Tech Briefs

Wallops Flight Facility 6U Advanced CubeSat Ejector (ACE)

Goddard Space Flight Center, Greenbelt, Maryland Six-unit (6U) CubeSats are recognized as the next nanosatellite to be considered for standardization. The CubeSat standard established by California Polytechnic University (Cal Poly), which applies to 1U–3U sizes, has proven to be a valuable asset to the community. It has both provided design guidelines to CubeSat developers and a consistent, low-risk interface to launch service providers. This has ultimately led to more flight opportunities for CubeSats. A similar path is desired for the 6U CubeSat. Through this process of standardization, a consistent, low-risk interface for the 6U needs to be established.

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Improved Attachment Design for Ceramic Turbine Blades Via Hybrid Concepts

This approach facilitates increased precision and ease of handling the blades during assembly. John H. Glenn Research Center, Cleveland, Ohio This innovation is a hybrid metal-ceramic matrix composite (CMC) turbine blade in which a SiC/SiC CMC airfoil section is bonded to a single-crystal superalloy root section in order to mitigate risks associated with an all-CMC blade inserted in a superalloy disk. This will allow current blade attachment technology (SX blade with a dovetail attachment to a slotted Ni disk) to be used with a ceramic airfoil. The bond between the CMC and single crystal will be primarily mechanical in nature, and enhance with clamping arising from thermal expansion mismatch. Two single-crystal root sections will be bonded to each other using diffusion bonding at temperatures near 1,200 °C. The single crystals will form a clamshell around the CMC, with little or no gap between the metal and ceramic. Upon cooling, the metal will shrink around the CMC to firmly clamp it. It is envisioned that this will allow the blade root to operate at temperatures up to about 800 °C. Single crystals will resist stress relaxation at this temperature, thus maintaining clamping loads for long lives. The hybrid concept plus the method of manufacture is new technology.

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Powdered Copper Cryogenic Heat Exchanger

This technology provides a high level of thermal performance while dramatically simplifying the chore of determining safety factors. John F. Kennedy Space Center, Florida This work involved designing a liquid nitrogen cold-plate heat exchanger with a high thermal mass using code-standard, high-pressure tubing. High thermal mass requires a substantial amount of material, so heat exchangers of this type are usually fabricated from a solid piece of metal (such as copper) with fluid paths machined into the component. However, standard tubing was desired for the fluid path due to its pressure rating and predictability. The key problem was how to embed copper tubing into a larger mass while maintaining good heat transfer properties.

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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.

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