Tech Briefs

Accurate Spring Testing

Load-testing machine features can affect the accuracy, precision, repeatability, and reproducibility of test results. Virtually all spring manufacturers must test their products with some kind of load testing machine. Testing ensures that the product is produced and shipped within the customer's specifications. Or does it? Disputes over test results still occur that can cause a multitude of costly problems: returned product, delayed payment, product liability, or customer dissatisfaction. The quality of a spring testing program can largely affect these problems and their associated cost.

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Pneumatically Actuated Miniature Peristaltic Vacuum Pumps

Small, rugged, low-power pumps could be fabricated inexpensively. Pneumatically actuated miniature peristaltic vacuum pumps have been proposed for incorporation into advanced miniature versions of scientific instruments that depend on vacuum for proper operation. These pumps are expected to be capable of reaching vacuum-side pressures in the torr to millitorr range (from ≈133 down to ≈0.13 Pa). Vacuum pumps that operate in this range are often denoted roughing pumps. In comparison with previously available roughing pumps, these pumps are expected to be an order of magnitude less massive and less power-hungry. In addition, they would be extremely robust, and would operate with little or no maintenance and without need for oil or other lubricants. Portable mass spectrometers are typical examples of instruments that could incorporate the proposed pumps. In addition, the proposed pumps could be used as roughing pumps in general laboratory applications in which low pumping rates could be tolerated.

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Miniature Gas-Turbine Power Generator

Energy density would greatly exceed that of a typical battery system. A proposed microelectromechanical system (MEMS) containing a closed- Brayton-cycle turbine would serve as a prototype of electric- power generators for special applications in which high energy densities are required and in which, heretofore, batteries have been used. The system would have a volume of about 6 cm3 and would operate with a thermal efficiency >30 percent, generating up to 50 W of electrical power. The energy density of the proposed system would be about 10 times that of the best battery-based systems now available, and, as such, would be comparable to that of a fuel cell.

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Code for Analyzing and Designing Spacecraft Power System Radiators

GPHRAD is a computer code for analysis and design of disk or circular-sector heatrejecting radiators for spacecraft power systems. A specific application is for Stirlingcycle/linear-alternator electric-power systems coupled to radioisotope general-purpose heat sources. GPHRAD affords capabilities and options to account for thermophysical properties (thermal conductivity, density) of either metal-alloy or composite radiator materials. GPHRAD also enables specification of a heat-pipe radiator design with a radial location of the embedded heat-pipe condenser section determined numerically so that minimum radiator area is obtained. Alternatively, the user can specify a radial location of the heat-pipe condenser section for easier assembly with other components. In this case, GPHRAD determines the tradeoff cost in increased radiator area for this choice. A third option is to design a radiator without heat pipes, with heat flowing radially outward from the cylindrical cold section of the Stirling power system. A major subroutine, TSCALC, calculates an equilibrium sink temperature for a radiator, taking account of the solar absorptivity and thermal emissivity of the radiator surface, the spacecraft-to-Sun distance expressed in astronomical units (AU), the angle at which solar radiation is incident on the radiator surface, and the view factor to space of the radiator surface and the infrared absorptivity-to-emissivity ratio for planetary thermal radiation, if any. The sink temperature, along with the heatsource temperature and properties of the radiator material, serve as inputs to the GPHRAD code, which then calculates dimensions of, and temperature distribution within the radiator for a required heatrejection load at given heat-rejection source temperature, such as the Stirling power system “cold” side temperature. The option to specify the disk tip-to-hub thickness ratio permits investigation of mass savings achieved by trapezoidal of parabolic tapering of the disk radiator design.

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Decision Support for Emergency Operations Centers

The Flood Disaster Mitigation Decision Support System (DSS) is a computerized information system that allows regional emergency-operations government officials to make decisions regarding the dispatch of resources in response to flooding. The DSS implements a real-time model of inundation utilizing recently acquired lidar elevation data as well asreal-time data from flood gauges, and other instruments within and upstream of an area that is or could become flooded. The DSS information is updated as new data become available. The model generates real-time maps of flooded areas and predicts flood crests at specified locations. The inundation maps are overlaid with information on population densities, property values, hazardous materials, evacuation routes, official contact information, and other information needed for emergency response. The program maintains a database and a Web portal through which real-time data from instrumentation are gathered into the database. Also included in the database is a geographic information system, from which the program obtains the overlay data for areas of interest as needed. The portal makes some portions of the database accessible to the public. Access to other portions of the database is restricted to government officials according to various levels of authorization. The Flood Disaster Mitigation DSS has been integrated into a larger DSS named REACT (Real-time Emergency Action Coordination Tool), which also provides emergency operations managers with data for any type of impact area such as floods, fires, bomb emergencies, and the like.

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NASA Records Database

The NASA Records Database, comprising a Web-based application program and a database, is used to administer an archive of paper records at Stennis Space Center. The system begins with an electronic form, into which a user enters information about records that the user is sending to the archive. The form is “smart”: it provides instructions for entering information correctly and prompts the user to enter all required information. Once complete, the form is digitally signed and submitted to the database. The system determines which storage locations are not in use, assigns the user’s boxes of records to some of them, and enters these assignments in the database. Thereafter, the software tracks the boxes and can be used to locate them. By use of search capabilities of the software, specific records can be sought by box storage locations, accession numbers, record dates, submitting organizations, or details of the records themselves. Boxes can be marked with such statuses as checked out, lost, transferred, and destroyed. The system can generate reports showing boxes awaiting destruction or transfer. When boxes are transferred to the National Archives and Records Administration (NARA), the system can automatically fill out NARA records-transfer forms. Currently, several other NASA Centers are considering deploying the NASA Records Database to help automate their records archives.

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Real-Time Principal-Component Analysis

A recently written computer program implements dominant-element-based gradient descent and dynamic initial learning rate (DOGEDYN), which was described in “Method of Real-Time Principal-Component Analysis” (NPO-40034) NASA Tech Briefs, Vol. 29, No. 1 (January 2005), page 59. To recapitulate: DOGEDYN is a method of sequential principal-component analysis (PCA) suitable for such applications as data compression and extraction of features from sets of data. In DOGEDYN, input data are represented as a sequence of vectors acquired at sampling times. The learning algorithm in DOGEDYN involves sequential extraction of principal vectors by means of a gradient descent in which only the dominant element is used at each iteration. Each iteration includes updating of elements of a weight matrix by amounts proportional to a dynamic initial learning rate chosen to increase the rate of convergence by compensating for the energy lost through the previous extraction of principal components. In comparison with a prior method of gradient-descent-based sequential PCA, DOGEDYN involves less computation and offers a greater rate of learning convergence. The sequential DOGEDYN computations require less memory than would parallel computations for the same purpose. The DOGEDYN software can be executed on a personal computer.

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