Tech Briefs

Simultaneous Product Development Provides a New Approach to Design Collaboration

This approach enables sharing and merging of any element of a digital model, and allows collaborative data to flow in any direction. Product development is becoming increasingly global and as a result, new challenges have emerged,such as coordinating geographically dispersed teams of suppliers and partners. Consequently, the modern enterprise is more similar to a network of interconnected nodes that work in parallel and need constant dynamic synchronization. The widespread adoption of digital design documents, the introduction of collaboration tools like Web-based review and mark-up, and Internet-accessible databases have made design data more readily available.

Posted in: Briefs, Information Sciences

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Brazing SiC/SiC Composites to Metals

Success depends on suitable process conditions and adequate titanium contents in brazing alloys. Experiments have shown that active brazing alloys (ABAs) can be used to join SiC/SiC composite materials to metals, with bond strengths sufficient for some structural applications. The SiC/SiC composite coupons used in the experiments were made from polymer-based SiC fiber preforms that were chemical-vapor- infiltrated with SiC to form SiC matrices. Some of the metal coupons used in the experiments were made from 304 stainless steel;others were made from oxygen-free, high-conductivity copper.

Posted in: Briefs, Materials

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Composite-Material Tanks With Chemically Resistant Liners

Liner materials are chosen for compatibility with reactive and/or unstable fluids. Lightweight composite-material tanks with chemically resistant liners have been developed for storage of chemically reactive and/or unstable fluids — especially hydrogen peroxide. These tanks are similar, in some respects, to the ones described in — Lightweight Composite-Material Tanks for Cryogenic Liquids — (MFS-31379), NASA Tech Briefs, Vol.25, No.1 (January, 2001), page 58; however, the present tanks are fabricated by a different procedure and they do not incorporate insulation that would be needed to prevent boil-off of cryogenic fluids.

Posted in: Briefs, TSP, Materials

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Improved BN Coatings on SiC Fibers in SiC Matrices

Outside debonding would be favored over inside debonding. Modifications of BN-based coatings that are used as interfacial layers between the fibers and matrices of SiC-fiber/SiC-matrix composite materials have been investigated to improve the thermomechanical properties of these materials. Such interfacial coating layers, which are also known as interphases (not to be confused with "interphase" in the biological sense), contribute to strength and fracture toughness of a fiber/matrix composite material by providing for limited amounts of fiber/matrix debonding and sliding to absorb some of the energy that would otherwise contribute to the propagation of cracks.

Posted in: Briefs, TSP, Materials

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Simulating Operation of a Planetary Rover

Simulating Operation of a Planetary Rover Rover Analysis, Modeling, and Simulations (ROAMS) is a computer program that simulates the operation of a robotic vehicle (rover) engaged in exploration of a remote planet. ROAMS is a rover-specific extension of the DARTS and Dshell programs, described in prior NASA Tech Briefs articles, which afford capabilities for mathematical modeling of the dynamics of a spacecraft as a whole and of its instruments,actuators, and other subsystems. ROAMS incorporates mathematical models of kinematics and dynamics of rover mechanical subsystems, sensors, interactions with terrain, solar panels and batteries, and onboard navigation and locomotion-control software. ROAMS provides a modular simulation framework that can be used for analysis, design, development, testing,and operation of rovers. ROAMS can be used alone for system performance and trade studies. Alternatively, ROAMS can be used in an operator-in-the-loop or flight-software closed-loop environment. ROAMS can also be embedded within other software for use in analysis and development of algorithms,or for Monte Carlo studies, using a variety of terrain models, to generate performance statistics. Moreover, taking advantage of real-time features of the underlying DARTS/Dshell simulation software, ROAMS can also be used for real-time simulations.

Posted in: Briefs, TSP, Mechanical Components

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Silicone-Rubber Microvalves Actuated by Paraffin

Relative to other microvalves, these would be simpler. Microvalves containing silicone-rubber seals actuated by heating and cooling of paraffin have been proposed for development as integral components of microfluidic systems. In comparison with other microvalves actuated by various means (electrostatic, electro-magnetic, piezoelectric, pneumatic, and others), the proposed valves (1) would contain simpler structures that could be fabricated at lower cost and (2) could be actuated by simpler (and thus less expensive) control systems.

Posted in: Briefs, TSP, Mechanical Components

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Flexible Shields for Protecting Spacecraft Against Debris

A report presents the concept of Flexshield —a class of versatile, light-weight, flexible shields for protecting spacecraft against impacts by small meteors and orbiting debris. The Flexshield concept incorporates elements of, but goes beyond, prior space-craft-shielding concepts, including those of Whipple shields and, more recently, multi-shock shields and multi-shock blankets. A shield of the Flexshield type includes multiple outer layers (called “bumpers” in the art) made, variously, of advanced ceramic and/or polymeric fibers spaced apart from each other by a lightweight foam.As in prior such shields, the bumpers serve to shock an impinging hypervelocity particle, causing it to disintegrate, vaporize, and spread out over a larger area so that it can be stopped by an innermost layer (back sheet). The flexibility of the fabric layers and compressibility of the foam make it possible to compress and fold the shield for transport,then deploy the shield for use. The shield can be attached to a spacecraft by use of snaps, hook-and-pile patches,or other devices. The shield can also contain multilayer insulation material, so that it provides some thermal protection in addition to mechanical protection.

Posted in: Briefs, Mechanical Components

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