Development of a space qualified high reliability rotary actuator for spaceflight use. Volume 2: Appendices to technical report

A space-qualified, high reliability, 150 ft-lb rated torque rotary actuator is described. This drive is an integrated variable reluctance orbit motor-epicyclic transmission actuator. The performance goals were based on future control moment gyrotorquer applications and represent an advancement in the torque-to-weight ratio, backlash, inertia and response characteristics of electric rotary drives. The program accomplishments have been in two areas (1) the development of two high ratio (818:1) actuator configurations (breadboard and flightweight) and (2) the invention of a reliable proximity switch sensor system for self-commutation without use of optical or electrical brush techniques

Development of a space qualified high reliability rotary actuator. Volume 1: Technical report

A space-qualified, high reliability, 150 ft-lb rated torque rotary acutator based on the Bendix Dynavector drive concept was developed. This drive is an integrated variable reluctance orbit motor-epicyclic transmission actuator. The performance goals were based on future control moment gyro torquer applications and represent a significant advancement in the torque-to-weight ratio, backlash, inertia and response characteristics of electric rotary drives. The program accomplishments have been in two areas: (1) the development of two high ratio (818:1) actuator configurations (breadboard and flightweight), and (2) the invention of a reliable proximity switch sensor system for self-commutation without use of optical or electrical brush techniques

Characterization of surficial units on Mars using Viking orbiter multispectral image and thermal data

Albedo and thermal property correlations of the topography of Mars were conducted with emphases upon the types and origins of materials exposed in the central equatorial region. This area displays a wide variation in color, albedo and thermal properties, and is relatively free of dust and haze. The physical, mineralogical and elemental characteristics of this area are discussed

An examination of the work of Sir Dennis Holme Robertson on industrial fluctuation

This thesis is not intended as a biography of Sir Dennis Holme Robertson. It is an examination of one important aspect of his work as an economist: his theory of industrial fluctuation

Numerical solutions of several reflected shock-wave flow fields with nonequilibrium chemical reactions

The method of characteristics for a chemically reacting gas is used in the construction of the time-dependent, one-dimensional flow field resulting from the normal reflection of an incident shock wave at the end wall of a shock tube. Nonequilibrium chemical reactions are allowed behind both the incident and reflected shock waves. All the solutions are evaluated for oxygen, but the results are generally representative of any inviscid, nonconducting, and nonradiating diatomic gas. The solutions clearly show that: (1) both the incident- and reflected-shock chemical relaxation times are important in governing the time to attain steady state thermodynamic properties; and (2) adjacent to the end wall, an excess-entropy layer develops wherein the steady state values of all the thermodynamic variables except pressure differ significantly from their corresponding Rankine-Hugoniot equilibrium values

On the natural rates of unemployment and interest: the Robertson connection

The paper explores the connection between the natural rates of unemployment and interest put forward by Robertson in the 1930s. This looks at monetary dynamics in the business cycle and assesses the Robertsonian contribution to post-Keynesian developments in macroeconomic theory and policy. Robertson’s approach is that of getting the correct balance between economic progress and economic stability, getting the relations right between cyclical changes in prices, output and employment and their long run equilibrium values over time

A simple squeezer for removal of interstitial water from ocean sediments

A simple and inexpensive squeezer employed in the removal of interstitial water from ocean sediments has been designed. Squeezing is carried out with nitrogen at pressures of 500 to 1000 lb/in2 (35 to 70 kg/cm2). The apparatus is lined with teflon, thus insuring complete freedom from metallic contamination

