you reference an ICE article "currently" on the front page, I think this comment would benefit from an explicit link to that discussion since it is ephemeral and I am unable to make sure I find the right one.
> Space is a vacuum. i.e. The lack-of-a-thing that makes a thermos great at keeping your drink hot.
1) The heat can be transported by a heat carrier conducting heat standing still.
2) The heat can be transported by a heat carrier in motion.
3) The heat can be transported by thermal radiation.
The first 2 require massive particles, the latter are spontaneous photons.
A thermos bottle does not simply work by eliminating the motile mass particles.
Lets consider room temperature as the outer thermos temperature and boiling hot water as the inner temperature, that is roughly 300 K and 400 K.
Thermal radiation is proportional to the fourth power of temperature and proportional to emissivity (which is between 0 and 1).
Lets pretend you are correct and thus thermally blackened glass (emissivity 1) inside the vacuum flask would be fine according to you. That would mean that the radiation from your tea to the room temperature side would be proportional to 400^4 while the thermal radiation from room temperature to the tea would be proportional to 300^4. Since (400/300) ^ 4 = 3.16 that means the heat transport from hot tea to room temperature is about 3 times higher.
If on the other hand the glass was aluminized before being pulled vacuum the heat transports are proportional to 0 * 400 K ^ 4 and 0 * 300 K ^ 4 . So the heat transport in either direction would be 0 and no net heat transport remains.
If you believe the shiny inside of your thermos flask is an aesthetic gimmick, think again.
You are making a non-comparison.
Imagine comparing a diesel engine car to an electric car, but first removing the electric motor. Does that make a fair comparison???
I literally quote a person attributing the thermal insulation capabilities of vacuum flasks mono-causally to the lack of gas. I didn't imagine this, its right there to verify. Reminding people of laws of nature that have been known for 150 years and have withstood the test of time of investigation by physicists isn't "dunking on" anything, just reminding people of how the universe works.
The original vacuum flasks were made of glass, and a lot of laboratory grade vacuum flasks and Dewars are still made of glass. The consumer level Thermoses eventually switched to stainless steel.
Lets assume an electrical consumption of 1 MW which turned into heat and a concommitant 3 MW which was a byproduct of acquiring 1 MW of electrical energy.
So the total heat load if 4 MW (of which 1 MW was temporarily electrical energy before it was used by the datacenter or whatever).
Let's assume a single planar radiator, with emissivity ~1 over the thermal infrared range.
Let's assume the target temperature of the radiator is 300 K (~27 deg C).
What size radiator did you need?
4 MW / (5.67 * 10 ^ -8 W / ( m ^2 K ^4 ) * 300 K ^4) = 8710 m ^2 = (94 m) ^2
so basically 100m x 100m. Thats not insanely large.
The solar panels would have to be about 3000 m ^2 = 55m x 55m
The radiator could be aluminum foil, and something amounting to a remote controlled toy car could drive around with a small roll of aluminum wire and locally weld shut small holes due to micrometeorites. the wheels are rubberized but have a magnetic rim, on the outside theres complementary steel spheres so the radiator foil is sandwiched between wheel and steel sphere. Then the wheels have traction. The radiator could easily weigh less than the solar panels, and expand to much larger areas. Better divide the entire radiator up into a few inflatable surfaces, so that you can activate a spare while a sever leak is being solved.
It may be more elegant to have rovers on both inside and outside of the radiator: the inner one can drop a heat resistant silicone rubber disc / sheet over the hole, while the outside rover could do the welding of the hole without obstruction of the hole by a stopgap measure.
As I've pointed it out to you elsewhere -- how do you couple the 4MW of heat to the aluminum foil? You need to spread the power somewhat evenly over this massive surface area.
Low pressure gas doesn't convect heat well and heat doesn't conduct down the foil well.
It's just like how on Earth we can't cool datacenters by hoping that free convection will transfer heat to the outer walls.
Lets assume you truly believe the difficulty is the heat transport, then you correct me, but I never see you correct people who believe the thermal radiation step is the issue. It's a very selective form of correcting.
Lets assume you truly believe the difficulty is the heat transport to the radiator, how is it solved on earth?
> Lets assume you truly believe the difficulty is the heat transport, then you correct me, but I never see you correct people who believe the thermal radiation step is the issue
It's both. You have to spread a lot of heat very evenly over a very large surface area. This makes a big, high-mass structure.
