Manufacturing & Prototyping

Gratings Fabricated on Flat Surfaces and Reproduced on Non-Flat Substrates

A method has been developed for fabricating gratings on flat substrates, and then reproducing the groove pattern on a curved (concave or convex) substrate and a corresponding grating device. First, surface relief diffraction grating grooves are formed on flat substrates. For example, they may be fabricated using photolithography and reactive ion etching, maskless lithography, holography, or mechanical ruling. Then, an imprint of the grating is made on a deformable substrate, such as plastic, polymer, or other materials using thermoforming, hot or cold embossing, or other methods. Interim stamps using electroforming, or other methods, may be produced for the imprinting process or if the same polarity of the grating image is required. The imprinted, deformable substrate is then attached to a curved, rigid substrate using epoxy or other suitable adhesives. The imprinted surface is facing away from the curved rigid substrate.

Posted in: Briefs, TSP, Manufacturing & Prototyping, Fabrication, Manufacturing equipment and machinery, Stamping

Fabricating Radial Groove Gratings Using Projection Photolithography

Projection photolithography has been used as a fabrication method for radial grove gratings. Use of photolithographic method for diffraction grating fabrication represents the most significant breakthrough in grating technology in the last 60 years, since the introduction of holographic written gratings. Unlike traditional methods utilized for grating fabrication, this method has the advantage of producing complex diffractive groove contours that can be designed at pixel-by-pixel level, with pixel size currently at the level of 45×45 nm. Typical placement accuracy of the grating pixels is 10 nm over 30 nm. It is far superior to holographic, mechanically ruled or direct e-beam written gratings and results in high spatial coherence and low spectral cross-talk. Due to the smooth surface produced by reactive ion etch, such gratings have a low level of randomly scattered light. Also, due to high fidelity and good surface roughness, this method is ideally suited for fabrication of radial groove gratings.

Posted in: Briefs, Manufacturing & Prototyping, CAD, CAM, and CAE, Lasers, Fabrication, Finishing

Discrete Fourier Transform Analysis in a Complex Vector Space

Alternative computational strategies for the Discrete Fourier Transform (DFT) have been developed using analysis of geometric manifolds. This approach provides a general framework for performing DFT calculations, and suggests a more efficient implementation of the DFT for applications using iterative transform methods, particularly phase retrieval. The DFT can thus be implemented using fewer operations when compared to the usual DFT counterpart. The software decreases the run time of the DFT in certain applications such as phase retrieval that iteratively call the DFT function. The algorithm exploits a special computational approach based on analysis of the DFT as a transformation in a complex vector space. As such, this approach has the potential to realize a DFT computation that approaches N operations versus Nlog(N) operations for the equivalent Fast Fourier Transform (FFT) calculation.

Posted in: Briefs, Manufacturing & Prototyping

Self-Assembling, Flexible, Pre-Ceramic Composite Preforms

Pliable, unfired preforms deploy in-situ to save fuel and weight costs.

In this innovation, light weight, high temperature, compact aerospace structures with increased design options are made possible by using self-assembling, flexible, pre-ceramic composite materials. These materials are comprised of either ceramic or carbon fiber performs, which are infiltrated with polymer precursors that convert to ceramics upon thermal exposure. The preform architecture can vary from chopped fibers formed into blankets or felt, to continuous fibers formed into a variety of 2D or 3D weaves or braids. The matrix material can also vary considerably. For demonstration purposes, a 2D carbon weave was infiltrated with a SiC polymer precursor. The green or unfired material is fabricated into its final shape while it is still pliable. It is then folded or rolled into a much more compact shape, which will occupy a smaller space. With this approach, the part remains as one continuous piece, rather than being fabricated as multiple sections, which would require numerous seals for eventual component use. The infiltrated preform can then be deployed in-situ. The component can be assembled into its final shape by taking advantage of the elasticity of the material, which permits the structure to unfold and spring into its final form under its own stored energy. The pre-ceramic composites are converted to ceramics and rigidized immediately after deployment.

