## 4 Conclusions  
This paper has described the development and the validation of a preliminary design tool for medium-low-power (<5 kW) gridded ion thrusters using as input power or thrust, required by a generic space mission. The tool makes use of a curve-fitting approach, analytical equations, and an FEMM simulation to obtain such important parameters as efficiencies, specific impulse, discharge current, and mass flow rate.  
The methodology has been verified by comparing the performances and working parameters obtained by the tool with the performances of some conventionally sized thrusters like NSTAR and the mini-ion thruster developed by [PERSON]. The results obtained by the tool are in good agreement with the real performance and working parameters of the selected thrusters, obtaining a very small error for most of them (in average less than 5-10%), demonstrating the validity of it both for conventionally sized and miniaturized gridded ion thrusters. Slightly higher errors have been obtained for XIPS-13 and ETS-8 ion thrusters in the estimation of the beam voltage \(V_{b}\) (41.6% and 30.6%), probably due to the different grid geometries exploited by the thrusters with respect to the one considered in the tool, and in the calculation of the total efficiency \(\eta_{T}\) (12.9%) for the [PERSON]'s GIT because the estimation of the \(\eta_{T}\) is made with a function that interpolates data from conventionally sized thrusters. Furthermore, for almost every thruster the error in the estimation of the accelerator grid voltage \(V_{acc}\) is slightly higher (5.5-44.4%), due to the calculation methodology of this parameter.  
The tool has been also compared with a preliminary design tool found in the literature that exploits simple macroscopic plasma-source simulation (SMPS) combined with a genetic algorithm (GA). The developed tool demonstrated the achievement of slightly lower errors in predicting NSTAR ion thruster data in TH15, and more design and performance parameters.  
Finally, to demonstrate the potential of the tool, it was used to make the preliminary design of a miniaturized GIT for missions such as LUMIO and M-ARGO, requiring low power (100 W) and low thrust (2 mN).  
The method has been shown to have a very low computational weight and a relatively low number of degrees of freedom, due to the curve-fitting approach exploited in the methodology.  
Future research in the development of this tool will focus on the implementation of an optimization technique, e.g., PSO (particle swarm optimization), to optimize the values of the degrees of freedom, such as the discharge chamber length.  
Conceptualization, F.B.; methodology, F.A. and F.B.; software, F.A.; validation, F.A; formal analysis, F.A.; data curation, F.A. and M.P.; writing--original draft preparation, F.A.; writing--review and editing, M.P. and F.B.; visualization, F.A. and M.P.; supervision, M.P.; and project administration, F.B. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Italian research program in aerospace, PRORA (_Programma Operativo Ricerche Aerospaziali_) entrusted by MIUR (_Ministero dell'Istruzione, Ministero dell'Universita e della Ricerca_).  
Not applicable.  
The data presented in this study are available on request from the corresponding author.  
The authors would like to thank [PERSON] (University of Naples, Federico II) who entrusted his graduated student (F.A.) to the CIRA space propulsion laboratory, giving him the possibility to contribute to this study.  
The authors declare no conflict of interest.