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Your assumptions are incorrect. A space ship (once it has escaped Earth) will also continue travelling - in fact it will only need fuel to change its trajectory and velocity outwith gravitational effects from other bodies. You will need sufficient fuel or power for life support, if you have a manned ship, and a reserve of fuel to manoeuvre at your ...


10

Spaceships will keep travelling in their orbits just the same as comets or asteroids, without fuel. The exception is that spacecraft in low orbit are affected by the upper fringe of the atmosphere, and need a slight boost every few months. Spaceships need fuel to change their course or to fly from the ground into space and back. Typically they only run their ...


5

If there were no forces on an object, then Newton's First Law tells us that a stationary object would remain stationary, and a moving object will keep moving. So a moving comet or asteroid keeps moving. When there is a force on an object, Newton's Second Law essentially tells us that the object will speed up, slow down, and/or change directions. Rockets ...


3

As other answers have said, they don't need to for maintaining speed. Back in the 1600s, Isaac Newton discovered maths for the movement of objects which matched observations, especially the movement of objects in space where there is no friction. We call them Newton's Laws of Motion. Newton's First Law is that you only need to apply a force to change your ...


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