Tech Briefs

Optimization of Orientations of Spacecraft Reaction Wheels

A report presents a method of optimizing the orientations of three reaction wheels used to regulate the angular momentum of a spacecraft. The method yields an orientation matrix that minimizes mass, torque, and power demand of the reaction wheels while maximizing the allowable duration between successive angular-momentum dumps. Each reaction wheel is parameterized with its own unit vector, and a quadratic cost function is defined based on requirements for torque, storage of angular momentum, and power demand. Because management of angular momentum is a major issue in designing and operating an orbiting spacecraft, an angular-momentum-management strategy is parameterized and included as part of the overall optimization process. The report describes several case studies, including one of a spacecraft proposed to be placed in orbit around Europa (the fourth largest moon of Jupiter).

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Analytic Method for Computing Instrument Pointing Jitter

Jitter can be computed more efficiently. A new method of calculating the root-mean-square (rms) pointing jitter of a scientific instrument (e.g., a camera, radar antenna, or telescope) is introduced based on a state-space concept. In comparison with the prior method of calculating the rms pointing jitter, the present method involves significantly less computation.

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Deforming Fibrous Insulating Tiles To Fit Curved Surfaces

Flat billets are heated and pressed gently against curved mold surfaces. A curved tile of refractory silica-fiber-based or alumina-fiber-based thermal-insulation material can be formed from an initially flat billet in a process that includes pressing against a curved mold surface during heating. The mold or tile curvature can be concave or convex. Curved tiles are needed for thermal protection of curved surfaces of spacecraft reentering the terrestrial atmosphere; curved thermal-protection tiles may also be useful on Earth in some industrial applications.

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Micromachining of a Mesoscale Vibratory Gyroscope

High-performance miniature gyroscopes would be fabricated by established micromachining techniques. A micromachining-based fabrication process has been proposed for low-volume production of copies of a mesoscale vibratory gyroscope. The process would include steps of photolithography, metallization, deep reactive-ion etching (RIE), Au/Au thermal-compression bonding, and anodic bonding. In the present state of the art, these process steps are well established and the process as a whole would be considered reproducible.

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Software Optimizes Piping System for Sewage Treatment Plant

A $90 million AUS (Australian dollar) upgrade ($49 million USD) to the Cronulla Sewage Treatment Plant in Southern Sydney, Australia, was undertaken to meet the requirements of a growing population and to add advanced sewage treatment processes including ultraviolet disinfection. During the design phase, a cost-effective engineering solution needed to be developed for a new aeration system that provides air to the biological reactors. Design, Detail and Development, a division of Blenray Pty. Ltd., used ALGOR's piping design and analysis software, PipePak, to analyze modifications to the aeration system to ensure that the new design could withstand expected thermal strains. The initial design contained numerous, expensive stainless steel bellows to account for thermal expansion and contraction. The final design of the system replaced bellows with spiral-wound stainless steel, which saved $150,000 AUS ($81,800 USD) and helped to keep the project on budget. The system has been installed and is functioning successfully.

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Quantum Search in Hilbert Space

A large database would be searched in one quantum computing operation. A proposed quantum-computing algorithm would perform a search for an item of information in a database stored in a Hilbert-space memory structure. The algorithm is intended to make it possible to search relatively quickly through a large database under conditions in which available computing resources would otherwise be considered inadequate to perform such a task.

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Wavelet-Based Real-Time Diagnosis of Complex Systems

Changes in hardware and software can be simultaneously examined for signs of loss of control. A new method of robust, autonomous real-time diagnosis of a time-varying complex system (e.g., a spacecraft, an advanced aircraft, or a process-control system) is presented here. It is based upon the characterization and comparison of (1) the execution of software, as reported by discrete data, and (2) data from sensors that monitor the physical state of the system, such as performance sensors or similar quantitative time-varying measurements. By taking account of the relationship between execution of, and the responses to, software commands, this method satisfies a key requirement for robust autonomous diagnosis, namely, ensuring that control is maintained and followed.

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