The increasing demand for on-orbit servicing (OOS) tasks, such as satellite repair, space debris removal, refueling, and upgrades, has driven the need for advanced robotic systems capable of autonomous and precise operations in space. At the core of these tasks are unmanned spacecraft equipped with robotic manipulators designed to execute critical capture and manipulation maneuvers. This paper presents a comprehensive review of space robotic missions and methodologies for effective OOS and space debris removal. It examines control strategies applied across different phases of these missions, with a focus on their implementation in 2 operational modes: free-floating and free-flying. Detailed discussions are provided on methodologies for the pre-capture phase, covering both motion planning and vision-based estimation. For the post-capture phase, the paper explores control methods designed to stabilize captured targets. Additionally, it investigates ground verification experiments, which are crucial for validating the performance of space robots under microgravity-like conditions. These experiments yield valuable insights into the dynamic behavior of space robotic systems and play an important role in advancing space robotics research. By consolidating recent advancements and identifying key technological gaps, this review highlights future research directions aimed at improving the reliability, adaptability, and safety of robotic manipulators in addressing the challenges of OOS and space debris removal.

This paper presents a novel design for a Dyson-Harrop CubeSat aimed at harvesting energy from the solar wind. Unlike current photovoltaic-based satellite energy generation, the Dyson-Harrop satellite generates energy based on the photoelectric effect, which has the potential to achieve significantly higher efficiency than current photovoltaic technology. The proposed CubeSat system consists of three main components: a tether unit, an energy harvesting unit, and the central 3U CubeSat body. The tether unit generates a cylindrical magnetic field along its main tether, effectively concentrating electrons from the solar wind to the energy harvesting unit. The energy harvesting unit includes a spherical electron receiver, functioning as a capacitor, which attracts electrons from the solar wind, as well as an annular flat solar sail that captures photons in the solar wind to eject electrons via the photoelectric effect, resulting in an electric current in the system. The Dyson-Harrop CubeSat is shown to be highly efficient as an energy-generation system, producing approximately 1 kW of power by a 3U CubeSat. This energy can be transmitted via microwave beams to other spacecraft or ground stations on the Earth. It is important to note that this estimation is based on first-principle estimations, and thorough theoretical analysis and experimental validation are required to confirm the feasibility of the concept.

This paper studies the equilibrium state and trajectory dynamics of an axially symmetric Electric solar wind sail (E-sail) at arbitrary sail angles. The E-sail is assumed operating in a heliocentric-ecliptic orbit at approximately one astronomic unit (au) from the Sun, and experiencing various dynamic disturbances like solar wind pressure, tether tension oscillations, and centrifugal forces. The study derives analytical expressions for the E-sail’s equilibrium state and its maximal coning angle under small coning angle assumption. Subsequently, an improved propulsion model is developed for the E-sail in this equilibrium state. To assess the precision of these formulations, a high-fidelity E-sail dynamic model is constructed using the nodal position finite element method, where the tethers are modeled as two-noded tensile elements and the central spacecraft and remote units are simplified as lumped masses. Through thorough parametric analyses, this paper conclusively demonstrates that the operation of the E-sail at the equilibrium state can be achieved in accordance with the derived analytical prediction of the equilibrium state. Furthermore, the improved propulsion model is employed in trajectory analyses for a mission to reach the solar system’s boundary. The study provides valuable insights and findings and foundation for the practical application and further advancement of the E-sail technology.

This study examines the impact of electric solar wind sail (E-sail) parameters on the attitude stability of E-sail's central spacecraft by using a comprehensive rigid-flexible coupling dynamic model. In this model, the nodal position finite element method is used to model the elastic deformation of the tethers through interconnected two-node tensile elements. The attitude dynamics of the central spacecraft is described using a natural coordinate formulation. The rigid-flexible coupling between the central spacecraft and its flexible tethers is established using Lagrange multipliers. Our research reveals the significant influences of parameters such as tether numbers, tether's electric potential, and solar wind velocity on attitude stability. Specifically, solar wind fluctuations and the distribution of electric potential on the main tethers considerably affect the attitude stability of the spacecraft. For consistent management, the angular velocities of the spacecraft must remain at target values. Moreover, the attitude stability of a spacecraft has a pronounced dependence on the geometrical configuration of the E-sail, with axisymmetric E-sails proving to be more stable.

A floating partial space elevator (PSE) is a PSE with a floating main satellite. This work aims to keep the orbital radius of the main satellite of a floating PSE in cargo transposition without the use of thrusts. A six-degree-of-freedom two-piece dumbbell model was built to analyze the dynamics of a floating PSE. By adjusting the climber’s moving speed and rolling of the end body, the main satellite’s orbital radius can be kept. A novel control strategy using a proportional shrinking horizon model predictive control law containing a self-stability modified law is proposed to stabilize both the orbital and libration states to regulate the speed of only the climber. Simulation results validated the proposed control strategy. The system provides a successful approach to the desired equilibrium by the end of the transposition.