One unit, over and over: the yard builds the same pile again and again, and proves each one by making it work before it is allowed to leave.
An artistic imagining, not existing hardware: a yard on Deimos where the same small fission power unit is built again and again along one arc of bays, and where each one is proved at full power on a test stand, radiators lit, before a tug carries it off to whatever it will run. Reactors really are exercised on the ground before they fly, their output dumped into a resistive load bank: the KRUSTY test of 2018 took a real fission core and its Stirling converters through a full mission profile exactly that way.Image: poweringspace.com. Artistic imagining.