The quantity 2 a − − R is the height the ellipse extends above the surface, plus the periapsis distance (the distance the ellipse extends beyond the center of the Earth). For the Earth and a just little more than R the additional specific energy is ( g R / 2 ) ; which is the kinetic energy of the horizontal component of the velocity, i.e. 1 2 V 2 = 1 2 g R , V = g R .