Application of Pressure Sensitive Paint in Hypersonic Flows

It is well known in the aerodynamic field that pressure distribution measurement over the surface of an aircraft model is a problem in experimental aerodynamics. For one thing, a continuous pressure map can not be obtained with the current experimental methods since they are discrete. Therefore, interpolation or CFD methods must be used for a more complete picture of the phenomenon under study. For this study, a new technique was investigated which would provide a continuous pressure distribution over the surface under consideration. The new method is pressure sensitive paint. When pressure sensitive paint is applied to an aerodynamic surface and placed in an operating wind-tunnel under appropriate lighting, the molecules luminesce as a function of the local pressure of oxygen over the surface of interest during aerodynamic flow. The resulting image will be brightest in the areas of low pressure (low oxygen concentration), and less intense in the areas of high pressure (where oxygen is most abundant on the surface). The objective of this investigation was to use pressure sensitive paint samples from McDonnell Douglas (MDD) for calibration purpose in order to assess the response of the paint under appropriate lighting and to use the samples over a flat plate/conical fin mounted at 75 degrees from the center of the plate in order to study the shock/boundary layer interaction at Mach 6 in the Von Karman wind-tunnel. From the result obtained it was concluded that temperature significantly affects the response of the paint and should be given the uppermost attention in the case of hypersonic flows. Also, it was found that past a certain temperature threshold, the paint intensity degradation became irreversible. The comparison between the pressure tap measurement and the pressure sensitive paint showed the right trend. However, there exists a shift when it comes to the actual value. Therefore, further investigation is under way to find the cause of the shift

Detecting User’s Behavior Shift with Sensorized Shoes and Stigmergic Perceptrons

As populations become increasingly aged, health monitoring has gained increasing importance. Recent advances in engineering of sensing, processing and artificial learning, make the development of non-invasive systems able to observe changes over time possible. In this context, the Ki-Foot project aims at developing a sensorized shoe and a machine learning architecture based on computational stigmergy to detect small variations in subjects gait and to learn and detect users behaviour shift. This paper outlines the challenges in the field and summarizes the proposed approach. The machine learning architecture has been developed and publicly released after early experimentation, in order to foster its application on real environments

Pyogenic Granuloma of the Sigmoid Colon causing Intussusception in an Infant

Pyogenic granuloma is a benign vascular tumor that may affect the gastrointestinal tract. This report describes a rare case of sigmoid-colon pyogenic granuloma in a 4-month-old boy causing intussusception. Resection and anastomosis were curative. The mother had history of high dose of progesterone exposure during initial weeks of conception for vaginal bleeding. This may point towards etiology of the lesion

Heat treatment procedure of the Aluminium 6061-T651 for the Ariel Telescope mirrors

The Atmospheric Remote-Sensing Infrared Exoplanet Large Survey (Ariel) is the M4 mission adopted by ESA’s ”Cosmic Vision” program. Its launch is scheduled for 2029. The purpose of the mission is the study of exoplanetary atmospheres on a target of ∼ 1000 exoplanets. Ariel scientific payload consists of an off-axis, unobscured Cassegrain telescope. The light is directed towards a set of photometers and spectrometers with wavebands between 0.5 and 7.8 µm and operating at cryogenic temperatures. The Ariel Space Telescope consists of a primary parabolic mirror with an elliptical aperture of 1.1· 0.7 m, followed by a hyperbolic secondary, a parabolic collimating tertiary and a flat-folding mirror directing the output beam parallel to the optical bench; all in bare aluminium. The choice of bare aluminium for the realization of the mirrors is dictated by several factors: maximizing the heat exchange, reducing the costs of materials and technological advancement. To date, an aluminium mirror the size of Ariel’s primary has never been made. The greatest challenge is finding a heat treatment procedure that stabilizes the aluminium, particularly the Al6061T651 Laminated alloy. This paper describes the study and testing of the heat treatment procedure developed on aluminium samples of different sizes (from 50mm to 150mm diameter), on 0.7m diameter mirror, and discusses future steps

The detector control unit of the fine guidance sensor instrument on-board the ARIEL mission: design status

