To find the orbital energy of an elliptical or hyperbolic trajectory, calculate the sum of kinetic energy and gravitational potential energy at any point along the path. For an elliptical orbit, the orbital energy can be determined using the formula -GM/(2a), where G is the gravitational constant, M is the mass of the central body, and a is the semi-major axis. In contrast, the orbital energy for a hyperbolic trajectory is given by GM/(2a). Proving these formulas involves understanding the relationships between kinetic and potential energy in gravitational fields. Understanding these concepts is crucial for analyzing orbital mechanics.