Survey of Inter-satellite Communication for Small Satellite Systems: Physical Layer to Network Layer View

Small satellite systems enable whole new class of missions for navigation, communications, remote sensing and scientific research for both civilian and military purposes. As individual spacecraft are limited by the size, mass and power constraints, mass-produced small satellites in large constellations or clusters could be useful in many science missions such as gravity mapping, tracking of forest fires, finding water resources, etc. Constellation of satellites provide improved spatial and temporal resolution of the target. Small satellite constellations contribute innovative applications by replacing a single asset with several very capable spacecraft which opens the door to new applications. With increasing levels of autonomy, there will be a need for remote communication networks to enable communication between spacecraft. These space based networks will need to configure and maintain dynamic routes, manage intermediate nodes, and reconfigure themselves to achieve mission objectives. Hence, inter-satellite communication is a key aspect when satellites fly in formation. In this paper, we present the various researches being conducted in the small satellite community for implementing inter-satellite communications based on the Open System Interconnection (OSI) model. This paper also reviews the various design parameters applicable to the first three layers of the OSI model, i.e., physical, data link and network layer. Based on the survey, we also present a comprehensive list of design parameters useful for achieving inter-satellite communications for multiple small satellite missions. Specific topics include proposed solutions for some of the challenges faced by small satellite systems, enabling operations using a network of small satellites, and some examples of small satellite missions involving formation flying aspects.Comment: 51 pages, 21 Figures, 11 Tables, accepted in IEEE Communications Surveys and Tutorial

