Orbital Assembly Research Articles

Robotic technologies for in-orbit assembly of a large aperture space telescope: A review

Space telescopes have been instrumental in enlightening our understanding of the universe, from the iconic Hubble Space Telescope to specialized instruments like Chandra and Kepler. Pushing the frontiers of cosmic exploration, the future of space exploration hinges on modular Large Aperture Space Telescopes (LAST), much larger than the recently launched 6.5 m James Webb Space Telescope, necessitating robotic assembly in orbit. This paper introduces a paradigm shift in astronomical observation by featuring robotic in-orbit assembly of a large aperture space telescope. This review paper starts by tracing the evolution of telescopes and presents a comprehensive overview of the state-of-the-art space telescopes. This paper then reinforces the need for LAST to address the constant clamour for higher-resolution astronomy. While current semi-autonomous robotic manipulators operate from the International Space Station, their limited walking capabilities constrain their workspace, making them unsuitable for the LAST mission. This paper presents a detailed trade-off analysis of the challenges associated with the in-orbit assembly of LAST using candidate robots to understand the technological gaps. Further, the evolution of space robotic manipulators is presented, highlighting design features, advantages, and drawbacks for in-orbit spacecraft servicing and assembly missions. To tackle design and modelling challenges for robotic systems in space, amidst the various perturbations in the extreme space environment, linear and non-linear control systems necessary for achieving ultra-high precision performance are also discussed. This paper advances the walking space manipulator technology by introducing the next generation of walking space manipulators – the End-Over-End Walking Robot (E-Walker). The dexterous and modular design of the E-Walker makes it an ideal candidate for missions involving assembly, manufacturing, servicing, and maintenance.

An introductory review of swarm technology for spacecraft on‐orbit servicing

AbstractThis review paper presents a comprehensive evaluation and forward‐looking perspective on the underexplored topic of servicing target objects using spacecraft swarms. Such targets can be known or unknown, cooperative or uncooperative, and pose significant challenges in modern space operations due to their inherent complexity and unpredictability. Successfully servicing space objects is vital for active debris removal and broader on‐orbit servicing tasks such as satellite maintenance, repair, refueling, orbital assembly, and construction. Significant effort has been invested in the literature to explore the servicing of targets using a single spacecraft. Given its advantages and benefits, this paper expands the discussion to encompass a swarm approach to the problem. This review covers various single‐spacecraft approaches and presents a critical examination of the existing, although limited, body of work dedicated to servicing orbital objects using multiple spacecraft. The focus is also broadened to include some influential studies concerning the characterization, capture, and manipulation of physical objects by general multiagent systems, a subject with significant parallels to the core interest of this manuscript. Furthermore, this article also delves into the realm of simultaneous localization and mapping, highlighting its application within close‐proximity operations in space, especially when dealing with unknown uncooperative targets. Special attention is paid to the benefits that this field can receive from distributed multiagent architectures. Finally, an exploration of the promising field of swarm robotics is presented, with an emphasis on its potential to revolutionize the servicing of orbital target objects. Concurrently, a survey of general research directly engaging swarms in the orbital context is conducted. This review aims to bridge the knowledge gap and stimulate further research in the underexplored domain of servicing space targets with spacecraft swarms.

Formation of an approach to modeling orbital operations assembly of a reconfigurable spacecraft on geostationary orbit

The aim of the study is to form an approach to modeling the operations of the orbital assembly of a reconfigurable spacecraft (RS) in geostationary orbit. Reconfigurable spacecraft are a set of modular spacecraft (MS), where, in a particular case, one MS can be assigned the functions of the service systems module (MSS), and the second - the functions of the payload module (MPN). To ensure the assembly of the RC, or the replacement of some MC, for example, in case of its failure with a new one, it is necessary to provide a solution to the problem of bringing the MS with the RS. The article analyzes and studies the operation of the motion control system of the MS during the convergence of the MS with the RS. A list of necessary mathematical models for performing operations in solving the problem of convergence of the MS with the RS is formed, and a block diagram of the interaction of mathematical models is presented. The paper presents a brief description of the mathematical apparatus that allows modeling the operations of convergence of the MS with the RS. This mathematical apparatus includes: a model of the orbital motion of the MS and the RS, models of the angular motion of the MS and the RS, sensitive elements and executive bodies. In this paper, the mathematical modeling of the MS with the RS convergence operations is considered as the subject of research. The object of the study is the motion control system of the MS, which ensures the implementation of the approach of the RS in geostationary orbit.

