Mars cycler spacecraft. Artwork of two astronauts in manned manoeuvring units on a spacewalk as their cycler spacecraft nears Earth. A cycler spacecraft is a permanently orbiting space station that follows a path between two objects, here Earth and Mars. Once accelerated into orbit it continues on its own momentum, only needing to use propellant for occasional adjustments. Smaller spacecraft are used to carry astronauts between the planets and the cycler.