Manufacturing & Prototyping

Surface Densification of Phenolic Impregnated Carbon Ablator

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.

Posted in: Briefs, Manufacturing & Prototyping, Resins, Spacecraft

Low-Density Flexible Ablators

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.

Posted in: Briefs, Manufacturing & Prototyping, Insulation, Polymers, Resins, Spacecraft

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.

Posted in: Briefs, Manufacturing & Prototyping, Solar energy, Fabrication, Nanomaterials

Fiber Metal Laminates Made by the VARTM Process

Fiber metal laminates combine the best properties of the metal and composite.

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, Manufacturing & Prototyping, Manufacturing processes, Coatings Colorants and Finishes, Coatings, colorants, and finishes, Fibers, Metals, Resins

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.

Posted in: Briefs, Manufacturing & Prototyping, Wiring, Wiring, Copper, Nanomaterials

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.

Posted in: Briefs, TSP, Manufacturing & Prototyping, Conductivity, Polymers

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.

Posted in: Briefs, Manufacturing & Prototyping, Human factors

Low-Pressure Casting of Bulk Metallic Glasses for Gears and Other Applications

Applications include the automotive, aeronautics, aerospace, robotics, commercial, and military/defense industries.

With the correct selection of composition, some bulk metallic glasses (BMGs) have been demonstrated that have excellent combinations of hardness, fracture toughness, and wear resistance so that their use in gears and gearboxes is a potentially commercially viable application. For BMGs to be used as a low-cost alternative to steel gears, rapid fabrication strategies are needed to cast the BMGs into net-shaped gears that require little or no post-casting machining prior to use. Die casting, suction casting, and other cold-mold casting techniques have been widely demonstrated for BMGs in the past, but the unique nature of gears precludes traditional techniques from being used in an optimal way.

Posted in: Briefs, Manufacturing & Prototyping, Casting, Glass, Metals, Transmission gears, Transmissions

Aluminum Rocket Engine Injector Fabricated Using 3D Additive Manufacturing

Marshall Space Flight Center, Alabama

Liquid rocket engine injectors can be extremely expensive to manufacture and hard to iterate to achieve high performance. Internal sealing points can also be the source of reliability issues. The technology disclosed here covers the application of a 3D additive manufacturing (AM) process to produce a functional aluminum injector for liquid propellant rocket engines, along with injector and overall engine design features that optimize the application of such processes to improve performance, reliability, and affordability relative to components produced using standard machining processes and designs. Aluminum was used for the injector instead of higher- temperature metals like stainless steel because its thermal conductance properties provide more opportunity to leverage the cooling potential of liquid oxygen and other cryogenic propellants.

Posted in: Briefs, Manufacturing & Prototyping, Machining processes, Aluminum, Fuel injection, Liquid propellant rocket engines

Making Flexible Ablators that are Flexible Char Formers

Ames Research Center, Moffett Field, California

An approach was developed for making low-density, flexible ablators for a thermal protection system (TPS) from a flexible fibrous carbon substrate and a polymer resin. The material is foldable and stowable, and can be deployed in space without compromising performance. In addition, the material can be stowed in space for very long periods of time (years) without compromising deployability or performance. These flexible ablators offer an alternative to rigid TPS materials, thereby reducing design complexity and cost. On charring, the flexible ablative TPS retains its flexibility. After charring, the TPS has comparable flexibility and mechanical properties to the virgin material.

Posted in: Briefs, Manufacturing & Prototyping, Thermal management, Thermal management, Heat resistant materials, Resins

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