Aerothermodynamic Characteristics of 16 - 22 km/s Earth Entry

摘要

This paper presents a model for simulating the aerothermodynamic environment of vehicles entering Earth at velocities between 16 and 22 km/s. To accommodate the vibrational-electronic temperatures above 20,000 K present in the shock layer at these entry velocities, the following enhancements to the flowfleld model are identified and modeled: 1) Thermodynamic curve fits for atomic species and their associated ions extended beyond their typical 20,000 K limit; 2) Addition of double ionized species N~(++) and O~(++) within the flowfleld model; 3) Addition of a nonequilibrium radiation model from N~+; 4) Treatment of ionization potential lowering effects on the thermodynamic properties of ionized species. Additionally, the flowfleld computation includes coupled ablation and radiation, which both significantly impact the total heating. Using the developed model, simulations are performed for free-stream velocities and densities ranging from 10 to 22 km/s and 5×10~(-5) to 1×10~(-2) kg/m~3, respectively. Prom these simulations, stagnation-point convec-tive and radiative heating values are tabulated for simulations with coupled radiation only, and for simulations with both coupled radiation and ablation. Ablation rates and wall temperatures are also tabulated for the coupled ablation cases, which assume a heritage Pioneer-Venus carbon phenolic ablator. This work enables velocities above 16 km/s, which were previously beyond aerothermodynamic modeling capabilities, to be considered for future sample return missions.