Transcript:

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ambience: Arc-Jet

How do you test a new material that’s designed to protect a high-speed aircraft? I’m Jim Metzner and this is the Pulse of the Planet. To make such a test, Facility Engineer John Balboni of Ames Research Center uses an arc-jet, a high-temperature wind tunnel that’s like a huge blowtorch. Here’s how the tests work.

“Well, first, there’s visual, so there will be a video recording of what the sample looks like in and out of the stream. There can be infrared images taken. Infrared video is commonly used, which would then give you an indication of what the surface temperatures are. There also can be sensors embedded right into the material. Typically, these would be temperature sensors. There can also be pressure sensors, and there can also be thickness sensors that literally measure the thickness of the material. And as it burns away, it can get thinner, and, as it gets thinner, then the sensors will measure how thin it is. Those sensors are all recorded then on a data system in real-time.”

The arc-jet only allows for the testing of a small area, about the size of a dinner plate.

“Extrapolating data from a very small sample tested in an arc-jet to the full-scale vehicle that flies in the air can be very difficult simply because there are nooks and crannies, which can simply not be simulated in a small piece. There are many details on an aircraft that take up larger space than just a dinner plate. Then we have to use computational techniques to extrapolate how the material will behave. And then, of course, ultimately, the only way to know if it’s going to work is to fly it in the atmosphere at these very high speeds. In other words, launch it on a rocket.”

Pulse of the Planet is made possible by the National Science Foundation, with additional support from NASA. I’m Jim Metzner.