Date: Jul 15, 2010 Author: Dale McGeehon Source: MDA (
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by Dale McGeehon/dmcgeehon@nttc.edu
An MDA-funded company has developed a carbon-fiber-reinforced ceramic composite material that stands to supplement erosion-resistant metals used in extremely hot environments—bringing with it the advantages of low cost, low weight, and simplicity.
For 40 years, Fiber Materials, Inc. (FMI; Biddeford, ME), has manufactured carbon-carbon materials, which are often used for rocket booster applications. However, for nozzles in divert and attitude control systems (DACS), MDA uses refractory metals, such as rhenium, columbium, and molybdenum. These metals are costly and heavy, so the agency sought proposals on manufacturing processes that would yield technologies that are cheaper, lighter, and have reduced part counts, while maintaining performance requirements, such as stability in extreme heat.
FMI received a 2004 Phase II SBIR contract that leveraged its carbon-carbon manufacturing process, developing a carbon/carbon-silicon-carbide material system. This innovation is suitable for propulsion components, including throats for rocket combustion chambers, as well as for the leading edges of a rocket's structure.
FMI's development attracted the attention of a NASA prime developer, and the company is now under contract to manufacture carbon/carbon-silicon-carbide composite valves for the launch-abort system for the space agency's Orion spacecraft, the successor to the Space Shuttle. FMI's material is being used for attitude control motor components. Attitude control motors provide steering to direct the Orion crew capsule away from its rocket in the event of an emergency. The company already has supplied components for three eight-valve demonstration motors. Incorporating the material in vehicles such as rockets, airplanes, or automobiles could realize weight savings—reducing fuel costs or enabling users to pack in more devices or cargo without adding to a vehicle's overall weight.
The new product's advantage over FMI's tried-and-true carbon-carbon product is that the newer material will not erode at temperatures often found in DACS (approaching 4,000°F), whereas carbon-carbon will. Carbon-carbon is "still very much alive and well in booster applications," said Matt Levesque, FMI's marketing and technical coordinator. The erosion resistance of carbon/carbon-silicon-carbide offers an expansion of carbon-carbon capability in these applications, he said.
The refractory metals used now in throat and nozzle components do not erode, but they are many times heavier than carbon/carbon-silicon-carbide materials. For example, rhenium has a density of 20 grams per cubic centimeter. Carbon/carbon-silicon-carbide material has a density of just 2 grams per cubic centimeter. If FMI's composite were used instead of the metals, the resulting lower weight could allow for heavier payloads on a missile, according to Mark Lippold, FMI's advanced development manager. Also, the carbon/carbon-silicon-carbide composite can be machined into intricate shapes more easily than the refractory metals, thereby reducing the number of parts needed for components.
The manufacturing process starts with a carbon-fiber preform, which is then impregnated with a liquid pitch and processed to become a low density carbon-carbon material. Later in the process, a liquid silicon-carbide polymer is used to form the silicon-carbide component of the matrix. At completion of densification, the final block of material is machined to shape and seal-coated.
FMI researchers continue to work on improving their material, and the company has been working with the prime contractor toward qualifying the material for flight. The company is focused on making the manufacturing process as efficient as possible and tailoring it to the specific application.
