[notahacker]

Radiators are raised because it's a known constraint and we know that Stefan Boltzmann implies a lot of radiator mass to be launched even at 100% cooling efficiency and there are also theoretical limits to launch efficiency which Starship is rapidly approaching.

Nobody is saying orbital datacentres can't be cooled, they're saying people arguing launching the mass of the required radiators into space is a better, more cost-effective cooling solution than pumping local water because "space is cold" are talking nonsense. Potential solutions don't look like trying to get 5000 engineers to invent radiators which defy the laws of physics, they probably look like amortising the costs over multiple decades of operation and ideally assembling the radiator portion of the datacentre from mass that's already in orbit, but that's not a near term profit pitch....

[pveierland]

I read the comment that I replied to as these challenges being a large prohibitor to this development, and I pointed out that these seem like challenges that can be dealt with mostly in isolation from other challenges and in particular not require a large number of engineers to deal with.

Of course the major exercise becomes about total cost efficiency, but I think a large attraction is that once you've solved space deployment sufficiently, you don't need to keep dealing with local circumstances and power production adaptations to every new site you're dealing with on Earth, as it's more about producing a set of modules you can keep launching without individual adaptation - not about "space being cold".

[notahacker]

The point is that they're absolutely not in isolation from other challenges because designing something to radiate heat at maximum possible radiative cooling efficiency is not considered to be a problem, solving the unit economics of launching the required radiator tonnage and burning 100 tonnes of rocket fuel to per tonne launched that's the problem. Cutting edge stuff like in-space refuelling and modular in-space reassembly and patient capital are crucial to making those work because the radiators aren't getting beyond 100% radiative cooling efficiency however well designed they are.

Optimizing for local circumstances is a benefit to doing things on earth: if having a production line and the ability to plug into wherever energy happens to be cheapest was better we'd all be sticking inference chips in shipping containers and not worrying about HVACs being relatively inefficient at cooling.

[pveierland]

> The point is that they're absolutely not in isolation from other challenges because designing something to radiate heat at maximum possible radiative cooling efficiency is not considered to be a problem, solving the unit economics of launching the required radiators tonnage and burning 100 tonnes of rocket fuel to per tonne launched that's the problem.

I was pointing out relative coupling, not absolute coupling. The coupling between the different design decisions involved in Terafab or Starship seems far greater as there are so many design levels to unite jointly - while figuring out the structural and thermal design of these satellites appears to be something that to a greater degree can be resolved with less design constrained coupling - i.e. making it more feasible to figure out with a lower number of people.

> Optimizing for local circumstances is a benefit to doing things on earth: if having a production line and the ability to plug into wherever energy happens to be cheapest was better we'd all be sticking inference chips in shipping containers and not worrying about HVACs being relatively inefficient at cooling.

I did not reference energy cost directly. In many countries there are year-long lines for data centers to even be allowed to connect to the grid, which is why many also resort to local gas turbine power plants etc. Having a cost effective (the unknown is if/when this becomes possible) method of deploying large units of compute without dealing with this power access issue - zoning issues - local policies etc - appears to be one of the large attractions to this endeavor, in addition to being able to avoid longer term scaling issues. Inference sticks are not cost effective at scale now and that does not seem to be on the horizon. Space based compute however seems to be a more open question depending on your timeline.

[notahacker]

> I was pointing out relative coupling, not absolute coupling. The coupling between the different design decisions involved in Terafab or Starship seems far greater as there are so many design levels to unite jointly - while figuring out the structural and thermal design of these satellites appears to be something that to a greater degree can be resolved with less design constrained coupling - i.e. making it more feasible to figure out with a lower number of people.

Sure, but you're missing the point which people familiar with spacecraft systems engineering are actually making, which isn't "radiators are a problem because they're hard to design" but that "radiators are a problem because it's hard to design everything else to offset their relatively large mass budget, and thus every other aspect of designing and operating an ODC as a profitable alternative to terrestrial ODCs is coupled to the theoretical limits to how low the radiator launch mass can be". The number of engineers required to design radiators themselves is totally irrelevant, but you can't isolate the radiators' required launch mass from the overall concept of operations and operating economics.

[pveierland]

One issue with this argument is that there are very few engineers that have had the opportunity to design satellites that are; this large, are designed for mass manufacturing, rapid iteration, failure allowance, and with access to a reusable launch vehicle with the capability of Starship (where it's also unknown what launch mass capability they will end up reaching).

The satellites built by SpaceX so far, and their engines, are quite unlike most previous space engineering due to these reasons. Given the undeniable success they've had in building Starlink, with each version growing considerable in size, I just don't see which engineers would be able to fully rule out the math that SpaceX might be working on here, exactly because there are so many parts of the total equation and where SpaceX are moving outside the previous design envelopes in many dimensions.

Of course I'm personally not convinced or able to know whether this is economically sensible - I just believe it's very difficult to fully rule out given the track record of SpaceX - and given that there doesn't appear to be any singular insurmountable thing that needs to be figured out here. Hence why I said in my original post that this is why I'm excited to see the design space explored.

[echoangle]

I don't think anyone is saying that it's impossible to build a datacenter in space. Of course you can do that if you really want to.

But to make sense, it needs to be cheaper than on earth, and that seems unrealistic.

[rob74]

Space is cold. Space is also an excellent thermal insulator - there's a reason why Thermos bottles use vacuum for insulation...