Realistic and detailed vehicle characteristics are input to NSEG to permit accurate mission analysis. NSEG allows engine scaling so as to fit the design under analysis. NSEG contains several approximate flight path optimization capabilities based on Rutowski energy-like criteria for considering minimum time or fuel flight segments and maximum range segments during climb or descent. Takeoff and landing analysis is based on the Air Force Flight Dynamics Laboratory DATCOM method of high lift aerodynamic modelling. There are three main atmosphere options available; the 1962 U.S. Standard atmosphere, a stratified atmosphere model, and an external atmosphere model supplied by the user. The stratified atmosphere model requires the input of the number of layers (maximum 25), altitudes, temperatures, and pressures. The mission specification is open-ended in that the upper limit on the number of flight segments to be included in a mission profile can be increased with a simple program change. Input consists of vehicle characteristic data, data to specify details of the mission, and selection of program options. Output can be printer-generated tabular data or contour plots on a Calcomp plotter, CRT, or Houston plotter.