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Paper: Alta FT-150: The Thruster for LISA Pathfinder and LISA/NGO Missions
Volume: 467, 9th LISA Symposium
Page: 245
Authors: Paita, L.; Cesari, U.; Nania, F.; Priami, L.; Rossodivita, A.; Giusti, N.; Andrenucci, M.; Estublier, D.
Abstract: FT-150© FEEP thruster has successfully completed an endurance test at Alta's Micropropulsion laboratory. The updated thruster design dramatically enhances performance with respect to previous FEEP devices and marks a major step forward in the LISA Pathfinder and NGO programmes as well as space propulsion capability in general. The test campaign took place in two parts. Firstly, the new design was tested to validate that the new configuration was compliant with the requirements of the Lisa Pathfinder mission with particular emphasis on the achievement of required total impulse and minimum and maximum thrust levels.The second part of the campaign was aimed at testing a worst-case DFACS profile of the LISA Pathfinder mission using the Elegant Breadboard Power Control Unit (EBB PCU) commanding at 10 Hz and acquiring at 50 Hz. Both purposes of the campaign were successfully met. A total impulse of more than 1080 Ns and a firing time of more than 3500 hours were achieved. No degradation of efficiency and performance was recorded over the entire test. During the first part, more then 600 Ns of total impulse and about 2000 hours of firing time were achieved. Different thrust profiles were commanded with an average thrust of about 87 μN. The minimum and maximum thrust were 1 μN and 150 μN respectively. Short periods at zero N (i.e. thruster switched-off) were also commanded. The measured mass efficiency and specific impulse, 60% and 8000 s respectively, demonstrated that the current design of the thruster is fully compatible with the much larger impulse requirement of LISA mission. The simulation of the worst-case DFACS cycles at 10 Hz was also successfully performed. Three different DFACS cycles representative of the worst cases were performed. These cycles highlighted one of the main advantages of this technology: the controllability and response time that can be verified immediately with electrical feedback parameters like total voltage and beam current (data collected at 50 Hz during the test). The thrust noise was also calculated from electrical parameters, filtered to obtain flawless acquisition at 50 Hz. The article provides a view of the thruster configuration, vacuum facility and test set-up, the electrical parameters of the thruster, the main parameters recorded by the diagnostic system and the details of the behavior of the TA-PCU system during the performance of the worst DFACS profile of the LISA Pathfinder mission.
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