A ducted fan is a type of propulsion system that consists of a fan enclosed within a cylindrical duct. This design helps to improve efficiency and reduce noise compared to open propellers. Ducted fans are commonly used in various applications, including drones, aircraft, and marine vessels, where they provide thrust while minimizing drag. The enclosed design of ducted fans allows for better control of airflow, which enhances lift and stability. They are particularly useful in situations where space is limited or where safety is a concern, as the duct protects the fan blades from damage and reduces the risk of injury.