Space Robot On-Orbit Operation of Insertion and Extraction Impedance Control Based on Adaptive Neural Network

The on-orbit operation of insertion and extraction of space robots is a technology essential to the assembly and maintenance in orbit, satellite fuel filling, failed satellite recovery, especially modular in-orbit assembly of micro-spacecraft. Therefore, the force/posture impedance control for the on-orbit operation of insertion and extraction is studied. Firstly, the dynamic model of space robots’ system in the form of uncontrolled carrier position and controlled attitude is derived by using the momentum conservation principle. Through the kinematic constraints of the replacement component plug, the Jacobi relationship of the plug motion in the base coordinate system is established. Secondly, to achieve the output force control of the plug during the on-orbit operation of insertion and extraction, a second-order linear impedance model is established based on the dynamic relationship between the plug posture and its output force and the impedance control principle. Then, in order to improve the stability, robustness, and adaptability of the controller, an adaptive Radial Basis Function Neural Network (RBFNN) is used to approximate the uncertainties in the dynamic model for the force/posture control of the plug. Finally, the stability of the system is verified by the Lyapunov principle. The simulation results show that the designed neural network impedance control strategy can achieve a control accuracy of less than 10−3 rad for the plug’s attitude tracking error, less than 10−3 m for its position tracking error, and less than 0.5 N for its output force tracking error.

Optimal consensus control for multi-satellite assembly in elliptic orbit with input saturation

This paper presents an optimal control design method for multi-satellite assembly in an elliptic orbit in close proximity operations considering input saturation constraints. Tschauner–Hempel (T–H) equations are utilized to model the relative motion dynamics of the satellites in the Local Vertical Local Horizontal (LVLH) frame of the target satellite, where every satellite in the assembly is modeled as a point mass. The communication topology between the satellites in the assembly is modeled using graph theory, where the graph has several nodes representing the satellites and several edges representing the data exchange direction. It is assumed that every satellite exchanges its states with a few neighbors in the team, where the neighbors of every satellite are prespecified and do not change during the mission. This graph is utilized to construct the global dynamic model of the assembly, in which every node is represented by the dynamic model of a single satellite. The local control law, which is applied to every satellite in the assembly, consists of a state feedback gain and a coupling gain. The state feedback gain is designed using the discrete-time periodic Riccati equation to guarantee the local stability of every satellite separately, while the coupling gain is selected to satisfy the Lyapunov condition to guarantee the global stability of the assembly. The invariant-set method is utilized to prove the stability of the global dynamic system that is subjected to symmetric input saturation. The precision and optimality of the proposed control law are successfully demonstrated by numerical nonlinear simulations in a MATLAB environment for a cubic formation satellite assembly.

Future trends of commercial In- Orbit Satellite Servicing, Active Debris Removal and End-Of Life services

Abstract Space debris growth has become a major threat not only to satellites as well as to the safe operations of the International Space Station (ISS). In September 2021, there were more than 4,700 operational satellites, 36,5000 space debris objects larger than 10 cm and 1 000 000 pieces in the 1cm to 10 cm range. The total mass of all space objects in Earth Orbit is 9,600 tonnes[1]. The launches of Starlink, Amazon Kuiper and OneWeb satellite constellations will increase the threat of space debris collisions. Satellite owners, operators, space agencies and commercial players owning the mega-constellations will need to find economically viable ways to inspect, refuel, augment, extend and manage the lifetime of their satellites. Some of the emerging trends taking place in the space industry are on- orbit satellite servicing, active debris removal services and end-of life services. With the technology demonstrations on orbit of Mission Extension Vehicles (MEV-1), MEV-2 and ELSA-d missions promising In Orbit Satellite (IOS), markets are emerging and expected to reach up to $ 6.2 bln by 2030[2]. The objective of this paper is to identify the role of Bulgarian organisations in the future emerging of in- orbital satellite (IOS) and space situational services markets. Bulgaria’s historical space competencies can contribute to the development of user-driven services/ solutions for space debris inspection, collision avoidance, space robotics and in- orbit servicing and assembly. By encouraging the creation of a new space eco-system in the domain of space debris and space situational awareness in South-Eastern Europe, Bulgarian companies and research organisations are bound to play an important role in the future space robotics markets.

