Sistemi multifunzionali integrati (Integrated multifunctional systems)

This thesis was born in the context of a research activity conducted by Thales Alenia Space Italia, and called Integrated Multifunctional Systems. The name is quite self-explanatory: the research is devoted to the study of Multifunctional Systems (MFSs). The work hereafter described addresses MFSs combining thermal, structural, electronic, and control functionalities. The rationale behind this activity comes from a careful evaluation of mission drivers and constraints for space systems. In the last 30 years, studies have shown that the largest contributors of total spacecraft dry mass are two technology areas: structure and packaged electronics. This information indicates a potentially fruitful area of technology development that would provide significant spacecraft dry mass reduction. Possible interesting areas to be addressed are bus architectures, novel electronic packaging and layout, electronic chassis that also function as structural members, minimization of harness. Moreover, there is increasing interest in the unnoticeable distribution of thermal control and monitoring hardware throughout the system. The challenge is to meet mission requirements taking into account an integrated design that addresses all areas of structural, electrical, component packages, and thermal elements. In particular, for this thesis the aim was to identify different ways of combining electrical and thermal control functions with mechanical structures in order to create a multifunctional system able to save mass and volumes, and simplify integration. The goal of the work was to screen materials and technologies to be used for structural elements, thermal solutions, and integrated electronics, to conceive, design, manufacture, and test suitable prototypes, and to evaluate the application of multidisciplinary design and optimization techniques to this field. The work has been conducted in close collaboration with Thales Alenia Space Italia S.p.A. (TAS-I), and with the Jet Propulsion Laboratory (JPL)/California Institute of Technology (Caltech). Over a three year timespan, four different demonstrators have been considered: three of them have been developed with TAS-I, and one with JPL. In chronological order, the first prototype is the Advanced Bread Board (ABB), which is a thermostructural panel built in Carbon/Carbon and equipped with distributed electronics and sensors. The second prototype was implemented into three different demonstrators, SDA, SDB, and SDC (respectively, STEPS Demonstrator A, B, and C). They consist of an intelligent, modular, flat, and flexible motherboard which has been mounted on an aluminium sandwich panel, a curved aluminium plate, and a layer of Kevlar fabric. The third prototype is the ROV-E smart skin demonstrator, which is a development of the STEPS motherboard concept, and the fourth prototype is the JPL μRover, which consists of a small 4-wheeled robot made of thermostructural Printed Circuit Boards (PCBs). The four prototypes represent subsequent steps toward the realization of a multifunctional system where electronics in flex and rigid-flex form is bounded with structure. The goal is to achieve a more distributed architecture equipped with enough intelligence to handle communication, thermal/environmental control, and actuation. ABB is the first example, where small flat and flex boards with limited intelligence are mounted on a structural substrate with high thermomechanical performances. After the results obtained from ABB, the design flow is ideally split in two branches. The first research branch keeps on the development of flex electronics as a mean to integrate communication capabilities, health monitoring, signal and power harness on many different support materials: the STEPS demonstrators and the ROV-E smart skin concept are products coming from this approach. The STEPS demonstrators show increased dimensions, expanded capabilities, and higher level of on-board intelligence. The ROV-E smart skin brings these characteristics to their maximum extent: the design is focused on an extremely flexible board, able to monitor the surrounding structure and environment, able to actuate loads and to take care of signal and power distribution. On the other hand, the second research branch explores the possibility of using the electronic boards themselves (in rigid-flex configuration) as structural elements: the JPL μRover is the product of this approach. The micro rover is supposed to show the viability of eliminating electronic boxes by transferring all the components on the primary structure, which is therefore made of Printed Circuit Boards based on particular thermostructural materials. This thesis describes the work conducted for the development of integrated multifunctional systems from 2010 to 2012, and is divided in five main chapters, introduced by a preface. The preface itself presents the topic and scope of the work, and describes the research methodology used during activities. It also describes the structure of the thesis and acknowledges relevant contributions. The first chapter is dedicated to the literature review. Its goal is to explore the state of the art, to gather and summarize information on activities that have been performed up to now in the field of Multifunctional Systems. These activities are the foundations on which the work described in this thesis has been conceived, and represent the benchmark for the evaluation of achieved results. Therefore, a section is also included which contains a critical analysis of the activities most strictly related to this thesis. The second chapter presents how the research has been actually conducted, the activities regarding technology study and design, the factual implementation of concepts, the technical description of all different prototypes, and a first glance on results obtained. The third chapter describes in more detail all the findings, including test results and interpretation of data. The fourth chapter focuses on analysis and discussion of results and findings, with particular attention to their position in the context of the initial literature review and possible comparison with closest rivals. The fifth chapter draws conclusions and explains where further work is needed and which activities are going on to bring the multifunctional systems approach from the laboratory to the space vehicle. To broaden the discussion on given topics, or to give additional information on specific technologies, an appendix has been added.