Improved Design of the VASIMR Radio Frequency Transmission Line

This proposal addresses technology innovation within the sub-topic Z10.04 ldquo;High Temperature, High-Voltage Electric Propulsion Harness Connectors and Cablesrdquo; moving from Phase I to Phase II in response to NASArsquo;s 2023 SBIR Phase II solicitation. In Phase I of this project, Ad Astra developed and completed the design of the fourth generation (Gen-4) ldquo;Rhino Horn,rdquo; the step-down, low impedance section of the VASIMRnbsp;radiofrequency (RF) transmission line. The VASIMRnbsp;is a high power, RF-driven two-stage plasma rocket and this component must handle up to 120 kW of steady-state RF power to the enginersquo;s second stage. Also in Phase I, a numerical model was developed to digitally assess the Rhino Horn performance. A sub-scale test article that reproduced the main thermal characteristics of the Rhino Horn was built and tested in vacuum to help validate both the numerical model and the teamrsquo;s assumptions on weight savings, manufacturability, and ease of assembly. The positive Phase I results point to a full-up construction of the unit in Phase II and an integrated test in Ad Astrarsquo;s VX-200SSnbsp;thruster. Therefore, these are the main Phase II objectives. Also, the Phase I numerical model will be further validated with experimental data from these tests. A detailed report of results and lessons learned will also be produced. Three generations of Rhino Horn designs have preceded the Gen-4, each with improved thermal management over its predecessor. The new design continues this trend. The proposed Gen-4 Rhino Horn introduces several modifications capturing lessons learned by the Ad Astra team experimenting with the three prior designs. These improvements, in aggregate, have resulted in a more thermally effective, electrically robust, compact, and lightweight assembly. It is worth noting that while our focus has been the Rhino Horn, the proposed innovation is systemic in nature and hence relevant to the low impedance step-down section of the VASIMRnbsp;first stage ldquo;ionizerrdquo; as well.