Air Launching Eart-to-Orbit Vehicles: Delta V gains from Launch Conditions and Vehicle Aerodynamics

Abstract

The advantages and disadvantages of the various methods for air launching expendable or reusable space launch vehicles are described. Many different air launch scenarios are modeled and simulated using trajectory optimizations. The trajectory optimization is conducted using POST, a numerical integration program based on the three-degree-of-freedom equations of motion of a flight vehicle. Results in terms of change in velocity gains are reported as a function of launch conditions and launch vehicle aerodynamics. Air launch benefits are presented for a range of air speeds, altitudes, and flight path angles. The most beneficial launch vehicle parameters are in the following order; launch velocity, launch flight path angle, and launch altitude. Increasing launch vehicle size had the largest effect on payload size. There is an optimum launch flight path angle that maximizes the benefit from air launching. The results show that once above about 15000 meters (49,200 feet), added launch altitude has little additional benefit. Nomenclature Ae = Nozzle exit area = Angle of attack β =