Space system design for demise and survival

Abstract

In the past two decades, the attention towards a more sustainable use of outer space has increased steadily. The major space-faring nations and international committees have proposed a series of debris mitigation measures to ensure the sustainability of the space environment. Among these mitigation measures, the de-orbiting of spacecraft at the end of their operational life is recommended in order to reduce the risk of collisions in orbit. However, re-entering spacecraft can pose a risk to people and property on the ground. A possible way to limit this risk is to use a design-for-demise philosophy, where the spacecraft is designed such that most of its components will not survive the re-entry process. However, a spacecraft designed for demise still must survive the space environment for many years. As a large number of space debris populates the space around the Earth, a spacecraft can suffer impacts from these particles, which can be extremely dangerous. This means that the spacecraft design has also to comply with the requirements arising from the survivability against debris impacts. The demisability and survivability of a spacecraft are both influenced by a set of common design drivers, such as the material of the structure, its shape, dimension, and position inside the spacecraft. It is important to consider such design choices and how they influence the mission’s survivability and demisability from the early stages of the mission design process. The thesis addresses these points with an increasingly higher level of detail by a continuous and interlinked development of a demisability and a survivability model, of two criteria to evaluate the level of demisability and survivability, and of a common framework where both models communicate and interact to find optimal solutions. First, the initial versions of the models, which is limited to simple geometrical shapes, uniform materials, and dimensions, is used to study the sensitivity of the demisability and of the survivability indices as a function of typical design-for-demise options. As new features are introduced, such as the capability of considering internal components and sub-component together with their position inside the spacecraft, as well as the type of shielding, also the analyses become more detailed. As the demisability and the survivability of a spacecraft configuration are closely linked, it is important to assess them in a concurrent fashion for which a multi-objective optimisation framework has been developed. Here the survivability and the
demisability requirements are considered simultaneously and trade-off solutions of spacecraft configurations can be obtained. The final part of the thesis presents a test case for the application of the framework, targeting one of the most interesting components from both a demisability and a survivability standpoint that are tank assemblies. Finally, a preliminary study concerning the development of a new demisability index is presented.

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Identifiers

ORCID for Mirko Trisolini: orcid.org/0000-0001-9552-3565

ORCID for Hugh Lewis: orcid.org/0000-0002-3946-8757

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