So far, maybe forever, we can only use mass ejection/rocket fuel for propulsion in space travel.

The moon is very close. How much rocket fuel able to send a man to the moon? Travel to the moon is almost impossible, to other star systems is just pure fiction.

Escape velocity is mistake. A bullet at 11 km/s straight up, without air resistance, how high can it go? After it reaches the highest point, will it come down? How can anything escape from earth or solar system gravity attraction forever?

Read and believe, without understanding precise mechanism, not a good way of learning.