Plasma thruster design for space transportation

The "Plasma Thrusters Design for Sustainable Space Transportation" project is a research initia- tive born from the collaboration between La Sapienza University of Rome’s School of Aerospace Engineering (SIA) and the ENEA Research Centre in Frascati. This innovative plasma thruster project of arose from the PROTO-SPHERA experiment at the Frascati ENEA Research Centre, a new plasma magnetic confinement experiment aiming to generate a spherical, simply connected plasma with no central metallic conductor. This experiment inspired the study and conceptualiza- tion of a new nuclear fusion plasma thruster. The PROTO-SPHERA experiment is at the forefront of technology for machines that confine plasma magnetically, as it can generate a closed magnetic configuration for confining plasma from an axial plasma discharge. This magnetic configuration is also known as "simply connected" because it contains no voids or holes. This magnetic configuration is of interest in the study of magnetic reconnections, astrophysical space plasmas, and its potential to be transformed into a nuclear fusion reactor. The lightness, energy efficiency, simple construction and low enviromental impact of PROTO- SPHERA led to its investigation as a plasma thruster and fusion plasma thruster. Based on the experimental results obtained from the machine in terms of plasma production and generation of spherical plasmas, it was decided to evaluate the performance of a nuclear fusion thruster in a scaled configuration of the present machine. The idea of transforming the PROTO-SPHERA experiment into a plasma thruster gave rise to this PhD project, which focuses on designing a helicon plasma thruster for cislunar missions and a nuclear fusion thruster for interplanetary missions. This category of low-thrust thrusters can be used for space flight beyond the terrestrial atmosphere, either in orbit or during interplanetary flight. This design study enables experimentation with this type of technology in laboratory setting and with space missions that can be performed using these rocket engines. In an international scenario in which demand for access to space is increasing rapidly, with hundreds of satellites launched into orbit every year and the need to remove decommissioned satellites, studying and designing innovative propulsion systems enables safe orbital transfers with high efficiency. A plasma nuclear fusion thruster, for example, is a space transportation system with a very high specific impulse that can provide moderate thrust (from few Newtons to thousands of Newtons) and can be used for interplanetary space missions carrying heavy payloads. Therefore, its application in this PhD project was conceived for interplanetary transfers within the Solar System. The helicon thruster, on the other hand, is in the low thrust and high specific impulse category, although this is lower than that of nuclear fusion thrusters. It is suitable for orbital transfers within the sphere of influence of Earth. The design of the plasma thrusters is performed modelling the physics of their main compo- nents, which allows us to predict their behavior and performance and also determine their size. The resulting engines are then simulated using electromagnetic modelling to determine their operating conditions and propulsive performance. In particular, a design method is proposed for the helicon antenna and magnetic nozzle of the helicon thruster, based on analytical models and plasma sim- ulations that size the thruster for assigned mission requirements. A design method has also been developed for the nuclear fusion thruster of a scaled fusion magnetic configuration obtained from the PROTO-SPHERA experiment, combined with a mission analysis for an interplanetary nuclear fusion thruster mission to determine the engine size required to satisfy the mission’s specifications. These plasma thrusters are new technologies for space flight and are currently at the laboratory stage. They must be tested to increase their TRL (Technology Readiness Level), before they can be used. This PhD study proposes new modelling for both the helicon and nuclear fusion thrusters to increase the understanding of their main working principles and to facilitate their design using readily applicable sizing methods. The results obtained in this PhD study can be used in future new research projects on plasma thrusters and to design new propulsive systems based on the plasma technologies here reported.