= mh can be derived using and , where a is semi-major axis and b is semi-minor axis of the elliptical orbit, as follows - and alternately, Therefore, specific angular momentum , and Total angular momentum Practical applications Given the total mass and the scalars r and v at a single point of the orbit, one can compute r and v at any other point in the orbit. Given the total mass and the scalars r and v at a single point of the orbit, one can compute the specific orbital energy , allowing an object orbiting a larger object to be classified as having not enough energy to remain in orbit, hence being "suborbital" (a ballistic missile, for example), having enough energy to be "orbital", but without the possibility to complete a full orbit anyway because it eventually collides with the other body, or having enough energy to come from and/or go to infinity (as a meteor, for example). The formula for escape velocity can be obtained from the Vis-viva equation by taking the limit as approaches : Notes References External links Vis-viva equation calculators Orbits Conservation laws