What is it about?
Spacecraft re-entering Earth's atmosphere face extreme heat, necessitating rigorous testing and characterization of potitial reusable heat shield materials. Plasma wind tunnels simulate these re-entry conditions in ground-based experiments. This project employed a near-infrared spectrometer to demonstrate accurate temperature measurements using multi-wavelength pyrometry. Tests were conducted on sintered silicon carbide (SSiC) and grade 5 titanium (Ti6Al4V) samples in an oxygen plasma flow, replicating re-entry conditions and advancing heat shield material characterization techniques.
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Why is it important?
When exposed to high-enthalpy plasma flows encountered during re-entry, metals, specifically titanium, are susceptible to phase transitions, oxidation, and potentially melting. These processes are associated with changes in the emissivity of the surface. However, knowledge of the emissivity is critical for conducting accurate pyrometric temperature measurements. The multi-wavelength pyrometry method offers the possibility of determining the emissivity and temperature of a surface simultaneously. Although this method requires some initial assumptions about the spectral emissivity distribution, it offers improved accuracy of temperature measurements between 1000 K and 2000 K.
Perspectives
The challenge of protecting spacecraft during atmospheric re-entry is both fascinating and essential, particularly as the industry aims for reusability. The extreme conditions faced during this phase push the limits of material science and measurement techniques. Developing multi-wavelength pyrometry for accurate temperature measurements is a significant advancement, allowing real-time monitoring of temperature and emissivity changes during plasma wind tunnel ground tests for material characterization.
Clemens Kaiser
Universitat Stuttgart
Read the Original
This page is a summary of: Infrared Multiwavelength Pyrometry of SSiC and Ti6Al4V Surfaces in High-Enthalpy Oxygen Flows, July 2024, American Institute of Aeronautics and Astronautics (AIAA),
DOI: 10.2514/6.2024-4019.
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