X-rays and AI reveal how spacecraft heat shields burn in real time
Heat shields are one of the most important parts of any spacecraft that intends to enter an atmosphere. And the material they are made of is critical. Improving them has been a challenge, though, as researchers typically only get "before" and "after" pictures of a heat shield's job of helping a spacecraft land safely back on Earth.
Recent collaboration between NASA and the Advanced Light Source at Lawrence Berkeley National Laboratory has enabled researchers to observe a heat shield's ablation process in real time. This process, crucial for heat shields like those on Mercury capsules and Artemis Orion, involves thermal energy transferring into material pieces that then fall away from the spacecraft.
However, unlike traditional heat shields that are replaced after each use, this innovative method allows researchers to understand the material's behavior during reentry more accurately.
To achieve this, the team utilized a specialized chamber at the ALS, exposed to temperatures up to 900°C and variable pressure and gas composition to mimic reentry conditions. The imaging system used, X-ray micro-computed tomography (micro-CT), captured 3D structural images of the heat shield material as it ablated.
Two types of ablative materials were studied: SLA-561V, which includes ground cork that vaporizes rapidly, creating hollow voids, and SLA-220, a silicone-elastomer matrix material that degrades into branching microchannels. These differences in degradation mechanisms have significant impacts on spacecraft performance during reentry.
However, the researchers faced a challenge in balancing image detail and speed. To address this, they employed AI, specifically a generative adversarial network (GAN) algorithm, enabling them to generate high-resolution, fast 3D records of the material's transformation during ablation.
Despite these advancements, the researchers have not yet incorporated these findings into reentry simulations or analyzed heat shields used in commercial vehicles like SpaceX's Dragon or Starship. Nevertheless, the potential of this imaging system could soon attract interest from companies involved in more than half of today's reentries.
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