Posted in: Briefs, TSP, Manufacturing & Prototyping, Aircraft structures, Assembling, Ceramics, Composite materials, Fibers

Miniature Scroll Pumps Fabricated by LIGA

These would serve as roughing pumps for vacuum systems of miniature instruments.

Miniature scroll pumps have been proposed as roughing pumps (low-vacuum pumps) for miniature scientific instruments (e.g., portable mass spectrometers and gas analyzers) that depend on vacuum. The larger scroll pumps used as roughing pumps in some older vacuum systems are fabricated by conventional machining. Typically, such an older scroll pump includes (1) an electric motor with an eccentric shaft to generate orbital motion of a scroll and (2) conventional bearings to restrict the orbital motion to a circle.

Posted in: Briefs, TSP, Manufacturing & Prototyping

Mercuric Iodide Anticoincidence Shield for Gamma-Ray Spectrometer

A film-growth process was developed for polycrystalline mercuric iodide that creates cost-effective, large-area detectors for high- energy charged-particle detection. A material, called a barrier film, is introduced onto the substrate before the normal mercuric iodide film growth process. The barrier film improves the quality of the normal film grown and enhances the adhesion between the film and the substrate.

Posted in: Briefs, Manufacturing & Prototyping, Spectroscopy, Materials properties

Improved Method of Design for Folding Inflatable Shells

Designs of gores reflect multiple considerations of assembly, stowage, and deployment.

An improved method of designing complexly shaped inflatable shells to be assembled from gores was conceived for original application to the inflatable outer shell of a developmental habitable spacecraft module having a cylindrical midlength section with toroidal end caps.

Posted in: Briefs, TSP, Manufacturing & Prototyping

High-Efficiency Artificial Photosynthesis Using a Novel Alkaline Membrane Cell

Successful artificial photosynthesis is significant for future human/robotic exploration and terrestrial carbon emissions control.

A new cell designed to mimic the photosynthetic processes of plants to convert carbon dioxide into carbonaceous products and oxygen at high efficiency, has an improved configuration using a polymer membrane electrolyte and an alkaline medium. This increases efficiency of the artificial photosynthetic process, achieves high conversion rates, permits the use of inexpensive catalysts, and widens the range of products generated by this type of process.

Posted in: Briefs, TSP, Manufacturing & Prototyping

Silicon Wafer-Scale Substrate for Microshutters and Detector Arrays

These substrates can be used in photomask generation and stepper equipment used to make ICs and MEMS devices.

The silicon substrate carrier was created so that a large-area array (in this case 62,000+ elements of a microshutter array) and a variety of discrete passive and active devices could be mounted on a single board, similar to a printed circuit board. However, the density and number of interconnects far exceeds the capabilities of printed circuit board technology. To overcome this hurdle, a method was developed to fabricate this carrier out of silicon and implement silicon integrated circuit (IC) technology. This method achieves a large number of high-density metal interconnects; a 100-percent yield over a 6-in. (≈15-cm) diameter wafer (one unit per wafer); a rigid, thermally compatible structure (all components and operating conditions) to cryogenic temperatures; re-workability and component replaceability, if required; and the ability to precisely cut large-area holes through the substrate.

Posted in: Briefs, TSP, Manufacturing & Prototyping, Antennas, Architecture, Integrated circuits, Metals, Silicon alloys

Inert Welding/Brazing Gas Filters and Dryers

This system can be used in any process requiring reduction of inert-gas moisture level.

A system has been designed to reduce the hydrogen molecule content in inert gases that are used for shielding the welding arc and molten weld area during the manual fusion, automated welding, and induction brazing process. Two desiccant pipeline dryer cartridges are connected together using either aircraft or KC .250 fittings, and are installed in-line between the inert-gas facility source (argon and helium) and the welding machine. This process helps maintain alloy grain structure and integrity to engineering specifications during the welding and brazing processes. Also, this method enhances weldability when joining similar and dissimilar alloys. It is easy to restore the system to original drying capabilities by using a nitrogen purge or by oven drying. This design has low schedule impact or down time when being installed on machines or in systems. There is also a sight glass to indicate when servicing is needed.

Posted in: Briefs, TSP, Manufacturing & Prototyping, Drying, Welding, Gases

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