escape velocity is the speed at which the kinetic energy plus the gravitational potential energy of an object is zero.
It is the speed needed to "break free" from the gravitational
attraction of a massive body, without further propulsion, i.e., without
spending more fuel.
For a spherically symmetric body, the escape velocity at a given distance is calculated by the formula
In this equation atmospheric friction (air drag) is not taken into account. A rocket moving out of a gravity well does not actually need to attain escape velocity to do so, but could achieve the same result at any speed with a suitable mode of propulsion and sufficient fuel. Escape velocity only applies to ballistic trajectories.
The term escape velocity is actually a misnomer, and it is often more accurately referred to as escape speed since the necessary speed is a scalar quantity which is independent of direction (assuming a non-rotating planet and ignoring atmospheric friction or relativistic effects).
For a spherically symmetric body, the escape velocity at a given distance is calculated by the formula
In this equation atmospheric friction (air drag) is not taken into account. A rocket moving out of a gravity well does not actually need to attain escape velocity to do so, but could achieve the same result at any speed with a suitable mode of propulsion and sufficient fuel. Escape velocity only applies to ballistic trajectories.
The term escape velocity is actually a misnomer, and it is often more accurately referred to as escape speed since the necessary speed is a scalar quantity which is independent of direction (assuming a non-rotating planet and ignoring atmospheric friction or relativistic effects).
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