Design, fabrication and testing of porous tungsten vaporizers for mercury ion thrusters

The dispersions in the characteristics, performance and reliability of vaporizers for early model 30-cm thrusters were investigated. The purpose of the paper is to explore the findings and to discuss the approaches that were taken to reduce the observed dispersion and present the results of a program which validated those approaches. The information that is presented includes porous tungsten materials specifications, a discussion of assembly procedures, and a description of a test program which screens both material and fabrication processes. There are five appendices providing additional detail in the areas of vaporizer contamination, nitrogen flow testing, bubble testing, porosimeter testing, and mercury purity. Four neutralizers, seven cathodes and five main vaporizers were successfully fabricated, tested, and operated on thrusters. Performance data from those devices is presented and indicates extremely repeatable results from using the design and fabrication procedures

Drowning in Sacrifice: Maggie Tulliver’s Role in George Eliot’s The Mill on the Floss

Upon examining the personal rejection and eventual demise of Maggie Tulliver, the protagonist of The Mill on the Floss, it becomes evident that her death is a sacrifice through which she demonstrates the morality of George Eliot’s religion of humanity. Maggie is a headstrong, intelligent, and memorable character who does not fit into her community and ultimately drowns in a flood while attempting to save her loved ones. The story begs the question: why must such an endearing main character perish? One possibility is that her character flaws make her downfall inevitable. The high-class and hypocritical members of the town of St. Ogg’s exile Maggie because she is too different and too desperate for love. Others may argue that Maggie’s death is a consequence of natural selection. The daughter of two very disparate family lines, her mixed blood results in a temperament that does not belong in her society. The survival of the fittest hypothesis, therefore, requires her passing. In actuality, Maggie’s demise is not due to character flaws or nature’s dictates. Rather, it is a demonstration of the sacrificial love of the religion of humanity. Eliot herself had given up orthodox Christianity in favor of a religion of humanity that advocated human love and selflessness without religious dogma. In The Mill on the Floss, Eliot presents a society that has also outgrown religion. Maggie, who does not find comfort in an outmoded religion or a judgmental society, is the only person who can demonstrate the ideology that this post-Christian town should embrace. The sacrifices that result in her downfall and her unfortunate death are demonstrations of selfless love. Eliot’s memorable protagonist must suffer and die as a voice espousing the values of her religion of humanity

Deflectable beam linear strip cesium contact ion thruster system

Deflectable dual beam, linear strip cesium contact, ion thruster system design and performance testin