How cavity heat buildup weakens plasma jet control in hypersonic flow

What is it about?

When spacecraft or hypersonic vehicles fly at extremely high speeds—often faster than the speed of sound—they encounter intense aerodynamic forces and heat. One way to improve their performance is to use small, rapid bursts of plasma (high-speed shock and jet) to subtly reshape the shock waves that form around them. This technique, called an “opposing plasma synthetic jet,” can reduce drag and improve flight efficiency. However, when these plasma bursts are fired repeatedly in quick succession, their effectiveness drops over time. Our study shows why: heat builds up inside the tiny cavity that generates the plasma, preventing fresh air from entering and cooling it. This “thermal clogging” weakens each subsequent burst. Importantly, we also found that if the cavity is designed to encourage better mixing of hot and cold air—like stirring a cup of coffee—the problem can be reduced. In simple terms, this work explains how to keep a high-speed plasma “puff” operating reliably during repeated use, which is essential for real-world applications such as next-generation aircraft or reusable space launchers.

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Photo by SpaceX on Unsplash

Photo by SpaceX on Unsplash