Ferroelectric plasma thruster for micro-propulsion

Abstract

Summary form only given. Micro-spacecraft are of current interest, due to the possibility of reducing mission cost and risk by flying several spacecraft in formation. The applicability of micro-spacecraft to certain missions is predicted to depend on the availability of compact, lightweight, high specific impulse micro-propulsion systems. In addition, micro-propulsion will be required for attitude adjustment of space-based telescope interferometers, and imaging arrays. Chemical propulsion systems are capable of specific impulses of /spl sim/250 s. This may not be adequate to ensure a lightweight propulsion option for attitude adjustment, for instance. Electric propulsion options are capable of impulses of 1000 s or greater, making them a potentially attractive micro-propulsion option. The most highly developed electric propulsion concepts, ion and Hall thrusters, have been developed for larger craft and higher powers. Scaling these concepts to micro-propulsion relevance can be difficult. Therefore, there is a need for new, high impulse, compact electric micro-propulsion concepts. A new micro-propulsion option based on ferroelectric plasma production, with ponderomotive acceleration to achieve high ion exhaust velocities will be presented. Recent studies of a ferroelectric plasma source excited by RF applied power have shown significant emission of negatively and positively charged species from the surface of the dielectric. Positive currents from 30 to 370 mA have been observed emanating from an RF driven ferroelectric cathode. Ions produced in the surface plasma of the ferroelectric cathode can be accelerated ponderomotively, resulting in high ion velocities. The RF driven ferroelectric emitter produces a strong electric field gradient, enabling ponderomotive acceleration of the ions. The high dielectric constant of the ferroelectric helps to amplify the applied field gradient. Calculations of the ion exhaust velocity indicates that specific impulses in the 1000 s range are possible. Data from ferroelectric emission experiments will be presented in the context of the ion accelerator and electric micro-propulsion concept.