Aerothermal Analysis of the Project Fire Ⅱ Afterbody Flow

摘要

Computational fluid dynamics is used to simulate the afterbody heating of the Project Fire Ⅱ ballistic reentry to Earth at 11.35 km/s. Results are obtained over a portion of the trajectory between the initial heat pulse and peak afterbody heating. Although forebody convective heating results are in excellent agreement with previous computations, initial noncatalytic predictions of afterbody heating were a factor of two below the experimental values. However, analogy with currently manufactured thermal protection materials suggests that significant catalysis may be occurring on the afterbody heat shield. Computations including finite rate catalysis are in good agreement with the data over the early portion of the trajectory, but are conservative near the peak afterbody heating point, especially on the rear portion of the conical frustum. Further analysis of the flight data from Fire Ⅱ shows that peak afterbody heating on the frustum occurs before peak forebody heating, a result that contradicts computations and flight data from other entry vehicles. This result suggests that another mechanism, possibly pyrolysis, may be occurring during the later portion of the trajectory, resulting in less total heat transfer than the current predictions.