Fiber-Based Measurement of Bow-Shock Spectra for Reentry Flight Testing

Schott, Timothy D.; Herring, G. C.; Munk, Michelle M.; Grinstead, Jay H.; Prabbu, Dinesh K.

doi:10.2514/6.2010-301

Cited by 5 publications

(4 citation statements)

References 15 publications

(13 reference statements)

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“…Graybody assumption is common in pyrometric measurements on soot particles for the wavelength of interest. Previously, attempts have been made to predict the shock-layer temperature by fitting Planck's blackbody curve to the emission spectra obtained from the shock layer using fiber-based systems [22,23]. Emission spectroscopy performed in our shock tunnel also confirmed that the shock region majorly radiates as a continuous broadband source.…”

Section: Introductionsupporting

confidence: 53%

Time-resolved temperature characterization of a hypersonic shock layer using a single high-speed color camera for aerospace design applications

Deep¹,

Krishna²,

Jagadeesh³

2019

Meas. Sci. Technol.

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Two-color ratio pyrometry (TCRP) using a high-speed color camera has been used for temperature characterization of a hypersonic shock layer. The camera, used as a pyrometer, was calibrated in-house using a monochromator to determine its spectral responsivity and was used to acquire time-resolved images of the flow field over test models at a frame rate of 20 000 fps to understand the evolution of temperature inside the shock region. The optical efficiency of the monochromator and other optical equipment were determined separately and corrected for. Two test models, a flat-faced cylinder of diameter 70 mm and a hemisphere of diameter 80 mm, were used for the experiments to study the effect of geometry on the results. Experiments were performed in a free-piston-driven shock tunnel at a stagnation enthalpy of 5.2 MJ kg−1. The average steady-state temperature in the stagnation region in the cylinder was about 3650 K ± 3% (uncertainty in the shock layer due to camera noise), and for the hemisphere it was 3300 K ± 6%. The resolved temperature was 14% higher than that obtained from a similar, but time-integrated, measurement obtained using a digital single lens reflex (DSLR) camera. Steady 2D numerical simulations were performed to reconstruct the 3D flow assuming azimuthal symmetry, and an algorithm was developed to use the shape of the temperature profile along the line-of-sight (LOS) derived from simulations to predict the actual stagnation-plane temperature from the experimental LOS-integrated TCRP-derived temperature. The actual temperature in the stagnation region on the vertical plane of symmetry (stagnation plane) for the cylinder and the hemisphere were higher by 2.76% and 1.77%, respectively, than the corresponding TCRP-derived LOS-integrated temperature. The results are promising for future use in determining intense temperature gradients and heat flux in the vicinity of space vehicles and for the design of efficient thermal protection systems.

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Section: Introductionsupporting

confidence: 53%

Time-resolved temperature characterization of a hypersonic shock layer using a single high-speed color camera for aerospace design applications

Deep¹,

Krishna²,

Jagadeesh³

2019

Meas. Sci. Technol.

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“…This data is unlikely to come from a flight case, since even the Apollo 4 measurements at Lunar-return conditions did not contain enough ablation to influence the radiation significantly. The preliminary work by Schott et al 168 and D'Souza et al…”

Section: Suggested Future Workmentioning

confidence: 99%

“…Due to the limited information presented by Georg and Yakushin, the data presented in these papers was not suitable for comparison in the present work. Recent work by Schott et al 168 consist of radiative intensity measurements at the stagnation point of an ablating model in an arcjet facility. This preliminary work shows promise but has not yet published quantitative results that would allow consideration in the present uncertainty assessment.…”

