Nasa uses a mix of liquid hydrogen fuel and rocket petroleum to exit the earth atmosphere at 50 kilometers of altitude for missions to the international space station and higher almost escaping the gravitational influence of Earth at about 1.5 million kilometers of altitude.

NASA must maintain the right altitude with the right velocity to avoid losing the Earth and therefore entering the Sun's orbit, and this allows the spacecraft to position itself in low or high orbit whether if its circular with a fixed orbit velocity or elliptic influenced by gravity distance.

So, in theory, to exit the solar system in this context without gravity assist, a Nasa rocket would have to accelerate to 640 kilometers per second in a fraction of a second before it escapes the sphere influence of Earth, to exit out in a straight line, and this maneuver will have to be at night to avoid the sun.

NASA Rockets use a method by gravity called slingshot maneuvering, by using the gravity of celestial bodies to gain speed using a minimal amount of fuel.

In space above 1.5 million kilometers of altitude, the laws of gravity act different in terms of rocket forward velocity, as this is mainly influenced by celestial bodies gravity acting upon the spacecraft.

These velocities can change at any time as these can go from 7 to 7000 meters per second in a fraction of a second or vice versa and without being affected by the laws of motion except for the mechanical acceleration or deceleration of the rocket therefore, 7 m/s would feel the same as 7000 m/s, in vacuum without a point of reference and regardless of rocket orientation.

So,  if a rocket is flying in a straight line upward against gravity at 1 kilometer per second, per say, as soon as the rocket hits the 1.5 millionth-kilometer mark, the rocket will no longer be moving upward but both upward and sideways so, there is a mix of different velocities in space, the velocity of the rocket itself plus the velocity of the axis rotation of the Earth, plus the velocity of the Earth revolving around the sun, if the rocket escaped in a clockwise direction, and this is the main reason why the spacecraft would need to accelerate to this extreme high velocity to avoid all these celestial bodies gravitational pulls.

Therefore, to put this into context, if the rocket had to accelerate to 640 kilometers or 640 thousand meters per second in one second, the extreme amount of shear tension would cause the spacecraft airframe crash inward like aluminum foil even in a vacuum atmosphere according to the all the laws of motion acting upon it.

If a NASA rocket hits an altitude of 1.5 million kilometers in a straight line, 90 degrees or perpendicular towards the zenith and stops at the 1.5 million kilometer mark, the sphere influence of Earth will make it fall back towards Earth, gradually accelerating to about 1 kilometer per second by the time it hits the 30-kilometer mark of the upper atmosphere due to the fact that, there is no terminal velocity influenced by air resistance.

During reentry, the module heat shield will burn to about 1 to 2 thousand Celsius for a couple of seconds if the reentry angle of attack is 90 degrees perpendicular.

In space, traveling from point A to point B is challenging and going from point B to point A is impossible if the spacecraft was not in orbit because Nasa uses burning Hydrogen per minute; not per hour and that means the spacecraft cannot decelerate from orbit speed or much less land anywhere.