(2) To measure the plasma particles, wave, and luminosity of the MPD thruster plume from SFU or the co-orbiting STS. (3) To verify the altitude maintenance capability of MPD thruster as the SFU rebooster. Option 2. Long-Term Experiment: (1) To verify the endurance of MPD thruster system for 100-day operation. At present, these objectives are flexible enough to contain a life-cycle test of the MPD thruster system, because the SFU experiment will be limited in its duration, especially for the first flight. However, prolonged termination or a long-term stay in space of more than 30 to 100 days enables the endurance test of the MPD thruster corresponding to a few tens of million pulses. In case the SFU mission duration is not more than two weeks, this sort of test will have to be conducted on the ground. A one million pulses endurance test of an MPD head has already been finished in the vacuum tank [5]. Configuration and Characteristics Since the SFU has an octagonal structure, it will be suitable for EPEX that the MPD thruster module occupies two of those compartments to align the thrust vector, one towards the accelerating direction and the other towards the decelerating direction. However, the occupation of two compartments depends upon the furnishing tolerance of SFU. This configuration will give the highest manoeuverablity to SFU, although it may cause some interference between the solar array and the MPD thruster plume. The MPD thruster module in one compartment consists of a set of MPD heads, a capacitor bank, a charging control unit, a propellant supply system, a thermal control system, a command and data management system, and terminating or supporting structure. Fig. 8(a) shows a typical MPD thruster module installation configuration assembled in SFU. Another possible configuration is depicted in Fig. 8(b), where the MPD thruster module is installed on the bottom of the SFU structural body. This configuration will provide less manoeuverability than in the case of Fig. 8(a), although the interference between the solar array and the MPD thruster plume can be completely eliminated. The characteristics summary of the MPD thruster system is as follows:
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