A narrative review of solar electric propulsion for space missions: Technological progress, market opportunities, geopolitical considerations, and safety challenges

Solar Electric Propulsion (SEP) is an advanced technology ideally suited for long-duration space missions requiring high efficiency and low-thrust propulsion. SEP systems generate propulsion by converting onboard electricity, using electric thrusters powered by solar arrays. This review offers a comprehensive analysis of both established and emerging thruster technologies, including electrothermal (ET), electrostatic (ES), and the evolving electromagnetic (EM) thrusters, while considering mission-specific factors such as power availability, propellant choice, and spacecraft mass that influence thruster selection. The performance of SEP systems largely depends on solar arrays, typically utilizing III-V multijunction solar cells, which offer superior sunlight conversion efficiency compared to alternatives like perovskite cells, concentrated photovoltaics, and silicon heterojunction cells. Despite SEP's advantages—such as high efficiency, extended mission duration, and reliability— it faces challenges, including the requirement for large solar arrays and reliance on sunlight. However, ongoing research continues to enhance SEP technology, making it increasingly vital for future space exploration and scientific missions. The market outlook for SEP is promising, and its significant geopolitical implications highlight the necessity for stronger international collaboration in space ventures. Solar electric propulsion offers significant benefits for satellite and spacecraft operations but also poses safety challenges. Addressing collision avoidance, radiation protection, plume interactions, and end-of-life disposal is crucial. Ongoing research and collaboration among stakeholders will be essential for developing effective safety protocols and regulatory frameworks.