Composites Key to Journey to Mars

For the past seven years, San Diego Composites Inc. (SDC) has been working with NASA on the Orion spacecraft, designed to bring humans further into deep space than ever before – even reaching Mars. The company made more than 1,000 parts for Orion’s first unmanned Exploration Test Flight, EFT-1, which orbited earth in December 2014. Watching the test flight launch was “an amazing experience,” says SDC President Robert Kolozs. Two of the largest parts that SDC currently makes for Orion – the CFRP Fillet and ogive fairing for the Launch Abort System (LAS) – are clearly visible at the top of the spacecraft. Kolozs says it was thrilling to point across the bay during the flight launch and say, “That cone at the top is ours!” Founded in 2002, San Diego Composites began working with NASA more than 10 years ago when it helped invent a double-bag vacuum assisted resin transfer molding (VARTM) process to address the volatility that can occur when infusing high-temperature polyimides. In 2009, the company began working on Orion as a subcontractor to Lockheed Martin, which manages and leads the Orion program for NASA. [caption id="attachment_3662" align="alignleft" width="750"] During an ogive panel lay-up, San Diego Composites’ Orion manufacturing team secures bagging materials to the mold. Photo Credit: San Diego Composites Inc.[/caption] Ken Mercer, Orion program manager at SDC, says that the company’s first Orion components were CFRP angle brackets used to mount the spacecraft’s outer panels to the aluminum pressure vessel for EFT-1’s crew module and ground test vehicle. SDC supplied more than 100 brackets. “This was a very small part,” explains Mercer, “but we were lucky enough that they have trusted us with larger parts ever since.” SDC began work on sections of the Launch Abort System in 2011. Positioned at the top of the crew module, the nearly 53-foot-long LAS has several components, including a nose cone, motors, the Fillet and the ogive fairing. If a launch problem occurs, powerful motors pull the launch abort capsule away from the failing rocket within milliseconds. Mercer says it was challenging to develop a fabrication process for the Fillet. “The first ply down is a lightning strike material,” he says. “The curvatures of the Fillet are such that the copper mesh material is a challenge to put down. We’ve developed techniques over the years to avoid wrinkles and potential damage to that very sensitive material.” The Fillet is a co-bonded structure created by pre-curing the front facesheet and then co-curing the honeycomb sandwich core and back facesheet. Maintaining a good bond line between those two processes requires careful abrading and cleaning to ensure that the interface is not fouled between cure cycles. 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. So SDC created a process that uses microcontrollers and data recording to control vacuum level, flow path and pressure throughout infusion. “That’s what makes this a really unique process,” says Mercer. “We’re controlling three of these things to a very fine degree in this part, whereas normally you might only control one or two of them. And we’re staging them at times to make sure that we avoid creating voids.” SDC has since infused 32 billets of 3D-MAT material that will be used to make compression pads and other components for Orion’s next test flight, Exploration Mission 1 (EM-1) in 2018. Last fall, SDC received a special commendation from NASA for its contributions to the development of the 3D-MAT material. Kolozs says that all of the company’s engineers have worked on Orion at some point. “We’ve grown a lot with the program,” Kolozs reflects, adding that he hopes SDC can remain an Orion partner all the way through its ultimate mission – the journey to Mars. That would be quite a journey for San Diego Composites, too.