Development of On Orbit Assembly technologies to enable spacecraft servicing

The growing population of space debris represents a significant threat to operational satellites, increasing the need for effective mitigation strategies. Over the past decade, In-Orbit Servicing (IOS) and Active Debris Removal (ADR) missions have emerged as promising solutions to mitigate their growth. IOS missions aim to extend satellite lifespan by enabling refuelling, repairs, or upgrades, while ADR missions focus on capturing and safely deorbiting debris, ensuring long-term stability of the Earth orbits. This work investigates innovative technologies and methodologies aimed at supporting IOS and ADR missions, with a specific focus on enhancing key building blocks to improve the safety, reliability, and robustness of these missions. Typically, proposed or flown IOS and ADR missions involve the use of a large servicer satellite equipped with a robotic arm for performing the required tasks. To enhance the reliability and robustness of robotic arm operations in space, two control strategies are examined: the minimum base reaction control, investigating the kinetic energy minimization method, and the combined control approach. Particular focus is posed on the latter, presenting the validation, verification and testing of a novel Guidance, Navigation, and Control (GNC) system designed for close proximity operations between a servicer and a target satellite and developed under an ESA's project. The guidance and control functionalities were developed by Politecnico di Milano and the navigation algorithms by Università di Napoli. A realistic simulator was developed in the MATLAB/Simulink environment to test the GNC system in three different scenarios spanning from servicing to debris removal missions. However, large, complex, and expensive spacecrafts equipped with robotic arms used in IOS/ADR missions lead to high economic costs that can outweigh the benefits for operators. To address these challenges, the Thesis proposes to employ a 12U CubeSat equipped with a robotic arm for performing servicing or removal tasks. This approach addresses the limitations of traditional large servicer satellites, offering a low-cost, flexible alternative that reduces mission risks and debris generation. After the presentation of the mission concept that consists of a CubeSat that autonomously creates an assembly with the target satellite, the preliminary design of the CubeSat is presented. In addition, laboratory tests were performed for an initial validation of the proposed manoeuvre. The development of this concept builds upon the knowledge gained from the Alba CubeSat UniPD project that I founded and have managed since 2019. The project is developing a 2U CubeSat with four independent objectives. The team participated to the ESA's Fly Your Satellite! -- Design Booster programme and consolidated the system and payloads design. This thesis contributes to advancing the field of IOS and ADR by introducing and validating several innovative technologies. The study of free-flying space robots control strategies addresses critical challenges in IOS and ADR operations. The successful development and testing of a new GNC system represent a significant step forward in ensuring the robustness and safety of close proximity manoeuvres between satellites. Additionally, the proposal of a 12U CubeSat servicer offers a low-cost, flexible alternative to traditional servicer satellites.