The HERMES-technologic and scientific pathfinder

HERMES-TP/SP (High Energy Rapid Modular Ensemble of Satellites Technologic and Scientific Pathfinder) is a constellation of six 3U nano-satellites hosting simple but innovative X-ray detectors, characterized by a large energy band and excellent temporal resolution, and thus optimized for the monitoring of Cosmic High Energy transients such as Gamma Ray Bursts and the electromagnetic counterparts of Gravitational Wave Events, and for the determination of their positions. The projects are funded by the Italian Ministry of University and Research and by the Italian Space Agency, and by the European Union's Horizon 2020 Research and Innovation Program under Grant Agreement No. 821896. HERMES-TP/SP is an in-orbit demonstration, that should be tested starting from 2022. It is intrinsically a modular experiment that can be naturally expanded to provide a global, sensitive all sky monitor for high-energy transients

Tridimensional Modeling of Solid Rocket Motor Combustion Process

La regolazione dei sistemi di propulsione a razzo a propellente solido (Solid Rocket Motors) ha da sempre rappresentato una delle principali problematiche legate a questa tipologia di motori. L’assenza di un qualsiasi genere di controllo diretto del processo di combustione del grano solido, fa si che la previsione della balistica interna rappresenti da sempre il principale strumento utilizzato sia per definire in fase di progetto la configurazione ottimale del motore, sia per analizzare le eventuali anomalie riscontrate in ambito sperimentale. Variazioni locali nella struttura del propellente, difettosità interne o eterogeneità nelle condizioni di camera posso dare origine ad alterazioni del rateo locale di combustione del propellente e conseguentemente a profili di pressione e di spinta sperimentali differenti da quelli previsti per via teorica. Molti dei codici attualmente in uso offrono un approccio piuttosto semplificato al problema, facendo per lo più ricorso a fattori correttivi (fattori HUMP) semi-empirici, senza tuttavia andare a ricostruire in maniera più realistica le eterogeneità di prestazione del propellente. Questo lavoro di tesi vuole dunque proporre un nuovo approccio alla previsione numerica delle prestazioni dei sistemi a propellente solido, attraverso la realizzazione di un nuovo codice di simulazione, denominato ROBOOST (ROcket BOOst Simulation Tool). Richiamando concetti e techiche proprie della Computer Grafica, questo nuovo codice è in grado di ricostruire in processo di regressione superficiale del grano in maniera puntuale, attraverso l’utilizzo di una mesh triangolare mobile. Variazioni locali del rateo di combustione posso quindi essere facilmente riprodotte ed il calcolo della balistica interna avviene mediante l’accoppiamento di un modello 0D non-stazionario e di uno 1D quasi-stazionario. L’attività è stata svolta in collaborazione con l’azienda Avio Space Division e il nuovo codice è stato implementato con successo sul motore Zefiro 9.The regulation of propulsive performance in solid rocket motors is one of the biggest difficulties related to this type of space systems. The absence of any direct mechanism for controlling the combustion of solid propellant makes the prevision of internal ballistics the main tool adopted not only in defining grain configuration but also in reconstructing burning rate anisotropies. Local variations in grain composition, heterogeneities or surface imperfections can generate unexpected alterations in pressure profiles and consequently in thrust performance. Most of recent models propose a simplified approach to the problem, by using semi-empirical corrective functions known as HUMP factors which, however, cannot fully describe the spatial anisotropies inside the propellant volume. This work aims to present a new approach to the numerical prevision of SRMs performances and a new simulation code, named ROBOOST (Rocket Boost Simulation Tool), has been developed at that regard. Borrowing concepts and techniques from Computer Graphics, the code is able to reproduce the burning surface regression in a Lagrangian way, using a moving discrete triangle mesh to describe the grain volume. Spatial heterogeneities in local burn-rate values can be easily implemented and the solution of the chamber fluid-dynamics is achieved by coupling a 0D unsteady internal ballistic model and a 1D quasi-steady one. The activity has been carried on in collaboration with the Avio Space Division company and the new code has been successfully tested on the Zefiro 9 SRM. In parallel, a numerical analysis of solid propellant burning characteristics has been undertaken, in order to evaluate all possible conditioning elements and to implement them within simulation runs

