Original sentence: A zero value of aircraft specific energy is at the earth's surface and increases as speed and altitude increases.It is the total energy of the vehicle (relative to the earth's surface) per unit weight of the vehicle and being independent of the mass of the vehicle provides a powerful tool for the design of optimal trajectories.The specific energy is computed by the total energy (as defined above relative the earth's surface) divided by the mass of the vehicle
Edited sentence: A zero value of aircraft specific energy is at the Earth's surface and increases as speed and altitude increases.It is the total energy of the vehicle (relative to the Earth's surface) per unit weight of the vehicle and being independent of the mass of the vehicle provides a powerful tool for the design of optimal trajectories.The specific energy is computed by the total energy (as defined above relative the Earth's surface) divided by the mass of the vehicle