Since the first human spaceflight by the Soviet Union, citizens of 48 countries have flown in space.

a hypothetical method of space travel that involves the use of a propulsion system that generates a constant acceleration rather than the short, impulsive thrusts produced by traditional chemical rockets.

Space travel, or space flight (less often, starfaring or star voyaging) is a science fiction theme that has captivated the public and is almost archetypal for science fiction.