Turbogas Engines Rotational Speed Estimation Using Acoustic and Vibrational Measurements

The overall objective of this work is the development and validation of a real-time algorithm to estimate turbogas engine rotational speeds by using accelerometric or microphonic measurements. The main advantage of this method is the absence of any intrusive installation on the engine and the fact that it might be implemented, as redundant measurement, in parallel to typical tachometric instrumentation. The developed code analyses the acquired FFT spectrum in order to identify characteristic frequencies of engine rotating components and automatically track their evolution. Experimental tests have been performed on an Allison 250C18 turboshaft engine at the Propulsion Laboratory of the University of Bologna and estimated values have been compared with tachometric measurements. Preliminary results have demonstrated the feasibility of the proposed code and an appreciable accuracy of obtained estimations through both microphone and accelerometer

Numerical model for hybrid rocket internal ballistic

In 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

Prediction of Tail-Off Pressure Peak Anomaly on Small-Scale Rocket Motors

Numerical studies intended to predict solid rocket motors anomalies are the major contributors when developing strategies to both limit expensive fire tests and to investigate and understand the physical phenomena from which anomalies can arise. This paper aims to present a mathematical–physical method to evaluate the pressure peak, namely Friedman Curl, occurring at the tail-off phase of small-scale rocket motors. Such phenomenon is linked to the grain solid particles arrangement (i.e., packing effect); indeed, those particles show a tendency to accumulate at a certain distance from the metallic case, implying a local burn rate increment and a combustion chamber pressure rise close to the tail-off phase. Comparisons between experimental and simulated combustion chamber pressure profiles are outlined to prove the effectiveness of the mathematical–physical approach. Simulations were carried out with an internal ballistic simulation tool developed by the authors of this work

Numerical Simulation of the Zefiro 9 Performance Using a New Dynamic SRM Ballistic Simulator

This 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

Metis: the Solar Orbiter visible light and ultraviolet coronal imager

Aims. Metis is the first solar coronagraph designed for a space mission and is capable of performing simultaneous imaging of the off-limb solar corona in both visible and UV light. The observations obtained with Metis aboard the Solar Orbiter ESA-NASA observatory will enable us to diagnose, with unprecedented temporal coverage and spatial resolution, the structures and dynamics of the full corona in a square field of view (FoV) of ±2.9° in width, with an inner circular FoV at 1.6°, thus spanning the solar atmosphere from 1.7 R⊙ to about 9 R⊙, owing to the eccentricity of the spacecraft orbit. Due to the uniqueness of the Solar Orbiter mission profile, Metis will be able to observe the solar corona from a close (0.28 AU, at the closest perihelion) vantage point, achieving increasing out-of-ecliptic views with the increase of the orbit inclination over time. Moreover, observations near perihelion, during the phase of lower rotational velocity of the solar surface relative to the spacecraft, allow longer-term studies of the off-limb coronal features, thus finally disentangling their intrinsic evolution from effects due to solar rotation. Methods. Thanks to a novel occultation design and a combination of a UV interference coating of the mirrors and a spectral bandpass filter, Metis images the solar corona simultaneously in the visible light band, between 580 and 640 nm, and in the UV H 

The HERMES-technologic and scientific pathfinder

HERMES-TP/SP (High Energy Rapid Modular Ensemble of Satellites Technologic and Scientific Pathfinder) is a constellation of six 3U nano-satellites hosting simple but innovative X-ray detectors, characterized by a large energy band and excellent temporal resolution, and thus optimized for the monitoring of Cosmic High Energy transients such as Gamma Ray Bursts and the electromagnetic counterparts of Gravitational Wave Events, and for the determination of their positions. The projects are funded by the Italian Ministry of University and Research and by the Italian Space Agency, and by the European Union's Horizon 2020 Research and Innovation Program under Grant Agreement No. 821896. HERMES-TP/SP is an in-orbit demonstration, that should be tested starting from 2022. It is intrinsically a modular experiment that can be naturally expanded to provide a global, sensitive all sky monitor for high-energy transients