21 research outputs found
Development of On Orbit Assembly technologies to enable spacecraft servicing
No full textThe 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
A Simulation Tool for Robotic Active Debris Removal with minimum reaction space manipulator
No full textSimulation of robotic space operations with minimum base reaction manipulator
No full textAutonomous robotic capture has been identified as a key technology for On-Orbit Servicing (OOS) and Active Debris Removal (ADR) missions. However, manoeuvring spacecraft-mounted manipulators is a challenging task since it generates disturbance torques on the satellite. To mitigate this problem several minimum reaction control strategies have been developed to reach the desired End-Effector (EE) pose while minimizing the dynamic disturbances transferred to the spacecraft by the robotic arm.
This paper presents the development of a Simulation Tool in the MATLAB/Simulink environment capable of simulating the dynamics of a satellite equipped with a 7-DoF robotic arm during the target capture phase. The manipulator, as well as the spacecraft, is implemented by using Simscape Multibody and joint actuators are modelled as Brushless DC motors controlled by PID controllers. The spacecraft attitude is Nadir-Pointing, it is controlled by means of quaternion feedback and Linear-Quadratic-Regulator (LQR) and it is actuated by three Reaction Wheels (RW). Orbital perturbations such as non-spherical gravity potential (EGM2008 model) and atmospheric drag are considered. In addition, the minimum reaction control strategy called Kinetic Energy Minimization (MKE) is employed during the robotic arm manoeuvres.
The goal of this study is to compare the performances obtained with the MKE method with those achieved by using the classic Inverse Kinematics (IK) in the free-flying case. The numerical results confirmed that MKE method is to be preferred since it minimizes the control torque that the Attitude Control Subsystem (ACS) must provide and reduces the EE orientation and position errors
Overview of Spacecraft-Fragmentation Testing
No full textSpacecraft fragmentation due to collisions with space debris is a major concern for space agencies and commercial entities, since in the next years the production of collisional fragments is expected to become the major source of space debris. Experimental studies have shown that the fragmentation process is highly complex and influenced by various factors, such as the satellite design, the material properties, the velocity and angle of the debris impact, and the point of collision (e.g., central, glancing, on spacecraft appendages). This paper summarizes the current state of research in spacecraft fragmentation, including the methods and techniques used to simulate debris impacts, the characterization of fragment properties and the analysis of the resulting debris cloud. It provides an overview of the main experiments performed, underlining the most critical issues observed. Moreover, it presents a set of experiments performed at the University of Padova and proposes some future directions for this research
Overview of spacecraft fragmentation testing
No full textSpacecraft fragmentation due to collisions with space debris is a major concern for space agencies and commercial entities, since the production of collisional fragments is one of the major sources of space debris. It is in fact believed that, in certain circumstances, the increase of fragmentation events could trigger collisional cascade that makes the future debris environmental not sustainable. Experimental studies have shown that the fragmentation process is highly complex and influenced by various factors, such as the material properties, the velocity and angle of the debris impact and the point of collision (e.g. central, glancing, on spacecraft appendages). In recent years, numerous impact tests have been performed, varying one or more of these parameters to better understand the physics behind these phenomena. In this context some tests have been also performed at the hypervelocity impact facility of the university of Padova. This paper provides an overview of the main experime..
Development of a multi-payload 2U CubeSat: the Alba project
No full textAlba CubeSat UniPD is a student team of University of Padova with the aim to participate to the ESA Fly Your Satellite! (FYS!) programme and to launch for the first time at University of Padova a CubeSat made by students.
The proposed mission has three independent objectives: (1) to collect in-situ measurements of the sub-mm space debris environment in LEO, (2) to study the micro-vibration environment on the satellite throughout different mission phases, (3) to do precise orbit determination through laser ranging and evaluate procedures for fast satellite Pointing, Acquisition and Tracking (PAT) from ground. The proposed technological experiments aim to obtain data that will enrich the current knowledge of the space environment and will provide precious information useful for the further development of some research projects currently performed at University of Padova.
In order to reach the objectives, in these years the activities of the teams aimed to develop a 2U CubeSat equipped with three payloads. The first payload is an impact sensor that will be placed on one of the outer faces of the satellite and will be able to count the number of debris impacting the spacecraft thus being able to measure the energy/momentum transferred to the satellite. The second one is a Commercial Off The Shelf (COTS) sensor that measures the micro-vibrations experienced by payloads in a CubeSat in different mission phases. The third one consists in a number of COTS Corner Cube Retroreflectors that will be placed onboard the satellite. Thanks to this, Satellite Laser Ranging (SLR) will be done to collect data on the satellite range and range rate using a facility currently under development at University.
This paper presents the mission objectives and motivations. In addition, the mission phases and the preliminary design of the CubeSat reached during the activities of the project are shown. Particular attention is given to the payloads which are the most challenging aspect of this project
Mechanical and Pneumatic Design and Testing of a Floating Module for Zero-gravity Motion Simulation
No full textClose proximity operations demand an accurate control in a micro-gravity environment, hence they must be reproduced and simulated systematically. Consequently, laboratory tests are a crucial aspect to validate the performances of space systems. This paper presents the development of a floating pneumatic module, whose dimensions and mass are representative of a 12U CubeSat. The vehicle has been designed to perform planar low friction motion over a levelled table for docking experiments. The paper focuses on the pneumatic and mechanical designs and on the laboratory tests of the module. The pneumatic design regards the air-compressed pneumatic system. The major specifics have been determined by the requirement of performing a docking procedure by starting from a distance of 500 mm. The mechanical design has been guided by two main requirements. The first is the possibility to accommodate different docking systems (e.g.: docking port). The second is the possibility to control the position of the centre of mass of the module. Several tests have been performed to verify the capabilities of the vehicle, such as: (1) pneumatic tests to evaluate the thrust of the propulsion system through the execution of linear motions and (2) mechanical measurements with dedicated setups to improve the estimation of the position of the centre of mass from the CAD model of the system
Track your satellite before it is too late: a laser ranging enabled student CubeSat project
No full textERMES: TESTING AN AUTONOMOUS DOCKING MANOEUVRE DURING ESA FYT 2022 PARABOLIC FLIGHT CAMPAIGN
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