Optimizing Adamantane Plasma Thruster Efficiency via 2-D Simulations

Emerson Lo1, Mia Claire Chang1, Zolia Sarmiento1, Haron Samhan1, Aparna Krishnan1, Alana Smith1, Matthew Gilpin1, Lubos Brieda1 1The Advanced Spacecraft Propulsion and Energy Laboratory, University of Southern California, Los Angeles, CA, 90007 At the University of Southern California, the Advanced Spacecraft Propulsion and Energy (ASPEN) Lab has been developing a solid-fuel thruster and investigating the use of adamantane (C10H16) as fuel. The advantageous qualities of adamantane would allow for a reduced mass and complexity compared to other solid-fuel thrusters, and due to these qualities, it is worthwhile to investigate its potential as an alternative fuel source. While developing this thruster, simulating the plasma generated enables a more rapid iteration of the thruster design to increase fuel efficiency and specific impulse. From these simulations, we can gather data on electron density, plasma potential, the temperature of the resulting plasma, and a visualization of how the adamantane plume is flowing out of the thruster, allowing for a better understanding of what the adamantane plasma consists of and the efficiency of the thruster design. Two-dimensional plasma simulations are performed using the open-source rarefied gas code, Starfish. This program allows for the simulation of neutral adamantane molecules in the propellant tank and their dispersion dynamics over multiple time steps, utilizing the Electrostatic Particle in Cell (ES-PIC) method and Monte Carlo Collisions (MCC) method for ionization modeling. The results of these simulations are displayed in Paraview, an open-source post-processing visualization software. Through Paraview, multiple datum describing the plasma can be displayed, including plasma potential, charge density, electric field components, and magnetic field components. Several different thruster configuration models are input into Starfish by editing input boundary files. These boundary files consist of blocks of code that outline the shape of the thruster in multiple different geometries. By simulating each respective boundary, it is possible to visualize how different boundary dimensions and shapes affect the flow of adamantane. Comparing these simulated electric field lines from these different boundary configurations allows for the thruster design’s optimization. Variations of anode and cathode sizes and placements are also modeled to determine the most effective way to ionize adamantane, achieve plasma, and operate at optimized thruster efficiency. In the future, modeling the hydrocarbon adamantane that makes up the fuel in this thruster must take into account its complex structure since it will produce more complex hydrocarbons when ionized, which all need to be modeled accurately. The comparison of the experimental solutions to data achieved from the diagnostic team’s Langmuir probe will work to validate each others’ results or prompt further simulations and studies.