Universal Range Equation for Unconventional Aircraft Concepts

Rising environmental concerns has led the aviation industry around the world to set high targets to reduce carbon emission. Revolutionary concepts with unconventional propulsion systems and energy sources are seen as a necessity to achieve carbon neutrality. These include hydrogen combustion, electrified propulsion powered by batteries or hydrogen fuel cells, sustainable aviation fuels, and distributed propulsion. With several potential alternatives still being researched and developed, the path to sustainable aviation is still unclear. This research aims to develop a methodology to quickly assess different concepts based on performance as well as environmental metrics using simple analytical equations, and provide insights about the tradespace for these concepts. At the pre-conceptual design phase, a key performance indicator is the aircraft range, which takes into account the aerodynamics, propulsion and the weight of the aircraft. The objective of this paper is to propose a unified range equation that is applicable to concepts with one or more energy sources and any powertrain architecture. The mathematical equivalence of this equation to range equations derived by other authors, specifically for electrified propulsion, is demonstrated. Finally, the overall efficiency and range equations are derived for a complex aircraft architecture with dual energy sources, multiple propellers and unconventional powertrain configurations, to demonstrate the universality and ease of use of this method.