PPT Development for Nanosatellite Applications: Experimental Results
In this paper, the design and performances of a pulsed plasma thruster (PPT) for nanosatellite applications will be presented. The breadboard model PPT presented in this paper will be a part of six PPTs propulsion system designed to provide attitude and translational control for a 20-kg nanosatellite for a total delta-V of 40 m/s. The thruster performances have been characterized in terms of electrical parameters, mass bit, impulse bit, and specific impulse. The thruster was found to be compliant with the mission requirement. Moreover, preliminary electromagnetic noise interference measurements have been performed. The spark plug discharge was found to be the main source of noise as already found by previous authors. From the collected data, it can be inferred that the noise is mostly radiated.
High-voltage pulsed power supply for the igniter circuit of a pulsed plasma thruster
In nano-satellites, the pulsed plasma thruster (PPT) is a promising electric propulsion system for orbit maintenance and attitude control. In this paper, a pulse power supply based on a flyback circuit is investigated for the PPT igniter. The proposed circuit uses the resonance among the magnetizing inductance of transformer and parasitic capacitances to generate a high pulse voltage. When compared with other topologies, the flyback circuit does not require a physical high voltage capacitor. Consequently, the reliability is improved. With a reduced number of components, the circuit suits well to the size constraint of a nano-satellite. Moreover, the output pulse voltage can be easily controlled by adjusting the peak charging current. To validate the concept, a prototype circuit has been developed. The experimental results show that the proposed circuit has a medium voltage conversion gain, and the plasma can be generated in vacuum environment successfully.
Participation Improves Collective Decisions (When It Involves Deliberation): Experimental Evidence From Kenya
Abstract Citizen participation in decision making has been widely lauded as a method for improving societal outcomes. Deliberative discussion, in particular, is believed to be more transformative than a mere aggregation of individual preferences, leading to more socially optimal decision making and behavior. I report the results from a laboratory experiment with 570 subjects in Nairobi, directly testing the effect of participation in deliberative group decision making on collective outcomes. Participants engage in a group task to earn compensation toward a shared group fund. Randomly assigned treatments vary according to whether decision making over the task to be completed involves: (1) external assignment; (2) non-deliberative majority voting; or (3) consensus through deliberative discussion. I find that deliberation improves collective decision making. Deliberation is also associated with changes in preferences, greater agreement with decision outcomes, and greater perceived fairness. Evidence for behavior change is weaker, but there is some support for further research into the relationship between preference change and behavior change.