Research on Orbit Assembly Strategy of Large-scale Space Truss Structure

Background: With the rapid development of spatial technology and mankind's continuous exploration of the space domain, expandable space trusses play an important role in the construction of space station piggyback platforms. Therefore, the study of the in-orbit assembly strategy for space trusses has become increasingly important in recent years. The spatial truss assembly strategy proposed in this paper is fast and effective, and it is applied for the construction of future large-scale space facilities effectively. Objective: The four-prismatic truss periodic module is taken as the research object, and the assembly process of the truss and the assembly behaviors of the spatial cellular robot serving for on-orbit assembly are expressed. Methods: The article uses a reinforcement learning algorithm to study the coupling of truss assembly sequence and robot action sequence, then uses a q-learning algorithm to plan the strategy of the truss cycle module. Results: The robot is trained through the greedy strategy and avoids the failure problem caused by assembly uncertainty. The simulation experiment proves that the Q-learning algorithm of reinforcement learning used for planning the on-orbit assembly sequence of the truss periodic module structures is feasible, and the optimal assembly sequence with the least number of assembly steps obtained by this strategy. Conclusion: In order to address the on-orbit assembly issues of large spatial truss structures in the space environment, we trained the robots through greedy strategy to prevent failure due to the uncertainty conditions both in the strategy analysis and in the simulation study. Finally, the Q-learning algorithm in reinforcement learning is used to plan the on-orbit assembly sequence in the truss cycle module, which can obtain the optimal assembly sequence in the minimum number of assembly steps.

Ultra-low temperature effect on electron beam welding process

In recent years, electron beam welding has become the most important application technology for space welding and plays an important role in the orbital assembly and repair of spacecraft at home and abroad. In this paper, the combination of simulation calculation and experimental verification is used to design the welding deformation control process scheme and related fixtures for ultra-low temperature environment, and the deformation test verification study of welding/repair is carried out. TC4 welding and repairing weld static strength, the tensile strength reaches 90% of the strength of the base metal, and the micro-hardness is basically the same. It provides reference and reference for the future application of electron beam welding technology in space in China.

The Lunar Space Tug: A sustainable bridge between low Earth orbits and the Cislunar Habitat

The International Space Station is the first space human outpost and over the last 15 years, it has represented a peculiar environment where science, technology and human innovation converge together in a unique microgravity and space research laboratory. With the International Space Station entering the second part of its life and its operations running steadily at nominal pace, the global space community is starting planning how the human exploration could move further, beyond Low-Earth-Orbit. According to the Global Exploration Roadmap, the Moon represents the next feasible path-way for advances in human exploration towards the nal goal, Mars. Based on the experience of the ISS, one of the most widespread ideas is to develop a Cislunar Station in preparation of long duration missions in a deep space environment. Cislunar space is de ned as the area of deep space under the influence of Earth-Moon system, including a set of special orbits, e.g. Earth-Moon Libration points and Lunar Retrograde Orbit. This habitat represents a suitable environment for demonstrating and testing technologies and capabilities in deep space. In order to achieve this goal, there are several crucial systems and technologies, in particular related to transportation and launch systems. The Orion Multi-Purpose Crew Vehicle is a reusable transportation capsule designed to provide crew transportation in deep space missions, whereas NASA is developing the Space Launch System, the most powerful rocket ever built, which could provide the necessary heavy-lift launch capability to support the same kind of missions. These innovations would allow quite-fast transfers from Earth to the Cislunar Station and vice versa, both for manned and unmanned missions. However, taking into account the whole Concept of Operations for both the growth and sustainability of the Cislunar Space Station, the Lunar Space Tug can be considered as an additional, new and fundamental element for the mission architecture. The Lunar Space Tug represents an alternative to the SLS scenario, especially for what concerns all unmanned or logistic missions (e.g. cargo transfer, on orbit assembly, samples return), from Low Earth Orbit to Cislunar space. The paper focuses on the mission analysis and conceptual design of the Lunar Space Tug to support the growth and sustainment of the Cislunar Station. Particular attention is dedicated to the analysis of the propulsion subsystem effects of the Lunar Space Tug design. Main results are presented and discussed, and main conclusions are drawn.

Space Robotics: Current Status, Long-term Objectives, and Development Trends. Analytical Review

Prospects for space robotics concern both the development of used prototypes to extend the capabilities and the creation of new classes of systems, the operating analogues of which are, currently, unavailable. Thus, a uniqueness of the objects of space robotics, extreme operating conditions, difficulty in full-scale ground work and tests define a variety of design solutions and a wide scope of issues for further theoretical and experimental studies. The paper highlights the tasks successfully solved up to date, involving the space robotics equipment that was used in orbital environment, those of currently solved, involving the robotics equipment that is in use, and the long-term objectives, following from the logic of the space technology development to define the ways of its further development and require a development and creation of new equipment of space robotics. Thus, the development trends of space robotics are largely defined by its history of development, on the one hand, and by a growing demand for the robotic service as applied to the promising objects of space technology, on the other one. The paper considers the trends of space robotics development, which are a consequence of the natural logic of its development and are determined by a demand for advanced objects of space technology in robotic servicing. Highlights the most important elements of a design concept and the creating and operating features of the multipurpose extendable space systems, including those, which have no analogues and prototypes, are rolled into one demand for automation, and associated with their creation, operation, and problems of utilization. The concept of assembly and service autonomous robotic space modules has been under consideration. Within the orbital assembly procedure, the typical dynamic modes, relevant in terms of practical implementation of controlled movement are highlighted.

