The propagation characteristics of low frequency radio waves in magnetized hypersonic plasma sheaths

Communication blackouts have been a main threat to hypersonic vehicles for decades. The low frequency communication was considered a potential approach to mitigate the “blackout.” Nowadays, low frequency transmitters serving underwater communication have transmission power up to several megawatts. In other words, if low frequency communication signals could penetrate the plasma sheath, it would be a meaningful solution that using modern low frequency transmitters to give service to hypersonic vehicle communication, and the service area could be very large. Although the studies on blackouts using low frequency waves have lasted for many years, it still remains many unclear problems. The present study analyzes the characteristics of different frequency waves passing through a plasma sheath. The analysis revealed that the low frequency signals with high power could penetrate the plasma sheath and mitigate the blackout effectively. According to our simulation results, the transmission coefficient decreased with the flight speed and also increased with magnetic field intensity and the axial distance from the onboard antenna to the nose of the vehicle. Moreover, it is not sensitive to the frequency of signals. At last, two example models of using a ground low frequency station to communicate with the hypersonic vehicle were analyzed, which means that the low frequency communication can significantly be considered in the application of hypersonic vehicles in the near future.