when the cost of solar panels is taking a nosedive and cheap energy enables dumb storage solutions, and permitting, well, let's just take as given that it's right and permitting really is that hard. That still only gives you an advantage after you scale to the point your permits would be denied, and whereas a Falcon 1 didn't really have competition so could get away with cost inefficiency, a mini compute cluster in space is competing against a terrestrial server rack. None of the arguments seem physically implausible. Launch can get to <$5m/Starship. You can build 20km² of solar and radiation. You can hook up 5 GW of compute with remote space vehicles. It's just really shockingly hard in an Apollo sort of way. Somehow I doubt the permitting will be easy either.

reaperman 2y ago
> Launch can get to <$5m/Starship What are you basing this on? Just the GPU’s to utilize 40MW will weigh nearly 100 metric tons (40MW / 700W * 1.7kg). Thats an entire Starship payload just for the GPU’s and absolutely nothing else. Starship launches currently are $100 million and after adding in solar panels and radiator panels and radiation shielding you’ll need several of those Starship launches per single “40MW compute unit”. How do you get this down to “<$5 million”?
- Veedrac 2y ago
  Starship launches are not currently any price. The stated long run goal was $2-3m, per Elon Musk, and if you put aside practicalities like limits on how big the market is, and then not having a robust heatshield design yet, it's fundamentally coherent, because of full reuse. If you're looking for more practical medium term numbers, Gwynne Shotwell suggested around the $50m mark would be an early price goal.

atoav 2y ago

Does anybody have an argument against building floating cities? You just need ballons (5m) and a city (20m). Easy, right? Now imagine me phrasing that without sarcasm and really trying to sell you on it, while still never doing the actual math. That is the problem here. The idea is one that is designed to appeal to a specific audience. It is not an idea that makes sense to anybody who runs data centers or builds satellites. Let's talk physics: In space there is no air, that means fans are useless. That means the extremely cold outside temperature is absolutely useless for cooling, because it is essentially a vacuum. The kind of vacuum used by the thermos company to keep your tea warm. Only the tea is now a data center emitting megawatts of heat. If you don't want the datacenter to melt you will need to get heat out and in space you can only do that by passive radiation, which is essentially copper radiating heat out. We have the math to calculate how big that radiator needs to be to be able to move energy out, and to no surprise it is going to habe to be significantly bigger than any active cooling solution used in a data center (just like passive coolers in PCs have to be bigger to allow the same power dissipation). Now mind they estimated the cost for cooling with 0 USD. I don't know how much copper they are going to but with 0 USD, but either they haven't the slightest clue what they are doing or they try to trick you. Keeping the temperature of satelites stable is a major challenge and if I have heard that, they know that too. Keep in mind this is just cooling, there are other significant parts they skip entirely, like communications, maintenance, RND costs, massive amounts of radiators.. A data center in space is more than taking a satellite and a data center and mashing them together. There are specific challenges to operating a data center in space, some of which may make it so uneconomic that it doesn't make sense to do it, just like a floating city. It looks cool in the drawings tho.

raverbashing 2y ago

Here's a good comparison: how did MS's idea of submerged datacenters compare? - Much easier power supply/handling - Way less problems with cooling - Much simpler hw requirements - Sub-million dollar launches And still failed