%0 Journal Article %A Chiaverini, Martin J. %A Serin, Nadir %A Johnson, David K. %A Lu, Yeu-Cherng %D 1997 %I Begell House %N 1-6 %P 719-733 %R 10.1615/IntJEnergeticMaterialsChemProp.v4.i1-6.670 %T INSTANTANEOUS REGRESSION BEHAVIOR OF HTPB SOLID FUELS BURNING WITH GOX IN A SIMULATED HYBRID ROCKET MOTOR %U https://www.dl.begellhouse.com/journals/17bbb47e377ce023,43cb1df7484a24f3,07413a9b58afbc11.html %V 4 %X An experimental investigation using a high−pressure hybrid motor analog has been conducted to provide detailed solid fuel regression rate data at realistic operating conditions for both model validation and correlation development. The 2−D motor operated at a maximum pressure of 9 MPa (1300 psi) with maximum injected gaseous oxygen mass fluxes of 420 kg/m2·s (0.6 lbm/in2·s). Hydroxyl−Terminated Polybutadiene (HTPB, R−45 M) cured with Isonate 2143L was used as the baseline solid fuel. Either carbon black powder or ultra−fine aluminum (UFAL) powder was added to the HTPB fuel during the processing stage for some tests. Both ultrasonic pulse−echo and real−time X−ray radiography techniques were used to determine the instantaneous regression rate. An array of fine−wire thermocouples was used to determine fuel surface temperatures and subsurface temperature profiles. The deduced instantaneous regression rates displayed a complex dependency on axial location and flow conditions. Close to the sample leading edge, the regression rate, governed by the mixing motion of the entering GOX flow, did not vary with time. Following this region, the regression rates exhibited strong dependency on both axial location and flow structure. When the GOX mass fluxes were below 140 kg/m2·s (0.2 lbm/in2·s), gas−phase radiative heat transfer to the fuel surface was found to play a more important role in the regression of solid fuel. Solid fuel regression rates were found to correlate well with the injected oxidizer mass flux, chamber pressure, axial location, and port height. The addition of carbon black had no effect on regression behavior. Addition of 20% of UFAL powder, however, was found to increase the mass burning rate by 70%. %8 1997-01-01