Manufacturing & Prototyping

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.

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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.

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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.

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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.

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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.

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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.

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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.

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