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Back Actuators for Segmented Mirrors and Other Applications

Actuation mechanisms could be simpler. Back actuators have been proposed as alternatives to edge actuators considered previously for use in aligning hexagonal segments of lightweight segmented astronomical mirrors planned for use in outer space. The proposed back actuators could also be useful on Earth as parts of wafer-conveyance systems in the semiconductor industry.

Posted in: Mechanical Components, Briefs, TSP

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Mechanism for Self-Reacted Friction Stir Welding

This mechanism performs better than others that have been tried. A mechanism has been designed to apply the loads (the stirring and the resection forces and torques) in self-reacted friction stir welding. This mechanism differs somewhat from mechanisms used in conventional friction stir welding, as described below.

Posted in: Mechanical Components, Briefs

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Simple Systems for Detecting Spacecraft Meteoroid Punctures

A report describes proposed systems to be installed in spacecraft to detect punctures by impinging meteoroids or debris. Relative to other systems that have been used for this purpose, the proposed systems would be simpler and more adaptable, and would demand less of astronauts' attention and of spacecraft power and computing resources. The proposed systems would include a thin, hollow, hermetically sealed panel containing an inert fluid at a pressure above the spacecraft cabin pressure. A transducer would monitor the pressure in the panel. It is assumed that an impinging object that punctures the cabin at the location of the panel would also puncture the panel. Because the volume of the panel would be much smaller than that of the cabin, the panel would lose its elevated pressure much faster than the cabin would lose its lower pressure. The transducer would convert the rapid pressure drop to an electrical signal that could trigger an alarm. Hence, the system would provide an immediate indication of the approximate location of a small impact leak, possibly in time to take corrective action before a large loss of cabin pressure could occur.

Posted in: Mechanical Components, Briefs

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Using Iron To Treat Chlorohydrocarbon Contaminated Soil

Prompt chemical remediation is followed by longer-term enhanced bioremediation. A method of in situ remediation of soil contaminated with chlorinated hydrocarbon solvents involves injection of nanometer-size iron particles. This method should not be confused with a similar method, involving injection of emulsified iron particles, reported in “Treatment To Destroy Chlorohydrocarbon Liquids in the Ground” (KSC-12246), NASA Tech Briefs, Vol. 27, No. 6 (June 2003), page 56. Like that method, this method is implemented in a process that is safe, yields environmentally benign end products, takes less time and costs less than do traditional pump-and-treat processes, and is both less expensive and less environmentally disruptive than are cleanup processes that involve excavation, trans-port to facilities for incineration or other treatment, and reburial in landfills.

Posted in: Materials, Briefs

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Software For Use With Optoelectronic Measuring Tool

A computer program has been written to facilitate and accelerate the process of measurement by use of the apparatus described in “Optoelectronic Tool Adds Scale Marks to Photographic Images” (KSC-12201), NASA Tech Briefs, Vol. 27, No. 1 (January 2003), page 6a. To recapitulate: The tool contains four laser diodes that generate parallel beams of light spaced apart at a known distance. The beams of light are used to project bright spots that serve as scale marks that become incorporated into photographic images (including film and electronic images). The sizes of objects depicted in the images can readily be measured by reference to the scale marks.

Posted in: Information Sciences, Briefs, TSP

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Coordinating Shared Activities Shared Activity

Coordination (ShAC) is a computer program for planning and scheduling the activities of an autonomous team of interacting spacecraft and exploratory robots. ShAC could also be adapted to such terrestrial uses as helping multiple factory managers work toward competing goals while sharing such common resources as floor space, raw materials, and transports. ShAC iteratively invokes the Continuous Activity Scheduling Planning Execution and Replanning (CASPER) program to replan and propagate changes to other planning programs in an effort to resolve conflicts. A domain-expert specifies which activities and parameters thereof are shared and reports the expected conditions and effects of these activities on the environment. By specifying these conditions and effects differently for each planning program, the domain-expert subprogram defines roles that each spacecraft plays in a coordinated activity. The domain-expert subprogram also specifies which planning program has scheduling control over each shared activity. ShAC enables sharing of information, consensus over the scheduling of collaborative activities, and distributed conflict resolution. As the other planning programs incorporate new goals and alter their schedules in the changing environment, ShAC continually coordinates to respond to unexpected events.

Posted in: Information Sciences, Briefs, TSP

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Software Reduces Radio-Interference Effects in Radar Data

A computer program suppresses the effects of narrow-band radio-frequency interference (RFI) on the data collected by a wide-band radar system. The need for this program arises because some advanced wide-band synthetic-aperture radar systems utilize frequency bands that include frequencies used by other radio services. In this program, the RFI environment is represented by an autoregressive process, the frequency band of which is narrow relative to that of the radar. Most of the RFI signals, both narrow-and wide-band, are estimated in one pass of a least-mean-square (LMS) adaptive filter. The program implements three popular LMS algorithms:the time-domain LMS, the frequency-domain LMS, and the filter-bank LMS adaptive-filter algorithms. The program can be run in a manual or automatic mode. In the manual mode, the user selects the filter parameters prior to execution. In the automatic mode, the program utilizes median-filter and spectral-estimation techniques plus the variable-step-size LMS algorithm for automatic determination of filter parameters, and the parameters are adaptively changed as functions of the inputs, resulting in better overall performance.

Posted in: Information Sciences, Briefs, TSP

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