Aerotecnica Missili & Spazio最新文献

The relatively recent decision of NASA and ESA to plan new missions to the so-called Ice Giants, namely Uranus and Neptune, has prompted a resurgence of interest in the experimental analysis of the aero-heating environment that probes entering such atmospheres would experience. In the present study, arc-jet facilities, previously used to simulate space flight in the atmospheres of Earth, Mars, and Titan, are considered as a relevant basis for the implementation of a more complex framework adequately accounting for the atmospheric features of the Ice Giants. It is shown that the key to the successful realization of such an endeavor is a new operating mode for the plasma torch (relying on a nitrogen–hydrogen mixture) together with the inclusion of a new gas control unit, a new mixing chamber to generate relevant gas mixtures (mimicking to a sufficient extent the Ice Giants atmosphere) and a new thermo-chemical model of the overall flow process. The outcomes of some initial tests are presented to demonstrate the adequacy and performances of the implemented approach with respect to typical entry conditions related to these two planets.

HEMERA is a large research community which operates in the field of tropospheric and stratospheric balloon-borne research. The Hemera project is aimed to improve the technologies related to the balloons and to favour the research on balloons by offering the opportunity to fly scientific experiment to the international community. The project, described in this paper together with its major outcomes, involves major space agencies dealing with balloon infrastructures, companies operating the balloons, companies providing the necessary technologies and scientific experts.

AstroDART is a Python package that implements a pipeline for processing, analyzing, and managing files derived from observations performed by ground-based optical telescopes. The main goal is to develop a software capable of retrieving information about satellites’ tracklets. In between its functionalities the following are included: perform astrometric reduction using Astrometry.net, detect tracklets using contour tracing techniques with ASTRiDE Python Package, refine the detected tracklets and perform telescope calibration by comparing the observations of known objects with catalogue data and obtaining the celestial coordinates of the object at the observation epoch. In addition, it produces the light curve and TDM files derived from the observations. The computation times are in the order of 15 s per image when no astrometric reduction is performed, increased to 50 s when the astrometric reduction and light curve analysis are included. The average residuals for both right ascension and declination are found to be lower than 9 arcsecs for all of the three test campaigns.

The aviation accident investigation process includes the detailed examination of the aircraft wreckage, as well as the analysis of both primary and secondary elements of the aircraft structure. This requires examination of the wreckage at the accident site, and is followed by additional analysis, often driven by the first results on the field. Therefore, one of the most important tasks of investigators is to determine the sequence of events of the accident. This means that much evidence should be collected to accurately determine the order in which events occurred. With regard to construction materials involved, the interpretation of fracture surfaces can provide very important information. However, metallic and composite structures demonstrate very different behaviors during the operative service, from corrosion and fatigue to fire and combustion resistance. This paper performs a literature review on the identification of failure mode, damage and safety of polymer composite aircraft structures from a point of view that may be useful to aviation safety investigations, with the aim to provide suggestions for future research.

In the era of space exploration, the scientific community is strongly focusing on the analysis of hypersonic flows in the presence of shock wave/boundary layer interaction. In these conditions, the flow field presents a complex shock structure due to the interaction of different shock waves with the boundary layer. The strong adverse pressure gradient makes the boundary layer separate, giving rise to a separation bubble. In the reattachment zone, the temperature can reach very high values, inducing thermochemical non-equilibrium effects. This research field is recently achieving more and more relevance in aerospace research, as the analysis of turbulent shock wave/boundary layer interaction so far has been mainly focused on perfect gas flows. In this manuscript, a Reynolds averaged Navier–Stokes (RANS) approach is considered, the shear stress transport (SST) model being coupled with the multitemperature approach proposed by Park to investigate thermochemical non-equilibrium effects in hypersonic turbulent shock wave/boundary layer interaction. The first part of the manuscript is devoted to the validation of the solver, and results for low enthalpy flat plate and compression ramp flows are presented. The numerical results are shown to be in good agreement with numerical solutions and experimental measurements. Afterward, the free stream conditions are modulated to make non-equilibrium relevant and analyze a reacting flow.

