Guest Editorial Introduction to the Special Issue on Plasma Propulsion

This Special Issue is dedicated to the physics, technology, and application of plasma propulsion for spacecraft. The field of plasma propulsion includes a broad variety of thrusters that can achieve high propellant exhaust velocity, thereby offering a large mass savings for space vehicles compared to chemical (combustion) rockets. These thrusters are broadly categorized by their propellant acceleration mechanism into three groups: 1) electrothermal; 2) electrostatic; and 3) electromagnetic [1]. Research into plasma propulsion dates back several decades, with a first application in space in 1964 on the Soviet Zond-2, which used an ablative pulsed plasma thruster to control the spacecraft orientation. Today, plasma propulsion is a very rapidly growing area of plasma science and technology, with over 250 operational spacecraft employing plasma propulsion in a variety of applications. Many new plasma thrusters have been recently developed, including numerous successful attempts to scale previously known systems to lower and higher power levels, ranging from a few watts to over 100 kW [2], [3]. As space exploration shifts toward small and efficient satellites, or micro and nanosatellites [4], [5], there are many near-future space missions involving science, military, and commercial payloads utilizing micro and nanosatellite platforms. These platforms require very small levels of thrust for very fine attitude control, high resolution. Earth imaging and astronomy, as well as very precise positioning requirements and other very precise positioning requirements for spacecraft performing formation flying and interferometry missions. Miniaturized propulsion systems are required to satisfy these emerging needs for both the low-thrust missions and the propulsion on small-sized spac- craft.