Science editor, BBC News website Share Crew Dragon is able to dock autonomously to the ISS "All these sensors are feeding data back to our flight computer to say: 'Hey, how far away am I from the space station? What's my relative velocity to the space station?'" The flight computer then uses algorithms that determine - based on this information - how to fire the thrusters to most effectively get to the docking target. The vehicle's lifetime in orbit is limited to a few months because of its solar panels, which degrade in the harsh environment of space. Leaving for home When astronauts are ready to return home from the space station, Crew Dragon first undocks and then performs a de-orbit burn with its thrusters. The vehicle's heat shield, located at its base, must survive temperatures hotter than the surface of the Sun as the craft screams through the atmosphere at up to 25 times the speed of sound. The material used in the heat shield is ablative: it slowly burns away at high temperatures to carry away much of the extreme heat. "Thank you for flying SpaceX" - Doug Hurley and Bob Behnken return to Earth There's a minor chance that the spacecraft's asymmetric design - driven by the placement of its emergency escape system - could cause it to roll too much. Elon Musk has said that the issue, known as roll instability, has been extensively studied, but that it still worries him. "I think there's an argument that the return is more dangerous in some ways than the ascent," Musk says. Then, after the fiery re-entry phase, the spacecraft needs to deploy four parachutes to slow its descent. NASA/Bill Ingalls Finally, the Crew Dragon splashes down in the Atlantic Ocean, 450km off the coast of Florida, where recovery ships will take the astronauts to safety and retrieve the capsule. The spacecraft can then be refurbished. Nasa has agreed to let astronauts fly on re-used Crew Dragons - and Falcon 9 boosters - as soon as SpaceX completes its third launch to the ISS with humans.