Exploring advanced propulsion systems for CubeSats for now & for the future

CubeSats have significantly changed the landscape of modern space applications with their scalability, cost-efficiency, modularity, and rapid development time. Technological advancements have expanded their capabilities, leading to mission profiles where propulsion, active or passive, has evolved from an optional subsystem to a mission-critical requirement. Onboard propulsion enables mobility, transitioning small satellites from passive orbiters into manoeuvrable assets. This capability supports key mission functions — orbital correction, formation flying, drag compensation, and proximity operations — enhancing mission scope and responsiveness. To provide CubeSats with spatial manoeuvrability, propulsion engineers have developed a diverse set of approaches. Some systems are miniaturized versions of conventional technologies such as cold gas, liquid, or hybrid thrusters. Others—electromagnetic or propellant-less—represent novel alternatives designed especially for the CubeSat form factor. This paper presents a state-of-the-art review of propulsion technologies designed for CubeSats, with special emphasis on Differential Drag—a highly efficient passive propulsion method. The study focuses on propulsion strategies for Low Earth Orbits (LEO, <2000 km) and Very Low Earth Orbits (VLEO, <450 km) only. It also highlights systems that are currently flight-ready or near-term viable for rapid mission integration.