DURING HYPERBOLIC EARTH ENTRY RETURNING SPACECRAFT CAN ATTAIN ENTRY SPEEDS OF 10-16 KM/S. THIS RESULTS IN INTENSE RADIATION IN THE SHOCK LAYER THAT IS DIRECTED TOWARDS THE SPACECRAFT. THE RADIATION IS PREDOMINANTLY DUE TO ATOMIC LINES. IN ORDER TO WITHSTAND THIS HIGH RADIATIVE HEAT FLUX ABLATING HEAT SHIELDS ARE USED. SUCH HEAT SHIELDS HAVE AN OUTER LAYER WHICH UNDERGOES VAPORIZATION AND PYROLYSIS TO FORM A GAS LAYER WHICH CARRIES AWAY SOME OF THE HEAT BY CONVECTION. THE ABLATION SPECIES INJECTED INTO THE BOUNDARY LAYER ARE CONVECTED AWAY FROM THE SURFACE BUT ARE SUBSEQUENTLY TRAPPED IN THE RECIRCULATING WAKE OF THE VEHICLE. THESE SPECIES SIGNIFICANTLY DECREASE THE VIBRATIONAL TEMPERATURE IN A REGION WHERE THE ABSORPTION IS TYPICALLY STRONG THUS REDUCING THE SHIELDING EFFECT PROVIDED BY THE GAS AND CAUSING A SIGNIFICANT INCREASE IN RADIATIVE HEATING EXPERIENCED BY THE BACKSHELL. THE CHARACTERIZATION OF THE AEROTHERMAL ENVIRONMENT AND HEATING LOADS ON ENTRY VEHICLES DEPENDS CRITICALLY ON THE COMPLETENESS AND ACCURACY OF THE PHYSICAL MODEL USED TO DESCRIBE THE NON-EQUILIBRIUM PHENOMENA IN THE FLOW. RADIATION PREDICTIONS ARE SHOWN TO BE SENSITIVE TO ELECTRON-DRIVEN CHEMISTRY (E.G. IONIZATION OF NITROGEN ATOMS) ESCAPE FACTOR MODELING AND ABLATION PRODUCTS. OVER THE LAST DECADE SIGNIFICANT EFFORT HAS BEEN DEVOTED TO THE MODELING OF IONIZATION CHEMISTRY AND THE SELF-CONSISTENT COUPLING OF RADIATION AND FLUID-DYNAMICS. ON THE CONTRARY VERY LITTLE PROGRESS HAS BEEN MADE IN THE CHARACTERIZATION OF THE THERMO-PHYSICAL PROPERTIES OF THE ABLATION SPECIES AND THEIR INTERACTION WITH RADIATION. THE PROPOSED PROJECT DIRECTLY ADDRESSES THIS SHORTCOMING BY DEVELOPING AN ACCURATE THERMODYNAMIC AND KINETIC MODEL FOR ABLATION SPECIES BASED ON FIRST PRINCIPLES PHYSICS. THE MODEL WILL TARGET THE CHARACTERIZATION OF THE THERMO-PHYSICAL PROPERTIES OF IONIZED AIR COMPLEMENTED BY THE ABLATION SPECIES PRODUCED BY THE DECOMPOSITION OF A PHENOLIC IMPREGNATED CARBON ABLATOR (PICA) HEAT SHIELD. THE CALCULATION OF THE GROUND STATE AND LOW LYING EXCITED STATE ENERGIES OF SMALL CARBON CLUSTERS WILL BE PERFORMED BY USING ELECTRONIC STRUCTURE CALCULATIONS FOR THE DETERMINATION OF THEIR THERMODYNAMIC PROPERTIES. THIS IS FOLLOWED BY THE CALCULATION OF THE KINETIC PROCESSES FOR THE MOST IMPORTANT CHEMICAL COMPONENTS (E.G. CN CO) DRIVEN BY ELECTRONS AND HEAVY PARTICLES COLLISIONS. GIVEN THE LARGE NUMBER OF POSSIBLE REACTION PATTERNS AND RADIATION SYSTEMS A SENSITIVITY ANALYSIS WILL BE CONDUCTED TO PRIORITIZE THOSE PROCESSES WITH THE HIGHEST HEATING AUGMENTATION. THIS MODEL WILL BE USED IN A NEWLY DEVELOPED RADIATION/ABLATION/FLOW FIELD TIGHTLY COUPLED FRAMEWORK THAT WILL TAKE INTO ACCOUNT ALL THE RELEVANT PHENOMENA FOR THIS TYPE OF ANALYSIS INCLUDING: (I) ABLATION SPECIES-INDUCED RADIATIVE HEATING (II) RADIATION/FLUID DYNAMICS COUPLING AND (III) RADIATIVE HEAT FLUX AT THE SURFACE AND WITHIN THE ABLATOR. TO ELUCIDATE THE ROLE PLAYED BY THE ABLATION SPECIES ON THE RADIATION HEAT LOADS THE SIMULATION OF SHOCK-LAYER RADIATIVE HEATING TO THE AFTER-BODY SURFACE OF ATMOSPHERIC ENTRY CAPSULES AT VELOCITIES GREATER THAN 10 KM/S WILL BE INVESTIGATED. A PHYSICALLY CONSISTENT AND TIGHTLY COUPLED APPROACH WILL BE USED FOR THE COUPLING OF THE RADIATION AND ABLATION MODELS WITH FLUID DYNAMICS. USING THIS FRAMEWORK THIS PROPOSAL WILL EXPLORE A NOVEL CAPABILITY TO TAILOR THE RESPONSE IN FREQUENCY OF THE GAS BY DOPING THE TPS WITH A SHIELDING CHEMICAL (E.G. SF6) THAT ABSORBS THE MAIN SPECTRAL COMPONENTS OF THE HEATING LOADS AS A FINAL OBJECTIVE.