A mass and cost model for the selection of electric propulsion string size has been expanded to include the effects of nesting the discharge channels in Hall thrusters. The equations for three components were modified: the thruster, the xenon flow system, and the cabling. We developed an analytical expression for thruster specific mass as a function of the number of nested channels, then used that expression to evaluate the specific mass savings provided by an example channel nesting technique. Xenon flow system and cabling equations were modified to scale with number of channels instead of number of thrusters. The updated model was then applied to missions ranging in power from 500 kW to 1.25 MW for systems containing zero to five redundant thrusters. These results indicate that the example channel nesting would provide 4-7% system mass savings as compared to a single-channel thruster. The impact of nested Hall thrusters on system cost is also explored. It is argued that no modification to the original cost model is necessary to capture nested Hall thrusters. Results for 1-channel and 3-channel thrusters demonstrate that the mass savings translate to improved cost savings, ranging from 9-13% for the example nesting technique. Other potential nesting techniques are also detailed, and their mass and cost savings are explored using the modified model. These results indicate that system mass savings in excess of 8% and cost savings in excess of 14% may be possible with alternative channel nesting techniques. Ultimately, nested thrusters push the system mass minimum toward the cost minimum, providing a means for mission planners to more effectively optimize high-power electric propulsion strings for both cost and mass.
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