In January 2007, the Exploration Systems Mission Directorate chartered NASA’s Engineering and Safety Center (NESC) to design, build and test a full-scale crew module primary structure using carbon fiber-reinforced epoxy-based composite materials. The composite crew module (CCM) was to run concurrent with the Orion Project so that features could be compared and used to identify how composites could be streamlined into other projects.
By October 2009, the full-scale test article had been constructed and delivered to its Langley facility for testing. According to Mike Kirsch, NESC Principal Engineer, while NESC concluded there was no immediate benefit for changing a crew module to composites, the process and testing helped NASA understand more clearly the actual benefits and drawbacks of composites within NASA projects.
“Generally composites shine in certain applications, such as where you have a complex shape to manufacture. In that instance composites would be cost-effective. But most engineers go to composites for stiffness, which is different than strength,” Kirsch says. “For example, you can have two rackets, one made out of aluminum and the other made out of composites. The rackets could be equally strong, but the composite racket would be stiffer, meaning more energy from the racket would go back into the ball, instead of absorbed into the racket.” Kirsch also noted that composites offer improved fatigue, an ability to be directionally strength-bias and provide greater thermal stability, making it useful in many application such as space satellites.
“Unfortunately none of those benefits are necessary for a crew module,” he says. “It’s not thermal extreme, because it has people in it. It’s only used one time so structure fatigue isn’t as important as it would be on a commercial jet. And by the time we look at the final product, the weight saving composites offer was gone in order to make up for various problems,” says Kirsch. “So in the end we didn’t see much benefit of changing the actual crew module from its current design. However, we discovered invaluable applications that we can now apply to other programs, like the Orion Project.”
Kirsch says that NASA learned how to design, manufacture, inspect and repair composite components—all of which are applicable to the Orion Project. “There are many composite components that we developed from the CCM and because our timeline was ahead of them we could make those mistakes, learn those lessons and apply them to the Orion,” he says. “As a result 40 percent of Orion by weight is composites.”