The size of the Fillet, which is laid up by hand, also made fabrication tricky. The cone-shaped Fillet is 10 feet long. Fabricated in halves, it is eight feet in diameter when completed. Mercer says that a lot of thought went into how to provide technicians access to all locations on the molds for both the Fillet and the even larger ogive fairings.
The ogive fairing is a large curved structure – positioned below the Fillet and encapsulating the crew module – that shields the crew module from high shear and wind loads and, if necessary, from the launch abort motors. Nearly 30 feet in diameter, the ogive fairing is fabricated in four core panels measuring approximately 15 feet across and about 16 feet long.
To accommodate hand lay up of both the Fillet and ogive fairing, SDC built systems to bridge people over the molds and allow them to lay down the prepregs. “It sounds simple,” explains Kolozs, “but when you talk about getting out in the middle of something 8 feet in and 16 feet across and getting good compaction – and you want to lay down a certain amount of material per hour – it’s not.” SDC developed specialized tooling and used a laser projection system to help lay up both parts, which were then cured in the company’s new 16-foot diameter, 30-foot long high-pressure autoclave.
Like the Fillet, the ogive fairing is made of a high-strength carbon fiber/epoxy material, but with a thicker honeycomb core to accommodate a higher load profile. The ogive fairing tapers to a solid laminate at the edges and has syntactic foam placed in high shear load areas as well as foaming adhesive between the core segments. “Lockheed Martin has designed a structure that is best-in-class right now in terms of specific strength and specific stiffness,” Mercer states.
SDC also helped develop a process to infuse NASA’s 3-D Multifunctional Ablative Thermal Protection System (3D-MAT), a new 3-D stitched quartz fiber preform material. After developing the intricate weaving process with Bally Ribbon Mills, NASA discovered that infusion of the dry preform was a challenge. After NASA and several subcontractors struggled to infuse 3D-MAT, they brought the project to SDC. Like others, SDC initially tried to infuse the material using a traditional VARTM process and failed. Mercer says that 3D-MAT’s irregular and non-repeatable shape, as well as its thickness and stitch density, make managing resin flow using traditional VARTM impossible.