IRFP: Investigation of the Radiative Interaction between Plasmas and Ablating Heat Shields

Macdonald Megan, Oak Grove MO

Investigators

Abstract

The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support a twenty-four-month research fellowship by Dr. Megan E. MacDonald to work with Dr. Christophe Laux at Ecole Centrale Paris in Paris, France. Any spacecraft entering a planetary atmosphere requires thermal protection to prevent overheating and burn-up of the spacecraft upon entry. One method of protecting against such extreme heating environments is an ablative thermal protection system. As a method of transporting heat away from the spacecraft, this type of thermal protection is designed to pyrolyse. This results in a boundary layer between the heat shield and the atmospheric plasma which is rich with species from both the shield and the plasma. While it is known that this boundary layer mixture can play an important role in the radiative heating of the spacecraft by absorbing certain wavelengths radiated from the atmospheric plasma, few experimental efforts have been carried out to study the quantitative effects of these boundary layer species on radiative blocking. The current project studies both the composition of the boundary layer and the degree to which these ablator pyrolysis species absorb radiation. This is being carried out through spectroscopic studies of an air plasma/ablator system in a plasma torch laboratory. Concurrent modeling of the system with a plasma modeling code, SPECAIR, is being carried out to further validate this code. This project is of clear importance for reentry applications, where a direct result of the validation of the SPECAIR code will be its use as a predictive design tool for ablative heat shields. This will not only advance the state of-the-art in ablator capabilities in Europe (which will be essential to any future international planetary entry or sample-return missions) but also increase the state of the knowledge in the U.S., as Dr. MacDonald intends to return and join the U.S. research community at a national laboratory.