Cutting-Edge Space Exploration Technology Maturity Level Facilitation with Support of Space Debris Removal Missions

Considering current space debris situation in outer space environment,different methods for debris removal missions are proposed.In addition,advanced technologies are needed to be demonstrated for future human space exploration programs.The main issue regarding to these missions is high mission cost for both debris removal missions and space environmental tests to achieve high maturity level for new space-usable technologies.Since,these missions are unavoidable for future of human space activities,a solution which can tackle these challenges is necessary.This paper will address to an idea which has the possibility to give a solution for facilitating technology readiness level(TRL)maturity tests by debris removal mission platform consideration.

A Novel Two-Level Optimization Strategy for Multi-Debris Active Removal Mission in LEO

Recent studies of the space debris environment in Low Earth Orbit(LEO)have shown that the critical density of space debris has been reached in certain regions.The Active Debris Removal(ADR)mission,to mitigate the space debris density and stabilize the space debris environment,has been considered as a most effective method.In this paper,a novel two-level optimization strategy for multi-debris removal mission in LEO is proposed,which includes the low-level and high-level optimization process.To improve the overall performance of the multi-debris active removal mission and obtain multiple Pareto-optimal solutions,the ADR mission is seen as a Time-Dependant Traveling Salesman Problem(TDTSP)with two objective functions to minimize the total mission duration and the total propellant consumption.The problem includes the sequence optimization to determine the sequence of removal of space debris and the transferring optimization to define the orbital maneuvers.Two optimization models for the two-level optimization strategy are built in solving the multi-debris removal mission,and the optimal Pareto solution is successfully obtained by using the non-dominated sorting genetic algorithm II(NSGA-II).Two test cases are presented,which show that the low level optimization strategy can successfully obtain the optimal sequences and the initial solution of the ADR mission and the high level optimization strategy can efficiently and robustly find the feasible optimal solution for long duration perturbed rendezvous problem.

Optimal Rendezvous Sequence for LEO Debris Capture

The primary purpose of this study is to exploit the effect of Earth＇s non-sphericity perturbation, particularly due to the J2 term, in order to optimize the capture sequence of potential orbital debris, that is the cumulative AV associated to the transfers between one object and the others. As results of several researches and model predictions, many international agencies agree that the growing population of objects and debris in LEO （low earth orbits）, will follow a diverging trend in the future. This, in turn, would constitute a serious threat to circum-terrestrial space safety and sustainability. In LEO, the ,J disturbance is prevailing over the others, and it acts by affecting the longitude of the ascending node （Ω）, the argument of perigee （ω） and, accordingly, the true anomaly （v）. Therefore, the goal of optimizing the AV is achieved by taking advantage of the rate of variation of Ω and ω, thereby compensating for the △Ω and △ω, present between the orbital transfer vehicle （chaser） and the debris to be captured （target）. Obviously, the perturbation will lead to favourable variations of the orbital parameters only for some combinations of Ω and ω. Yet the presence of a debris population with random distribution of Ω and ω, makes this application particularly suited to the problem. The single maneuver has been modelled with a 4-impulse time fixed rendezvous and the optimization problem has been addressed by implementing a hybrid evolutionary algorithm, which adopts, in parallel, three different strategies, namely, genetic algorithm, differential evolution and particle swarm optimization.

Prediction and experimental verification of tether net entanglement for space debris capture

This study involved simulations and experiments aimed at assessing the efficacy of a tether net in encapsulating space debris.The tether net was modeled as a spring–mass–damper system considering the influence of aerodynamic and gravitational forces and the occurrence of debris collisions.To examine the influence of collision position and size disparity between the debris and the net on debris capture status,the entanglement nodes of the net were identified.Experiments were conducted to evaluate the wrapping capabilities of the tether net,focusing specifically on debris capture.Subsequently,the results were compared with those of the numerical simulation.In the experiments,radio frequency identification was used to identify the entanglement points of the tether net.Previous studies have indicated that the ideal collision point for capturing debris using a tether net with the debris intended to be captured is located at the center of the net.However,the experimental results of this study revealed that a collision position that is slightly shifted from the center of the tether net is more advantageous for capturing debris in terms of tether net entanglement.

Design and guidance of a multi-active debris removal mission

Space debris have become exceedingly dangerous over the years as the number of objects in orbit continues to increase.Active debris removal(ADR)missions have gained significant interest as effective means of mitigating the risk of collision between objects in space.This study focuses on developing a multi-ADR mission that utilizes controlled reentry and deorbiting.The mission comprises two spacecraft:a Servicer that brings debris to a low altitude and a Shepherd that rendezvous with the debris to later perform a controlled reentry.A preliminary mission design tool(PMDT)was developed to obtain time and fuel optimal trajectories for the proposed mission while considering the effect of J2,drag,eclipses,and duty cycle.The PMDT can perform such trajectory optimizations for multi-debris missions with computational time under a minute.Three guidance schemes are also studied,taking the PMDT solution as a reference to validate the design methodology and provide guidance solutions to this complex mission profile.

