How can the voyager spacecraft leave the solar system?
As far as i know it's almost left the system, although isn't out of sun's gravitation yet. How far it stretches out no-one knows, some astronomers think about 2 light years. So the Voyager still has a long road to go.
It has thrusters that can be fired for power. But most of it is from using gravity to sling shot it to its path