Manufacturing & Prototyping

Surface Densification of Phenolic Impregnated Carbon Ablator

Ames Research Center, Moffett Field, California PICA (phenolic impregnated carbon ablator) was developed for the forebody heat shield of the Stardust Return Capsule. Conventional thermal protection system (TPS) materials of the time (primarily carbon phenolics) had high densities and thermal conductivities, yielding a TPS mass fraction that exceeded mission constraints. PICA was developed in the 1980s and consists of a rigid carbon fibrous substrate infiltrated with phenolic resin, yielding a TPS with good ablation and pyrolysis behavior. In addition, PICA has the advantages of low density coupled with efficient ablative capability at high heat fluxes. Limitations of PICA include relatively low mechanical properties, high recession rates, and poor handling, as the material sheds phenolic powder and is prone to damage from low-velocity impacts.

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Low-Density Flexible Ablators

Ames Research Center, Moffett Field, California NASA has developed a class of low-density, flexible ablators that can be fabricated into heat shields capable of being packaged, stowed, and deployed in space. Several flexible versions have been developed by infiltrating a pyrolyzing silicone resin into flexible, low-density felts made of carbon, polymer, or ceramic materials. The material is produced by immersing a flexible fibrous substrate in a diluted polymer resin, curing the polymer resin using heat and/or catalyst, and removing the solvent.

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Solar-Powered Carbon Dioxide Conversions with Thin-Film Devices

Ames Research Center, Moffett Field, California A nanomaterial thin-film device provides a low-cost, facile fabrication pathway to commercialize the technology to the sustainable energy market. Metal oxide thin films have been fabricated to a photoelectrochemical cell by solar energy. The prototype device uses both low energy cost for manufacturing and low materials cost for devices. The self-modulated device platform can also find other applications in sensors and detectors. The resultant prototype device can be deployed to the automobile industry or power plants with very low initial costs. The device can also be made extremely compact and efficient. It uses solar energy as the only power source.

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Fiber Metal Laminates Made by the VARTM Process

Fiber metal laminates combine the best properties of the metal and composite. Langley Research Center, Hampton, Virginia Fiber metal laminates (FMLs) are multicomponent materials utilizing metals, fibers, and matrix resins. Tailoring their properties is readily achievable by varying one or more of these components. Two new processes for manufacturing FMLs using vacuum assisted resin transfer molding (VARTM) have been developed.

Posted in: Briefs, TSP

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Method to Produce Copper Nanowires for Interconnect Applications

Ames Research Center, Moffett Field, California Copper replaced aluminum nearly two decades ago as interconnect material in integrated circuit manufacturing due to its better electrical conductivity. The size of the interconnect wire has been steadily decreasing as Moore’s law has been progressing through various feature size generations. The diameter of the interconnect structure is further expected to decrease as silicon technology is poised to march through a few more generations. Alternatives to copper have been reported—notably, materials such as carbon nanotubes. Their success has been limited, and carbon nanotubes have not been integrated into manufacturing practice.

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All-Organic Electroactive Device Fabricated with Single- Wall Carbon Nanotube Film Electrode

These devices have applications as electromechanical sensors, sonar, medical and optical devices, artificial muscles, and noise control. Langley Research Center, Hampton, Virginia A novel, all-organic electroactive device system has been fabricated with a single-wall carbon nanotube (SWCNT) film used as an alternative electrode. This system was fabricated with LaRC-Electro Active Polymer (LaRC-EAP) active layer and the SWCNT films by pressing at 600, 3,000, and 6,000 psi (≈4.1, 20.7, and 41.4 MPa, respectively). Silicone elastomer plates (3-mm thick) were used on the press plate surfaces for better contact adhesion between the SWCNT film and the actuating layer. This polymeric electroactive device layered with the SWCNT-FE (SWCNT-Film Electrode) can serve as an actuator. The density (or modulus) of the SWCNT-FE can be controlled by adjusting the fabrication pressure. It is anticipated that less dense SWCNT-FE can provide less constrain displacement of the polymeric actuating layer by matching the modulus.

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Purifying Hydrogen for a Life Support Process

An advanced hydrogen purification technology is proposed to purify hydrogen of acetylene, carbon monoxide, and other gases to enable utilization of the hydrogen for oxygen recovery. Marshall Space Flight Center, Alabama NASA’s endeavor to further enable long-duration manned space exploration requires further closure of the oxygen loop of the life support system that is currently realized aboard the International Space Station. Currently, oxygen is recovered from crew-generated carbon dioxide via the use of a Sabatier carbon dioxide reduction system coupled with water electrolysis. Water is electrolyzed to form oxygen for crew consumption, as well as hydrogen. The hydrogen is reacted with carbon dioxide, forming water and waste methane gas. Since hydrogen is lost from the desired closed-loop system in the form of methane, there is insufficient hydrogen available to fully react all of the carbon dioxide, resulting in a net loss of oxygen from the loop. In order to further close the oxygen loop, NASA has been developing an advanced plasma pyrolysis technology that further reduces the waste methane to higher hydrocarbons in order to better utilize the hydrogen for oxygen recovery.

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