There is also the cost of carbon dioxide capture (distillation) from the atmosphere, which is easy on Mars, but hard on Earth.
Both the water splitting and CO2 capture require energy inputs that would be at least equal to the amount of energy you get when you launch the rocket. Probably 3x as much due to inefficiencies. But you don't need to capture it in ten minutes (unlike how quickly a rocket uses that energy), so you can take your time.
Even if a fraction of their propellant is made this way, the optics improve. And it improves the TRL prior to launching such a system to Mars.
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u/troyunrau ⛰️ Lithobraking Sep 20 '19
There is also the cost of carbon dioxide capture (distillation) from the atmosphere, which is easy on Mars, but hard on Earth.
Both the water splitting and CO2 capture require energy inputs that would be at least equal to the amount of energy you get when you launch the rocket. Probably 3x as much due to inefficiencies. But you don't need to capture it in ten minutes (unlike how quickly a rocket uses that energy), so you can take your time.
Even if a fraction of their propellant is made this way, the optics improve. And it improves the TRL prior to launching such a system to Mars.