Pretty slick!
I once saw a researcher from Eastern Europe (Romania? Chechoslovakia? Georgia?) present a similar but less refined concept. His idea was simply to use a pump to store CO2 in the empty fuel tanks of a landing stage, and then use it to hop from place to place.
Perhaps instead of a pellet bed, a heater coil could be wrapped around the landing stage engine combustion chamber, resulting in even higher ISP.
Once again, very nice work from Zubrin.
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