On the evaluation of human error probabilities for post-initiating events

Thesis (S.M. and S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2006.Includes bibliographical references (p. 109-111).Quantification of human error probabilities (HEPs) for the purpose of human reliability assessment (HRA) is very complex. Because of this complexity, the state of the art includes a variety of HRA models, each with its own objectives, scope and quantification method. In addition to varying methods of quantification, each model is replete with its own terminology and categorizations, therefore making comparison across models exceedingly difficult. This paper demonstrates the capabilities and limitations of two prominent HRA models: the Electric Power Research Institute (EPRI) HRA Calculator (using the HRC/ORE and Cause Based Decision Tree methods), used widely in industry, and A Technique for Human Error Analysis (ATHEANA), developed by the US Nuclear Regulatory Commission. This demonstration includes a brief description of the two models, a comparison of what they incorporate in HEP quantification, a "translation" of terminologies, and examples of their capabilities via the Halden Task Complexity experiments. Possible ways to incorporate learning from simulator experiments, such as those at Halden, to improve the quantification methods are also addressed. The primary difference between ATHEANA and the EPRI HRA Calculator is in their objectives. EPRI's objective is to provide a method that is not overly resource intensive and can be used by a PRA analyst without significant HRA experience. Consequently, EPRI quantifies HEPs using time reliability curves (TRCs) and cause based decision trees (CBDT). ATHEANA attempts to find contexts where operators are likely to fail without recovery and quantify the associated HEP. This includes finding how operators can further degrade the plant condition while still believing their actions are correct. ATHEANA quantifies HEPs through an expert judgment elicitation process.(cont.) ATHEANA and the EPRI Calculator are very similar in the contexts they consider in HEP calculation: both factor in the accident sequence context, performance shaping factors (PSFs), and cognitive factors into HEP calculation. However, stemming from the difference in objectives, there is a difference in how deeply into a human action each model probes. ATHEANA employs a HRA team (including a HRA expert, operations personnel and a thermo-hydraulics expert) to examine a broad set of PSFs and contexts. It also expands the accident sequences to include the consequences of a misdiagnosis beyond simple failures in implementing the procedures (what will the operator likely do next given a specific misdiagnosis?) To limit the resource burden, the EPRI Calculator is prescriptive and limits the PSFs and cognitive factors for consideration thus enhancing consistency among analysts and reducing needed resources. However, CBDT and ATHEANA have the same approach to evaluating the cognitive context. The Halden Task Complexity experiments looked at different factors that would increase the probability of human failures such as the effects of time pressure/information load and masked events. EPRI and ATHEANA could use the design of the Halden experiments as a model for future simulations because they produced results that showed important differences in crew performance under certain conditions. Both models can also use the Halden experiments and results to sensitize the experts and analysts to the real effects of an error forcing context.by Mary R. Presley.S.M.and S.B

Survey of sediment quality in Sabine Lake, Texas and vicinity

The toxicity of sediments in Sabine Lake, Texas, and adjoining Intracoastal Waterway canals was determined as part of bioeffects assessment studies managed by NOAA’s National Status and Trends Program. The objectives of the survey were to determine: (1) the incidence and degree of toxicity of sediments throughout the study area; (2) the spatial patterns (or gradients) in chemical contamination and toxicity, if any, throughout the study area; (3) the spatial extent of chemical contamination and toxicity; and (4) the statistical relationships between measures of toxicity and concentrations of chemicals in the sediments. Surficial sediment samples were collected during August, 1995 from 66 randomly-chosen locations. Laboratory toxicity tests were performed as indicators of potential ecotoxicological effects in sediments. A battery of tests was performed to generate information from different phases (components) of the sediments. Tests were selected to represent a range in toxicological endpoints from acute to chronic sublethal responses. Toxicological tests were conducted to measure: reduced survival of adult amphipods exposed to solid-phase sediments; impaired fertilization success and abnormal morphological development in gametes and embryos, respectively, of sea urchins exposed to pore waters; reduced metabolic activity of a marine bioluminescent bacteria exposed to organic solvent extracts; and induction of a cytochrome P-450 reporter gene system in exposures to solvent extracts of the sediments. Chemical analyses were performed on portions of each sample to quantify the concentrations of trace metals, polynuclear aromatic hydrocarbons, and chlorinated organic compounds. Correlation analyses were conducted to determine the relationships between measures of toxicity and concentrations of potentially toxic substances in the samples. Based upon the compilation of results from chemical analyses and toxicity tests, the quality of sediments in Sabine Lake and vicinity did not appear to be severely degraded. Chemical concentrations rarely exceeded effects-based numerical guidelines, suggesting that toxicant-induced effects would not be expected in most areas. None of the samples was highly toxic in acute amphipod survival tests and a minority (23%) of samples were highly toxic in sublethal urchin fertilization tests. Although toxic responses occurred frequently (94% of samples) in urchin embryo development tests performed with 100% pore waters, toxicity diminished markedly in tests done with diluted pore waters. Microbial bioluminescent activity was not reduced to a great degree (no EC50 <0.06 mg/ml) and cytochrome P-450 activity was not highly induced (6 samples exceeded 37.1 ug/g benzo[a]pyrene equivalents) in tests done with organic solvent extracts. Urchin embryological development was highly correlated with concentrations of ammonia and many trace metals. Cytochrome P450 induction was highly correlated with concentrations of a number of classes of organic compounds (including the polynuclear aromatic hydrocarbons and chlorinated compounds). (PDF contains 51 pages