Concept of SUb-atmospheric Radio-frequency Engine (SURE) for near space environment

A concept of SUb-atmospheric Radio-frequency Engine (SURE) designed for the near-space environment is proposed. The antenna wrapping quartz tube consists of two solenoid coils with variable separation distance and is driven by radio frequency power supply (13.56 MHz–1 kW). The discharge involves inductive coupling under each solenoid coil and capacitive coupling between them. This novel scheme can ionize the filling air efficiently for the entire pressure range of 32∼5332 Pa in near space. The formed plasma density and temperature are up to 2.23×1018 m-3 and 2.79 eV, respectively. The influences of separation distance, input power, filling pressure, and the number of solenoid turns on discharge are presented in detail. This air-breathing electric propulsion system has no plasma-facing electrode and does not require an external magnetic field and is, thereby, durable and structurally compact and light.