Microwave-Driven In-Tube Accelerator

A microwave-driven in-tube accelerator (MITA) concept is proposed to improve the thrust performance of microwave rockets driven by repeated intense microwave beam irradiation. A two-dimensional axisymmetric simulation model with a coupling module of electromagnetic wave propagation, plasma reaction diffusion, and neutral gas dynamics was developed, which captured the formation of the beam-induced plasma and shock wave on the MITA. The momentum coupling coefficient of the MITA increases with the beam frequency because a quality of beam focusing is improved, and the energy absorption at the plasma front is enhanced owing to an increase in the electric field intensity around the focal point. However, an increase in the thrust performance saturates when the plasma front, which propagates from the focal point, protrudes into the front side of the vehicle. Therefore, a design parameter, such as the vehicle radius, pulse width, beam intensity, and beam frequency, should be optimized to avoid gas heating at the vehicle front.