How Does A Space Ship Travel In The Space ?

A Space ship can maneuver by use of Newton's three laws of motion

I. Every object in a state of uniform motion tends to remain in that
state of motion unless an external force is applied to it.
II.  The relationship between an object's mass, m , its acceleration
a, and the applied force,  F=ma.  In this law the direction of the force
is the same as the direction of the acceleration.
III.  For every action there is an equal and opposite reaction

And of course, the ship is always under the influence  of Newton's Law of Gravity.

F=Gm1m2/r^2

Where: F is the magnitude of the gravitational force between the two masses, G is the Gravitational_constant.  M1 is the first mass, (the Sun or a nearby planet). M2 is the second mass, (the Space Ship, in this case).  R is the distance between the two masses.

A rocket motor is a reaction motor. The action of the hot gases leaving the rocket at high speed causes the rocket to react, to move in the opposite direction. A  textbook in introductory Physics will explain this in detail. And there are numerous sites on the Web about this.

Spaceships get into space by getting enough momentum to overcome gravity.  Momentum is mass x velocity.  Velocity is the speed and direction.  Earthlings use rockets to make their spaceships go fast.  After it is in space, it would travel because it would have momentum and there wouldn't be any forces acting on it to change the momentum (it wouldn't slow down).  It would be possible to use the thrust of rockets as a force to make changes to the speed or direction.  There are promising initiatives to make a solar sail to catch the momentum of solar flux to increase the speed of a spaceship.  While traveling through space, if it hit a small object, the spaceship and object would each have a new speed and direction.  Sometimes the gravity of a planet would also be a force to change the speed or direction.  If the spaceship traveld close to a large planet, the gravity may be a large enough force to continually change the direction of the spaceship so that the spaceship would orbit the planet.  If there were an atmosphere, the spaceship would collide with the molecules in the atmosphere and transfer momentum.  While transferring momentum to the molecules, the spaceship would move to an ever-closer orbit  - maybe burning up or crashing.

Once in space, a ship would use rocket power from a main engine to build up forward speed and use small thrusters, using compressed air , to change course. &tbsp;to slow down (to allow orbit or re-entry) the ship would use thrusters to turn itself right round then fire it's main engine long enough to get the right speed.