New Design Techniques for Dynamic Reconfigurable Architectures

L'abstract è presente nell'allegato / the abstract is in the attachmen

DISTRIBUTED ELECTRO-MECHANICAL ACTUATION AND SENSING SYSTEM DESIGN FOR MORPHING STRUCTURES

Smart structures, able to sense changes of their own state or variations of the environment they’re in, and capable of intervening in order to improve their performance, find themselves in an ever-increasing use among numerous technology fields, opening new frontiers within advanced structural engineering and materials science. Smart structures represent of course a current challenge for the application on the aircrafts. A morphing structure can be considered as the result of the synergic integration of three main systems: the structural system, based on reliable kinematic mechanisms or on compliant elements enabling the shape modification, the actuation and control systems, characterized by embedded actuators and robust control strategies, and the sensing system, usually involving a network of sensors distributed along the structure to monitor its state parameters. Technologies with ever increasing maturity level are adopted to assure the consolidation of products in line with the aeronautical industry standards and fully compliant with the applicable airworthiness requirements. Until few years ago, morphing wing technology appeared an utopic solution. In the aeronautical field, airworthiness authorities demand a huge process of qualification, standardization, and verification. Essential components of an intelligent structure are sensors and actuators. The actual technological challenge, envisaged in the industrial scenario of “more electric aircraft”, will be to replace the heavy conventional hydraulic actuators with a distributed strategy comprising smaller electro-mechanical actuators. This will bring several benefit at the aircraft level: firstly, fuel savings. Additionally, a full electrical system reduces classical drawbacks of hydraulic systems and overall complexity, yielding also weight and maintenance benefits. At the same time, a morphing structure needs a real-time strain monitoring system: a nano-engineered polymer capable of densely distributed strain sensing can be a suitable solution for this kind of flying systems. Piezoresistive carbon nanotubes can be integrated as thin films coated and integrated with composite to form deformable self-sensing materials. The materials actually become sensors themselves without using external devices, embedded or attached. This doctoral thesis proposes a multi-disciplinary investigation of the most modern actuation and sensing technologies for variable-shaped devices mainly intended for large commercial aircraft. The personal involvement in several research projects with numerous international partners - during the last three years - allowed for exploiting engineering outcomes in view of potential certification and industrialization of the studied solutions. Moving from a conceptual survey of the smart systems that introduces the idea of adaptive aerodynamic surfaces and main research challenges, the thesis presents (Chapter 1) the current worldwide status of morphing technologies as well as industrial development expectations. The Ph.D. programme falls within the design of some of the most promising and potentially flyable solutions for performance improvement of green regional aircrafts. A camber-morphing aileron and a multi-modal flap are herein analysed and assessed as subcomponents involved for the realization of a morphing wing. An innovative camber-morphing aileron was proposed in CRIAQ MD0-505, a joint Canadian and Italian research project. Relying upon the experimental evidence within the present research, the issue appeared concerns the critical importance of considering the dynamic modelling of the actuators in the design phase of a smart device. The higher number of actuators involved makes de facto the morphing structure much more complex. In this context (Chapter 2), the action of the actuators has been modelled within the numerical model of the aileron: the comparison between the modal characteristics of numerical predictions and testing activities has shown a high level of correlation. Morphing structures are characterized by many more degrees of freedom and increased modal density, introducing new paradigms about modelling strategies and aeroelastic approaches. These aspects affect and modify many aspects of the traditional aeronautical engineering process, like simulation activity, design criteria assessment, and interpretation of the dynamic response (Chapter 3). With respect the aforementioned aileron, sensitivity studies were carried out in compliance with EASA airworthiness requirements to evaluate the aero-servo-elastic stability of global system with respect to single and combined failures of the actuators enabling morphing. Moreover, the jamming event, which is one of the main drawbacks associated with the use of electro-mechanical actuators, has been duly analyzed to observe any dynamic criticalities. Fault & Hazard Analysis (FHA) have been therefore performed as the basis for application of these devices to real aircraft. Nevertheless, the implementation of an electro-mechanical system implies several challenges related to the integration at aircraft system level: the practical need for real-time monitoring of morphing devices, power absorption levels and dynamic performance under aircraft operating conditions, suggest the use of a ground-based engineering tool, i.e. “iron bird”, for the physical integration of systems. Looking in this perspective, the Chapter 4 deals with the description of an innovative multi-modal flap idealized in the Clean Sky - Joint Technology Initiative research scenario. A distributed gear-drive electro-mechanical actuation has been fully studied and validated by an experimental campaign. Relying upon the experience gained, the encouraging outcomes led to the second stage of the project, Clean Sky 2 - Airgreen 2, encompassing the development of a more robotized flap for next regional aircraft. Numerical and experimental activities have been carried out to support the health management process in order to check the EMAs compatibility with other electrical systems too. A smart structure as a morphing wing needs an embedded sensing system in order to measure the actual deformation state as well as to “monitor” the structural conditions. A new possible approach in order to have a distributed light-weight system consists in the development of polymer-based materials filled with conductive smart fillers such as carbon nanotubes (CNTs). The thesis ends with a feasibility study about the incorporation of carbon nanomaterials into flexible coatings for composite structures (Chapter 5). Coupons made of MWCNTs embedded in typical aeronautic epoxy formulation were prepared and tested under different conditions in order to better characterize their sensing performance. Strain sensing properties were compared to commercially available strain gages and fiber optics. The results were obtained in the last training year following the involvement of the author in research activities at the University of Salerno and Materials and Structures Centre - University of Bath. One of the issues for the next developments is to consolidate these novel technologies in the current and future European projects where the smart structures topic is considered as one of the priorities for the new generation aircrafts. It is remarkable that scientists and aeronautical engineers community does not stop trying to create an intelligent machine that is increasingly inspired by nature. The spirit of research, the desire to overcome limits and a little bit of imagination are surely the elements that can guide in achieving such an ambitious goal

The Fifth NASA/DOD Controls-Structures Interaction Technology Conference, part 1

This publication is a compilation of the papers presented at the Fifth NASA/DoD Controls-Structures Interaction (CSI) Technology Conference held in Lake Tahoe, Nevada, March 3-5, 1992. The conference, which was jointly sponsored by the NASA Office of Aeronautics and Space Technology and the Department of Defense, was organized by the NASA Langley Research Center. The purpose of this conference was to report to industry, academia, and government agencies on the current status of controls-structures interaction technology. The agenda covered ground testing, integrated design, analysis, flight experiments and concepts

