606 research outputs found

    Updated Stagnation Point Aeroheating Correlations for Mars Entry

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    The objective of this work was to develop new engineering correlations for stagnation point aeroheating for Mars entry vehicles. New convective and radiative heating relations have been formulated over a wide range of entry conditions. These relations have been formulated using information from recent experimental testing and modeling enhancements. The new correlations are compared to existing relations commonly used in engineering design and analysis. Finally the correlations are tested by applying them to the Mars Pathfinder entry trajectory to demonstrate their applicability. These new correlations are a significant improvement over existing relations in terms of the accuracy, domain of applicability, and the captured physics

    Shock Tube Radiation Measurements in Nitrogen

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    Spectrally and spatially resolved radiance has been measured in the Electric Arc Shock Tube (EAST) facility, with the aim of improving fundamental understanding of high enthalpy flows in pure nitrogen. These tests provide data to inform models used for simulations of high speed flight in nitrogen rich atmospheres, such as Earth or Titan. The experiments presented in this paper cover conditions from approximately 6 km/s to 11 km/s at an initial pressure of 0.2 Torr. A wide range of physics, with different degrees of non-equilibrium and nitrogen dissociation, are covered. The EAST data are presented in different formats for analysis and comparisons. These formats include the spectral radiance at equilibrium (where appropriate), the spatial dependence of radiance over defined wavelength ranges and the mean non-equilibrium spectral radiance (the so-called "spectral non-equilibrium metric"). All the information needed to simulate each experimental trace, including free-stream conditions, shock time of arrival (i.e. x-t) relation, and the spectral and spatial resolution functions, are provided. Equilibrium radiation calculations are shown as a reference. It is the intention of this paper to motivate code comparisons benchmarked against this data set

    Time and position sensitive single photon detector for scintillator read-out

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    We have developed a photon counting detector system for combined neutron and gamma radiography which can determine position, time and intensity of a secondary photon flash created by a high-energy particle or photon within a scintillator screen. The system is based on a micro-channel plate photomultiplier concept utilizing image charge coupling to a position- and time-sensitive read-out anode placed outside the vacuum tube in air, aided by a standard photomultiplier and very fast pulse-height analyzing electronics. Due to the low dead time of all system components it can cope with the high throughput demands of a proposed combined fast neutron and dual discrete energy gamma radiography method (FNDDER). We show tests with different types of delay-line read-out anodes and present a novel pulse-height-to-time converter circuit with its potential to discriminate gamma energies for the projected FNDDER devices for an automated cargo container inspection system (ACCIS).Comment: Proceedings of FNDA 201

    Analysis of Shockwave Radiation Data in Nitrogen

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    Data from a pure nitrogen test series in the Electric Arc Shock Tube Facility were previously reported for velocities spanning 6-12 km/s at a free-stream pressure of 0.2 Torr. This test series provides validation data for a range of physical phenomena to investigate, including vibrational relaxation, molecular radiation, nitrogen dissociation and ionization, and atomic radiation and ionization. This paper details analysis of data obtained at a nominal velocity of 10.3 km/s. The spectra are analyzed to extract temperatures and the densities of excited states as a function of position behind the shock. The effect of different methods for calculating state populations and ionization processes is assessed, as is a rigorous assessment of the atomic line lists, with both missing and extra lines identified

    Characterization of CO Thermochemistry in Incident Shockwaves

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    Incident shock waves in pure CO have been characterized in the Electric Arc ShockTube facility at NASA Ames Research Center. Spectrally and spatially resolved emissionspectra characterize radiative signatures from CO in the VUV and mid-infrared and atomiccarbon and C2 in the visible. CO absorption of a single vibrational line is also measuredwith a tunable diode laser. The experimental data analyzed here are at a pressure of 0.25Torr in the driven section and span a shock velocity range from 3.4-9.5 km/s. The emissionand absorption signals are analyzed to extract temperature relaxation behind the shockwhich is used to derive the rate of CO dissociation. The emission spectra are compared toresults using different kinetic parameters for CO dissociation and C2 dissociation andexchange. Different rates from the literature are found to match the data from 3.4-6.6 km/sand 6.6-9.5 km/s. Areas for improvement in CO and C2 radiation modeling are suggested onthe basis of the analysis

