If an astronaut leaves his spacecraft during a journey, he cannot walk about in the ordinary way. There is nothing but empty space. There is not even any gravity to pull him in one particular direction. He can only guide himself by the same means as the spacecraft itself – by rocket propulsion. So when astronauts do leave their spacecraft during a flight – perhaps to help in docking operations with another spacecraft – they carry specially designed hand rockets with them. If they point the rocket exhaust in one direction, and give the engine a burst of power, they will move in the opposite direction. In this way they can steer themselves.