Vishnu Oruganti watched tiny bubbles form and grow inside a piece of spacecraft heat shield as it heated up, just like it would during a fiery dive through Earth's atmosphere. This wasn't a simulation — it was real-time X-ray footage captured at the Advanced Light Source in Berkeley, California, showing for the first time how heat shield materials actually break down under extreme heat.
When spacecraft return from space, they slam into the atmosphere at speeds over 24,000 miles per hour. Friction heats the outside to more than 3,000 degrees Fahrenheit — hot enough to melt steel. To survive, these vehicles use heat shields made of special materials called ablators. These materials don't just resist heat — they slowly burn away, carrying heat with them and protecting the crew and equipment inside. But to design better shields, scientists need to see exactly how that burning happens — not just before and after, but as it unfolds.
Now, thanks to a breakthrough at the Department of Energy's Lawrence Berkeley National Laboratory, they can. Using powerful X-rays and a custom setup that mimics real reentry conditions, researchers from the University of Illinois Urbana-Champaign and NASA watched two common heat shield materials — SLA-220 and SLA-561V — degrade in real time. They heated the samples to 1,652 degrees Fahrenheit and captured 3D images at the micrometer scale, revealing how gases form, how pores open up, and how the material’s internal structure changes second by second.
This level of detail is revolutionary. After the Artemis I mission, engineers noticed the heat shield had eroded more than their models predicted. By studying actual material from that mission using this new technique, they’re now refining their models to make future missions safer. Every major NASA heat shield material — including those for Artemis II and future Mars landings — has been analyzed this way.
"Directly observing how heat shield materials degrade during heating with this technique has been transformative for atmospheric entry research," said Oruganti, now at NASA's Johnson Space Center. The work, published in npj Materials Degradation, is already helping engineers build more accurate simulations, reduce risks, and plan missions with greater confidence. As humans prepare to return to the Moon and eventually land on Mars, knowing exactly how our protective shields behave — down to the tiniest bubble and crack — could make all the difference.