An approximate inviscid radiating flow-field analysis for sphere-cone Venusian entry vehicles

Falanga, Ralph A; Olstad, W. B.

doi:10.2514/6.1974-758

Cited by 19 publications

(6 citation statements)

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“…)/ (p w T w ) mol/kg. Under a nonequilibrium sublimation environment the vapor is formed with an evaporation coefficient j8 4 …”

Section: Governing Equationsmentioning

confidence: 99%

“…The convective and radiative heating rates were determined using the methods described by Moss et al 3 and Falanga and Olstad. 4 The phenomenon of conduction, pyrolysis, ablation of the heat shield, and resulting temperature rise within the heat shield were calculated using a material response code named charring materials ablation (CM A). 5 Accuracy of the CM A code was verified by conducting a laboratory experiment.…”

Section: Introductionmentioning

confidence: 99%

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Stagnation-Point Heat Transfer Rates for Pioneer-Venus Probes

Park

Ahn

1999

Journal of Thermophysics and Heat Transfer

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The convective and radiative heat transfer rates are calculated for the stagnation region of the Pioneer-Venus Probe vehicles during their entry flights into the planet Venus. The nonequilibrium thermochemical state of the flow is calculated using a viscous shock-layer method accounting for oxidation of the heat shield surface by atomic oxygen and for pyrolysis-gas injection. Radiative transport along the stagnation streamline is calculated using a line-by-line technique and tangent-slab approximation. For both radiative and convective heating rates, the present results are substantially smaller than the earlier values obtained assuming equilibrium. Nomenclature C = (pn)/(pjj) s D t = mass diffusion coefficient for species /, N-m-s/kg / = dimensionless velocity function, Eqs. (3) and (4) f w = normalized ablation rate, Eq. (21) f wp = normalized pyrolysis-gas injection rate, Eq. (19) g = normalized enthalpy g r = normalized energy gain by radiation J = number flux, mol/(m 2 -s) k = Boltzmann constant k w i = surface-oxidation velocity, m/s k w2 = surface-ionic recombination velocity for C + , m/s k w3 = surface-ionic recombination velocity for O + , m/s k w4 = sublimation velocity, m/s Mi = mass of species /, kg m = ablation rate, kg/(m 2 -s) m p = pyrolysis-gas injection rate, kg/(m 2 -s) Pr = Prandtl number p = pressure, Pa q c = convective heat transfer rate, W/m 2 q r = radiative heat transfer rate, W/m 2 q* = effective radiative heat transfer rate (q r + increment in q c because of radiation absorption), W/m 2 R = nose radius, m SCj = Schmidt number for species i T = temperature, K t = time, s u -velocity in x direction, m/s V f = freestream velocity, m/s v = velocity in y direction, m/s Wf = rate of production of species /, mol/(kg-s) x = distance along wall, m y = distance from wall, m /?! = surface-oxidation probability /3 2 = surface-ionic recombination probability for C + j8 3 = surface-ionic recombination probability for O + j8 4 = evaporation coefficient for C 3 ji = concentration of species i, mol/kg e = ionization fraction 77 = dimensionless distance in y direction, Eq. (2b) K = thermal conductivity, W/(m-K) JJL = viscosity, N-s/m 2 f = dimensionless distance in x direction, Eq. (2a) p = density, kg/m 3 Subscripts E = equilibrium / = freestream p = pyrolysis-gas s = immediately behind shock wave w = wall

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“…)/ (p w T w ) mol/kg. Under a nonequilibrium sublimation environment the vapor is formed with an evaporation coefficient j8 4 …”

Section: Governing Equationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Stagnation-Point Heat Transfer Rates for Pioneer-Venus Probes

Park

Ahn

1999

Journal of Thermophysics and Heat Transfer

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“…6 This program utilizes the thin shocklayer approximations of Maslen 7 of computing either adiabatic (no heat loss) or nonadiabatic (radiation coupling) results. Both options were exercised, but only, the adiabatic results, which yield higher electron number densities than the nonadiabatic results, are presented.…”

