[disposeofnick9]

FES is used in non-kill-zone habitable solutions like datacenters, bottoms of passenger trams/hybrid buses and electromagnetic aircraft catapults. The historical issue with FES is unscheduled, rapid disassembly, but carbon/kevlar composites have been shown to have greater integrity with least unsprung structural mass (because you want the most mass as close to the rim as possible to ensure highest moment of inertia.)

FES has 10x specific energy than supercapacitors or batteries with no memory and precise state of charge. Magnetic bearings and hard vacuums make them quite efficient.