Optimization of Air-Breathing Electric Hybrid Engines for Atmospheric-to-Orbit Vehicles

Abstract

Air-breathing electric hybrid engines have emerged as a promising concept for future atmospheric-to-orbit (ATO) vehicles and very low Earth orbit (VLEO) missions. The primary advantage of this technology lies in its ability to reduce dependence on carried propellant by utilizing ambient atmospheric particles as the working fluid, thereby improving mission efficiency and extending operational lifespan. This review synthesizes the core principles of air-breathing propulsion, electric propulsion, hybrid engine architecture, and mission-level performance analysis, with emphasis on how these systems may enable next-generation space access. The review also examines the principal engineering challenges involved in realizing this concept. These include intake capture efficiency, aerothermal loading, onboard power availability, multi-mode transition stability, and system resilience across varying flight conditions. Performance enhancement strategies such as plasma-assisted combustion, magnetohydrodynamic (MHD) flow control, intake compression and shock optimization, and precooler thermal management are discussed as enabling technologies. In addition, thermodynamic analysis, multi-objective optimization frameworks, and mission-level design methodologies are addressed. The review concludes that air-breathing electric hybrid propulsion remains in an early but promising phase of development, offering a compelling research direction for efficient and reusable ATO systems.