What is the term for the speed needed to escape a gravitational field?

Escape velocity is defined as the minimum speed an object must attain in order to break free from the gravitational pull of a celestial body without any further propulsion. This speed varies depending on the mass and radius of the body from which the object is attempting to escape. For instance, the escape velocity from Earth’s surface is approximately 11.2 kilometers per second (about 25,000 miles per hour).

Understanding this concept is crucial in aerospace and astrophysics, as it determines the conditions necessary for spacecraft to leave Earth’s atmosphere and travel into space. The nature of escape velocity also implies that the object must reach this speed to overcome gravitational attraction—meaning that if it fails to reach this threshold, the object will fall back to the body rather than enter space.

In contrast, orbital speed refers to the speed required to maintain a stable orbit around a celestial body, which is significantly lower than escape velocity. Terminal velocity describes the constant speed an object reaches when it is falling through a fluid, where the force of gravity is balanced by drag, and initial speed typically refers to the speed of an object at the moment of launch or at a given starting point, rather than the speed needed to escape gravity altogether.