Section: Inviscid Wakementioning

confidence: 99%

Analysis of Communications Blackout for Pioneer Venus Entry Probes

Grose

Falanga

Sutton

1975

Journal of Spacecraft and Rockets

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Estimates of the maximum duration of communications blackout are presented for a proposed Pioneer Venus mission involving a multiprobe entry targeted to individual impact sites. Calculations of the inviscid flow about the probes have been made using both finite-rate chemistry and equilibrium chemistry computer codes. Equilibrium boundary-layer calculations, including ablation, are also presented both with and without the presence of alkali metal contaminants from the heat shield. Methods are described for estimating maximum electron density in the inviscid wake and the recirculation region at the base of the probes. The results presented provide a conservative basis for planning for storage and subsequent telemetry of data during the entry phase of the mission. Nomenclaturee = electron charge / = frequency m = electron mass N e = electron number density R -radius vv = probe mass y = normal distance from body | 8 = probe ballistic coefficient 7 £ = entry angle 5 = shock standoff distance e 0 = electric permittivity of free space B c = cone half-angle Subscripts B = base cr = critical e = boundary-layer edge n = nose p = plasma s = shoulder

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“…Extensive research on the topic was conducted in the late sixties [6,35,70,83,209] and early seventies [42,47,49,48,55,124,128,188]. These early efforts were motivated by a certain number of upcoming deep space exploration missions, including Apollo, Pioneer Venus Multiprobe (1978), and Galileo (launched in 1989).…”

Section: Radiative Couplingmentioning

confidence: 99%

“…The mission designers were aware of those limitations and applied a liberal margin of safety in the heat shield thickness. Some of them can be consulted chronologically in [140,48,180,129].…”

Section: E4 Numerical Studies E41 Pre-flight Of Pioneer Venusmentioning

confidence: 99%

On binary scaling and ground-to-flight extrapolation in high-enthalpy facilities

Looringhe¹,

Arwid²

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The binary scaling law is commonly used to study the aerothermodynamics of hypersonic vehicles in high-enthalpy facilities. It enables the duplication of the shock layer in the vicinity of the stagnation point, including binary chemistry and nonequilibrium processes, through the reproduction of the Péclet and wall Damköhler numbers. These are both conserved through the duplication of the composition of the gas, the free-stream enthalpy h ∞ and the product of a density and a length-scale of the flow ρL.Binary scaling is built on the assumption of a flow devoid of radiation coupling and governed by binary reactions. These two conditions drastically narrow down the envelope of flows for which binary scaling can be used. Moreover, diffusive transport and wall chemistry have never been addressed although they can have an important impact on the wall heat flux.The first part of this thesis consists in an effort to better understand the theoretical role and effect of the different assumptions done to build the binary scaling. It is first shown that diffusive transport and wall chemistry should scale appropriately. Second, that non-binary chemistry will cause the shock layer in the laboratory flow to be hotter and less dissociated. A methodology is proposed to identify clearly what free-stream conditions will affect the least the flow variables of interest. Lastly, that radiation coupling will be weaker in the laboratory flow than in flight, causing the enthalpy contained in the shock layer to be greater in the laboratory flow.These findings are verified in the second part with two experiments. The first experiment was performed in the Plasmatron plasma wind tunnel at the von Karman Institute, Belgium. Binary scaled boundary layers were obtained for flows where diffusion and wall chemistry contribute significantly to the heat flux. The stagnation point heat fluxes were measured and exhibit a good agreement with the theoretical scaling law. This also validates the use of the binary scaling law in subsonic high-enthalpy facilities.The second experiment was performed in the X2 expansion tube at the Centre for Hypersonics, Australia. Three flows were obtained over cylinders of different radii, adapting the free-stream density according to the binary scaling law. The free-stream conditions were determined in order to ensure a significant radiative coupling. Its effect could clearly be identified through measurements of the shock standoff distance, stagnation point heat flux, and shock layer radiation. A new method, based on a mix of experiments, computational fluid dynamics, and informed use of engineering correlations is proposed to perform ground to flight extrapolation for cases for which the radiative coupling is non-negligible. Declaration by authorThis thesis is composed of my original work, and contains no material previously published or written by another person except where due reference has been made in the text. I have clearly stated the contribution by others to jointly-authored works that I have include...

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An approximate inviscid radiating flow-field analysis for sphere-cone Venusian entry vehicles

Cited by 19 publications

References 1 publication

Stagnation-Point Heat Transfer Rates for Pioneer-Venus Probes

Stagnation-Point Heat Transfer Rates for Pioneer-Venus Probes

Analysis of Communications Blackout for Pioneer Venus Entry Probes

On binary scaling and ground-to-flight extrapolation in high-enthalpy facilities

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