1,721,084 research outputs found
High level requirements impact on configuration trade-off analyses in a multidisciplinary integrated conceptual design methodology
Full text linkThis paper aims at suggesting rational algorithms for the selection of general characteristics of trans-atmospheric vehicles, such as the staging and propulsive strategies, take-off and landing solutions and aero-thermodynamic configurations. The presented selection algorithms exploit different types of high level requirements coming from Stakeholders’ Analysis, Market Outlook, Regulatory Framework Analysis and Strategic Plan, to support drivers and criteria definition process for the selection of the optimal solution among the alternatives. The theoretical description of each single algorithm is supported by the results obtained from the application of the methodology to a suborbital vehicle aimed at parabolic flight and to a point-to-point hypersonic transportation system. Eventually, suggestions for on-going software implementation of the algorithms as well as their integration within a complex conceptual and preliminary design workflow are provided
Influence of high level requirements in aircraft design: From scratch to sketch
Full text linkThis paper suggests an innovative sketch procedure, especially envisaged for very complex and innovative transportation systems. In order to face with the increasing complexity and innovation levels, reducing development schedule and budget, a rational approach is developed and presented. At first, high level requirements, coming from different sources are elicited and then, through a detailed impact analysis, each design parameter used to sketch the vehicle layout is connected to one or more of these requirements. Then, different semi-empirical models, exploiting available statistical data, regulations and best practices, are developed and proper sizing algorithms are suggested to provide a quantitative base to the qualitative sketching procedure. In this approach, special attention is devoted to the evaluation of the impact of the integration of main subsystems (for example, propulsion, propellant, landing gear subsystems) into the final vehicle layout. Eventually, results of the application of the described procedure to an innovative hypersonic transportation system is reported, highlighting the benefit of the increased traceability of requirements into the final product
Flight Control System Design and Sizing Methodology for hypersonic cruiser
Full text linkFlight Control System is considered a key enabler for future high-speed aircraft and therefore, the anticipation of its impact onto the aircraft layout and performance is crucial. On one side, a preliminary characterization of the control surfaces is essential for a precise estimate of the aerodynamic characteristics of the vehicle throughout the mission. On the other side, traditional design approaches widely used in subsonic aircraft design and based on on-design and standalone system sizing, may lead to wrong estimates of the peak power demand. Conversely, typical supersonic and hypersonic design solutions are investigated by means of numerical simulations which guarantee higher accuracy but may not be directly applicable during the early design stages. Therefore, this paper discloses an innovative methodology (i) to anticipate the Flight Control System design of future high-speed aircraft at conceptual design stage, (ii) to properly consider the interactions with other subsystems and (iii) to properly predict the behavior of the Flight Control System throughout the entire mission. The integrated subsystems design methodology disclosed in this paper starts with the suggestion of the most promising semi-empirical models for control surfaces geometrical definition. The newly defined surfaces can be analyzed to predict their single contribution to the vehicle lift and drag coefficients. At this stage, the interaction with the propellant system is fundamental to identify the minimum surfaces deflections required to guarantee the aircraft trim. Indeed, in order to minimize the exploitation of control surfaces and thus limiting the detrimental effects onto the aerodynamic efficiency, propellant tanks can be properly shaped and integrated on board, and ad-hoc depletion sequencies can be adopted to match the desired center of gravity shift throughout the mission. Maximum required control surfaces deflections are used as inputs for the estimation of hinge moments to be counteract by the actuation system. A novel approach is here suggested to extend the formulation available in literature beyond the transonic regime. Eventually, the Flight Control System design is completed with the selection of actuators and finalization of the System architecture including power distribution lines and connections with the avionic system. The integrated design methodology has been developed in the context of the H2020 STRATOFLY Project and it has been exploited for the design and sizing of the Flight Control System of the STRATOFLY MR3 vehicle, a Mach 8 waverider concept for civil antipodal flights
Propellant subsystem design for hypersonic cruiser exploiting liquid hydrogen
Full text linkThe possibility of establishing a new paradigm for commercial aviation towards high-speed flight in the next decades shall be inevitably preceded by the increase of Technology Readiness Level for those relevant enabling technologies associated to propulsion, thermal management and on-board subsystems, with particular attention also to environmental sustainability and economic viability of the proposed concepts. New design methodologies for both aircraft and on-board subsystems design shall then be based on holistic approaches able to catch the strong interactions between vehicle configuration, mission and subsystems architecture, which characterize high-speed aircraft layouts. This paper proposes a methodology for the preliminary sizing of propellant subsystems for liquid hydrogen powered hypersonic cruisers. Making benefit of traditional approaches, the process aims at introducing new design aspects directly connected to the peculiar multifunctional architecture of on-board subsystems for high-speed vehicles, so to be able to include additional analyses in early design stages, especially in case of high level of on-board integration. Notably, impact of requirements for Center of Gravity control, thermal, and, in general, energy management are considered as integral part of the method, with crucial implications on architecture selection. After the introduction of design algorithms for subsystem sizing, the STRATOFLY MR3 hypersonic cruiser is taken as reference case study in order to provide a practical example of application of the proposed approach on a highly integrated platform
Sustainable supersonic fuel flow method: An evolution of the boeing fuel flow method for supersonic aircraft using sustainable aviation fuels
Full text linkThis paper discloses a new algorithm, called sustainable supersonic fuel flow method, to complement the conceptual design of future supersonic aircraft with pollutant and greenhouse gases emissions estimation. Starting from already existing algorithms currently used to assess the environmental impact of already developed and operating aircraft, the authors suggest revisions to improve the formulations, thus extending their application. Specifically, this paper has two objectives: to support the design of future supersonic aircraft and to evaluate the impact of the exploitation of more sustainable aviation fuels, with special focus on biofuels and biofuel blends, since the conceptual design stage. The core of the algorithm developed to predict in-flight emissions of a supersonic aircraft has been validated with public data of Concorde flight experiments. In addition, corrective factors accounting for the most recently developed and certified biofuels have been included in the formulation
Innovative Multiple Matching Charts approach to support the conceptual design of hypersonic vehicles
Full text linkSeveral well-established best practices and reliable tools have been developed along the years to support aircraft conceptual and preliminary design. In this context, one of the most widely used tool is the Matching Chart (MC), a graphical representation of the different performance requirements (curves representing the thrust-to-weight ratio (T/W) requirement as function of the wing loading (W/S)) for each mission phase. The exploitation of this tool allows the identification of a feasible design space as well as the definition of a reference vehicle configuration in terms of maximum thrust, maximum take-off weight, and wing surface since the very beginning of the design process. Although the tool was originally developed for conventional aircraft, several extensions and updates of the mathematical models have been proposed over the years to widen its application to innovative configurations. Following this trend, this paper presents a further evolution of the MC model to support the conceptual design of high-speed transportation systems, encompassing supersonic and hypersonic flight vehicles. At this purpose, this paper reports and discusses the updates of the methodology laying behind the generation of the MC for high-speed transportation. Eventually, the results of the validation of the updated methodology and tool are reported, using as case study, the STRATOFLY MR3 vehicle configuration, a Mach 8 antipodal civil transportation system, currently under development within the H2020 STRATOFLY project
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
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