Reusable space tug concept and mission

The paper deals with the conceptual design of a space tug to be used in support to Earth satellites transfer manoeuvres. Usually Earth satellites are released in a non-definitive low orbit, depending on the adopted launcher, and they need to be equipped with an adequate propulsion system able to perform the transfer to their final operational location. In order to reduce the mass at launch of the satellite system, an element pre-deployed on orbit, i.e. the space tug, can be exploited to perform the transfer manoeuvres; this allows simplifying the propulsion requirements for the satellite, with a consequent decrease of mass and volume, in favour of larger payloads. The space tug here presented is conceived to be used for the transfer of a few satellites from low to high orbits, and vice versa, if needed. To support these manoeuvres, dedicated refuelling operations are envisaged. The paper starts from on overview of the mission scenario, the concept of operations and the related architecture elements. Then it focuses on the detailed definition of the space tug, from the requirements’ assessment up to the budgets’ development, through an iterative and recursive design process. The overall mission scenario has been derived from a set of trade-off analyses that have been performed to choose the mission architecture and operations that better satisfy stakeholder expectations: the most important features of these analyses and their results are described within the paper. Eventually, in the last part of the work main conclusions are drawn on the selected mission scenario and space tug and further utilizations of this innovative system in the frame of future space exploration are discussed. Specifically, an enhanced version of the space tug that has been described in the paper could be used to support on orbit assembly of large spacecraft for distant and long exploration missions. The Space Tug development is an activity carried on in the frame of the SAPERE project (Space Advanced Project Excellence in Research and Enterprise), supported by Italian Ministry of Research and University (MIUR), and specifically in its STRONG sub-project (Systems Technology and Research National Global Operations) and related to the theme of space exploration and access to space.

Guidance Navigation and Control for Autonomous Multiple Spacecraft Assembly: Analysis and Experimentation

This work introduces theoretical developments and experimental verification for Guidance, Navigation, and Control of autonomous multiple spacecraft assembly. We here address the in-plane orbital assembly case, where two translational and one rotational degrees of freedom are considered. Each spacecraft involved in the assembly is both chaser and target at the same time. The guidance and control strategies are LQR-based, designed to take into account the evolving shape and mass properties of the assembling spacecraft. Each spacecraft runs symmetric algorithms. The relative navigation is based on augmenting the target's state vector by introducing, as extra state components, the target's control inputs. By using the proposed navigation method, a chaser spacecraft can estimate the relative position, the attitude and the control inputs of a target spacecraft, flying in its proximity. The proposed approaches are successfully validated via hardware-in-the-loop experimentation, using four autonomous three-degree-of-freedom robotic spacecraft simulators, floating on a flat floor.

A review on large deployable structures for astrophysics missions

As the performance of space based astrophysics observatories is directly limited by the size of the spacecraft and the telescope it carries, current missions are reaching the limit of the launchers’ capabilities. Before considering to develop larger launchers or to implement formation flying missions or in orbit assembly, the possibility of deploying structures once in orbit is an appealing solution. This paper describes the different technologies currently available to develop deployable structures, with an emphasis on those that can allow achieving long focal lengths. The review of these technologies is followed by a comparison of their performance and a list of trade-off parameters to be considered before selecting the most appropriate solution for a given application. Additionally, a preliminary structural analysis was performed on a typical deployable structure, applied to the case of a mission requiring a 20 m focal length extension. The results show that by using several deployable masts, it is possible to build stiff deployed structures with eigen frequencies over 1 Hz. Finally, a discussion on metrology concepts is provided, as knowledge of the relative position between the telescope and the deployed focal plane instruments is critical.

DYNAMICS AND CONTROL OF FLEXIBLE SPACE STRUCTURES DURING THEIR ASSEMBLY IN AN ORBIT

Some of the control problems and analysis of the construction dynamic properties of a discretely evolving space structure (DES) during the process of its in orbit assembly are considered. The equations of the DES attitude motion are deduced taking into account discrete change with time of the construction and its essential flexibility. The analysis of the changeable dynamic properties of the DES is presented. This control object is featured by variable parameters, high and variable number of freedom degrees and characteristics of a multi-frequency vibrating system. Sequence of the attitude control strategies that guarantee stable and high precision of the control throughout all stages of the assembly is suggested.

