Dear Colleagues,

In order to address the current needs linked to space, such as the implementation of a strong satellite infrastructure close to Earth, the execution of various types of maneuvers or space exploration, the exploration of small satellites, particularly the CubeSats, and the complexity of their missions, increasingly efficient means of propulsion, including even its miniaturization, have become necessary. Nowadays, chemical propulsion is the basis of rocket launch systems and continues to be used frequently in propulsion in space. However, electric thrusters are challenging this monopoly and are increasingly emerging as strong candidates for space missions as they lack many of the intrinsic limitations associated with thermodynamic systems. Electric engines can be much more fuel efficient than chemical or jet engines, which convert the energy released in chemical reactions between the fuel and an oxidizer into kinetic energy. Since electric propulsion systems require very little mass to accelerate a space vehicle, they are limited by the electric power on board and are suitable for operations that require low propulsion (in the range of micro to milli newton).

Propulsion is required for the movement of satellites in space and operates according to the basic principle of action–reaction, leading to momentum transfer. A force, called thrust, is exerted on a space vehicle, usually by the ejection of a working gas that has acquired a high value of kinetic energy. Electrically propelled spacecrafts use electrical energy to accelerate a propellant through different electrical and/or magnetic mechanisms. Electric propulsion that uses electrical energy to energize the propellant, creating a plasma, is known as plasma propulsion. In this case, electrical energy is first used to ionize the propellant and then transfer energy to the resulting plasma, which results in its acceleration.

Depending on the acceleration mechanism, electric propulsion systems are traditionally subdivided into three types: (i) electrothermal thrusters (which use electric energy to heat the propellant—the acceleration mechanism being based on the pressure gradient, as in chemical propellants. This category includes, for example, resistojet and arcjet thrusters); (ii) electrostatic thrusters (which directly use an electric field to accelerate ions; here, it is customary to include field emission electrostatic propulsion (FEEP), gridded electrostatic ion thrusters and the various types of Hall thrusters); (iii) electromagnetic thrusters (which use a combination of electric and magnetic fields to accelerate the propellant—pulsed plasma thrusters (PPT), magnetoplasmadynamic (MPD) or vacuum arc thrusters (VAT)) can be included in this group).

This Special Issue on “Electrical Propulsion Technology” is open, but not limited, to recent findings in novel and possible future applications of plasmas in electrical propulsion technologies.

Papers providing fundamental insights into the understanding of plasmas and detailed analysis of electrical discharges, pushing forward cutting-edge techniques in plasma propulsion science and technology, are especially welcome.

Prof. Dr. Paulo A. Sá
Guest Editor

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• thrust
• spacecraft propulsion
• plasma propulsion
• electrothermal propellers
• electrostatic propellers
• electromagnetic propellers
• micro-propulsion
• cubesats
• figures of merit
• \({\overset{\rightarrow}{E} \times \overset{\rightarrow}{B}}\) drift
• charged particle motion
• boltzmann equation
• general transport equation
• conductivity
• diffusion
• proplellant mass flow
• plasma–wall interaction
• micro and macro-instabilities
• EHD propulsion and ionic wind