Systems Evaluation of Subsonic Hybrid-Electric Propulsion Concepts for NASA N+3 Goals and Conceptual Aircraft Sizing

Abstract

The air-travel demand is anticipated to grow in future and therefore the worldwide airtraffic is forecast to increase significantly. This growth in demand further increases the concerns pertaining to environmental and human health, which results in stringent aviation policies. Emission regulations have been set for the aviation sector to reduce its climate change impacts, and these support the efforts to meet the goals of the UN’s Paris treaty on climate change. The aviation sector is exploring sustainable and improved technologies to become more energy and cost efficient. Along these lines, NASA has developed the concept of ‘N+i’ goals to decrease fuel consumption, noise, and landing and take-off (LTO) oxides of nitrogen (NOx) emissions, and to enhance aircraft performance. The ‘N+3’ represents three technology generations into the future, where ‘N’ represents the current aircraft generation, with a forecasted technology readiness level 4-6, in year 2025 timeframe which will enable year 2035 service-entry. To meet NASA’s N+3 goals, significant improvements must be made in the air transportation system, airframe, mission design, and propulsion systems. A pivotal element to achieve these goals, is the propulsion system. This is because the role of propulsion system can be crucial in reducing emissions, noise, and fuel burn. This work evaluates the N+3 concepts in detail, based on the systems engineering approaches and selects the best of those concepts. A detailed analysis is presented for phase one of such a project using Georgia Institute of Technology’s Integrated Product-Process Development (IPPD) method. This work finds that the NASA N3-X turbo-electric distributed propulsion (TeDP) is the best concept for meeting the NASA N+3 goals, based on the systems engineering approach.