A Summary of NASA Rotary Wing Research: Circa 20082018

The general public may not know that the first A in NASA stands for Aeronautics. If they do know, they will very likely be surprised that in addition to airplanes, the A includes research in helicopters, tiltrotors, and other vehicles adorned with rotors. There is, arguably, no subsonic air vehicle more difficult to accurately analyze than a vehicle with lift-producing rotors. No wonder that NASA has conducted rotary wing research since the days of the NACA and has partnered, since 1965, with the U.S. Army in order to overcome some of the most challenging obstacles to understanding the behavior of these vehicles. Since 2006, NASA rotary wing research has been performed under several different project names [Gorton et al., 2015]: Subsonic Rotary Wing (SRW) (20062012), Rotary Wing (RW) (20122014), and Revolutionary Vertical Lift Technology (RVLT) (2014present). In 2009, the SRW Project published a report that assessed the status of NASA rotorcraft research; in particular, the predictive capability of NASA rotorcraft tools was addressed for a number of technical disciplines. A brief history of NASA rotorcraft research through 2009 was also provided [Yamauchi and Young, 2009]. Gorton et al. [2015] describes the system studies during 20092011 that informed the SRW/RW/RVLT project investment prioritization and organization. The authors also provided the status of research in the RW Project in engines, drive systems, aeromechanics, and impact dynamics as related to structural dynamics of vertical lift vehicles. Since 2009, the focus of research has shifted from large civil VTOL transports, to environmentally clean aircraft, to electrified VTOL aircraft for the urban air mobility (UAM) market. The changing focus of rotorcraft research has been a reflection of the evolving strategic direction of the NASA Aeronautics Research Mission Directorate (ARMD). By 2014, the project had been renamed the Revolutionary Vertical Lift Technology Project. In response to the 2014 NASA Strategic Plan, ARMD developed six Strategic Thrusts. Strategic Thrust 3B was defined as the Ultra-Efficient Commercial VehiclesVertical Lift Aircraft. Hochstetler et al. [2017] uses Thrust 3B as an example for developing metrics usable by ARMD to measure the effectiveness of each of the Strategic Thrusts. The authors provide near-, mid-, and long-term outcomes for Thrust 3B with corresponding benefits and capabilities. The importance of VTOL research, especially with the rapidly expanding UAM market, eventually resulted in a new Strategic Thrust (to begin in 2020): Thrust 4Safe, Quiet, and Affordable Vertical Lift Air Vehicles. The underlying rotary wing analysis tools used by NASA are still applicable to traditional rotorcraft and have been expanded in capability to accommodate the growing number of VTOL configurations designed for UAM. The top-level goal of the RVLT Project remains unchanged since 2006: Develop and validate tools, technologies and concepts to overcome key barriers for vertical lift vehicles. In 2019, NASA rotary wing/VTOL research has never been more important for supporting new aircraft and advancements in technology. 2 A decade is a reasonable interval to pause and take stock of progress and accomplishments. In 10 years, digital technology has propelled progress in computational efficiency by orders of magnitude and expanded capabilities in measurement techniques. The purpose of this report is to provide a compilation of the NASA rotary wing research from ~2008 to ~2018. Brief summaries of publications from NASA, NASA-funded, and NASA-supported research are provided in 12 chapters: Acoustics, Aeromechanics, Computational Fluid Dynamics (External Flow), Experimental Methods, Flight Dynamics and Control, Drive Systems, Engines, Crashworthiness, Icing, Structures and Materials, Conceptual Design and System Analysis, and Mars Helicopter. We hope this report serves as a useful reference for future NASA vertical lift researchers