1,721,082 research outputs found
Conceptual design of a human mission to the near-earth asteroid 1999 AO10 in 2025-2026
No full textA human mission to the Near-Earth Asteroid (NEA) 1999 AOlO in 2025-2026 represents an intermediate and incremental step towards the human exploration of Mars. It would bring a large suite of benefits: high scientific return, operational experience on human space exploration missions beyond LEO, tests of technologies and assessment of human factors for future long-duration missions, tests of asteroid collision avoidance techniques and nevertheless evaluation of In-Situ Resource Utilization (ISRU). A space system modular architecture composed of 5 elements: 1 NASA Orion MPCV-like Command Module (CM), 1 Mission Habitation Module (MM) and 3 Propulsions Modules (PMl, PM2 and a Service Module SM of the CM), that use chemical storable cryogenic propulsion for the main orbital maneuvers (total ΔV = 7.23 km/s), is able to send in 2025-2026 a crew of 3 astronauts to the NEA 1999 AO10 for a space mission lasting 165 days, and bring them back safely to the Earth. The whole 5 modules Spacecraft (S/C) of almost 240 MT in total is launched separately by 2 equal crew and cargo Heavy Lift Launcher Vehicle (HLLV) of around 125 MT, still to be developed. The assembly in LEO anticipates the injection into the NEA Transfer Orbit (NTO) by the PMl, then expended. Once the S/C is in proximity of the asteroid, a rendez-vous maneuver is performed by the PM2, successively expended. Afterwards the MM, CM and SM attend a docking to a pre-installed platform, anchored on the NEA surface by a previous robotic mission. After 14 days of operations, including the deployment of instrumentation and the performance of high challenging EVAs, the remained 3 modules S/C come back to the Earth where the CM, with the crew on board, shall be able to land safely after an atmospheric direct re-entry. The S/C preliminary design includes the determination of S/C modules power budgets, the S/C elements interfaces functional analysis, the S/C subsystems definition and top-level functions allocation, nevertheless the assessment of preliminary single modules and whole space system mass budgets. The space human mission the NEA 1999 AO10 would be the first human expedition to an interplanetary body beyond the Earth-Moon system. The challenge of increasing the interest of the international community on the human spaceflight and inspiring the new generations about science, technology and space has been accepted. Copyright ©2011 by the International Astronautical Federation. All rights reserved
Innovative unmanned airship: Avionics and power supply development
No full textThe present work describes, divided into two parts, the development process of the on board avionics, at first, and then of the power supply and electric system of a low speed, low altitude advanced unmanned platform, named Elettra Twin Flyers, which should be employed for reconnaissance, monitoring and telecommunication purposes both in military and civil area. This innovative remotely-piloted airship has been designed and patented by Nautilus S.p.A. and equipped with high precision sensors and communication devices by Galileo Avionica and Selex Communication. For technical and commercial reason a lowcost-high-fidelity Flight Simulator has been also implemented and used to develop a new Ground Station Concept. In particular, the paper focuses on the strong design integration, especially required by the unconventional characteristics of the airship, among the flight controls, the electric power generation and distribution, and the avionic systems. To cut down costs and development time, the avionics of the prototype has been conceived by integrating both aerospace qualified and COTS devices. The use of COTS Inertial Measuring Unit based on MEMS technology, that is getting more and more precise and reliable, has also contributed to the reduction of the avionics weight. A particular subject has been the choice of the digital data network architecture in order to come to a necessary balance between flexibility ad modularity, needed for the prototype development, and complexity in software coding. Copyright © 2005 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved
Innovative sensor networks for massive distributed thermal measurements in space applications under different environmental testing conditions
Full text linkOptical fiber has seen significant development in the technical fields where it has been used in the last years. In the first place, obviously, for the Internet and, more broadly, to improve communication efficiency; but, more recently, for medicinal, structural, or lighting engineering applications. Furthermore, many optical solutions are beginning to be researched in the aerospace sector. The use of optical fiber, in particular, is strongly related to the employment of FBG type optical sensors, which may be particularly suitable for specific measurements of relevant physical parameters to be performed on specimens with typical aeronautical and/ or space employment. More specifically, the performance of several FBG sensors for temperature measurement in vacuum for validation tests of space products has been examined during this work. Unlike typical thermocouples, the adoption of this new type of sensor can provide substantial benefits, beginning with a significant gain in terms of the size of the fiber, which ensures a minimum disturbance on thermal data. Furthermore, if supplied with a suitable coating (in polyimide), the optical fiber may guarantee a very high