The necessity of on board oxygen for airbreathing single-stage-to-orbit vehicles

Vehicle performance and sizing impacts of stored oxygen are examined for SSTO vehicles such as the National Aerospace Plane. The relationship between propulsion efficiency and thrust-to-drag ratio is presented. Idealistic and substantive values for these parameters are compared. The impact of these two parameters as well as propellant density on vehicle sizing is investigated. Representative configurations are provided for comparison purposes.