Astrodynamics最新文献

Tsinghua University and the Shanghai Institute of Satellite Engineering organized the 12th edition of the Global Trajectory Optimization Competition (GTOC12) on June 19, 2023. The problem for GTOC12, entitled “Sustainable Asteroid Mining”, explores how spacecraft can be dispatched from the Earth to various asteroids for resource extraction. The primary challenge involves designing coupled trajectories for multiple spacecraft to maximize the collected mineral mass. A novel game model is introduced to encourage the mining of rarely mined asteroids. GTOC12 saw significant participation, with 102 teams registered. By the end of the competition, 28 teams provided feasible solutions, highlighting a growing interest in the field. This study describes the design process of the GTOC12 problem and presents a review and analysis of the results from the participating teams.

Establishing a sustainable mining expedition for the asteroids of the main belt over the 2035–2050 horizon is the visionary problem of the 12th Global Trajectory Optimisation Competition. A fleet of mining ships must rendezvous twice with asteroids to deploy miners and collect minerals. In this paper, we describe the approach of the CS Group team, OptimiCS, to solve this challenging problem. We present the symmetrical construction of upstream and downstream semi-sequences of asteroids, maximizing the mining time expectancy via a beam search with tabu iterations, and the composition of these semi-sequences into complete fleet routes, maximizing the total collected mass via simulated annealing. While representative Earth–asteroid legs are precomputed, the delta-V costs of the asteroid-to-asteroid hops composing the sequences are initially approximated during exploration via a method that refines the accuracy of the maximum initial mass. The resulting high-fidelity trajectories are adjusted and optimized via a direct method and nonlinear programming.

Asteroid mining is a potentially lucrative method for extracting resources from space. Water resources found on asteroids can serve as fuel supplies for spacecrafts in deep space, and some asteroids are rich in precious metals, offering immense potential economic value. The 12th Global Trajectory Optimization Competition, held in 2023, introduced a challenge to trajectory design for sustainable asteroid mining. Participating teams were tasked with maximizing the mining quantity over a 15-yr period by utilizing as many mining ships as possible to depart from the Earth, deploy miners on multiple asteroids, recover minerals, and return to the Earth. Σ team devised a strategy in which one ship completes one sequence, enabling the collection of minerals from 203 asteroids using 26 mining ships. This paper outlines the design methodology and outcomes of this approach, encompassing a preliminary analysis of the problem, optimization for the Earth departure and return, flight sequence search, and low-thrust conversion and optimization. Through methods such as asteroid selection and clustering, database building for Earth–asteroid transfers, global search with an impulsive model, local optimization with a low-thrust model, and conversion of remaining fuel into mining time, the computational efficiency was significantly enhanced, fuel consumption per unit mineral collection was reduced, and mining quantity was improved. Finally, the design outcomes of this approach are presented. The proposed trajectory design method enables the completion of multiple asteroid rendezvouses in a short time, providing valuable insights for future missions involving a single spacecraft conducting multiple rendezvouses with multiple asteroids.

This paper presents the results and design methods of team Nanjing University of Aeronautics and Astronautics in the 12th edition of the Global Trajectory Optimization Competition. To address the problem of sustainable asteroid mining, we focus on the following: analyzing the constraints and asteroids involved; selecting a candidate set of asteroids for which mining missions can be performed easily; establishing an algorithmic flow using phasing indicators, multiobjective beam search, and a genetic algorithm to determine the sequence of asteroid visits for mining ships; and optimizing low-thrust trajectories via an indirect method and global optimization. In addition, a central-node method is proposed to simplify the design process and reduce the computational cost of performing repetitive asteroid-rendezvous missions. The methods developed in the competition enable the mining of 161 asteroids via 20 mining ships, with a total collected mass of 11,513 kg.

Future missions to the Moon and beyond are likely to involve low-thrust propulsion technologies due to their propellant efficiency. However, these still present a difficult trajectory design problem, owing to the near continuous thrust, lack of control authority and chaotic dynamics. Lyapunov control laws can generate sub-optimal trajectories for such missions with minimal computational cost and are suitable for feasibility studies and as initial guesses for optimisation methods. In this work a Reinforced Lyapunov Controller is used to design optimal low-thrust transfers from geostationary transfer orbit towards lunar polar orbit. Within the reinforcement learning (RL) framework, a dual-actor network setup is used, one in each of the Earth- and Moon-centred inertial frames respectively. A key contribution of this paper is the demonstration of a forwards propagated trajectory, removing the need to define a patch point a priori. This is enabled by an adaptive patch distance and extensive initial geometry exploration during the RL training. Results for both time- and fuel-optimal transfers are presented, along with a Monte Carlo analysis of the robustness to disturbances for such transfers. Phasing is introduced where necessary to aid rendezvous with the Moon. The results demonstrate the potential for such techniques to provide a basis for the design and guidance of low-thrust lunar transfers.

