1. Infinity doesn't use fuel in the traditional sense. It uses a fusion reactor. 2. They do not. There are some failsafes put in their design (See: Undid Iridium), but a kill switch? No. Because Cortana was the first AI created from a living brain, Halsey did implement a failsafe in case something went wrong. However, Cortana at the moment of her creation, detected the failsafe worm and destroyed it.