Exploration system technology aspects in the exploration programme of the European Space Agency

Within its exploration programme Aurora, the European Space Agency is preparing activities for human exploration of the solar system to be implemented in the next 5–10 years. These activities will be based on a long-term plan for exploration with a horizon of 30 years. As ESA is convinced that exploration can only be done via international collaboration, this long-term plan will be harmonised with the intentions of other potential international partners. Consequently, the Agency will concentrate in the near future mainly on activities which it wishes to introduce into an international partnership for exploration. The near term programme will contain robotic activities towards Mars i.e. the implementation of one mission and the preparation of subsequent missions. This will be accompanied by technology developments to support future missions. Concerning human exploration activities ESA is preparing a role for the return to the Moon, which it sees as a way-station on the route to Mars. Potential contributions will leverage on past investments. Capabilities considered in this context are habitation, life support and assembly in orbit.

Graph Models of Orbital Assembly and Dynamics of a Large Space Structure

Graph-model of assembly on an orbit of a large space structure (LSS) (Kirk C., 1993; Rutkovsky and Sukhanov, 1996) is suggested. This model enables to represent the modification of the LSS' dynamic properties during all process of their assembly in a compact form. The notion of a discretely developing structure (DDS) as a sequence of particular mechanical structures is introduced. The program packages, which realize transformation of original (Lagrange's) equations in graph-model, is developed. Possible approaches of model's constructive use for solving important task are found out. These tasks can be connected both with the LSS' assembly and with its orientation.

Development of flight hardware for a large, inflatable-deployable antenna experiment

Large, space-based antennas are needed for a variety of different applications. Since there is no meaningful orbital assembly capability planned at this time, any large space structures will have to be self-deployable. Current concepts for large, conventional, mechanical, self-deployable space structures tend to be very expensive and mechanically complicated. Current antenna-user requirements are so stringent (with respect to the need for very low-cost, high-deployment reliability, low weight, and packaged-volume and usable aperture precision) that new and innovative approaches to accommodate large space structures are needed. Fortunately, a newly developed class of space structures, called inflatable-deployable structures, has great potential for satisfying these stringent user requirements. A concept under development at L'Garde, Inc., for a large, inflatable-deployable antenna represents an excellent example of this new type of structure.

Optimization of Space Station components using design code CometBoards

Weight minimization is an important requirement in the design of components of the Space Station, since it can directly save launch cost, reduce the number of space shuttle missions, and facilitate on orbit assembly and fabrication. Preliminary optimum designs for such flight components are obtained using a design tool, termed ‘CometBoards’ and utilizing an animation feature of PATRAN software. Salient features of CometBoards include multiple non-linear programming optimizers; industrial strength analyzers; component synthesis concepts through a design variable formulation; constraint grouping scheme; and substructuring optimization technique, etc. The optimum design capability of CometBoards is illustrated using two flight components: (a) a ‘spacer structure’ of the solar power module of the Space Station, and (b) a ‘support system’ for integration in the space shuttle cargo bay. Optimum designs for both components have been obtained for multiple pseudo-static flight loads for behavior constraints confirming to specifications of the Space Station. The design optimization process generated lighter structures, with a reduction in the weights of about one third those obtained by the traditional manual design. Brief organization of CometBoards, description of the Space Station components, their design environments, behavior limitations, dynamic animation via PATRAN, along with the optimum designs are presented in this paper.

Verification of Space Station Freedom elements and systems

Space Station Freedom is composed of many distributed systems and elements being designed, built and tested at various work centers and international locations. The station will be assembed on orbit over a period of time greater than 4 years with the station conducting research and experimentation throughout the assembly process. Because of this extended time period of assembly and limited available resources, it is impractical to perform an integrated ground test of the complete orbital assembly. Accordingly, the Space Station Freedom Program verification program offers a unique challenge not experienced in other programs. The Space Station Freedom verification program includes development, qualification, acceptance and prelaunch phases to ensure that the station will meet the design and operational requirements prior to launch. This verification program places emphasis on verifying on the ground the physical and functional compatibility of interfaces for the different elements and launch packages prior to their being mated on orbit.

MALEO: Modular Assembly in Low Earth Orbit. Prestressed Truss Structure for Lunar Base Design

MALEO: Modular Assembly in Low Earth Orbit. Prestressed Truss Structure for Lunar Base Design