operating temperature range, which is extensively compatible with the high-temperature range existent in space. The measurements were divided into two independent phases. First, a preliminary test was performed in the laboratory using a climatic chamber to evaluate several sensor network integration methodologies on the specimens and select the most effective one for the vacuum test. The test demonstrated that a simple adhesive bonding of the fiber to the specimens ensures a precise temperature measurement under vacuum and stable conditions. The following vacuum test program confirmed that FBGs could be used as temperature sensors even at very high temperatures. The good results of this test encourage us to consider FBG strategic for space applications and, particularly, for thermal characterizations, thanks to the high number of available sensors, combined with the minimal cable's size. However, further studies are required in cryogenic cases to validate the entire range of extreme temperatures that characterize the space environment
MDO techniques integrated with system modeling framework: MBSE methodologies applied to space system design and analysis
No full textThis paper presents the results of a research study related to the integration of a Design Optimization Framework in a Model Based System Engineering (MBSE) environment. The main aim of this work concerns the feasibility of such connection in order to assess actual advantages and possible drawbacks. The objective is to show how the Multidisciplinary Design Optimization (MDO) methods may be managed in the context of a MBSE environment with respect to the traditional design approach. Basically this analysis is addressed to the demonstration of the benefits of MBSE methodology in the field of aerospace engineering. The state of the art of the considered methodology is briefly introduced in the first part of the paper where also a survey on the role of MDO techniques is reported. The following part concerns the description of the modeling activities that have been used to define system characteristics. System data model is defined on the basis of MBSE paradigm and managed through a web application tool. In this section the focus is on the definition of conceptual relationships between the objects involved in the modeling activities. This part allows to assess how a web service can be used to support concurrent engineering activities. In the following part is described how a design optimization functionalities are integrated within the proposed framework to verify if possible advantages can be obtained. In particular the evaluation of framework benefits concerns mainly the management of system design variables and the possibility to trace their evolution throughout the design phase. A reference case referring is presented in the following section to show how the analyzed modeling tool can be used on a project development. The main aim of this study is to assess the feasibility of the considered approach for the management and support of engineering problems. Copyright (2013) by the International Astronautical Federation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Thermomechanical calibration of FBG sensors for aerospace applications
Full text linkOptical fibers have found widespread use in engineering, from communication to sensors. Among them, Fiber Bragg Gratings are allowed to detect several parameters. Scope of this work is to assess their performances as temperature and mechanical strain sensors for aerospace: in this regard, an experimental calibration is discussed. Then, alternative approaches are tested in order to distinguish thermal from mechanical contributes. This is first addressed by using a hybrid system of digital and optical sensors, and then then with a fully optical system. Both the presented solutions reached the scope. A concept of a third, innovative approach, is also described
Enhanced hybrid prognostic approach applied to aircraft on-board electromechanical actuators affected by progressive faults
No full textIn the last generation aircraft, the architecture of the powered flight control system adopted Electromechanical Actuators (EMAs). Being some on-board actuator safety critical, the practice of monitoring their behavior to determine their health condition is a task of growing importance. The choice of the best prognostic algorithm is driven primarily by their effectiveness in correctly identifying the health conditions of the system since each technique might be more or less useful in a given situation. In this contest, the authors propose a new GA-based fault detection tool, relying on a model-based approach, comparing the system output to that of a Monitor Model (MM), which is able to reproduce accurately the dynamic response of the actual EMA in terms of position, speed and equivalent current, even under the effects of different failure modes while keeping a reasonably low computational cost; this Fault Detection and Identification (FDI) algorithm have been extended to seven progressive failures. A numerical simulation test environment has been developed to simulate progressive faults and to evaluate the accuracy of this prognostic method. Results showed an adequate robustness and a suitable ability to early identify malfunctions with low risk of false alarms or missed failures. Moreover, the effect of a failures different from those considered was studied, to avoid safety concerns related to the missed identification of an incipient failure, hidden by another unknown failure mode
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