1,721,038 research outputs found
Numerical Evaluation of the Effects of Inclusions on Solid Rocket Motor Performance
Full text linkThis work describes the application of original computer graphics methods to examine the effect of inclusionswithin the solid rocket motor thrust chamber. The adoptance of a dynamic three-dimensional triangular mesh with aself-intersection removal algorithm, as the core of the burning surface regression module, allows the aforementionedtargetto bereached.Manyphenomena notmeasurablein an analyticalclosed form, likedifferent-shapedvoidswithinthe grain, can be investigated. Indeed, both local heterogeneities and surface imperfections could generate unexpectedvariations in the combustion chamber pressure pattern and early thermal protections exposure. The aforementionedtechniques are developed and tested on a ballistic simulator developed using computer graphics methods to improvemesh handling. Simulation results are carried out and discussed
Influence of Nozzle Radiation on Solid Rocket Motors Tail-Off Thrust
Full text linkThe aims of this work are focused on the evaluation of the solid rocket motor residual thrust and
on the impact of thermal protection properties on such thrust. Indeed, tail-off thrust of solid rocket
motors upper stages can last tens of seconds after motor burn-out, affecting the performance of
the rocket on sequencing of stage separation. Hence, the knowledge of the tail-off thrust profile is
fundamental to properly design wait times and separation systems total impulse of a multi-stage
launcher. Therefore, although it has been shown in the past that pyrolysis gases responsible for the
residual thrust are mostly produced by alumina molten slag deposited next to the nozzle nose within
the combustion chamber, this study is aimed at suggesting that the portion of the nozzle within
the combustion chamber can act as the main radiative heat source leading to thermal protection
material ablation, and then to residual thrust production. An analysis of an actual solid rocket
motor has been performed in the direction of proving the effectiveness of the overall procedure. Then
a sensitivity analysis with respect to the quantities identifying the thermal protection properties has
been computed in order to evaluate the impact of such variations on the residual thrust profile
Impact of Thermal Protections Insulation Layer on Solid Rocket Motor Performance
No full textThe aim of the paper is to reproduce thermal protections ablation phenomenon in solid rocket motors focusing on its influence on rocket performance. A physical model able to predict thermal protections ablation behavior coupled with an internal ballistics simulator is outlined. The main outcome of the abovementioned model is the estimation of residual thrust occurring after burn-out at high altitudes whose evaluation is particularly important when solid rocket motors are used as upper stages and after burn-out operations take place in vacuum. During these phases residual thrust is generated by pyrolysis gases produced by case insulation layer due to ablation of thermal protections materials. The nozzle radiative power has been identified as the main source enabling thermal protections to ablate. An investigation of a commercial motor performance is obtained and discussed. Numerical methods are explained in detail
Vehicle Dynamics Modeling for Real-Time Simulation
No full textThis paper presents a 14 degrees of freedom vehicle model. Despite numerous software are nowadays commercially available, the model presented in this paper has been built starting from a blank sheet because the goal of the authors was to realize a model suitable for real-time simulation, compatible with the computational power of typical electronic control units, for on-board applications. In order to achieve this objective a complete vehicle dynamics simulation model has been developed in Matlab/Simulink environment: having a complete knowledge of the model's structure, it is possible to adapt its complexity to the computational power of the hardware used to run the simulation, a crucial feature to achieve real-time execution in actual ECUs
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
Numerical model for hybrid rocket internal ballistic
No full textIn order to predict the propulsion characteristic of an hybrid rocket, the knowledge of its internal ballistic is essential. The purpose of this work is to write a numerical code, in FORTRAN environment, in order to predict and analyze the propulsion characteristics of the rocket itself. The thermo-fluid dynamics is performed using a zero-dimension non steady model and it is coupled with a mono-dimensional quasi-steady one. In contrast with other codes, in this, one a moving combustion surface is used, in order to better model the internal fluid-dynamic during all the simulation itself. Even though, due to the high complexity level, some approximation are used. Finally the code is validate and set, with good final results, using some real tests having GOX and HTPB as oxidizer and fuel
Numerical Simulation of the Zefiro 9 Performance Using a New Dynamic SRM Ballistic Simulator
No full textThis work describes the application of a new three-dimensional ballistic model, named ROBOOST (ROcket BOOst Simulation Tool), developed at the Laboratory Propulsion and Mechanics of the University of Bologna (Department of Industrial Engineering), to the Vega - Zefiro 9 Solid Rocket Motor, manufactured by the Avio company in Colleferro (Rome). The code uses an original graphical approach and a point-by-point description of the propellant burning surface regression. The main purpose of the newly developed model is to investigate non homogeneous behaviors of the surface regression rate or non-isotropic characteristics of the grain. A zero-dimensional unsteady thermo-dynamic model, coupled with a mono-dimensional quasi-steady one, computes the internal fluid-dynamics of the combustion chamber and contributions by igniter, nozzle erosion and thermal protections ablation are also considered. Comparisons with reference curves and experimental data, in terms of volume and surface regression and mean pressure time evolution, have been performed and final results are presented and 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
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