| Popis: |
The paper deals with results from the experimental characterization of the Double-Stage Hall-effect Thruster prototype developed, under the European Space Agency sponsorship, by AASI, as prime contractor and ALTA, as AASI sub-contractor. The thruster architecture implements an intermediate electrode along the discharge chamber, designed to be an additional electrons source other than the external cathode, and a magnetic circuit providing a radial magnetic field profile with two different peaks, the most internal one conceived for generating an Hall-effect ionisation mechanism. Although experimental results show interesting performance, especially in terms of thrust efficiency, in the range of 50% for most of the investigated conditions, thruster has not been able to operate in a real DoubleStage configuration for the inability of the intermediate electrode of emitting a sufficient amount of electrons for propellant ionisation, independent on cathode electrons contribution. This fact seems imputable to space charge effect negatively affecting emission from dispenser cathodes, chosen for the intermediate electrode design. Some beneficial effect on thruster performance due to the presence of the active intermediate electrode has been observed at lowest powers, where possibly the weight of the intermediate electrode current with respect to the total discharge current is higher. |