ARIEL is an ESA mission whose scientific goal is to investigate exoplanetary atmospheres. The payload is composed by two instruments: AIRS (ARIEL IR Spectrometer) and FGS (Fine Guidance System). The FGS detection chain is composed by two HgCdTe detectors and by the cold Front End Electronics (SIDECAR), kept at cryogenic temperatures, interfacing with the F-DCU (FGS Detector Control Unit) boards that we will describe thoroughly in this paper. The F-DCU are situated in the warm side of the payload in a box called FCU (FGS Control Unit) and contribute to the FGS VIS/NIR imaging and NIR spectroscopy. The F-DCU performs several tasks: drives the detectors, processes science data and housekeeping telemetries, manages the commands exchange between the FGS/DPU (Data Processing Unit) and the SIDECARs and provides high quality voltages to the detectors. This paper reports the F-DCU status, describing its architecture, the operation and the activities, past and future necessary for its development

Preliminary surface charging analysis of Ariel payload dielectrics in early transfer orbit and L2-relevant space environment

Ariel [1] is the M4 mission of the ESA’s Cosmic Vision Program 2015-2025, whose aim is to characterize by lowresolution transit spectroscopy the atmospheres of over one thousand warm and hot exoplanets orbiting nearby stars. The operational orbit of the spacecraft is baselined as a large amplitude halo orbit around the Sun-Earth L2 Lagrangian point, as it offers the possibility of long uninterrupted observations in a fairly stable radiative and thermo-mechanical environment. A direct escape injection with a single passage through the Earth radiation belts and no eclipses is foreseen. The space environment around Earth and L2 presents significant design challenges to all spacecraft, including the effects of interactions with Sun radiation and charged particles owning to the surrounding plasma environment, potentially leading to dielectrics charging and unwanted electrostatic discharge (ESD) phenomena endangering the Payload operations and its data integrity. Here, we present some preliminary simulations and analyses about the Ariel Payload dielectrics and semiconductors charging along the transfer orbit from launch to L2 include

FEA testing the pre-flight Ariel primary mirror

Ariel (Atmospheric Remote-sensing Infrared Exoplanet Large-survey) is an ESA M class mission aimed at the study of exoplanets. The satellite will orbit in the lagrangian point L2 and will survey a sample of 1000 exoplanets simultaneously in visible and infrared wavelengths. The challenging scientific goal of Ariel implies unprecedented engineering efforts to satisfy the severe requirements coming from the science in terms of accuracy. The most important specification – an all-Aluminum telescope – requires very accurate design of the primary mirror (M1), a novel, off-set paraboloid honeycomb mirror with ribs, edge, and reflective surface. To validate such a mirror, some tests were carried out on a prototype – namely Pathfinder Telescope Mirror (PTM) – built specifically for this purpose. These tests, carried out at the Centre Spatial de Liège in Belgium – revealed an unexpected deformation of the reflecting surface exceeding a peek-to-valley of 1µm. Consequently, the test had to be re-run, to identify systematic errors and correct the setting for future tests on the final prototype M1. To avoid the very expensive procedure of developing a new prototype and testing it both at room and cryogenic temperatures, it was decided to carry out some numerical simulations. These analyses allowed first to recognize and understand the reasoning behind the faults occurred during the testing phase, and later to apply the obtained knowledge to a new M1 design to set a defined guideline for future testing campaigns

Aerothermodynamic Design of an Inductively Coupled Plasma Wind Tunnel

A new type of high-enthalpy continuous wind tunnel is being developed at the von Karman Institute, cofunded by ESA and the Belgian government to provide an unpolluted facility capable of testing TPS samples for future reentry missions. The facility was designed to meet specific total pressure and stagnation point heat flux conditions and a computer model has been written to allow the determination of all flow parameters. The code uses an engineering approach of quasi-one-dimensional nozzle with inviscid and adiabatic flow of high-temperature air in thermal and chemical equilibrium and includes a calculation of heat flux rates based on Fay and Riddell's formulation which, to be accurately used, needed an analytic expression for the velocity gradient for a supersonic flow impinging on the flat base of a cylinder. The model has been validated against measurements taken in Russian facilities. It predicts values of stagnation point heat fluxes with an accuracy of 15%, including all errors d..