Influence of Ablation Products on the Radiation at the  Surface of a Blunt Hypersonic Vehicle at 10 km/s

Laux, Christophe O.; Winter, Michael; Merrifield, J. A.; Smith, Arthur; Tran, Philippe; St, EADS-Astrium

doi:10.2514/6.2009-3925

Cited by 18 publications

(13 citation statements)

References 4 publications

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“…The approximate radiative heat flux _ q rad;VUV from the measured VUV spectral region is _ q rad;VUV 2π · Z 196 nm 116 nm L λ dλ 235 kW∕m 2 (15) which corresponds to roughly 6% of the total measured heat flux (see Table 1) [16]. However, the recorded spectra stem from radiation at an angle of 28 deg to the center axis.…”

Section: Discussionmentioning

confidence: 99%

“…The situation in flight can differ from this, as a significant amount of radiation is produced in the shock [16,87].…”

Section: Discussionmentioning

confidence: 99%

“…The local emission coefficient of molecular band radiation is used to determine the rotational and vibrational temperature by matching the measured spectra to a simulation [16,[47][48][49] (see Fig. 12).…”

Section: A Rotational and Vibrational Temperaturementioning

confidence: 99%

“…As the reentry speed increases, radiative heating becomes more and more dominant [10][11][12]. It has previously been found that the vacuum ultraviolet (VUV) spectral region, which is the 100-200 nm wavelength interval, contributes a major part to the total radiative heat flux [5,[13][14][15][16][17]. Ablative materials interact with the flowfield, which can have a significant effect on the radiative heat flux encountered by the vehicle.…”

mentioning

confidence: 99%

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Characterization of a Reentry Plasma Wind-Tunnel Flow with Vacuum-Ultraviolet to Near-Infrared Spectroscopy

Hermann

Löhle

Zander

et al. 2016

Journal of Thermophysics and Heat Transfer

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This paper presents the analysis of optical emission spectroscopic measurements from vacuum ultraviolet (120 nm) to near infrared (960 nm) in a high-enthalpy air plasma flow corresponding to superorbital reentry conditions. The vacuum ultraviolet measurements have been realized with a new experimental setup allowing measurements through a bore hole in the sample. Using the commonly applied optical emission spectroscopy from the side, the radiation transport along the line of sight of the vacuum ultraviolet measurements has been assessed. This allowed the determination of the local ground state densities of atomic oxygen and atomic nitrogen from a branching ratio analysis and the blackbody limiting correction of the vacuum ultraviolet radiation. Through the analysis of the absorption in the borehole, the spectra have been corrected, resulting in a stagnation point radiative heat flux in the vacuum ultraviolet of 235 kW∕m 2 .= local mass-specific enthalpy, MJ∕kg I = arc current, A K = proportionality constant for air, W∕MJ∕kg·Pa 0.5 ·m 1.5 k = Boltzmann constant, J∕K k cal = calibration factor, W∕m 2 · nm · sr∕counts∕s L λ = spectral radiance, W∕m 2 · nm · sr L λ;Limit = blackbody limit spectral radiance, W∕m 2 · nm · sr M = magnification _ m = mass flow, g∕s n = number density, m −3 n i = excited state population density, m −3 n 0 = ground state population density, m −3 P = electric power, kW P k = spectral line shape, nm −1 p = pressure, hPa _ q = heat flux, kW∕m 2 R eff = effective nose radius, mm r = radial distance, mm S = raw signal, counts/s s = distance from the probe surface, mm s 0 = distance between object and focusing element, mm= vibrational quantum number x = axial distance from the nozzle, mm y = horizontal distance from the nozzle, mm z = vertical distance from the nozzle, mm α λ = absorption coefficient, m −1 δ = full width at half-maximum of line broadening, nm ε λ = emission coefficient, W∕m 3 · nm · sr ε = spectrally integrated emission coefficient, W∕m 3 · sr λ = wavelength, nm σ λ = absorption cross section, m 2 Subscripts BB = blackbody DL = deuterium lamp exc = electronic excitation IS = integrating sphere l = lower state rot = rotational tot = total trans = translational u = upper state vib = vibrational

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Section: Discussionmentioning

confidence: 99%

“…The situation in flight can differ from this, as a significant amount of radiation is produced in the shock [16,87].…”