> how is it solved on earth?
We pump fluids (including air) around to move large amounts of heat both on Earth and in space. The problem is, in space, you need to pump them much further and cover larger areas, because they only way the heat leaves the system is radiation. As a result, you end up proposing a system that is larger than the cooling tower for many nuclear power plants on Earth to move 1/5th of the energy.
The problem is, pumping fluids in space around has 3 ways it sucks compared to Earth:
1. Managing fluids in space is a pain.
2. We have to pump fluids much longer distances to cover the large area of radiators. So the systems tend to get orders of magnitude physically larger. In practice, this means we need to pump a lot more fluid, too, to keep a larger thing close to isothermal.
3. The mass of fluids and all their hardware matters more in space. Even if launch gets cheaper, this will still be true compared to Earth.
I explained this all to you 15 hours ago:
> If this wasn't a concern, you could fly a big inflated-and-then-rigidized structure and getting lots of area wouldn't be scary. But since you need to think about circulating fluids and actively conducting heat this is much less pleasant.
You may notice that the areas, etc, we come up with here to reject 70kW are similar to those of the ISS's EATCS, which rejects 70kW using white-colored radiators and ammonia loops. Despite the use of a lot of exotic and expensive techniques to reduce mass, the radiators mass about 10 tonnes-- and this doesn't count all the hardware to drive heat to them on the other end.
So, to reject 105W on Earth, I spend about 500g of mass; if I'm as efficient as EATCS, it would be about 15000g of mass.
Then you picked the wrong thread to insert yourself, it's literally about that.
Which is funny, there are multiple other replies to you, explaining at length that while your ideas are physically possible, they are completely impractical. And yet you think they still could be "minor".
> There is to little matter in space to absorb excess heat.
If that were true the Earth would have overheated, molten and turned to plasma long ago. Earth cools by.... radiative cooling. Dark space is 4 K, thats -267.15 deg C or -452.47 deg Fahrenheit. Stefan-Boltzmann law can cool your satellite just fine.
> You'd need thermal fins bigger than the solar cells.
Correct, my pessimistic calculation results in a factor of 3,...
but also Incorrect, there wouldn't be "fins" thats only useful for heat conduction and convection.
That wasn't the original question. The head of this thread was quoting Musk's claim, which I repeat here:
> it is possible to put 500 to 1000 TW/year of AI satellites into deep space
This is 500-1000 times as much as current global production.
Musk is talking about building on the Moon 500-1000 times as much factory capacity as currently exists in aggregate across all of Earth, and launching the products electromagnetically.
Given how long PV modules last, that much per year is enough to keep all of Earth's land area paved with contiguous PV. PV doesn't last as long in space, but likewise the Moon would be totally tiled in PV (and much darker as a consequence) at this production rate.
In fact, given it does tile the moon, I suspect Musk may have started from "tile moon with PV" and estimated the maximum productive output of that power supply being used to make more PV.
I mean, don't get me wrong, in the *long term* I buy that. It's just that by "long term" I mean Musk's likely to have buried (given him, in a cryogenic tube) for decades by the time that happens.
Even being optimistic, given the lack of literally any experience building a factory up there and how our lunar mining experience is little more than a dozen people and a handful of rovers picking up interesting looking rocks, versus given how much experience we need down here to get things right, even Musk's organisation skills and ability to enthuse people and raise capital has limits. But these are timescales where those skills don't last (even if he resolves his political toxicity that currently means the next Democrat administration will hate his guts and do what they can to remove most of his power), because he will have died of old age.
> Clearly this person was referencing a financial efficiency predominantly through uptime.
I read the person you are quoting differently, as them misunderstanding and thinking that the current 1 TW-peak/year manufacturing was 1 TW-after-capacity-factor-losses/year.
if the thermal radiation panels have ~3 x the area of the solar panels, the temperature of the satellite can be contained to about 300 K (27 deg C). Ctrl+F:pyramid to find my calculations.
I looked, and you outlined a solution that would be hard to achieve in a vacuum chamber on earth. Now we're going to launch it into orbit and it will work great?
Building data centers in Antarctica with nuclear power would be easier. And still way harder than necessary.
Yes, how would you simulate a 4K background in a vacuum chamber on earth... or you could just trust a law that has withstood 150 years the test of time by physicists...
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