Low-Earth-Orbit (LEO) region congestion is becoming one of the big issues of the modern space era. To avoid the Kessler syndrome, now more than ever it is needed to improve awareness about space traffic, and upgrade the entire monitoring process. Extensive literature is available covering the topics of orbital conjunction filtering techniques and computation of the Minimum Orbital Intersection Distance (MOID). The present paper investigates Funding and/or Conflicts of interests/Conflict of interest. An alternative filtering method exploits the near-circularity of certain orbits (a condition often verified in LEO), to improve conjunction analysis performance. Elliptical orbits are reshaped through an auxiliary deferent model, inspired by C. Ptolemy’s orbital theory, replacing the real motion along conjunction analysis. To recover satellites’ averaged mean orbital elements, CelesTrack LEO catalogue was considered and propagated. Based on averaged parameters, off-centric circular orbits are considered instead of elliptical ones. The resulting deferents (off-centric circles) are not far from osculating orbits due to LEOs low eccentricities, becoming the basis for the conjunction analysis algorithm. The algorithm is conceived as a sequence of pre-filters and a final MOID computation. Performances are inspected through an all-vs-all analysis, taking as reference a combination of Hoots’ and Gronchi’s algorithms. This method achieves good performance as compared with these traditional benchmarks. Adopting this approach could reduce the time needed for a preliminary conjunction inspection during the first phases of the Collision Avoidance (CA) process, especially in LEO, where pre-filtering aims to reduce the number of orbit couples where precise MOID computation is needed.

A novel high-order accurate approach to the analysis of beam structures with bulk and thin-walled cross-sections is presented. The approach is based on the use of a variable-order polynomial expansion of the displacement field throughout both the beam cross-section and the length of the beam elements. The corresponding weak formulation is derived using the symmetric Interior Penalty discontinuous Galerkin method, whereby the continuity of the solution at the interface between contiguous elements as well as the application of the boundary conditions is weakly enforced by suitably defined boundary terms. The accuracy and the flexibility of the proposed approach are assessed by modeling slender and short beams with standard square cross-sections and airfoil-shaped thin-walled cross-sections subjected to bending, torsional and aerodynamic loads. The comparison between the obtained numerical results and those available in the literature or computed using a standard finite-element method shows that the present method allows recovering three-dimensional distributions of displacement and stress fields using a significantly reduced number of degrees of freedom.

This paper presents an application of the functional resonance analysis method (FRAM) to the risk assessment of low-speed legs of a helicopter flight mission. A combination of low forward speed and a specific rate of vertical descent could lead to meet a region of the helicopter’s flight envelope that shall be avoided to prevent the vortex ring state, an aerodynamic phenomenon which could cause uncontrolled high rates of descent. A fully developed vortex ring state (VRS) is characterized by an unstable situation in which the helicopter experiences uncommanded pitch and roll oscillations, with a reduced or no collective authority, and a helicopter descent rate that may approach more than 5000 feet per minute. If the recognition of VRS signs is performed early by the pilot in a condition of sufficient altitude, then the required recovery may be performed. However, some mission legs require to descend close to the ground, as the case of a firefighting mission, in which one of the fundamental task requires to fill a tank with water. This type of mission has been selected as the case study of this paper, and a qualitative risk assessment is performed using FRAM. The model developed using FRAM is systemic, where both accidents and successes are seen to emerge in the system from combinations of normal variability. Moreover, the model is complex and non-linear, providing a complete overview of functions and tasks performed by the whole system and the related couplings. The paper presents the potential events related to the mission selected and provides results in terms of possible safety barriers.

The meshing technique represents the capability to discretize the domain of interest, to fit the real physical continuum in the best possible way. The most used approach is the finite-element method (FEM), a numerical method to solve partial differential equations. To overcome the classical issues presented by FEM, other models are investigated. The goal is to allow the problem domain to be discretized by elements represented by arbitrary polygons, which can be concave and convex. Moreover, different polynomial consistency is sought within these methods with the possibility to handle non-conforming discretizations, mainly for local refinement and so on. This work aims to present the new adaptive elements, which are finite elements based on Carrera unified formulation, to demonstrate that all the previous capabilities can be done with these new elements, with easy implementation of the relative model. First, a classical patch test is done to investigate the mesh distortion sensitivity. Then, different study cases are presented with more complex meshes combining very distorted concave and convex elements.