Escape velocity is the minimum speed needed for a free and non propelled object to escape from the gravitational influence of a massive body and it is slower the farther away from the body of an object and becomes slower than the massive body. This requires to send a ballistic object on a trajectory that will allow the object to escape the gravity of the mass.If we take an example of a rocket it does not actually need an escape velocity to escape but can achieve the same result at any speed with a suitable mode of propulsion.
The scenarios of escape velocity.
There are multiple scenarios including practical considerations, the surface of the body, rotating body, an orbiting body, and barycentricescape velocity. Escape velocity is relative to the surface of a rotating body depends on the direction in which escape body travels and the surface velocity decreases cosine with the surface latitudes so this is the reason why space facilities are located close to the equator so as they can be feasible. There are some reasons and situations where it is impractical to achieve escape velocity because of the accelerated implied or hypersonic sped involves. That is why for an actual escape orbit a spacecraft accelerate steadily out of the atmosphere until or unless it reaches the escape velocity and the escape velocity at a given height is two square root timesthe speed in a circular orbit at the same height. First cosmic velocity is the velocity corresponding to the circular orbits and the escape velocity is known as second cosmic velocity.
What is barycentric escape velocity?
It is important to understand that gravitational potential energy is negative since gravity is an attractive force. As mentioned the escape velocity can either be measured as relative to the other central body or barycentric escape velocity. So for a system of two bodies escape velocity can be ambiguous but usually intended to mean barycentric escape velocity of the fewer masses bodies. Mostly in gravitational field escape velocity or barycentric escape velocity is referred to as escape velocity of zero masses and unlike escape velocity, the direction especially vertically upward is important to achieve maximum heights. There is a theory that escaping a compound system such as the moon orbiting a planet or planet orbiting the sun the rocket which leaves escape velocity for the first time will not be able to travel to an infinite distance because of its need of even higher speed to the escape gravity of the second body.