Sigur, Wanda Anne Alexander 1958–

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Wanda Anne Alexander Sigur 1958–

Mechanical and materials engineer

As leader of a team of specialists who design materials for space shuttle fuel tanks, Wanda Sigur has achieved considerable success in a field in which women and people of color remain largely underrepresented. Her work has been instrumental in helping the National Aeronautics and Space Administration (NASA) advance its space shuttle program.

Sigur was born Wanda Anne Alexander on May 26, 1958 in New Orleans, Louisiana, to Alvin Maurice and Louella Clara Boyd Alexander. Not much is known about her early life, but it is known that she graduated in 1979 from Rice University in Houston, Texas, where she majored in natural science and engineering. During her undergraduate years she worked as a lab technician at General Electric in Houston. After obtaining her bachelor’s degree she joined Martin Marietta Manned Space Systems, where she began work testing construction materials used for spacecraft. She continued her work through the merger of Martin Marietta and Lockheed in 1995.

Patented New Manufacturing Process

Because spacecraft encounter such extremes of heat, cold, and pressure, the materials used in their construction must be extraordinarily durable. They must also be as light as possible, because every extra pound on a spacecraft means that a large volume of additional fuel must be used to launch it into orbit. These requirements have posed considerable challenges in construction of spacecraft components. The exterior fuel tanks on NASA space shuttles, which are the largest spacecraft fuel tanks in the world, are made of a lightweight aluminum alloy. Because the manufacturing process requires that the metal be subjected to simultaneous heat and pressure, components are made in an autoclave (a vessel in which high heat and pressure are used). But autoclaves are expensive to build and are relatively small. They cannot accommodate large components, so spacecraft fuel tanks must be manufactured in small segments and joined together. These intersections must be carefully sealed to avoid leaks. Not only does the sealant add weight to the tanks, but intersections are vulnerable to cracks.

To resolve some of these problems, Sigur invented a process by which low-weight laminates could be manufactured to the specifications required for space shuttle fuel tanks. These materials are stronger and lighter than metal alloys. Graphite/epoxy composites, for example, are approximately nine times stronger than stainless steel and three-and-one-half times stronger than aluminum alloys. A polyaramide/epoxy composite made from KEVLAR fibers is approximately eleven times stronger than stainless steel and three-and-three-quarter times stronger than aluminum. Use of such materials, according to information from the Marshall Space Flight Center Technology Transfer Program, is associated with a 15 to 40 percent reduction in weight for aerospace and aircraft components, and production cost savings of between 5 and 25 percent.

But existing technology has made it difficult to process such materials because of the required application of high pressure and heat. Sigur’s process, as described in her U.S. patent application, solves this problem by

At a Glance…

Born Wanda Anne Alexander on May 26, 1958, in New Orleans, LA; daughter of Alvin Maurice Alexander and Louella Clara Boyd Alexander; married Michael Gerard Sigur, 1981; children: Michael Jr. Education: Rice University, Houston, TX, BS, 1979.

Career: General Electric, Houston, TX, lab technician, 1977-79; Martin Marietta Manned Space Systems (now Lockheed Martin), New Orleans, LA, materials engineer, 1979–.

Awards: Research and Development Investigator Award, Martin Marietta Manned Space Systems Company, 1986; Author Award, Martin Marietta, 1987; American Institute of Aeronautics and Astronautics Author Award, 1988; Technology Disclosure Award, U.S. Patent and Technology Disclosure Office, 1989; Principal Investigator of the Year, Martin Marietta, 1989.

Addresses: Office —Michoud Operations, Lockheed Martin Space Systems Company, P.O. Box 29304, New Orleans, LA 70189

“sandwiching the composite material between a material having a high coefficient of thermal expansion (hereinafter C.T.E.) and a stiff material having a low C.T.E.” When heat is applied to the structure, “the differential in thermal expansion of the sandwiching materials creates a pressure differential which acts to compress the composite structure.” Essentially, heating coils are wrapped around the exterior of the structure. Because this fiber overwrap is stiffer than the composite material, when the overwrap expands due to heat, it applies the required external force to the composite.

Sigur’s process, which she patented in 1992 (patent #5,084,219), holds the potential not only for use in future aerospace manufacturing, but also for a range of commercial applications including industrial and automobile manufacturing. Though the process was designed with the space shuttle in mind, NASA initially decided not to use it because of the cost of constructing new facilities for manufacturing composites. Instead NASA focused on improving its existing aluminum alloy. By the early 2000s, though, Lockheed Martin and NASA had begun testing composite tank construction. Initial tests showed that a composite tank could significantly reduce the weight of a spacecraft and possibly reduce the cost of launching a payload from $10,000 per pound to $1,000 per pound.

Advanced Steadily in Career

At Martin Marietta (now Lockheed Martin), Sigur advanced through several engineering positions, leading a team that inspects the intersections of shuttle tanks for cracks and that devises solutions for any intersection flaws. She was recently named Director of Engineering and Technical Laboratories at Lockheed Martin’s Michoud Operations.

Sigur has received many awards for her research. In 1986 she received Martin Marietta’s Research and Development Investigator Award, and the following year received the company’s Author Award. In 1988 she received the American Institute of Aeronautics and Astronautics Author Award. She received a Technology Disclosure Award from the U.S. Patent and Technology Disclosure Office in 1989. That same year, she was named Martin Marietta’s Principal Investigator of the Year.

The engineering profession has historically attracted disproportionately low numbers of women and African Americans (the national average of women in the engineering workforce in 2003 was only 8 percent; the percentage of engineering degrees awarded to under-represented minorities—including blacks, Hispanics, and Native Americans—was only 9.2 percent in 1995). In addition, women engineers often face barriers to promotion that appear to be associated with gender bias. Despite these challenges, Sigur has achieved particular distinction in her field and, at midcareer, is poised to make continued contributions to aeronautic technologies. She currently lives in New Orleans with her husband, Michael Gerard Sigur, and her son, Michael, Jr.

Sources

Books

Henderson, Susan K., African American Inventors II, Capstone Press, 1998.

Periodicals

Journal of Engineering Education, July 1997, pp. 241-242.

On-line

“Defining Moments,” Lockheed Martin Space Systems Company, www.lockheedmartin.com/wms (February 13, 2004).

“Method of Fabricating Composite Structures,” Marshall Space Flight Center Technology Transfer Program, http://techtran.msfc.nasa.gov/Patents/(37).html (February 12, 2004).