Electrical power system architectures and design concerns for future Mach 3 to 25 aerospace vehicles are discussed. Three conceptual electrical power system architectures were developed to meet the requirements of a future aerospace vehicle. Architectures developed include a hybrid 270 Vdc/115 Vac four- bus architecture, a 270 Vdc four-bus architecture, and a 115 Vac four-bus architecture. The vehicle requirements chosen for this study include electrically driven flight control surface actuators and main engine propellant boost pumps, A trade study was performed to determine the optimum distribution architecture based on total system weight, compatibility of the system with the vehicle loads, component availability, corona susceptibility, development risk, and personnel safety. The trade study identified the hybrid 270 Vdc/115 Vac four bus architecture as the optimum configuration for the given requirements.