M. Lavagna

Equilibrium Analysis of a Large Multi-Hinged Space System

Abstract This paper presents the analytic solutions for the equilibrium configurations with respect to an orbiting reference frame of a three-body hinged space system. The analysis is carried out in order to highlight the correlation between these configurations and some chosen geometrical and inertial parameters. Both the orbital and the attitude motion are thought to be planar. Dynamic equations have been setup by using a Lagrangian formulation for a physical solution made of three extended masses linked together with pins. Since we deal with an extended system, the gravity gradient effects have been taken into account. The equilibrium analysis has been carried at for two particular physical solutions: the first is made of a central extended body and two dot masses linked to the central one through booms. The second one presents two dot masses linked together with booms with an extended body at the extremity of the system, likewise a bi-pendulum. Both physical solutions highlighted 12 basic equilibrium configurations. One configuration for each physical system arrangement is analyzed in detail. The chosen solutions permit to achieve a similar attitude configuration of the main body with different dispositions of the other two hung masses. Several attitude angle values quite different from classic solutions known for a single body system can be achieved by the extended body just varying geometric or inertia parameter values. The analytical solutions for the attitude angles and the boundary surfaces of the volumes the chosen parameters must belong to in order to satisfy equilibrium configurations are obtained.

Large Multi-Hinged Space Systems: a Parametric Stability Analysis

Abstract The paper presents the parametric stability analysis of a set of equilibrium configurations with respect to an orbiting reference frame for a three-hinged space system. Both the orbital and the attitude motions have been thought to be planar. As the system is assumed to be extended, the gravity gradient effects have been taken into account. The analysis is done with respect to the system inertial and geometry properties and their thresholds are highlighted to define the stability zones for each visited configuration. A Lagrangian approach has been chosen to set the dynamic equations, as it would be useful for future numerical simulations. A particular physic system is presented made of three masses, two of them represented by a dot-model and one maintained extended; consecutive masses are linked through massless booms. A dynamic equation linearization has been done around each equilibrium configuration, and the correspondent eigenvalue functions have been studied with respect to the selected parameter set, according to the stability conditions. The stability analysis results for the detected equilibrium configurations are presented in detail.

State Tracking and Control of a lifted Autonomous Space Vehicle during the Atmospheric re-Entry Phase: a Lyapunov Approach

the first Unmanned Space Vehicle (USV) Italian prototype, currently under development under the CIRA procurement; the PRORAUSV project is focused on testing a new reentry vehicle completely unmanned. The paper presents the tracking and control of a selected set of state variables for a technological demonstrator re-entry vehicle, during the final phase of its descent towards the Earth.

Planetary atmosphere entry vehicles: multiobjective optimization PSO algorithm applied to a multi-body multiple flight regime modelling

The paper presents the Particle Swarm Optimization (PSO) technique as a possible approach to identify the globally optimal guidance history and configuration deployment sequence within different flight regimes an atmospheric entry-descent-landing (EDL) vehicle with a variable architecture has to deal with. The aerodynamics data set is dynamically generated according to the configuration solution identified by the current optimization iteration. The flight history is split according to the flight regime experienced by the vehicle in parallel Particle Swarm Optimization architectures to better exploit and visit the wide solution space. A 3D dynamics is modelled to generate the differential constraints the optimization must answer to. The optimization criteria vector is focused on multidisciplinary aspects such as the heat load experienced together with the precision landing conditions. Simulations on Mars atmosphere entry revealed the efficiency of the optimization architecture to detect the related Pareto front.

Spacecraft Design as a Multi-Criteria Decision-Making

The chapter deals with a method to automate the preliminary spacecraft design through a multi-criteria optimization process based on the fuzzy logic theory. The heart of the matter is to simulate the designers’ teams behavior in making refined choices within a universe of on-board subsystem solutions — to optimize, typically, the gross mass and the requested power of the whole space system. Decisions making is often based on qualitative relationships, driven by the selector’s expertise. The fuzzy logic theory revealed to be the best fitting method to model those kinds of mental processes. It permits to translate qualitative relationships, typically uncertain, into a precise mathematical formulation and it overcomes the Boolean representation true-false by defining a satisfaction degree of the inputs with respect to a set of given qualities.

PRELIMINARY SPACECRAFT DESIGN: GENETIC ALGORITHMS AND AHP TO SUPPORT THE CONCURRENT PROCESS APPROACH

A comparison with a completely transparent optimization process, implemented by applying a Multi-criteria optimization based on a revised Genetic Algorithm approach, highlighted the capability of the proposed approach to move towards the final Pareto front solution. This paper proposes a method to support decisions to be taken within a concurrent approach for the space system preliminary design: the defined architecture is based on a Multi-Criteria Decision Making approach mixed with methodologies coming from the Approximate Reasoning domain.