Applications
The field of trajectory optimization has made use of the concept since the 1950s in the form of energy analysis. In this approach, the specific energy is defined as one of the dynamic states of the problem and is the slowest varying state. All other states such as altitude and flight path angle are approximated as infinitely fast compared to the specific energy dynamics. This assumption allow the solution of optimal trajectories in a relatively simple form.
The specific energy is computed by the total energy (as defined above relative the Earth's surface) divided by the mass of the vehicle. It is a key element in performance of aircraft and rockets. For a rocket flying vertically (in a vacuum), it is the apogee that the rocket would obtain. It is used extensively in Energy–maneuverability theory that is used to determine the optimal paths for aircraft in dogfights.
Read more about this topic: Aircraft Specific Energy