Comment on Made in space? Start-up brings factory in orbit one step closer to reality

• UniversalBasicJustice@lemmy.dbzer0.com ⁨2⁩ ⁨days⁩ ago

  There are three modes of heat transfer; conduction, convection, and radiation.

  Conduction happens when two bodies at different temperatures come into contact with each other. The total heat transfer depends primarily on the difference in temperature, contact surface area and time spent in contact.

  Convection takes place when a fluid (I.e. a gas such as air or a liquid such as water) comes into contact with another body. Here, again, heat transfer depends on difference in temperature, contact (“wetted”) surface area and time in contact which is primarily dictated by how fast the fluid is moving over the body.

  On Earth we generally leverage these two modes. An example of mixing the two modes is a CPU heatsink and fan setup. The heatsink conducts heat away from the CPU and is (usually) distributed throughout several extended surfaces I.e. fins. The fins increase the surface area in contact with air, enhancing the rate of heat transfer.

  Now, we can’t really take advantage of those in space. The lack of an independent physical medium means the heat ultimately has no where to go; this is known as a “closed system”. So if we generate or store enough heat in a body subject to the void of space without promoting radiative heat transfer, that heat will more or less stay put.

  Radiative heat transfer is fucked up. Everything above absolute zero radiates heat. You mostly can’t see this exact for one glaringly obvious example; the Sun. Sol is so fucking hot that it heats the Earth through the vacuum of space purely via anger aka photons. And thanks to the miracle of science, you radiate anger right back at it.

  Explaining radiative heat transfer further is outside the scope of this reply and will be left as an exercise to the reader.

  I hope I explained this well enough for you or other readers to impart a ‘basic’ idea of a complex engineering discipline that I adore. I’m absolutely willing to answer any questions.

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  • Blisterexe@lemmy.zip ⁨22⁩ ⁨hours⁩ ago

    Maybe a stupid question, but you’d have to have something to hold the really hot thing, right? And obviously you’d need a bunch of stuff connected to the furnace to keep it in orbit and supplied with energy. So in that case wouldn’t the heat from the thing being heated spread to the rest of the satellite anyways? Like, clearly you can’t just use non-conductive materials because then we’d already have that on earth.

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    • UniversalBasicJustice@lemmy.dbzer0.com ⁨19⁩ ⁨hours⁩ ago

      Not stupid at all, that’s an excellent question! I’m not privy to the details of this furnace satellite but I have an idea or two on how I’d approach the problem. Pure (somewhat educated) speculation ahead.

      Firstly, you mentioned nonconductive materials. Insulating material isn’t perfectly nonconductive but can get pretty close. I’d imagine combining insulation with the vacuum of space would limit conductive heat transfer between furnace and the other equipment.

      Insulating and limiting the conductive transfer of heat doesn’t eliminate it though. You’d still need an active form of transfer to shed the heat. I’d investigate the feasibility of a convective heat exchanger; use coolant to transfer heat from the furnace to a radiator.

      From there I’d study how the James Webb Space Telescope maintains equilibrium. It uses a reflective shade to shield the radiator from the sun but I lack specific knowledge of the design. The temperature difference between hot side and cold side is a driving factor in heat transfer; maximizing the difference between the two leads to more efficient, effective control.

      Honestly though, its been a few years since my senior heat transfer course. Radiative heat transfer in the vacuum of space is Master’s if not PhD level specialization. I’m not at that level yet, so please take this answer with a large block of pink Himalayan salt.

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  • feannag@sh.itjust.works ⁨2⁩ ⁨days⁩ ago

    Are you sure it’s engineering you adore. Left as an exercise for the reader? That’s physicist speak.

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    • UniversalBasicJustice@lemmy.dbzer0.com ⁨2⁩ ⁨days⁩ ago

      Hah! My adoration of partial differential equations is far purer than even physicists could hope to achieve.

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