America's space program is benefiting from the expertise of an SIUC faculty member.

Tsuchin Philip Chu, an associate professor of mechanical engineering and energy processes, regularly works with NASA scientists and engineers to help solve complex problems. His current project, funded through a $30,000 collaborative grant, involves developing a software system for more precise detection of hydrogen leaks in the nozzle of the space shuttle main engine.

The engine nozzle contains more than 1,000 metal alloy tubes, each about the diameter of a straw, which run through its length. They are attached to a stainless steel jacket lining the inner wall of the nozzle.

Liquid hydrogen is pumped through the tubes to cool the nozzle while it is firing. The hydrogen eventually flows into the main combustion chamber, where it is used as fuel.

During flight, cracks or tiny holes can develop in the tubes from stress, temperature changes, or corrosion, Chu explains. Those defects allow hydrogen to leak into the spaces between the tubes and the jacket.

Although no space shuttle accidents have resulted from such leakage, NASA knows that it occurs. Inspection teams routinely detect leaks after a shuttle flight. The situation poses a real danger: if cooling efficiency were reduced too much during flight, serious engine problems could result--not to mention the fact that leaked hydrogen could explode.

NASA inspects and tests the main engine nozzles after each flight before they are sent to Florida for installation on another shuttle. Newly manufactured nozzles are checked extensively as well. Chu's software will aid this inspection process by enabling engineers to zero in on leaks and repair defective tubes.

The current procedure for detecting the location of leaks is inexact and "very tedious," Chu says. "They may have to open up 20 or 30 tubes to insert a [detection] scope, and they still may not find the leak."

Chu is part of NASA's "nondestructive evaluation" (NDE) team, which develops better, faster, noninvasive ways to inspect shuttle parts. In this case, leaks in the coolant tubes can be pinpointed with thermography--detecting and analyzing slight temperature changes using an infrared camera system and image analysis software. Chu is developing the software for a new camera system that NASA is implementing.

"We can detect the exact location of the leak and can do it faster and without cutting tubes," he says. "Once the detection system is in place, you can save a lot of money, because you can inspect a large area at one time."

"Right now [our] evaluation techniques give us a general area," says NASA spokeswoman June Malone. "Dr. Chu's software is going to give us more accuracy. That will save a lot of time if you can pinpoint exactly where a leak is coming from."

Chu has been traveling back and forth to the Marshall Space Flight Center in Huntsville, Ala., to work on the new system. The project will last through October 2004.

Chu's collaboration with NASA engineers dates to 1994, when he participated in the NASA Faculty Fellowship Program, a 10-week summer research residency. An expert on composite materials and image analysis, Chu has held other NASA grants subsequently and has worked at the Marshall Space Flight Center almost every summer since 1997 on thermographic inspection modeling and other projects.

--by Pete Rosenbery, Media & Communication Resources, and Marilyn Davis, ed.

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