Section: Discussionmentioning

confidence: 99%

Section: A Rotational and Vibrational Temperaturementioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Characterization of a Reentry Plasma Wind-Tunnel Flow with Vacuum-Ultraviolet to Near-Infrared Spectroscopy

Hermann

Löhle

Zander

et al. 2016

Journal of Thermophysics and Heat Transfer

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“…The mechanisms whereby ablative surfaces provide thermal protection are complex, and cannot be precisely modeled at present (Laux 2009). Current designs contain a large degree of empiricism, and generally use substantial safety factors to account for the unknown parameters.…”

Section: Introductionmentioning

confidence: 99%

Radiation Measurements in Simulated Ablation Layers

Morgan¹

2010

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Report Documentation PageForm Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. REPORT DATE DEC 20102. REPORT TYPE In this study, radiation in ablating shocklayers over a scale Stardust model at 9 km/s was measured during the 80 μs steady test flow produced in a high enthalpy super-orbital expansion tunnel. The presence of an ablating shock layer when an epoxy coating is used with air and nitrogen test gases is shown by spectrometric and high speed camera data, and is in agreement with previous experimental results. Shock layer radiation is found to be strongest in the UV and visible portions of the electromagnetic spectrum, in both ablating and non-ablating shock layers. Shock layer radiation is greatly increased in ablating shock layers than in non-ablating shock layers when both air and nitrogen test gases are used. A nitrogen test gas is thought to produce a higher temperature shock layer than when air is used, implying that oxygen in air has a cooling effect on shocklayer radiation, due to the dissociation of the oxygen molecules which occurs. Shocklayer radiation in the near-IR is far weaker than that in the UV and consists of atomic, rather than molecular, transitions. As such, no distinct ablation layer is visible in the IR spectral data, however there is a doubling in radiance in the presence of an epoxy coating. SUBJECT TERMS Ablation, Thermal Environments, Reentry vehicles, Expansion tunnel AbstractThe interaction between an ablating shocklayer and radiative heat transfer to a surface, such as occurs on an ablating hypervelocity re-entry vehicle, is poorly understood. Ablative products act as absorbers and emitters, the net effect of which is strongly dependent on gas composition, enthalpy and wavelength. This paper presents the results of an experimental study investigating radiation in an ablating shocklayer over a 1:13.5 scale Stardust forebody model in an expansion tunnel in air, and nitrogen atmospheres at 9 km/s. The model was coated with a low-pyrolysis temperature hydrocarbon coating, permitting its thermal decomposition and the release of carbon-containing gaseous species into the shocklayer within the 80 μs test time. Shocklayer radiation is visualised using a high speed camera, whilst the emission spectra along the stagnation...

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Measurement of the aerothermodynamic state in a high enthalpy plasma wind-tunnel flow

Hermann

Löhle

Zander

et al. 2017

Journal of Quantitative Spectroscopy and Radiative Transfer

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This paper presents spatially resolved measurements of absolute particle densities of N 2 , N + 2 , N, O, N + , O + , e − and excitation temperatures of electronic, rotational and vibrational modes of an air plasma free stream. All results are based on optical emission spectroscopy data. The measured parameters are combined to determine the local mass-specific enthalpy of the free stream. The analysis of the radiative transport, relative and absolute intensities, and spectral shape is used to determine various thermochemical parameters. The model uncertainty of each analysis method is assessed. The plasma flow is shown to be close to equilibrium. The strongest deviations from equilibrium occur for N, N + and N + 2 number densities in the free stream. Additional measurements of the local mass-specific enthalpy are conducted using a mass injection probe as well as a heat flux and total pressure probe. The agreement between all methods of enthalpy determination is good.

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Influence of Ablation Products on the Radiation at the Surface of a Blunt Hypersonic Vehicle at 10 km/s

Cited by 18 publications

References 4 publications

Characterization of a Reentry Plasma Wind-Tunnel Flow with Vacuum-Ultraviolet to Near-Infrared Spectroscopy

Characterization of a Reentry Plasma Wind-Tunnel Flow with Vacuum-Ultraviolet to Near-Infrared Spectroscopy

Radiation Measurements in Simulated Ablation Layers

Measurement of the aerothermodynamic state in a high enthalpy plasma wind-tunnel flow

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