What makes the twin Voyager 1 and 2 spacecraft fly?

They fly since the 70s, right? Do they have a motor or a battery on board? What keeps them going? 

quantumclaustrophobe2021-01-19T16:29:28Z

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They were given enough speed to escape the gravity of the solar system. After their initial boost on rockets, each proceeded on their momentum, until they came into the gravitational influence of the planets they flew by. Those fly-bys gave each Voyager craft a 'gravitational boost', that accelerated them, and projected them to the next planet (or, out of the solar system...)  
Here's a chart showing the speed versus time - it shows how the speed of Voyager 2 was boosted by each planetary fly-by, and also plots the sun's escape velocity over distance: 

nineteenthly2021-01-19T07:12:26Z

Newton's Laws of Motion state that an object will continue to move at the same velocity unless acted on by a force.  That's what they're doing.  There's no need for a method of propulsion once the initial impulse has accelerated them sufficiently.  We are misled by living on a planet, which is a special case where friction and drag, along with gravity, makes objects behave anomalously.

Bill-M2021-01-18T20:32:24Z

They are just drifting through space.  There is nothing to stop them.  No air resistance.
They were initially sent into space with rockets to get them away from Earth's gravity.
Then they used Gravity Assist by flying by Jupiter.  This gravity assist speeded them up and now they are just drifting along.

Mr. Smartypants2021-01-18T18:46:26Z

Newton's first law.  An object in motion tends to stay in motion unless acted upon by something.  IOW a spacecraft, once moving, in the vacuum of space, will move forever until it hits something.  (Or someone!  But let's not think about that.)

Anonymous2021-01-18T18:39:14Z

inertia keeps them going, they have a small nuclear reactor for power and warmth 

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