Seriously, if we could just build 2-3 air-cooled Plutonium fission per each megalopolis core and use e-Fuel on existing hybrids we'd solve everything in modern society ever. The reactor could double as cityscale thermojet ventilation system as well, eliminating heat and atmosphere problems once and for all. It will of course work as a training exercise for coming real Space Age in which humanity builds bunches after bunches of cylindrical habitats fabricated and populated in space. The only two roadblocks towards that path are some NIMBYism/NPT fears and cost.