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At the 50th anniversary of Apollo 11, the Moon is back to the scene of scientific and commercial space exploration interests. During the next decade, the establishment of a Gateway in cislunar non-Keplerian orbits will open the space frontiers to sustainable manned and robotic missions on and around the Moon. Such infrastructure will require several logistic operations for its assembly and maintenance, which lean on rendezvous and docking capabilities. Even if few missions have flown on non-Keplerian orbits, Rendezvous and Docking (RV&D) operations have not been performed but in Low Earth Orbit (LEO). Investigations about 6 Degrees Of Freedom (DOF) relative dynamics in non-Keplerian environment are now mandatory to highlight criticalities in the design of the cislunar gateway and to translate RV&D protocols, consolidated in LEO for the International Space Station (ISS), to the new non-Keplerian environment. In this direction, the paper analyses the 6DOF natural orbit-attitude dynamics within the Circular Restricted Three-Body Problem (CR3BP) framework. A novel perspective of the dynamical structures, constituting 6DOF manifolds, allows to better characterise the natural relative dynamics in proximity of non-Keplerian orbits. The importance of orbit-attitude manifolds exploitation is underlined for designing reliable and efficient rendezvous trajectories, enhanced by natural cislunar dynamics. Then, an ephemeris cislunar dynamical model is exploited to address guidance laws for proximity operations. The control capability is included in the dynamics of a chaser vehicle, which is employed to solve the 6DOF guidance problem in proximity of a target spacecraft. The results obtained with the controlled dynamics are compared to those available thanks to natural motion, discussing the energetic and time costs to complete the manoeuvres. A control parametrisation to solve the optimal energy rendezvous problem is proposed. Finally, a feasible operational rendezvous scenario is discussed about the identified favourable locations along the non-Keplerian orbit to perform complex proximity operations. Significant relations between RV&D time and non-Keplerian orbit's period are discussed as well. • Floquet Modes characterise proximity 6DOF relative motion about non-Keplerian orbit. • Find favourable natural dynamics and locations for proximity controlled maneuvers. • Relate control energy cost with time cost and initial offset chaser conditions. • Propose a novel rendezvous and docking strategy with natural and controlled phases. • Particular attention is given to safety and flexibility considerations. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the design of a fully magnetic attitude control subsystem for a picosat platform is discussed. The developed control law is based on a simple and reliable architecture, which can be easily implemented on small spacecrafts for de-tumbling and three-axis stabilization purposes. The subsystem design follows a practical engineering approach, exploiting global optimization methods, which lead to an integral actuation compliant with typical pointing accuracy requirements for picosat missions. Performance of the proposed attitude control subsystem is demonstrated by numerical simulations. [ABSTRACT FROM AUTHOR]

The global exploration roadmap suggests, among other ambitious future space programmes, a possible manned outpost in lunar vicinity, to support surface operations and further astronaut training for longer and deeper space missions and transfers. In particular, a Lagrangian point orbit location - in the Earth- Moon system - is suggested for a manned cis-lunar infrastructure; proposal which opens an interesting field of study from the astrodynamics perspective. Literature offers a wide set of scientific research done on orbital dynamics under the Three-Body Problem modelling approach, while less of it includes the attitude dynamics modelling as well. However, whenever a large space structure (ISS-like) is considered, not only the coupled orbit-attitude dynamics should be modelled to run more accurate analyses, but the structural flexibility should be included too. The paper, starting from the well-known Circular Restricted Three-Body Problem formulation, presents some preliminary results obtained by adding a coupled orbit-attitude dynamical model and the effects due to the large structure flexibility. In addition, the most relevant perturbing phenomena, such as the Solar Radiation Pressure (SRP) and the fourth-body (Sun) gravity, are included in the model as well. A multi-body approach has been preferred to represent possible configurations of the large cis-lunar infrastructure: interconnected simple structural elements - such as beams, rods or lumped masses linked by springs - build up the space segment. To better investigate the relevance of the flexibility effects, the lumped parameters approach is compared with a distributed parameters semi-analytical technique. A sensitivity analysis of system dynamics, with respect to different configurations and mechanical properties of the extended structure, is also presented, in order to highlight drivers for the lunar outpost design. Furthermore, a case study for a large and flexible space structure in Halo orbits around one of the Earth-Moon collinear Lagrangian points, L1 or L2, is discussed to point out some relevant outcomes for the potential implementation of such a mission. [ABSTRACT FROM AUTHOR]

