Roberto Gardi

Numerical/Experimental Correlation of a Plasma Wind Tunnel Test on a UHTC-Made Nose Cap of a Reentry Vehicle

The nose cap demonstrator named Nose_2 has been tested for the second time in the plasma wind tunnel (PWT) facility which is part of the sharp hot structure (SHS) technology project, focused on the assessment of the applicability of ultrahigh temperature ceramics (UHTC) to the fabrication of high performance vehicles and SHS for reusable launch vehicles. In this paper the FEM based thermal analyses, carried out for the rebuilding of this PWT test, are presented. Experimental data measured in the PWT have been compared with numerical ones in order to validate the FEM model and to help in interpreting the experimental test itself. The knowledge on the physical phenomenon under investigation has been greatly improved, thanks to the synergy between numerical and experimental activities. In particular, a qualitative study of the modeling of the tip-dome interface has been performed in order to estimate the thermal contact resistance that heat flux encounters in passing through the demonstrator. The correlation...

CIRA activities on UHTC's: on-ground and in flight experimentations

CIRA has been working since almost a decade on the possibility to use a new class of ceramic materials, the so called Ultra High Temperature Ceramics (UHTC’s), for space applications, and specifically for some critical parts of thermal protection systems.It is well known that sharp aerodynamic configurations could provide much more efficiency in “flying” during the re-entry phase of spacecrafts, and/or the hypersonic cruise of futuristic aerospace planes.However such innovation in the design criteria, implies a dramatic increase of the localized heat fluxes at the stagnation points of the leading edges of the aerodynamic surfaces that, as matter of fact, might then require dedicated thermal protection systems, able to sustain thermal loads much higher than those typically experienced by conventional materials applied on blunt bodies.In this perspective CIRA started its own investigations on the design methodology, characterization methods, manufacturing procedures, and qualification tests of medium size components based on exotic ceramic materials able to sustain temperatures even exceeding 2000°C.This paper summarizes CIRA experience achieved so far trough the test opportunities conducted on-ground in the SCIROCCO plasma wind tunnel, and in-flight onboard re-entry experimental platforms (SHARK, and EXPERT capsules).Then such conclusions related to the level of maturity (TRL), today reached by such materials and their structural parts, for the foreseen applications, will be critically analyzed and discussed.

Thermo-structural design of Ultra High Temperature Ceramic (UHTC) winglets of a re-entry space vehicle

The purpose of this paper is to present a general overview of a re-entry space vehicle study and a synthesis of the methodologies developed as well as the main results obtained. The final objective is to give a contribution to implement and evaluate the thermo-structural performance of a pair of Ultra High Temperature Ceramic (UHTC) winglets developed by CIRA. Therefore, the test-case consists of two winglets made of fibber reinforced massive UHTC coupled with a metallic interface. A plasma sprayed UHTC coating has also been applied on refractory metal. The winglets are mounted on a carrier vehicle which will fly at Mach numbers approximately equal to 8 over the altitude range 27-32 Km. A massive numerical study has been performed. In order to assess the capability of finite element models to predict the winglet thermo-structural behavior, several models have been developed. Finally, a solid finite element model is necessary. Solid meshes are first developed in order to identify the highly accurate numerical solution and to study the influence of mesh refinement. The performed convergence analysis shows the “just necessary model” is a solid FEM model whose mean element size for the winglet is 0.9 mm. A thermal as well as a structural analysis have been performed. The main thermal results show that the launch phase is not critical while the re-entry is more demanding. Indeed, the UHTC tip gets close to about 1500°C in a short time and the aluminum is heated up to 362°C at the end of the flight. The heating on the aluminum surface of the vehicle is mostly caused by conduction from the winglet to the vehicle, and not by the wake of the winglet. The hot spot downstream the winglet is always cooler than the area just beneath the winglet. A zirconium coating will be applied to the aluminum to let these temperatures to be sustained by the material without any relevant degradation. The combination of thermal and mechanical load have also been analyzed. Heat fluxes applied are timechanging depending by the wall temperature. Numerical predictions show how the structure is not affected by the inducted stress. The two winglets as well as the whole vehicle are actually being manufactured and the numerical prediction will be shortly validated by several experimental tests in CIRA’s GHIBLI and SCIROCCO plasma wind tunnels facilities.

SHARK: Flying a self-contained capsule with an UHTC- based experimental nose

SHARK (Sounding Hypersonic Atmospheric Re-entering ‘Kapsule’) is a small capsule designed and realized by CIRA. It was launched on March the 26th 2010 on board the European Space Agency sounding rocket MAXUS 8 flight. During the ascent parabola, the capsule was released and successfully executed its 15 minutes ballistic flight and then reentered in the atmosphere and landed. The aim of the project was to prove the possibility to set up a low cost experimental space platform and execute a re-entry test flight by dropping a capsule from a sounding rocket. Since CIRA is investigating new technologies for the re-entry and in particular new ceramic materials for sharp thermal protection systems (TPS), this flight opportunity has been chosen to test in a real flight an UHTC (Ultra High Temperature Ceramic) component, machined from scraps of previous ground tests executed in the Plasma Wind Tunnel SCIROCCO. The paper describes the mission genesis and development, the design and the subsystems of the capsule and then shows the first results from the preliminary analysis of the recorded data.

In-Flight Test of Ultra High Temperature Ceramic Materials on Scramspace

This paper describes the activities carried out by CIRA in the frame of the SCRAMSPACE flight activities. CIRA is investigating applications of Ultra High Temperature Ceramics (UHTC) for space applications. In order to test new UHTC based technologies, in real flight conditions, CIRA and University of Queensland carried out cooperation for the SCRAMSPACE project. CIRA contributed to the flight experiment realizing two ceramic fins, embedding different newly developed technologies. The paper describes shortly the development of the materials used for the test articles, the thermostructural analyses carried out for the design of the payloads. The payload integration is then described along with the launch activity in Andoya, Norway. Unluckily the first stage of the rocket suffered a failure at the beginning of the flight and, even if the payload operated as expected, it was never injected in the correct trajectory and the flight failed in providing the expected scientific results. The final part of the paper describes the activities carried out in CIRA for the design of a model holder that shall permit to test the Qualification Models of the fins in CIRA Plasma Wind Tunnel SCIROCCO.

CIRA Experiments and Payloads flying on EXPERT - The ESA Experimental Re-Entry Vehicle.

The ESA European Space Agency is currently developing the project EXPERT – Experimental Re-entry Vehicle Test-bed. The EXPERT capsule features a generic simple shape and will perform a sub-orbital ballistic hypersonic flight; with a selection of major shape parameters to avoid any surface active oxidation, degradation and flow contamination. In the frame of Expert Project, CIRA has covered a double role: Payloads Coordinator with the main objectives to supervise all scientific aspects of embarked experiments, to coordinate all main and critical mechanical tests, to harmonize and optimize their integration on the EXPERT vehicle and their interfaces from mechanical, electrical and software point of view: and as Principal Investigator of 3 Payloads corresponding to the following experiments: a) Natural LTT Laminar-To-Turbulent Transition, b) SWBLI Shock Layer – Boundary layer Interaction ahead the ceramic flaps, c) Flying Winglet – UHTC Sharp Hot Structure “SHS”. In this paper a detailed overview of the designed experiment, correlation with the theoretical aspects, results of the on-ground qualification activities and expected results from the data collected in the coming flying mission are reported and discussed.