Aero-thermo-elastic methods for the analysis of a hypersonic deployable aerodynamic decelerator

La tesi si è concentra sulla ricerca e lo sviluppo di adeguate metodologie di calcolo aero-termo-dinamiche e aero-elastiche non-lineari al fine di indagare nuove configurazioni strutturali e tecnologie per lo studio di capsule dispiegabili per il rientro atmosferico e l'esplorazione planetaria in configurazione “umbrella-like”. A tal fine, sono state prese in considerazione diverse configurazioni di capsule dispiegabili e diverse condizioni d'ingresso supersoniche / ipersoniche, al fine di dimostrare la bontà di una configurazione flessibile del tipo "umbrella-like" per essere utilizzata come Thermal Protection System (TPS), invece delle attuali capsule per il rientro atmosferico che montano uno schermo termico fisso. Nel lavoro di tesi sono presentati studi su software commerciali (strutturali e fluido dinamici) e lo sviluppo di strumenti analitici aeroelastici. Lo studio preliminare sulla traiettoria di immissione in atmosfera marziana su diversi landers del passato dimostrano che i carichi termici e dinamici agenti sullo scudo termico su una configurazione dispiegabile rispetto una configurazione con scudo fisso, possono essere ridotti da 2,5 a 3 volte. Uno studio aero-termico basato sull'interazione dei software commerciali più avanzati CFD e agli elementi finiti ha dimostrato che un approccio completamente accoppiato, fornisce i risultati più accurati in termini di previsione della temperatura attraverso lo spessore del TPS. Inoltre, è stato sviluppato e validato un modello analitico non lineare aero-elastico in grado di derivare le equazioni del moto usando un codice numerico basato sui modi naturali della struttura di un TPS utilizzando i risultati sperimentali e un modello agli elementi finiti. Tale modello ha dimostrato che questo semplice, ma abbastanza preciso, modello può indagare diverse configurazioni strutturali in un breve lasso di tempo. Ciò può ridurre notevolmente i costi di progettazione, dando la possibilità di studiare una vasta gamma di configurazioni strutturali e condizioni prima delle prove sperimentali. Anche se interessanti risultati sono stati raggiunti grazie alla ricerca e lo sviluppo di metodologie di calcolo di tali configurazioni, questo lavoro ha aperto la strada a nuovi studi e domande sul comportamento aero-termo-elastico del TPS in flusso ipersonico

Association of kidney disease measures with risk of renal function worsening in patients with type 1 diabetes

Background: Albuminuria has been classically considered a marker of kidney damage progression in diabetic patients and it is routinely assessed to monitor kidney function. However, the role of a mild GFR reduction on the development of stage 653 CKD has been less explored in type 1 diabetes mellitus (T1DM) patients. Aim of the present study was to evaluate the prognostic role of kidney disease measures, namely albuminuria and reduced GFR, on the development of stage 653 CKD in a large cohort of patients affected by T1DM. Methods: A total of 4284 patients affected by T1DM followed-up at 76 diabetes centers participating to the Italian Association of Clinical Diabetologists (Associazione Medici Diabetologi, AMD) initiative constitutes the study population. Urinary albumin excretion (ACR) and estimated GFR (eGFR) were retrieved and analyzed. The incidence of stage 653 CKD (eGFR < 60 mL/min/1.73 m2) or eGFR reduction > 30% from baseline was evaluated. Results: The mean estimated GFR was 98 \ub1 17 mL/min/1.73m2 and the proportion of patients with albuminuria was 15.3% (n = 654) at baseline. About 8% (n = 337) of patients developed one of the two renal endpoints during the 4-year follow-up period. Age, albuminuria (micro or macro) and baseline eGFR < 90 ml/min/m2 were independent risk factors for stage 653 CKD and renal function worsening. When compared to patients with eGFR > 90 ml/min/1.73m2 and normoalbuminuria, those with albuminuria at baseline had a 1.69 greater risk of reaching stage 3 CKD, while patients with mild eGFR reduction (i.e. eGFR between 90 and 60 mL/min/1.73 m2) show a 3.81 greater risk that rose to 8.24 for those patients with albuminuria and mild eGFR reduction at baseline. Conclusions: Albuminuria and eGFR reduction represent independent risk factors for incident stage 653 CKD in T1DM patients. The simultaneous occurrence of reduced eGFR and albuminuria have a synergistic effect on renal function worsening

Preliminary Validation of Fluid-Structure Interaction Modeling for Hypersonic Deployable Re-Entry Systems

The aim of the present work is to provide a first attempt to set an aero-thermo-elastic methodology for deployable atmospheric re-entry decelerators operating at high Mach number and high dynamic pressure. Because of the severity of re-entry conditions such as high temperatures, high pressures and high velocities, the behavior of their flexible structures is a hard target to assess. In this paper a partitioned Fluid Structure Interaction (FSI) approach based on the integration of different commercial software (STAR-CCM+ and ABAQUS) is presented. In order to validate the specific codes and the overall strategy for structural and fluid dynamics analyses of flexible structures, different test cases are considered, including numerical and experimental literature results related to the problem under investigation. The paper shows that a good description of the physical behavior is possible with the proposed FSI partitioned approach. The model is preliminarily applied to investigate structural, fluid dynamic and aero-thermal behavior of a flexible deployable umbrella-like configuration along a typical suborbital re-entry trajectory based on sounding rocket

Catherine Sforza,

Mode of access: Internet

The Small Mars Satellite: a European small-size Mars lander

The Small Mars Satellite (SMS) is a proposed mission to Mars. The project is being funded by the General Studies Programme of the European Space Agency and has recently successfully concluded Phase 0 (feasibility study). The prime contractor is ALI S.c.a.r.l. (Naples), and the study team includes the University of Naples “Federico II” (UniNA), the Astronomical Observatory of Capodimonte (INAF-AOC, Naples) and the Space Studies Institute of Catalonia (IEEC, Barcelona). The objectives of the mission are technological and scientific, and consist in delivering to Mars a small lander carrying a dust particle analyser (DPA), developed by INAF-AOC, and an aerial drone (AD), proposed and designed by UniNA. The former shall perform in situ measurements of the size distribution and abundance of the dust particles suspended in the Martian atmosphere, whereas the latter shall execute multiple, low-altitude flights in the rarified environment of the red planet. The mission-enabling technology is an innovative deployable heat shield (DHS), whose original design is known as IRENE (Italian ReEntry NacellE), developed and patented by ALI

FORCE: A FORmation Flying SAR Based on CubEsat Assemblies

Space systems exploiting modularity, formation flying, payload distribution and fractionation concepts can be used for a variety of applications, including Earth observation and on-orbit servicing. Concerning Earth observation, in a Formation Flying SAR (FF-SAR) the Synthetic Aperture Radar (SAR) payload is distributed among several smaller platforms to enhance performance of a monolithic SAR, by exploiting the physical separation among the receivers. In this paper, a FF-SAR concept is described that exploits a cluster of three receiving-only platforms flying with separations of a few hundred meters. The cluster is then separated of about 100 km from an illuminator of opportunity, i.e. a transmitting-receiving SAR. The system is completely passive in the meaning that it exploits the signal transmitted by an illuminator of opportunity already in orbit. The paper presents an overview of the mission concept as well as system and platform design. Each platform is 12 U and has a modular architecture, being realized by assembling subsystems or modules, each composed by a number of Cubesat Units. In the paper, the antenna, propulsion and relative navigation modules are described. In addition, FF-SAR performance are preliminary evaluated within a realistic simulation environment, including orbit and attitude propagation, scene simulation, and image synthesis