Manoeuvring in space
Objects move in a different way in space. When a thruster is fired the ship will accelerate forward. When the thruster stops firing, the ship will still continue to move at a constant speed becuase there is no friction to slow it down. To stop the vehicle we would have to fire a thruster in the opposite direction.
Space travel requires large amounts of energy for to reach the high velocities needed to escape the Earth's gravity.
Almost all of the fuel used for a space mission is burnt up during launch. Because of this scientists developed engines that can maneuver the ship or satellite, once in space, using small amounts of fuel. Ion drive engines are designed to do this. The ions are ejected from the satellite at a very high velocity and this provides a small but constant thrust to increase speed.
The photo above shows one of NASA's Manned Maneuvering Units (MMU), which allows an astronaut to maneuver in space by using small propulsion units using charged ions.
We can also manoeuvre the object that is travelling in space close to a planet or large asteroid so that it accelerates towards them but ultimately misses it.
As it heads towards the planet or large asteroid, the object that is travelling accelerates and increases its velocity, meaning that it flies past at a greater velocity than before. This is referred as a gravitational slingshot or catapult.