Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper is well constructed, and the topic on single-fluid magnetohydrodynamic (MHD) thruster is quite interesting to me. I only have a few questions before the paper can be published.

1. The scientific structure of the introduction part is strange. A thorogh literature review should be appeared rather than equations and theory.
2. The electron density ne in this work is not high, while viscous term is till considered. What is the purpose of considering viscosity here?
3. How does the authors determine whether ions are magnetized?
4. The author mentioned the measurement of PIV and thrust, but why was it not shown in the results？I am very interested in the results of thrust.
5. The schematic of the thruster indeed affects the ionization and acceleration, thus I suggest the authors to clarify the physical meaning of the motional-field ratio. This will also make sense in aiding thruster design.
6. Furthermore, the author appears to assume that the axial electric field within the Hall thruster is uniformly distributed. However, the formation of the ionization region creates a local potential barrier. Is it therefore reasonable to simply use uBr/Ez to define local acceleration effects? 
7. Part 5 is Proposed Numerical and Experimental Validation, but I did not see any experimental validation. I think the authors want to use the velocity field and magnetic field measurement results to verify their calculations. But no experimental results is shown. 
8. Another point is also confusing me, how does the authors use PIV to obtain plasma velocity distribution? From my plasma diagnostics knowledge, the plasma IEDF could only be obtained through retarding potential analyzer or a PLIF. I don’t think PIV can be used on plasma velocity measurement. 

Author Response

Dear Reviewer,

Please find attached a PDF summarizing the tasks we have completed to address your requirements. We appreciate your feedback and hope the revised manuscript meets your expectations.

Kind regards.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This paper proposes a helicity-aware design framework based on the motional-field ratio χ. By deriving a clear thrust criterion (χ > 1) using a single-fluid MHD model and combining numerical simulation with an experimental validation scheme, it provides quantitative guidance for thruster design, demonstrating both theoretical innovation and potential engineering applications. The paper has a clear structure and coherent core logic. 

1. In the baseline case, the integrated thrust is slightly negative, and the authors propose expanding the χ > 1 region as a solution, but no specific optimization cases are provided. It is suggested to add 1-2 sets of comparative experiments to intuitively demonstrate the effect of design levers on improving the thrust sign, thereby enhancing the persuasiveness of the conclusions.
2. The experimental result only mentions diagnostic equipment but does not specify the control accuracy and error range of key parameters. It is recommended to supplement.
3. Most references in the paper are from 2021 or earlier. It is recommended to supplement relevant research in the field of Hall thrusters from 2023 to 2025 (e.g., new magnetic topology designs, high-conductivity plasma regulation, etc.), and compare the similarities and differences between this study and the latest achievements to highlight the cutting-edge nature of the work.

Author Response

Dear Reviewer,

Please find attached a PDF summarizing the tasks we have completed to address your requirements. We appreciate your feedback and hope the revised manuscript meets your expectations.

Kind regards,

Mario J. Pinheiro

Author Response File: Author Response.pdf