Manufacturing & Prototyping

Fabrication of Submillimeter Axisymmetric Optical Components

Surfaces of components can be arbitrarily shaped to optimize spectral responses. It is now possible to fashion transparent crystalline materials into axisymmetric optical components having diameters ranging from hundreds down to tens of micrometers, whereas previously, the smallest attainable diameter was 500 m. A major step in the fabrication process that makes this possible can be characterized as diamond turning or computer numerically controlled machining on an ultrahigh-precision lathe. This process affords the flexibility to make arbitrary axisymmetric shapes that have various degrees of complexity: examples include a flat disk or a torus supported by a cylinder (see figure), or multiple closely axially spaced disks or tori supported by a cylinder. Such optical components are intended mainly for use as whispering-gallery- mode optical resonators in diverse actual and potential applications, including wavelength filtering, modulation, photonic generation and detection of microwaves, and research in quantum electrodynamics and quantum optics.

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Process for Polishing Bare Aluminum to High Optical Quality

India-ink polishing following single-point diamond turning yields superior aluminum optics. A process for making precise, high-quality curved or flat mirror surfaces on bare aluminum substrates has been devised. The process consists of (1) diamond turning to establish the desired surface figure, followed by (2) a polishing subprocess that is mostly conventional except for the composition of the polishing compound. This process can maintain a surface figure accurate to within a peak-to-valley error of as little as 1/8 wavelength (at a wavelength of 6,328 Å) and can produce a finish characterized by a root-mean-square roughness of

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Radiation-Shielding Polymer/Soil Composites

Radiation shields could be fabricated in situ at relatively low cost. It has been proposed to fabricate polymer/soil composites primarily from extraterrestrial resources, using relatively lowenergy processes, with the original intended application being that habitat structures constructed from such composites would have sufficient structural integrity and also provide adequate radiation shielding for humans and sensitive electronic equipment against the radiation environment on the Moon and Mars. The proposal is a response to the fact that it would be much less expensive to fabricate such structures in situ as opposed to transporting them from Earth.

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Film/Adhesive Processing Module for Fiber-Placement Processing of Composites

Films, foils, or adhesives may be interleaved while fiber-placing composite material structures. An automated apparatus has been designed and constructed that enables the automated lay-up of composite structures incorporating films, foils, and adhesives during the automated fiberplacement process. This apparatus, denoted a film module, could be used to deposit materials in film or thin sheet form either simultaneously when laying down the fiber composite article or in an independent step. Examples of materials that may be processed with this device include structural core and joining adhesives, permeation barrier films/foils, surfacing films, lightning-strike materials and IVHM (Integral Vehicle Health Monitoring) arrays. The use of this technology will reduce composite fabrication time and will allow for new concepts/ designs to be considered for fiber-placed composite structures.

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Automated Solvent Seaming of Large Polyimide Membranes

Success depends on precise control of all relevant process details. A solvent-based welding process enables the joining of precise, cast polyimide membranes at their edges to form larger precise membranes. The process creates a homogeneous, optical - quality seam between abutting membranes, with no overlap and with only a very localized area of figure disturbance. The seam retains 90 percent of the strength of the parent material. The process was developed for original use in the fabrication of wide - aperture membrane optics, with areal densities densities of less than 1 kg/m2, for lightweight telescopes, solar concentrators, antennas, and the like to be deployed in outer space. The process is just as well applicable to the fabrication of large precise polyimide membranes for flat or inflatable solar concentrators and antenna reflectors for terrestrial applications.

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Manufacturing Precise, Lightweight Paraboloidal Mirrors

Success depends on the proper selection of materials and process conditions. A process for fabricating a precise, diffraction- limited, ultralightweight, composite-material (matrix/fiber) paraboloidal telescope mirror has been devised. Unlike the traditional process of fabrication of heavier glass-based mirrors, this process involves a minimum of manual steps and subjective judgment. Instead, this process involves objectively controllable, repeatable steps; hence, this process is better suited for mass production.

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Heat Treatment of Friction-Stir-Welded 7050 Aluminum Plates

Strength, ductility, and resistance to stress corrosion cracking are increased. A method of heat treatment has been developed to reverse some of the deleterious effects of friction stir welding of plates of aluminum alloy 7050. This alloy is considered unweldable by arc and high-energy-density beam fusion welding processes. The alloy can be friction stir welded, but as-welded workpieces exhibit low ductility, low tensile and yield strengths, and low resistance to stress corrosion cracking. Heat treatment according to the present method increases tensile and yield strengths, and minimizes or eliminates stress corrosion cracking. It also increases ductility.

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