Astronautic rhymes with:
hypnotic, antibiotic, aquatic, chaotic, despotic, erotic, exotic, hypnotic, idiotic, narcotic, neurotic, patriotic, psychotic, quixotic, robotic, semiotic, symbiotic, unpatriotic
Astronautic sounds like:
accouterments, accoutrements, astronaut's, astronautics, astronauts, astronauts'