Or at least it was obligatory for Izzy. For a single arklet, it didn’t matter whether it got struck by a rock the size of a baseball or one the size of a stadium. It was equally dead in either case. Izzy, on the other hand, could survive the first of these with the loss of a few modules, but the second would obliterate the whole space station and probably lead to the slow death of the entire Cloud Ark. Izzy had to be capable of maneuvering out of a large bolide’s path.