Lazlo says we only need 200 petajoules!
Lazlo says we only need 200 petajoules!
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33 comments
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Send this to xkcd and we'll know how many tons of uranium are required to get it done
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Randall Munroe might be busy, so I'll try.
Okay, according to cooking StackOverflow, a popcorn kernel pops at about 180-200C. Once Iowa is dry enough for the corn to pop, that's the target temperature, and according to the USDA Iowa produced 2.58 billion bushels of corn in 2024. It appears in Iowa it's still cold enough they have just one harvest, and we'll assume by timing our microwave burst right we can get 2 billion. If we approximate the kernel as all water, we can consult the steam tables for energy absorbed heating water at STP to 190C at 10 bars, and with the fact a bushel of corn weighs ~25kg get (2602.8-83.83)kJ/kg 2 10^9 bushels 25kg/bushel = 125.9 PJ. Reactor-grade uranium has an energy density 3.456TJ/kg in practice, per Wikipedia. So, the unrealistic answer is 125.9PJ/(3.456TJ/kg) ~= 36.5 metric tons, which you could actually fit in a cargo aircraft.
I'm going to come back and add in more realistic answers including the (alleged) non-corn things in Iowa, and then including the need to store that energy in a way that can be quickly turned into microwaves.
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You also need enough heavy water to go between the u rods right? Seems like a lot of additional volume and mass for that
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Fine, I'll include plant mass with the (almost certainly much larger) mass of all the ultracapacitors when I start on part 2.
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Hey, I'm already happy with your answer. Just saying it's starting to look less like an aircraft and more like a building
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There will also be some atmospheric loss, so increase the PJ a bit, depending on what altitude you deploy the satellite to.
Also, it'll need to recharge, Kansas is next.
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I'll leave waiting for a clear day and adding 10% as an exercise for the reader. It will definitely be rechargeable, just supply more uranium to the reactor and wait again.
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It clearly says it's solar powered.
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So what? Like five?
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Who says the solar array didn't get to space with nuclear powered rockets?
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Hmmm, a nuclear based propellant. Might be easiest to make it a pulse based rocket so you can use a bunch of tiny nuclear explosions to propel yourself into space. I'm sure that won't have any environmental ramifications.
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The satellite is just to monitor popping, the blast itself handles themals.
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Can XKCD also figure out how big a space based solar panel has to be to cast a visible shadow?
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33 comments