How do rockets work in space?
Rockets work in space because of Newton's third law: pushing exhaust gas out the back pushes the rocket forward. They do not need air to push against.
A common misconception is that rockets push against the air. In fact, the rocket pushes against its own exhaust. When fuel burns, hot gas shoots out of the nozzle in one direction, and the rocket moves in the opposite direction. This works even better in the vacuum of space, because there is no air resistance.
You can see the same principle with a balloon. When you let go of an inflated balloon, air rushes out one end, and the balloon flies the other way. An astronaut floating in space who throws a tool in one direction will drift slowly in the opposite direction.
Steering in space
Spacecraft use small thrusters to change direction and orientation. Some use ion engines, which push out charged particles at very high speeds. Ion engines produce gentle thrust but are extremely efficient, letting probes like NASA's Dawn mission travel great distances.
Did You Know?
Rockets carry their own oxidizer because there is no oxygen in space to burn fuel, unlike jet engines, which take oxygen from the air.