The interest in the Moon exploration and colonization is constantly growing. One of the most critical technologies to be developed to achieve this ambitious goal is the In-Situ Resources Utilisation (ISRU) and extraction. In particular, the water and oxygen extraction from the Lunar Regolith could simplify both manned and unmanned missions, since it can be used for biological purposes or as rocket fuel. To extract oxygen from the regolith, different approaches are under study and development (Schwandt et al., 2012): the most promising are the carbothermal process (Troisi et al., 2022; Gustafson et al., 2010) and the electrochemical reduction (known as FFC Cambridge process (Meurisse et al., 2022)). The paper is focused on the design, manufacturing and testing of the ISRU facility developed at the Department of Aerospace Science and Technologies of the Politecnico di Milano. The plant was realized to demonstrate and validate the carbothermal process for the water extraction from Lunar Regolith simulant, thanks to the activities started under the cap of an ESA study (ESA-E3P-ISRU-SOW-001 –Appendix 1 to AO/1–9183/NL/JK) in a consortium with OHB-I and OHB-S. • The carbothermal process is demonstrated in a plant designed and built at PoliMi. • The plant elements were designed to meet the process requirements. • Each element was successfully tested to ensure the safety and its proper working. • The plant is ready to start an experimental campaign on the carbothermal process. [ABSTRACT FROM AUTHOR]

The present work develops an accurate and robust axisymmetric SPH method by introducing the Riemann solver into the framework of axisymmetric SPH. To reduce numerical dissipations caused by the intrinsic numerical viscosity of the Riemann solver, PVRS Riemann solver with MUSCL reconstruction is embedded into the scheme of the axisymmetric Riemann SPH. In addition, in order to maintain the uniformity of particle distributions, the volume adaptive scheme and the particle shifting technique are applied in this work. The advantage of the present axisymmetric Riemann SPH method is that it can consider the real compressibility of the air, which allows a larger stable time step in the simulation of the strongly-compressible flows. Through the three benchmark tests, including the Sod shock tube test, the Sedov point explosion test and the blast wave problem test, the accuracy of the present axisymmetric Riemann SPH method is verified. Then this method is applied to the simulations of some practical issues in ocean engineering, including the shockwave propagation of the underwater explosion, the water entry of the sphere and the coalescence of an oscillating bubble pair. • An accurate and robust axisymmetric Riemann-SPH method is developed by introducing the Riemann solver into the axisymmetric SPH. • Through the three basic cases, the accuracy and convergence of the present axisymmetric Riemann SPH method are verified. • The proposed SPH is used to simulate the underwater explosion, the water entry of a sphere and the coalescence of a bubble pair. [ABSTRACT FROM AUTHOR]

Recent studies highlighted the benefits of a support infrastructure located in Cislunar environment, which would ease the design of forthcoming space missions with a favorable access from and to the lunar surface, the Earth and many interplanetary destinations. Multi-body orbits rose a peculiar interest and were selected to stage a human-robotic exploration outpost; the family of Near Rectilinear Halo Orbits (NRHO), in particular, appears specifically suitable in these regards. Among the different capabilities that such outpost will tend to, the docking with other crewed or autonomous vehicles is a key feature that shall be present. Although low Earth orbit (LEO) rendezvous and docking is well assessed, no mission has performed such task in a multi-body gravitational environment. The paper presents a guidance, navigation and control (GNC) framework for 6 degrees of freedom (6DOF) coupled Cislunar rendezvous and docking. A feasible operational rendezvous scenario is detailed and exploited to define open-loop and closed-loop GNC functions for far-range and close-range. Then, the final approach is analyzed, proposing a closed-loop GNC that encompasses coupled translational-rotational dynamics. Vision-based only relative navigation techniques are applied to Cislunar multi-body dynamics to guarantee a coupled state estimation with a simple suite of sensors and a broad applicability range, ranging from passively cooperative to non-cooperative or unknown target spacecraft. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a numerical analysis of the time behaviours of mechanical and internal fluid energies during generation, propagation and absorption of gravity waves. The analyses are performed through a Smoothed Particle Hydrodynamics (SPH) model in which the viscous and diffusive dissipations are determined through the turbulence closure model presented in Di Mascio et al. (2017) and therefore are a function of the local and instantaneous flow conditions. The wave generation is obtained through the action of a moving paddle. Particular attention is given to the analysis of the energy introduced in the fluid domain as the work made by the moving solid boundary on the fluid mass. In a first problem, a comparison on the time evolution of the energy components is presented for a wave reflecting case, obtained by a flat bottom flume which ends with a vertical wall, and a wave absorbing case, obtained through the generation of breaking waves induced by a sloping bottom. Successively, the energy analysis is applied to study the performances of waves interacting with a curtain breakwater for which reference data are available in the literature. The time evolutions of the single energy components are analyzed separately for two sub-regions of the domain: the first one is the wave propagation region, while the second one is the breakwater region. A specific analysis is thus devoted to determine the amount of energy dissipated, only due to the presence of the curtain breakwater. Highlights • Numerical study of the energy balance during generation, propagation and absorption of gravity waves, through the δ -LES-SPH model. • Analysis of the energy introduced in the fluid domain as the work made by the action of a moving solid boundary. • Comparison of the time evolution of potential, kinetic, dissipated and elastic energy components, in wave-absorbing and wave-reflective conditions. • Energy analysis for waves interacting with a curtain breakwater. [ABSTRACT FROM AUTHOR]