About this Research Topic
Over the last years, the plasma physics community became involved in aerospace research. There are many different applications of plasmas in this field. A subject of large interest is the atmospheric entry of space vehicles, for landing on Earth and also on outer planets, like Mars, in view of future space missions. In this context, a theoretical approach based on the so-called state-to-state model, commonly used to describe weakly ionized gases, is fundamental to describe non-equilibrium in the shock wave in front of the entry vehicle in the upper atmosphere. This approach is also useful to describe ground test facilities (plasma wind tunnels).
Important applications are propulsion technologies based on plasma. The most important among them is the Hall thruster that has already been used for satellite positioning and orientation. Large research activities are devoted to this subject in order to extend the capabilities of this device also to interplanetary flights. Another interesting subject related to the Hall thruster is the interference between the engine and the radio communication. There are also other propulsion technologies based on plasma, such as plasma jets and laser propulsion.
Plasma-assisted combustion finds its interest in the field of propulsion in order to use more economic propellants in rocket engines. Methane, being widely present in the solar system, can be used for the return from an outer planet exploration avoiding charging of propellant for the outward trip. However, methane combustion is not adequate for rockets and plasma can be a good candidate to improve its combustion capabilities. Another application of plasma-assisted combustion can be to sustain the process in supersonic flow conditions as it happens in SCRAMJET engines, where hydrogen is used as propellant. In supersonic flow, the flame is highly unstable and to sustain the combustion, nanosecond discharges and Dielectric Barrier Discharge (DBD) devices are promising techniques.
Another plasma application is to control the flow properties through an electromagnetic field. It has been shown that pulsed discharge changes the flow properties and in particular controls the transition to turbulence, with a consequent reduction of noise. Controlling the flow is also a relevant aspect for the SCRAMJET, which operational conditions are very limited, because the flow must enter in the engine only in particular configuration, determined by the design of the vehicle. Plasma flow control can be used to extend the operational conditions.
In return mission from outer planets, the temperature in the shock wave in front of the vehicle is much higher than at the return from orbital mission, and the traditional thermal protection system based on insulator or ablative materials are not sufficient to protect the capsule from the thermal load. At this purpose, being ionization in the shock very high, Magnetohydrodynamic (MHD) heat shield can be an interesting alternative. The feasibility of flow control by MHD has been shown in some experiments.
In this Research Topic, we aim to give an overview of the most recent activities in plasma physics for aerospace applications, from fundamental and basic research to technological exploitation.
Keywords: Plasma, High-Enthalpy Flows, non-equilibrium, MHD, Propulsion, Magnetohydrodynamic
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