Institution: | Department of Physics, University of Giessen, Giessen, Germany and Department of Astronautics, Technical University of Munich, Germany |
Abstract: | The large mass as well as the low first ionization potential and the large electron impact ionization cross-section make Buckminsterfullerene (C60) potentially attractive as an ion engine propellant. To evaluate the advantages of C60 it was necessary to calculate characteristic quantities like the thrust-beam-power ratio and the different efficiencies. It was found that, compared with xenon, the use of C60 would significantly reduce the necessary beam power by 57 percent for the same power level, resulting in a reduction of power supply mass and thus in a higher payload capacity. Calculations of the efficiencies show a clear increase in overall efficiency. Particularly, the mass efficiency and the electrical efficiency would increase significantly over that obtained with a xenon-fuelled ion engine. Together with the exceptionally high flexibility of the molecular structure of C60, this results in a very low ablation in the grid system, and consequently in a longer lifetime. One of the most severe problems in using C60 as propellant for ion engines is the temperature sensitivity of C60. High temperatures cause fragmentation of the C60 molecule, low temperatures lead to resublimation of C60 on the inner walls of the engine. Both would result in a decrease of the mass efficiency. Therefore, extensive experiments with a special ion source were carried out to determine the temperature behavior of an ion thruster. This and the theoretical research yield in a temperature window (400–700°C) for systems operating with C60. |