Section: Past Radiation Measurements With Ablationmentioning

confidence: 99%

Assessment of Radiative Heating Uncertainty for Hyperbolic Earth Entry

Johnston

Mazaheri

Gnoffo

et al. 2011

42nd AIAA Thermophysics Conference

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This paper investigates the shock-layer radiative heating uncertainty for hyperbolic Earth entry, with the main focus being a Mars return. In Part I of this work, a baseline simulation approach involving the LAURA Navier-Stokes code with coupled ablation and radiation is presented, with the HARA radiation code being used for the radiation predictions. Flight cases representative of peak-heating Mars or asteroid return are defined and the strong influence of coupled ablation and radiation on their aerothermodynamic environments are shown. Structural uncertainties inherent in the baseline simulations are identified, with turbulence modeling, precursor absorption, grid convergence, and radiation transport uncertainties combining for a +34% and −24% structural uncertainty on the radiative heating. A parametric uncertainty analysis, which assumes interval uncertainties, is presented. This analysis accounts for uncertainties in the radiation models as well as heat of formation uncertainties in the flowfield model. Discussions and references are provided to support the uncertainty range chosen for each parameter. A parametric uncertainty of +47.3% and −28.3% is computed for the stagnation-point radiative heating for the 15 km/s Mars-return case. A breakdown of the largest individual uncertainty contributors is presented, which includes C3 Swings cross-section, photoionization edge shift, and Opacity Project atomic lines. Combining the structural and parametric uncertainty components results in a total uncertainty of +81.3% and −52.3% for the Mars-return case.In Part II, the computational technique and uncertainty analysis presented in Part I are applied to 1960s era shock-tube and constricted-arc experimental cases. It is shown that experiments contain shock layer temperatures and radiative flux values relevant to the Mars-return cases of present interest. Comparisons between the predictions and measurements, accounting for the uncertainty in both, are made for a range of experiments. A measure of comparison quality is defined, which consists of the percent overlap of the predicted uncertainty bar with the corresponding measurement uncertainty bar.

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“…These have been attributed to ionized calcium (Ca + ) in a similar arcjet experiment where PICA was tested. 12 However other species have emission lines at these same wavelengths such as iron (Fe) at 393.0, hydrogen (H) at 397.0. A weak emission line also appears near 656.3 nm, where the strongest H line is expected.…”

Section: B Flow Over Pica Test Sample 1 Species Identificationmentioning

confidence: 99%

Quantitative Spectral Radiance Measurements in the HYMETS Arc Jet

Danehy

Hires

Johansen

et al. 2012

50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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Calibrated spectral radiance measurements of gaseous emission spectra have been obtained from the HYMETS (Hypersonic Materials Environmental Test System) 400 kW arc-heated wind tunnel at NASA Langley Research Center. A fiber-optic coupled spectrometer collected natural luminosity from the flow. Spectral radiance measurements are reported between 340 and 1000 nm. Both Silicon Carbide (SiC) and Phenolic Impregnated Carbon Ablator (PICA) samples were placed in the flow. Test gases studied included a mostly-N 2 atmosphere (95% nitrogen, 5% argon), a simulated Earth Air atmosphere (75% nitrogen, 20% oxygen, 5% argon) and a simulated Martian atmosphere (71% carbon dioxide, 24% nitrogen, 5% argon). The bulk enthalpy of the flow was varied as was the location of the measurement. For the intermediate flow enthalpy tested (20 MJ/kg), emission from the Mars simulant gas was about 10 times higher than the Air flow and 15 times higher than the mostly-N 2 atmosphere. Shock standoff distances were estimated from the spectral radiance measurements. Within-run, run-to-run and day-to-day repeatability of the emission were studied, with significant variations (15-100%) noted.

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Fiber-Based Measurement of Bow-Shock Spectra for Reentry Flight Testing

Cited by 5 publications

References 15 publications

Time-resolved temperature characterization of a hypersonic shock layer using a single high-speed color camera for aerospace design applications

Time-resolved temperature characterization of a hypersonic shock layer using a single high-speed color camera for aerospace design applications

Assessment of Radiative Heating Uncertainty for Hyperbolic Earth Entry

Quantitative Spectral Radiance Measurements in the HYMETS Arc Jet

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