Just to clarify, the last syllable of all three terms is spelt 'aut', but I'm sure some folk would love to send their 'aunt' into orbit. "Hey Auntie, how would you like to trade your broomstick for a Longmarch III ?"
lol Mike! So eventually there will be a kiwinaut and a aussienaut... no, thinking it over more clearly, the other island (West Island also known as Oz) won't evolve as far as NZ so the word won't need to be invented.