Manufacturing & Prototyping

Sidewall Passivation of GaN Avalanche Photodiodes via Atomic Layer Deposition

Atomic layer deposition is explored as a sidewall passivation method for mesa-isolated gallium nitride. NASA’s Jet Propulsion Laboratory, Pasadena, California The visible-blind detection of UV light has important applications in planetary imaging and spectroscopy, astronomy, communications, and defense-related imaging. Future instruments for imaging in the ultraviolet will require improvements in detector capabilities. An all-solid-state ultraviolet detector will enable substantial improvements in mass, volume, complexity, power, and robustness compared with conventional image-tube-based technologies. One new class of solid-state UV detectors includes those based on the gallium nitride (GaN) family of materials. The electronic passivation methods described here are one promising way to produce detectors with the required low dark current characteristics, and show a significant improvement over current state-of-the-art passivation methods. These methods will contribute to a next-generation solar-blind, solid-state UV detector for a wide range of space-based UV instruments.

Posted in: Briefs

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Design and Analysis of Metal-to-Composite Nozzle Extension Joints

A design concept and subcomponent are identified that mitigate the stress associated with the coefficient-of-thermal mismatch. Marshall Space Flight Center, Alabama Analysis, design, fabrication, and testing were performed to create a new joint design for potential use in attaching a domestically available carbon-carbon (C–C) nozzle extension to the turbine exhaust manifold of a J-2X engine. Various attachment methods were investigated for a C–C-to-metallic joint, including the use of higher-thermal-expansion ceramic matrix composites both mechanically attached and also integrally fabricated to the C–C nozzle extension. The goal was to determine the advantages and disadvantages of different material and joint systems in order to converge on a design for a domestic joint and nozzle extension design that resulted in all positive margins of safety.

Posted in: Briefs

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Modeling Laser Ablation and Plume Chemistry in a Boron Nitride Nanotube Production Rig

Langley Research Center, Hampton, Virginia The future of manned and unmanned spaceflight and exploration depends on economical access to space through multifunctional, lightweight materials. Boron nitride nanotube (BNNT) composites offer distinct advantages for enhanced survivability during long-term flights. A production technique has been developed to manufacture BNNTs that implements laser energy deposition on a boron sample in a pressurized test rig.

Posted in: Briefs, TSP

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Damage-Free Finishing of Silicon X-Ray Optics Using Magnetic Field-Assisted Finishing

Goddard Space Flight Center, Greenbelt, Maryland Thin, segmented mirrors have been fabricated from monocrystalline silicon blocks. The material is economically viable, and is virtually free of internal stress because of its nearly perfect crystalline structure. The mirror surfaces will first be accurately figured and finished on thick silicon blocks, then sliced off at the desired thickness by wire electro-discharge machining. A finishing process has been conceived in which existing mirror-finishing processes are adapted to be capable of quickly and accurately figuring and finishing damage-free, segmented, monocrystalline silicon mirrors in a cost-efficient manner.

Posted in: Briefs, TSP

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Smart Crucibles and Heat Pipes

Molybdenum and molybdenum alloys are the leading candidates for making the new heat pipe modules. Marshall Space Flight Center, Alabama Near-net-shape vacuum plasma spray (VPS) forming techniques were developed to produce advanced components with internal features such as smart heat pipes and crucibles. The initial results demonstrated the ability to incorporate features such as channels and a porous layer within the wall of a smart crucible.

Posted in: Briefs

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Multi-Step DRIE Process to Fabricate Silicon-Based THz Components

Commercial applications include airport screening systems, explosives detectors, nondestructive testing, and wireless communications. NASA’s Jet Propulsion Laboratory, Pasadena, California Terahertz (THz) frequency radiometers, spectrometers, and radars are promising instruments for the remote sensing of planetary atmospheres such as Mars, Venus, Jupiter, and Saturn, and their moons such as Titan, Europa, Ganymede, and others. For these long-term planetary missions, severe constraints are put on the mass and power budget for the payload instruments.

Posted in: Briefs, TSP

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Plasma Reduction of Lunar Regolith for In-Space Fabrication

Plasma processing effectively produced agglutinate and glassy spherules — analog particles similar to those found on the lunar surface. Marshall Space Flight Center, Alabama The in situ production of vital gases and raw materials on the lunar surface is an integral part of NASA’s exploration vision. Development of processes for extraction of oxygen and metallics from the lunar regolith will be vital not only for life support on the lunar surface, but also for spacecraft propulsion to travel further beyond low Earth orbit. This will have a direct impact on cost reduction associated with minimizing the raw material mass from Earth. Aside from utilization of in situ resources, one of the significant limitations of current simulant is the lack of constituents, such as agglutinates. These agglutinates are typically mineral fragments of the lunar regolith that are held together by glass and, depending on location, may constitute 60% to 70% of the lunar regolith.

Posted in: Briefs

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