Modeling the NEXT Multithruster Array Test With Nascap-2k

Tests of up to three simultaneously firing 40-cm NASA´s Evolutionary Xenon Thrusters took place at NASA Glenn Research Center. In addition to numerous engineering tests, the experiment was instrumented to measure plasma properties in the interacting plumes, charge exchange return current to the active and dormant thrusters, and current and plasma properties at various locations. This paper describes the use of Nascap-2k to calculate plume potentials and charge exchange ion return currents to active and dormant ion optics and to diagnostic probes. Calculations were performed varying the numbers of active thrusters, thruster power levels, and gimbaling. The results were extrapolated to space conditions. Despite several simplifying assumptions, we obtained good agreement with experimental results. No major problems associated with multiple thruster operation were found.