09 December 2002
09 December 2002
Southern Research Institute's Jim Tucker got the call from a colleague at NASA's Marshall Space Flight Center of Huntsville, Ala., on a Sunday afternoon, he knew the call had to be important.
It was, and it provided an opportunity for the Institute's engineering researchers to help investigate damage done to the Space Shuttle Endeavour's robotic arm, and clear the shuttle for launch.
"My wife said the call was from Marshall Space Flight Center. I told her I'd better take this call," says Tucker, manager of the Nondestructive Characterization Group at Southern Research. "We were told to pack a backpack and be available for a conference call the next morning."
After that conference call with NASA officials first thing Monday, Tucker, and David Stewart, supervisor of Southern Research's Nondestructive Characterization (NDC) Lab, flew to Cape Canaveral with an UltraSpecTM unit -- the Institute's patented nondestructive materials characterization technology. There they met with nondestructive testing experts from the Marshall Center, who directed their work at the Cape.
NASA engineers had requested further, more detailed inspection of the robotic arm - referred to as "the Canada arm" - damaged earlier during repairs of a leak in the orbiter. Officials were unsure as to whether the arm would be able to lift a new girder out of the shuttle's payload bay in its mission to the International Space Station, possibly causing a delay in the launch.
"UltraSpecTM is a good tool for evaluating damage to composite materials," says Tucker, its inventor. "It's especially adept at looking for microcracking and disbonding or delamination that sometimes occur in composite materials."
The robotic arm is composed of a composite material sandwiched between two layers of aluminum at the ends. "UltraSpecTM can be uniquely effective at inspecting multiple layer structures", adds Tucker.
UltraSpecTM is Southern Research's version of ultrasonic spectroscopy. As the name implies, the test looks at a spectrum of frequencies to see how they interact with a test part. Low frequencies respond differently than high frequencies that, along with resonance effects, tell the inspector a lot about a material's properties. The concept has been around for a long time, but Southern Research developments made the test practical for use as a portable nondestructive inspection technique. The technology was developed and patented by Southern Research Institute about five years ago. They began licensing the technology commercially about three years ago, and have sold two units to Marshall Space Flight Center.
By noon that Tuesday, the Southern Research and NASA teams, were on the shuttle platform, and finished testing that night. After reporting their findings to NASA, Tucker and Stewart then flew to Toronto to meet with officials at MD Space Robotics Corp., the company that designed the arm. "The company had already simulated the same damage that occurred on the launch platform in an effort to learn more about how it might affect performance. UltraSpecTM helped confirm that they did a great job of recreating it," says Tucker. The arm with simulated damage performed well in a proof test and Endeavour launched three days later with no repairs needed before the current mission. Tucker believes Southern Research got the call to work on this robotic arm because of similar work they had conducted two years ago at Johnson Space Center.