Review of Propulsion Technologies for N+3 Subsonic Vehicle Concepts

NASA has set aggressive fuel burn, noise, and emission reduction goals for a new generation (N+3) of aircraft targeting concepts that could be viable in the 2035 timeframe. Several concepts have been formulated, where the term N+3 indicate aircraft three generations later than current state-of-the-art aircraft, N. Dramatic improvements need to be made in the airframe, propulsion systems, mission design, and the air transportation system in order to meet these goals. The propulsion system is a key element to achieving these goals due to its major role with reducing emissions, fuel burn, and noise. This report provides an in-depth description and assessment of propulsion systems and technologies considered in the subsonic vehicle concepts. Recommendations for technologies that merit further research and development are presented based upon their impact on the goals and likelihood of being operational by 2035.