Building on CCM lessons learned
In space, every pound of weight affects mission capacity and overall project cost, which makes the use of composites very attractive. That’s why the NASA Engineering and Safety Center (NESC, Hampton, Va.) designed, built and tested a composite crew module (CCM) in parallel with the Constellation program’s Orion crew module development. Some of the lessons learned were applied to Orion and are now benefiting other programs within NASA and beyond.
“Members of the composite crew module team have had technical discussions with Blue Origin and Sierra Nevada regarding how we used composites, including our design, analysis, manufacturing and test processes,” says Mike Kirsch, NESC principal engineer and CCM project manager. “We have been asked to participate in design reviews of their systems,” he adds, confirming that both companies are using composites in their primary structures.
The NESC worked with a number of NASA and industry partners on the CCM project (see “Simulation simplifies fabrication ...." under Editor's Picks," at right ).
Fabricated at Alliant Techsystems (ATK, Iuka, Miss.), the CCM incorporated an innovative approach to joining composites developed by Northrop Grumman Aerospace Systems (Redondo Beach, Calif.) and carbon fiber tooling firm Janicki Industries (Sedro-Woolley, Wash.). The top and bottom halves of the CCM were hand layed sandwich structures with an aluminum honeycomb core and carbon fiber-reinforced facesheets. During layup, critical orthogonal joints were assembled, using preformed three-dimensional weaving technology. After they were autoclave-cured, the two halves were spliced together, using local heaters and vacuum bags, reports the NESC. According to the NESC, the use of complex composite shapes allowed the integration of the packaging backbone (used to secure internal components) with a membrane-lobed floor and pressure-shell walls, which reduced mass by approximately 150 lb/68 kg.
“As loads and environments change with program maturation, inner mold line tooling offers the opportunity to optimize or change design through tailoring of layups or core density,” reports the NESC. “Composite solutions offer opportunity for lower piece-part numbers, resulting in a lower drawing count, which helps minimize overall lifecycle costs. Also, a minimal number of tools are required to manufacture the primary structure.”
The module was pressurized to twice Earth’s atmosphere to “demonstrate the ultimate design capability of the structure,” explains Kirsch. This was followed by push-pull tests to simulate the on-mission forces. In all, the CCM showed that it could complete its mission, even with the kind of damage that is likely to occur in space.
A look at the process by which precursor becomes carbon fiber through a careful (and mostly proprietary) manipulation of temperature and tension.
Fiber-reinforced plastic (FRP) replacing coated steel in more reinforced-concrete applications.
Commercial production of recycled carbon fiber currently outpaces applications for it, but materials characterization and new technology demonstrations promise to close the gap.