Unlike traditional X-rays that make images by transmitting radiation through an object to a detector, backscatter technology makes images based on the electromagnetic radiation deflected back by the objects examined.

Pieces of foam fell from shuttle Columbia's tank during its January 2003 launch, causing serious damage to the spacecraft's left wing and resulting in the shuttle's destruction when it re-entered Earth's atmosphere on Feb. 1. The accident killed all seven astronauts aboard and grounded the shuttle while NASA engineers worked to solve the foam problem.

When shuttle Discovery finally lifted off last July, more foam chunks fell from the main fuel tank and sent engineers looking for more answers. The problem threatens to delay the next scheduled launch of Discovery in May.

Late last year, NASA asked Joe Gray, of Iowa State's Center for Nondestructive Evaluation, and his research team, to do a three-month study to answer two lingering questions about NASA's foam testing: They wanted to know more about the ability of X-ray technology to detect bubbles when layers of shuttle foam curve around corners, and they wanted to know more about the technology's ability to see any bubbles near the foam's layer lines.

The spray-on foam that insulates and protects the shuttle's super-cold external fuel tank is applied in thin layers. The top of the layer dries to a bumpy crust, marking each layer like rings mark a tree trunk.

The researchers have been taking X-ray images of foam samples and loading that information into a computer simulation program. Then they ran simulations that model the X-ray technology's ability to find defects in the foam.

Gray said he expects to send NASA a final report of the research results later this month.

"Our job has long been to do research, find new inspection technologies and develop a better understanding of those technologies," said R. Bruce Thompson, the center's director. "Now we're seeing those technologies put into practice on a real and national problem."

For the past four years, CNE researchers have been working on 17 NASA research projects that have focused on finding new technologies to monitor and inspect spacecraft.

Related Links
ISU Center For Nondestructive Evaluation
Space Shuttle
NASA

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