Scientific interest in asteroids and their physical characteristics is growing. These bodies provide insights into the primordial solar system and represent a valuable source of metals, silicates, and water. Several missions over the past few years have aimed to improve and better identify the main properties of these poorly known celestial bodies. However, these missions relied on touchdown(s) on the target asteroid to gather samples, which is complicated owing to the difficulty of accurately reaching and rendezvousing with the body. This study aims to assess the feasibility of an in-orbit asteroid sample collection mission. Such a strategy could prevent complex operations related to landing and touchdown maneuvers and avoid the dead times present in a mission requiring several landings. The presented collection scenario, which focuses on the asteroid Ryugu, proposes gathering samples using a spacecraft injected into a halo orbit around the second libration point, L₂. For this purpose, the orbits in the neck region of the zero velocity curves are analyzed. A novel methodology to characterize bouncing behavior is introduced. An interpolation-based approach was used to recover the appropriate restitution coefficients for each collision occurring at a specific impact angle. This was applied to both the rigid body model and the point mass approximation studied for two different sites on the asteroid. Furthermore, the study enlarged the region of interest from only L₂ to its neighboring zones to return a more global and realistic point of view. Considering the solar radiation pressure and asteroid aspherical potential, particles of different sizes ejected from different longitudes and with different ejection angles were classified according to their trajectories to finally build a database. Based on this analysis, an aerogel-based collection strategy inspired by that used in the Stardust-NExT (NASA) mission was investigated to assess its possible applicability to the analyzed scenario.

This paper investigates the heliocentric time-optimal rendezvous performance of Sun-facing diffractive solar sails with various deflection angles and acceleration capabilities. Diffractive solar sails, which generate tangential radiation pressure force, are proposed and schematically designed to achieve diverse radiation pressure distributions. The radiation pressure force model and the time-optimal control problem for these innovative Sun-facing diffractive solar sails are established. Utilizing an indirect method and the optimal control law, we explore typical heliocentric rendezvous scenarios to assess the variational trends of transfer time in relation to different deflection angles and acceleration capabilities. The results for Sun-facing diffractive sails in specific rendezvous missions are compared to reflective sails with the same area-to-mass ratio, focusing on transfer trajectory and attitude control. Our findings reveal that diffractive sails exhibit significant advantages over reflective sails, particularly in the context of normal acceleration, paving the way for more efficient space exploration.

Asteroids may contain valuable minerals. A method to exploit asteroid mines is to transfer them closer to the Earth for further mining processes. In this work, we optimally mount a set of fixed-angle spacecraft thrusters on the surface of an asteroid to conduct concurrent detumbling and redirecting to the desired orbit. The optimization objective reconciles the minimum duration of the mission with the minimum required fuel as well as the maximum uniformity of the fuel distribution required for all thrusters. Each thruster can respond to redirection and detumbling commands simultaneously. Redirection and detumbling are performed via the directional adaptive guidance method and PID controllers, respectively, and the weight factors for each orbital element and the gains of the rotational control channels are also optimized in the process. We use the particle swarm optimization algorithm to evaluate the objective function by simulating the entire mission to find the optimal design. The rotational control damps the tumbling of the asteroid without interfering with the simultaneous redirection process and eventually fixes the asteroid in the optimally selected orientation in the inertial reference frame. The rotational velocity and attitude of the asteroid are controlled via separate PID controllers, which are set robustly. We can effectively optimize the mission by collectively tuning both the system’s rotational and redirection behaviors as well as the thrusters’ configuration and optimally selecting the final attitude of the asteroid.

In this work, we attempt to investigate a luring cooperative guidance strategy for three-player inducer–defender–attacker engagement with field-of-view (FOV) and overload constraints against an attacker with speed advantages under incomplete information. We formulate the three-player inducer–defender–attacker engagement problem as the pursuit–evasion (defender–attacker) game problem. On this basis, an analytical luring cooperative guidance strategy based on backstepping control is proposed to facilitate the defender with zero overloads intercepting the attacker. Additionally, under incomplete information, we offer a parameter delay design approach to delay the unknown parameters and state design. Afterward, an improved adaptive update law is devised to address the incomplete information. The proposed luring cooperative guidance, which incorporates backstepping control and an improved adaptive update law, can guarantee that the defender captures the attacker with zero overloads under luring by the inducer. Additionally, the proposed design adopts the directed communication topology network structure. Finally, we also execute simulations that demonstrate the effectiveness of the designed luring cooperative guidance strategy and reveal that it can be extended to double-hierarchical interception and four-on-two engagement interception.

This technical note presents a practical approach to low-energy Earth–Moon transfer autonomous guidance considering high-fidelity orbital dynamics. Initially, autonomous guidance, delineated as a trajectory-tracking problem, is addressed within the framework of a predesigned reference trajectory solution, accompanied by empirical trajectory correction maneuver allocation. A series of two-point boundary value problems is subsequently formulated to incorporate guidance velocity increments. An algorithm employing quasilinearization, discretization, and recursion is proposed to address these boundary value problems, which results in enhanced convergence performance compared with traditional differential-correction-based guidance methods. Finally, a Monte Carlo analysis demonstrates the efficacy of the proposed autonomous guidance approach, indicating its potential for onboard applications.