If an astronaut is in space, how does he or she determine what time to pray?
Does it revolve around where the spaceship is in relation to the sun, or does he just follow zmanim on Earth?
In regards to time bound mitzvos in general Rabbi Menahem Kasher ruled that “The situation on the moon [or Mars] is equivalent to the north and south poles; therefore posit a 24-hour day, with alternating periods of 12 hours day and 12 hours night regardless of the presence or absence of light from the sun”. quoted here.
The same would presumably be true anywhere is space.