Survey on research and development of on-orbit active debris removal methods

Space debris is growing dramatically with the rapid pace of human exploration of space,which seriously threatens the safety of artificial spacecraft in orbit.Therefore,the active debris removal(ADR)is important.This review aims to review the ADR methods and to advance related research in the future.The current research and development status are clearly demonstrated by mapping knowledge domain and charts.In this paper,the latest research results are classified and summarized in detail from two aspects of space debris capture and removal.The scheme comparison and evaluation of all ADR methods are performed,and the applicable scopes of various methods are summarized.Each ADR method is scored using a cobweb evaluation model based on six indicators.Future development of ADR is discussed to promote further research interest.

Capture and detumbling control for active debris removal by a dual-arm space robot

Active debris removal(ADR) technology is an effective approach to remediate the proliferation of space debris, which seriously threatens the operational safety of orbital spacecraft. This study aims to design a controller for a dual-arm space robot to capture tumbling debris, including capture control and detumbling control. Typical space debris is considered as a non-cooperative target, which has no specific capture points and unknown dynamic parameters. Compliant clamping control and the adaptive backstepping-based prescribed trajectory tracking control(PTTC)method are proposed in this paper. First, the differential geometry theory is utilized to establish the constraint equations, the dynamic model of the chaser-target system is obtained by applying the Hamilton variational principle, and the compliance clamping controller is further designed to capture the non-cooperative target without contact force feedback. Next, in the post-capture phase,an adaptive backstepping-based PTTC is proposed to detumble the combined spacecraft in the presence of model uncertainties. Finally, numerical simulations are carried out to validate the feasibility of the proposed capture and detumbling control method. Simulation results indicate that the target detumbling achieved by the PTTC method can reduce propellant consumption by up to24.11%.

Timeline Club:An optimization algorithm for solving multiple debris removal missions of the time-dependent traveling salesman problem model

With the increase of space debris,space debris removal has gradually become a major issue to address by worldwide space agencies.Multiple debris removal missions,in which multiple debris objects are removed in a single mission,are an economical approach to purify the space environment.Such missions can be considered typical time-dependent traveling salesman problems(TDTSPs).In this study,an intelligent global optimization algorithm called Timeline Club Optimization(TCO)is proposed to solve multiple debris removal missions of the TDTSP model.TCO adopts the traditional ant colony optimization(ACO)framework and replaces the pheromone matrix of the ACO with a new structure called the Timeline Club.The Timeline Club records which debris object to be removed next at a certain moment from elitist solutions and decides the probability criterion to generate debris sequences in new solutions.Two hypothetical scenarios,the Iridium-33 mission and the GTOC9 mission,are considered in this study.Simulation results show that TCO offers better performance than those of beam search,ant colony optimization,and the genetic algorithm in multiple debris removal missions of the TDTSP model.

A grasp planning algorithm under uneven contact point distribution scenario for space non-cooperative target capture

The contact point configuration should be carefully chosen to ensure a stable capture,especially for the non-cooperative target capture mission using multi-armed spacecraft.In this work scenario,the contact points on the base and on the arms are distributed on the opposite side of the target.Otherwise,large forces will be needed.To cope with this problem,an uneven-oriented distribution union criterion is proposed.The union criterion contains a virtual symmetrical criterion and a geometry criterion.The virtual symmetrical contact point criterion is derived from the proof of the force closure principle using computational geometry to ensure a stable grasp,and the geometry criterion is calculated by the volume of the minimum polyhedron formed by the contact points to get a wide-range distribution.To further accelerate the optimization rate and enhance the global search ability,a line array modeling method and a continuous-discrete global search algorithm are proposed.The line array modeling method reduces the workload of calculating the descent direction and the gradient available,while the continuous-discrete global search algorithm reducing the optimization dimension.Then a highly efficient grasping is achieved and the corresponding contact point is calculated.Finally,an exhaustive verification is conducted to numerically analyze the disturbance resistance ability,and simulation results demonstrate the effectiveness of the proposed algorithms.

Dynamics of tether-tugging reorbiting with net capture

To control the growth of space debris in the geostationary earth orbit （GEO）, a novel solution of net capture and tether-tugging reorbiting is proposed. After capture, the tug （i.e., active spacecraft）, tether, net, and target （i.e., GEO debris） constitute a rig- id-flexible coupled tethered combination system （TCS）, and subsequently the system is transported to the graveyard orbit by a thruster equipped on the tug. This paper attempts to study the dynamics of tether-tugging leorbiting after net capture. The net is equivalent to four flexible bridles, and the tug and target are viewed as rigid bodies. A sophisticated mathematical model is developed, taking into account the system orbital motion, relative motion of two spacecraft and spacecraft attitude motion. Given the complexity of the model, the numerical method is adopted to study the system dynamics characteristics. Particular attention is given to the investigation of the possible risks such as tether slack, spacecraft collision, tether rupture, tether-tug intertwist and destabilizing of the rug＇s attitude. The influence of the initial conditions and the magnitudes of the thrust are studied.