Reliability and Radiation Assurance Techniques for Power Electronics in LEO Small Satellites

The latest era of space exploration is characterized by a rising interest in the commercialization of space, with private investors being involved in financing projects, which traditionally was only done by governments. This "new space economy" was made possible by the decrease in manufacturing and launch costs, making space more accessible. An important enabling factor is the development of a particular class of satellites, broadly referred to as "small satellites," which provide cost effective platforms for a variety of purposes, and are accessible even to small developers and manufacturers. Small satellites bring numerous advantages, including increased launch opportunities, simplicity, modularity, and short development times, but also some drawbacks, such as strict budget constraints, with regard to mass, volume and cost. These restraints pose problems when it comes to Mission Assurance, as it limits the amount of actions which can be pursued in order to reduce risks within the system operating in a hostile environment. A particularly important subsystem in the spacecraft is the Electrical Power System, which provides power to the entire platform, and in which a failure could potentially lead to catastrophic consequences, from loss of functionality to loss of the entire spacecraft. Electronic components which constitute the EPS are especially vulnerable to the radiation environment in space, which can cause numerous failures due to the interaction of energetic and charged particles and photons with semiconductors and insulating materials. Traditionally, the risk was reduced by using radiation-hardened components, in which the design and manufacturing process was modified to enhance radiation robustness. Nevertheless, these types of parts are generally very expensive, have long lead times and their technology is often not cutting-edge. While the high cost and long lead times are not always compatible with the restraints of small satellite missions, the less advanced technology contrasts with the necessity to provide high-performance in miniaturized platforms, requiring a high level of efficiency. This motivated the development of a new design strategy, called "careful COTS," based on the use of Commercial Off-the-Shelf components, generally not robust to radiation, combined with additional tests, redundancy, and other mitigation techniques, in order to make the system reliable, while limiting costs and development time, and preserving a high level of performance. Developers have numerous tools at their disposal to design reliable and efficient platforms, such as reliability analysis, including the Failure Modes, Effects, and Criticality Analysis, which allows the identification of all critical components within the system and their possible failure modes, assigning to each a risk category, and investigating potential mitigation techniques. Reliability analysis can be supported by the study of similar components in the available literature to compare and foresee their behavior under radiation, as well as, when necessary, on ground accelerated radiation testing on the items of interest. This is particularly important when using COTS components, since their radiation response is not generally known. This Thesis work was conducted in Argotec, an aerospace company which develops small satellite platforms, and consisted of the study and application of the previously described strategies to power electronics architectures having as reference scenario LEO missions.