Advancements to the Micro-Cathode Arc Thruster: Linear Actuator, Ablative Anode, and Modular Designs Open Access

The Micropropulsion and Nanotechnology Laboratory (MpNL) of The George WashingtonUniversity began designing the Micro-Cathode Arc Thruster (muCAT) in 2008 to improveupon the vacuum arc thruster design and efficiency. This system has worked verywell, successfully flying aboard two Cube Satellite (CubeSat) missions. The MpNL continuesto iterate and strives to optimize the thruster to find the ideal subsystem to fulfill thesmall satellite’s needs. The biggest obstacle is removing the external magnetic field, becauseit can interfere with the on-board instruments. Removing this feature would make thethrusters more desirable to the wider CubeSat community. Three newly designed versionsof the muCAT are presented. Each system contributes a change in order to see how thesenew models fair in comparison with the current scheme and if they can be just as effectivesans external magnetic field.Each of the new designs was characterized via arc current, ion current, ion velocity,erosion rate, and thrust stand experiments. The Linear Actuated muCAT entailedswapping the polarities of the central and outer electrodes to remove the external magneticfield, and utilizing a stepper motor in place of the spring-feed mechanism . The secondsystem was the Ablative Anode muCAT employing a metal with low melting temperatureand high vapor pressure to replace the standard anode, or positive, central electrode. Thethird system was the Modular muCAT consisting of multiple thruster heads allowing for athruster to be replaced once it has ceased arcing. After characterizing the systems, theywere compared to each other and the Standard muCAT to determine the optimal configuration.All three systems performed on par or better than the Standard muCAT in mostarenas. Once a magnetic field was added, the ion current increased and provided an averagetransport efficiency of 40%, in comparison to the standard system’s 35%. The ion velocitywas found to be on par or better at 12-13 [km/s] without a magnetic field, and achievingalmost 100 [km/s] with an external magnetic field seated slightly behind the face of thethruster. Furthermore, the hypothesis that the ablative anode materials would erode inaddition to the cathode, proved to be correct as it presented a positive erosion rate. Thethrust stand experiments conveyed that the Ablative Anode muCAT attained the highest thrustand thrust-to-power ratio. The data presented demonstrates that the systems are comparableto the standard system, and each other. Therefore, the MpNL can move forward to optimizeeach thruster design.The purpose of this work was to assess three new iterations of the muCAT andcompare them to the standard scheme , from which each system possessed a major differenceto be evaluated on its merit and usefulness. The results of this dissertation shed lighton which path is optimal to improve upon the muCAT.

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