As per definition of inertia we know that it is the property of mass which resist any change in the state of motion.
So if the object is moving in certain direction then it will continue in the same direction with same velocity until some external force will act upon it.
Here when force object is in infinite space then there is no force on that object so it will continue to move in the same direction with same velocity because of the property of inertia.
So here the motion remains in straight line without any change in the direction due to inertia of the body
i believe the answer is a hope it and is correct