PHY550 - Plasmas in space science and technology
This course deals with the physics of ionized environments, or plasma physics, from the space science and industry point of view. Plasma is by far the most common state of matter in the visible universe and therefore nearly all astrophysical objects are in fact plasmas. Plasmas are also present on Earth, either created by nature in the form of lightnings or auroras, or generated by human beings in a wide range of industrial applications. They play a central role in microelectronics since etching and deposition of thin films relies mostly on plasma processing. They are also used as air purifiers or to treat wounds in medicine. They might be used in the coming years to treat cancer or to achieve nuclear fusion, which would give humanity an almost unlimited source of energy. As we shall see in details in this lecture, they are now successfully used as efficient engines for satellite and spacecraft propulsion. Thus, plasmas are fundamental in space science and technology.
Satellites and spacecrafts mainly operate around Earth, or in the solar system in environments that are almost always significantly or fully ionized. The Sun continuously emits a magnetized plasma, mainly composed of electrons and protons, called the solar wind. This plasma interacts with the planets of the solar system, leading to complex phenomenon that are essential to understand the life and the dynamics of planets and their atmospheres. Planets that generate their own magnetic field, like Earth, are partially protected from the solar wind by a magnetosphere, which acts as a magnetic shield. Nevertheless, the higher atmosphere remains ionized by the solar wind (the ionosphere), particularly in the aurora regions. This course will therefore require a detailed description of the fundamental principles governing the solar environment, the solar wind, the magnetosphere and the Earth ionosphere.
The lecture will then describe in details the interaction between plasmas and satellites or spacecrafts. These are immersed in space plasmas and are subject to charged particles bombardment (electrons and ions). We will study the structure of the potential surrounding a satellite in a plasma and the variety of interactions between charged particles and parts of a satellite. The conductivity of its dielectric coating, also subjected to radiation, determines the charge differential or charge risk. The secondary emission of electrons resulting of the impact of the plasma electrons controls the sign of the electrostatic discharge, impacts the multipactor discharges which limit the power of telecom satellites, and modify the abnormal electronic conductivity in Hall effect thrusters.
In the last part of this course, we will describe the fundamental mechanisms at play in plasmas thrusters, that are now routinely used as satellite engines, and that will be essential for future space exploration missions. The principle of plasma thrusters is to ionize the gas propellant to achieve much higher exhaust velocities than conventional hydrodynamic nozzles. For the same thrust, the mass flow of the propellant is then drastically reduced, and the plasma thruster has a much better mass efficiency than conventional chemical engines. We will study in details two flight-proven engines, the gridded-ion thruster and the Hall effect thruster. Different types of plasma thrusters based on advanced concepts currently under development will also be discussed.
Course in French, course materials in English
- Teaching coordinator: Chabert Pascal