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Bhsapu r s S Approximate techniques for rapidly estimating ablation and charring of heat-shield materials in severe aerothennal/erosive environments are required for many practical situations. Pure heat balance integral (HBI) or quasi-steady-state (QSS) approaches, however, are less than satisfactory for predicting the response of materials that char, especially when surface heat flux and ablation rates an affected by the outgassing from indepth charring. This paper presents a new, hybrid expansion of the integral method that satisfactorily models charring ablator responG. Quasi-steady state techniques an used at cert&n steps to consmct the hybrid method. but the dependence on recession rate is eliminated so that the method applies even when the material undergoes non-quasi-steady response. As further contributions. this paper reviews thermal properties and modeling coefficients for carbon-phenolic. and it presents new curve-fit equations for carbon-phenolic ablation in air. A a B B ' gh gh0 Nomenclatun collision frequency, st blowing coefficient. Eq. (B20) activation temperam (E&, K mass transfer driving force ( n e e d ablation rate) B in the limit of no blowing specific heat, J/(g K) specific heat of virgin ablator, char ablator. and pyrolysis gases, respectively. J/(g K) activation energy. cal I mole exponential integral. Eq. (41) reacfion-rate transition factor, Eq. (830) heat transfer conductance. g/(cmZs) heat transfer mnductance in the absence of mass injection (Le.. no "blowing"), g/(cm%) enthalpy. J/g enthalpy of gawous m i x m on vapor side of wall J/ enthalpy of solid m a d a t the wall, Jig enthalpy of edge gas (air) at wall temperaom. J/g integral heat storage, Fq. (46). 11-2 k = mnductivity of ablator maurial. J/(cm s K) ril = mass flux, g/(cmk) n = reactionorder P = pressure,bar Q. = = universal gas constant, effective heat of ablation, JI 1.987 cal/(mole K) = heat flux, J/(cm2s) = Wlcm ! i 4 * Senior Scientist, Member AIAA 1 a P'i 0 7 h10w S&mlts ab cond cony CR C cw e a eq carbon yield surface recession, cm surface recession rate. c d s t e m p t u n . K time, s flow s p e d indepth distance from initial surface. cm indepth distance from current surface, cm thermal diffusivity of ablafor material. cm% initial volume fraction of resin initial mass fraction of resin heat of formation. J/g heat of pyrolysis per unit mass of gas produced. Jlg thermal penenation depth, cm effective char depth, cm emissivity virgin fraction, Eq. (A29) heat density, Eq. (27). J/cm3 density (of ablatar material unless subscripted by "e"). p/cm3 fractional density of species i, Eq. (AI) Stefan-Boltunann constant, 5.670 x 10-12 J/(cm2 sK4) time. s blowing correction, Eq. (820) ablation ftdy-chamd, or carbonanceous conduction COnVCCtiVC char residue cold wall at edge of boundary laya equitibrium erosion ew = edge gas composition at wall F --f = formation g = pyrolysis gas gw = value for pyrolysis gas at the wall underside i = speciesindex = pyrolysis gas 01 resin component index = mtconduction j nct R = naction-rate I = re...

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To measure flow velocity, a new technique, laser diode array velocimetry, generates multiple laser spots (four or more) separated by short distances (20-100 mum) at the probe volume. Particles that pass through the probe volume generate a signal that is analyzed by a digital signal processor for frequency content. The product of frequency and laser-to-laser spot separation determines the velocity. Rotating wire and wind-tunnel experiments confirm the performance of the new technique. An error analysis showed that the uncertainties in the processed diode array velocimetry signal frequency were less than 0.3%, and uncertainties in the beam-to-beam separation were less than +/-0.05%.