    Status of Shock Layer Radiation Validation Studies

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    This paper presents a status update for the shock layer radiation validation studies conducted at NASA. A review of the present capability for the simulation and validation of shock layer radiation is presented as well as providing an overview of the data obtained from the Electric Arc Shock Tube (EAST). The paper will include details covering updated convective and radiative heating correlations, provide an overview of the development of new kinetics for Mars entry and detail some recent work calculating after-body radiation. Furthermore, the paper will highlight conditions where there is high confidence in the validation of EAST data (e.g. Earth entry for speeds greater than approximately 10 kms and for many Mars entry conditions) and where further experimental data would be highly beneficial (e.g. lower speed Earth entry around 7.5 to 10 kms and higher speed CO2 entries relevant to Venus). Nominal test conditions for both Earth and Mars are provided for future potential facility-to-facility comparisons

    Professioneel

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    Het eerste B.I.L. bestuur zonder een oud-B.I.L. bestuurder. Voor sommigen reden om te vrezen voor de continuïteit, voor anderen een welkome verandering in het B.I.L. beleid. De ALV in oktober 1989 ontving het nieuwe bestuur 'hartverwarmend'; 'Waar zijn jullie in hemelsnaam mee bezig?' opende een net gewisseld bestuurslid die ontevreden bleek over de BB begroting. Die begroting was in goed overleg tussen het kandidaatsbestuur en de BB redactie tot stand gekomen, maar blijkbaar was niet iedereen 'binnen de BB' hiervan op de hoogte gesteld

    Simulation Schiaparelli's Entry and Comparison to Aerothermal Flight Data

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    The European Space Agency recently flew an entry, descent, and landing demonstrator module called Schiaparelli that entered the atmosphere of Mars on the 19th of October, 2016. The instrumentation suite included heatshield and backshell pressure transducers and thermocouples (known as AMELIA - Atmospheric Mars Entry and Landing Investigations and Analysis) and backshell radiation and direct heat flux-sensing sensors (known as COMARS (Combined Aerothermal and Radiometer Sensors Instrument Package) and ICOTOM (narrow band radiometers)). Due to the failed landing of Schiaparelli, only a subset of the flight data was transmitted before and after plasma black-out. The goal of this paper is to present comparisons of the flight data with calculations from NASA simulation tools, DPLR (Data Parallel Line Relaxation) / NEQAIR (NonEQuilibrium AIr Radiation) and LAURA (Langley Aerothermodynamic Upwind Relaxation Algorithm) / HARA (High-temperature Aerothermodynamic RAdiation ). DPLR and LAURA are used to calculate the flowfield around the vehicle and surface properties, such as pressure and convective heating. The flowfield data are passed to NEQAIR and HARA to calculate the radiative heat flux. Comparisons will be made to the COMARS total heat flux, radiative heat flux and pressure measurements. Results will also be shown against the reconstructed heat flux which was calculated from an inverse analysis of the AMELIA thermocouple data performed by Astrium. Preliminary calculations are presented in this abstract

    Reconstruction of Schiaparelli and Comars Flight Data

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    ESA recently flew an entry, descent, and landing demonstrator module called Schiaparelli that entered the atmosphere of Mars on the 19th of October, 2016. The instrumentation suite included heatshield and backshell pressure transducers and thermocouples (known as AMELIA) and backshell radiation and direct heatflux-sensing sensors (known as COMARS and ICOTOM). Due to the failed landing of Schiaparelli, only a subset of the flight data was transmitted before and after plasma black-out. The goal of this paper is to present comparisons of the flight data with calculations from NASA simulation tools, DPLR/NEQAIR and LAURA/HARA. DPLR and LAURA are used to calculate the flowfield around the vehicle and surface properties, such as pressure and convective heating. The flowfield data are passed to NEQAIR and HARA to calculate the radiative heat flux. Comparisons will be made to the COMARS total heat flux, radiative heat flux and pressure measurements. Results will also be shown against the reconstructed heat flux which was calculated from an inverse analysis of the AMELIA thermocouple data performed by Astrium. Preliminary calculations are presented in this abstract. The aerodynamics of the vehicle and certain as yet unexplained features of the inverse analysis and forebody data will be investigated

    Experiment Design and Characterization for the Study of Afterbody Radiation During Mars Entry

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    Recent work has shown that a significant contributor to the afterbody aeroheating during Mars entry is radiation. However, relevant ground test data is not available to help assess the uncertainty associated with prediction of the radiation when designing the thermal protection system for the aeroshell afterbody. The present work is aimed at designing an experiment which allows the study of the afterbody radiation experienced during Mars entry. The X2 expansion tube at the University of Queensland is used to generate the relevant experimental freestream flow conditions. Analysis is carried out to accurately characterize the generated experimental freestream conditions. A two dimensional wedge model is used to produce the expanding flow which simulates aspects of the afterbody flow around Mars entry vehicles. Preliminary analysis of the generated expanding flow shows that it produces significant radiation in the mid-infrared region and has a steady duration of about 50-110 s. This allows emission spectroscopy to be conducted in the future
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