Comment by andsoitis
10 hours ago
>> Dyson Sphere
> What do you think the limiting factor is?
You need to be able to harness enough raw material and energy to build something that can surround the sun. That does not exist in the solar system and we do not yet have the means to travel further out to collect, move, and construct such an incredibly huge structure. It seems like a fantasy.
The inner planets contain enough mass to create a shell of 1 AU radius with mass of 42 kg/m^2. That sounds like a plausible thickness and density for a sandwich of photovoltaics - GPUs - heat sinks.
You don't build a rigid shell of course, you build a swarm of free-floating satellites in a range of orbits.
See https://www.aleph.se/Nada/dysonFAQ.html#ENOUGH for numbers.
I am dying to know where you’ll get the energy and manufacturing scale in order to achieve this with current, or current+50-years technology.
Do tell.
The energy to build the system comes from the partial assembled system, plus some initial bootstrap energy. It grows exponentially. We seem to have enough today to build small factories in orbit.
The manufacturing scale comes from designing factory factories. They aren't that far in the future. Most factory machinery is made in factories which could be entirely automated, so you just need some robots to install machines into factories.
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Great. Now run the numbers to find the energy required to disassemble the planets and accelerating the pieces to their desired locations. For reference, it takes over 10 times of propellant and oxidant mass to put something in LEO.
The burned propellant and oxygen mass (as H2O and CO2) almost all ends up back in the atmosphere when you launch to LEO, so you can keep running electrolysis (powered by solar) to convert it back to fuel.
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Also it's gravitationally unstable, like Dyson Rings, where as soon as you have any perturbance from the center means that the closer side is more attracted to the sun so it enters a feedback loop.