my napkin gets almost the same with existing and relatively simple tech - solar or nuclear source of energy powering ionic drive (as the one already made and te

my napkin gets almost the same with existing and relatively simple tech - solar or nuclear source of energy powering ionic drive (as the one already made and tested/flown by NASA with 3500 Isp (vs. yet to be made 5000 mentioned in the article)). Solar can actually beat nuclear if it is made as very thin, ie. light, film. I think and hope that SpaceX would end up using solar+ionic combo instead of chemical for Mars (and nuclear + ionic for beyond Mars).