Independent Orbiter Assessment (IOA): Assessment of instrumental subsystem FMEA/CIL

The McDonnell Douglas Astronautics Company (MDAC) was selected in June 1986 to perform an Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL). The IOA effort first completed an analysis of the Instrumentation hardware, generating draft failure modes and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The IOA results were then compared to the NASA FMEA/CIL baseline. A resolution of each discrepancy from the comparison is provided through additional analysis as required. The results of that comparison for the Orbiter Instrumentation hardware are documented. The IOA product for Instrumentation analysis consisted of 107 failure mode worksheets that resulted in 22 critical items being identified. Comparison was made to the Pre 51-L NASA baseline with 14 Post 51-L FMEAs added, which consists of 96 FMEAs and 18 CIL items. This comparison produced agreement on all but 25 FMEAs which caused differences in 5 CIL items

Silicon MINP solar cells

The MINP solar cell concept refers to a cell structure designed to be a base region dominated device. Thus, it is desirable that recombination losses are reduced to the point that they occur only in the base region. The most unique feature of the MINP cell design is that a tunneling contact is utilized for the metallic contact on the front surface. The areas under the collector grid and bus bar are passivated by a thin oxide of tunneling thickness. Efforts must also be taken to minimize recombination at the surface between grid lines, at the junction periphery and within the emitter. Results of both theoretical and experimental studies of silicon MINP cells are given. Performance calculations are described which give expected efficiencies as a function of base resistivity and junction depth. Fabrication and characterization of cells are discussed which are based on 0.2 ohm-cm substrates, diffused emitters on the order of 0.15 to 0.20 microns deep, and with Mg MIS collector grids. A total area AM 1 efficiency of 16.8% was achieved. Detailed analyses of photocurrent and current loss mechanisms are presented and utilized to discuss future directions of research. Finally, results reported by other workers are discussed

Study of orbiter/payload interface communications configuration control board directive from an operational perspective

Orbiter/payload data and communications interface was examined. It was found that the Configuration Control Board Directive (CCBD) greatly increases the capability of the orbiter to communicate with a wide variety of projected shuttle payloads. Rather than being derived from individual payload communication requirements, the CCBD appears to be based on an operational philosophy that requires the orbiter to duplicate or augment the ground network/payload communication links. It is suggested that the implementation of the CCBD be reviewed and compared with the Level 1 Program Requirements Document, differences reconciled, and interface characteristics defined

Analysis of Selected Physicochemical Parameters of Soils Used for Cultivation of Garlic (Allium sativum L.)

Assessment of some selected physicochemical parameters in soil samples collected from four agricultural areas of East Gojjam Zone (Debre Markos, Dejen, Bichena and Debre Werk), Ethiopia was studied. The soil characterization was carried out for parameters like moisture content (MC), pH, electrical conductivity (EC), organic carbon (OC), organic matter (OM), cation exchange capacity (CEC), potassium, sodium, calcium and magnesium. Na and K in the soil samples were analyzed using flame photometer, Ca and Mg were analyzed by atomic absorption spectrophotometer while conventional analytical methods were employed for the determination of the rest of the physicochemical parameters. The results obtained revealed that the concentrations of physicochemical parameters in the soil samples were in the range of; 7.35-11.01% for MC, 6.53-7.64 for pH, 0.09-0.34 mS/cm for EC, 1.25-3.44% for OC, 2.16-5.93% for OM, 30.75-41.83 cmol/kg for CEC, 845-1014 mg/kg for Na, 1980-6065 mg/kg for K, 952–2118 mg/kg for Ca and1751–4288 mg/kg for Mg. pH was found to vary from neutrality to slightly alkaline. The values of EC indicated that all samples of the soils are non-saline. Statistical test of significance using ANOVA revealed that there were no significant differences (P>0.05) between the values of physicochemical parameters in the soil samples obtained from all the sampling sites. Correlation analysis was also employed to examine the relationship between the various parameters in the soil samples. The soil studied can be considered as good sources of essential nutrients and this information will help farmers to solve the problems related to soil nutrients, amount of which fertilizers to be used to increase the yield of crops

Investigation of high efficiency GaAs solar cells

Investigations of basic mechanisms which limit the performance of high efficiency GaAs solar cells are discussed. P/N heteroface structures have been fabricated from MOCVD epiwafers. Typical AM1 efficiencies are in the 21 to 22 percent range, with a SERI measurement for one cell being 21.5 percent. The cells are nominally 1.5 x 1.5 cm in size. Studies have involved photoresponse, T-I-V analyses, and interpretation of data in terms of appropriate models to determine key cell parameters. Results of these studies are utilized to determine future approaches for increasing GaAs solar cell efficiencies

Electro-optical characterization of GaAs solar cells

The electro-optical characterization of gallium arsenide p/n solar cells is discussed. The objective is to identify and understand basic mechanisms which limit the performance of high efficiency gallium arsenide solar cells. The approach involves conducting photoresponse and temperature dependent current-voltage measurements, and interpretation of the data in terms of theory to determine key device parameters. Depth concentration profiles are also utilized in formulating a model to explain device performance

Standing Portrait of Richard W. Thompson

Standing portrait of Richard W. Thompson, Congressman from Indiana. In the photograph, Thompson stands with his proper right hand resting on a pillar. He holds a cane and gloves in his proper left hand.https://scholarsjunction.msstate.edu/fvw-cdv/1506/thumbnail.jp

Standing Portrait of Richard W. Thompson

Standing portrait of Richard W. Thompson, Congressman from Indiana. In the photograph, Thompson stands with his proper right hand resting on a pillar. He holds a cane and gloves in his proper left hand.https://scholarsjunction.msstate.edu/fvw-artifacts/2329/thumbnail.jp