The student worked on the design of an electrical passivation system for a spacecraft electrical power system, aimed at providing a physical gap on the power line. The topic is particularly relevant for high-power satellites in geostationary orbit, where the system must reliably prevent further battery charging and safely remove stored electrochemical energy at the end of the mission. The work was consulted with both the supervisor and expert consultants from industry.

As part of the thesis, the student studied electrical spacecraft passivation, related legal and standardisation requirements, power system architectures, space environment effects, and existing solutions for battery and solar array passivation. He then defined design requirements, performed a radiation analysis for the intended environment, and prepared trade-off analyses to select a suitable mechanisms.

In the first part of the thesis, the student describes the space environment, electrical power systems and the topic of passivation itself. The work discusses the difference between soft and hard passivation, methods of electrical passivation of batteries and solar arrays, and examples of existing or currently developed solutions. The following chapters are focused on the student’s own design, where he discusses the requirements, selects the reference architecture and subsequently develops the required designs.

I especially appreciate the systematic approach used in the design. The student does not focus only on the switching element itself, but works with the overall architecture of the passivation system, its connection to the EPS, the requirement to prevent unintended passivation and the requirement to reliably perform passivation at the end of the mission. I also positively evaluate that the student compares several possible solutions, including cable cutters, semiconductor switches and magnetic relays or contactors, and supports the final selection with a clearly prepared trade-off analysis.

A significant part of the work is the design of the control concept, redundant branches, a capacitor bank and a physically implemented delay before activation becomes possible. This approach appropriately addresses the risk of unintended passivation, which would mean the loss of the mission for a real spacecraft. The student also correctly distinguishes between different types of failures and their impact either on the ability of the system to perform passivation or, on the contrary, on the ability to prevent its spontaneous activation.

I very positively evaluate the reliability analysis part of the thesis. The student performed an FMEA and subsequently carried out reliability quantification using FTA and RBD methods. He analysed in particular the risk of spontaneous passivation and the risk of failure to perform passivation on command. The results of these analyses show compliance with the defined requirements and also provide a good basis for further technical discussion and future design iterations. Although the reliability model is based on available database values and certain simplifying assumptions, it represents a very useful output.

The thesis also includes the design of a scaled breadboard model implemented on a PCB. The student appropriately describes the differences between the target design and the breadboard version, including the replacement of selected components and modifications. This demonstrator is intended for future verification of the proposed solution. The work also correctly describes the main areas of further development.

The thesis also has some weaker points. For example the proposed solution has not yet been physically manufactured and experimentally verified, and therefore some conclusions remain only at the level of design and supporting analyses.

From the formal point of view, the thesis is clearly structured and written in English using LaTeX. The language level is at good level. The text is technically understandable, well organised and specific and cited literature is relevant to the topic. Although there are occasional less polished formulations and minor language issues, they do not significantly reduce the readability or the technical quality of the thesis.

The student worked independently and proactively during the thesis and always came to consultations prepared. I also positively evaluate that the student presented and successfully placed among the top papers with the results of his work at the EEICT student conference. I appreciate his ability to approach a technically narrow but system-level demanding topic, translate it into a set of requirements, select a suitable architecture and support the design with reliability analysis and a proposal for a future demonstrator. In my opinion, the thesis fulfils the assignment and provides a very good basis for further development of an electrical passivation system suitable for satellite applications. Points proposed by supervisor: 94

The thesis presents a solid PDR-level design of an electrical passivation switch for satellites. Its main strengths are the robust 2s×2p relay topology, well-justified COTS component selection and derating, and a reproducible reliability analysis using FMEA, FTA, and RBD. The demonstrator design is also well documented through schematics, PCB tracing, a 3D model, and a control concept based on ESP32 monitoring and switching.



The main limitations seems that the breadboard was not built or tested, and the required control system simulator is not clearly delivered as a separate software artefact.

Some details need clarification, especially the capacitor-bank sizing, SW181B derating value, SW201B voltage margin, and the relay failure-rate assumption. Overall, the work is technically coherent, transferable, and recommended for defense with grade B. Topics for thesis defence:

1. The resistor block must dissipate tens of kWh, but its sizing is still missing (p. 49). What current will flow immediately after switching on (100 V across a block in the MΩ–GΩ range), and does the resulting discharge time meet the requirement to complete discharge during eclipse?

Points proposed by reviewer: 85