Structural analysis of a bolted joint concept for the space shuttle's solid rocket motor casing

The Space Shuttle Challenger accident is thought to have been caused by the failure of one of the tang-clevis joints joining together the casing segments of the Solid Rocket Motors (SRM). Excessive displacement between the tang and clevis, possibly unseating the O-ring seals, may have initiated the resulting accident. An effort was made at NASA Langley Research Center to design an alternative concept for mating the casing segments. A bolted flange joint concept was designed and analyzed to determine if the concept would effectively maintain a seal while minimizing joint weight and controlling stress levels. It is shown that under the loading conditions analyzed the seal area of the joint remains seated. The only potential stress problem is a stress concentration in the flange at the edge of the bolt hole, which is highly localized. While heavier than the existing joint, this concept does have some advantages making the bolted joint an attractive alternative

Thermoradiation inactivation of naturally occurring organisms in soil

Samples of soil collected from Kennedy Space Center near spacecraft assembly facilities were found to contain microorganisms very resistant to conventional sterilization techniques. The inactivation behavior of the naturally occurring spores in soil was investigated using dry heat and ionizing radiation, first separately, then in combination. Dry heat inactivation rates of spores were determined for 105 and 125 C. Radiation inactivation rates were determined for dose rates of 660 and 76 krad/hr at 25 C. Simultaneous combinations of heat and radiation were then investigated at 105, 110, 115, 120, and 125 C. Combined treatment was found to be highly synergistic requiring greatly reduced radiation doses to accomplish sterilization

Finite Element Analysis of a NASA National Transonic Facility Wind Tunnel Balance

This paper presents the results of finite element analyses and correlation studies performed on a NASA National Transonic Facility (NTF) Wind Tunnel balance. In the past NASA has relied primarily on classical hand analyses, coupled with relatively large safety factors, for predicting maximum stresses in wind tunnel balances. Now, with the significant advancements in computer technology and sophistication of general purpose analysis codes, it is more reasonable to pursue finite element analyses of these balances. The correlation studies of the present analyses show very good agreement between the analyses and data measured with strain gages and therefore the studies give higher confidence for using finite element analyses to analyze and optimize balance designs in the future

The Photonic Band theory and the negative refraction experiment of metallic helix metamaterials

We develop a theory to compute and interpret the photonic band structure of a periodic array of metallic helices for the first time. Interesting features of band structure include the ingenuous longitudinal and circularly polarized eigenmodes, the wide polarization gap [Science 325, 1513 (2009)], and the helical symmetry guarantees the existence of negative group velocity bands at both sides of the polarization gap and band crossings pinned at the zone boundary with fixed frequencies. A direct proof of negative refraction via a chiral route [Science 306, 1353 (2004)] is achieved for the first time by measuring Gooshanchen shift through a slab of three dimensional bona fide helix metamaterial

Making Cereal Box Dioramas of Native American Historic Homes and Culture

Hands-on projects such as creating a three-dimensional diorama are among the most memorable of positive elementary school experiences, yet they are generally uncommon because these complex projects are daunting to undertake. Therefore, it is important to prepare preservice teachers with the skills to lead children in creating these types of projects. This document is a compilation of preservice teacher work completed during a social studies methods class that assists instructors in teaching students to create unique dioramas. After the preservice teachers had constructed dioramas and assisted elementary students in making their own, they reflected on previous social studies projects from their childhoods and considered the learning outcomes of the current project. Eighty preservice teachers enrolled in a social studies methods course participated in the study. These college students created their own Native American dioramas along with images for furnishing and finishing dioramas of the Native American group on which they focused. The five Native American groups explored through dioramas include the Iroquois of the northeastern United States, the Seminole of the Southeast, the Lakota of the Central Plains, Hopi (and Navajo) of the American Southwest and the Haida of the Northwest Coast. This document provides photoillustrated examples and steps of how to create an intricate diorama from a cereal box, recycled copy paper, white craft glue, paints, images, and common craft items. The cereal box base is cut to open like a book and a model of a Native American home made of recycled cardboard is affixed over a cut-out hole in the cover so that the box opens to reveal the interior of the home. All surfaces are covered with a layer of torn recycled copy paper that is securely glued, coated with white gesso base paint, and then decorated with acrylic craft paints. In the facing inside enclosure, a ceremony scene is displayed. The back of the cereal box features crafts of the Native American group, while the other cereal box exterior sides show foods, clothing, and other cultural Reflection data indicate that preservice teachers recognized the large amount of time and patience necessary to complete a quality diorama and the valuable amount of in-depth learning that results, including a deeper respect for Native American people and greater confidence in teaching these concepts. Therefore, we recommend diorama projects in teaching about diverse cultures (2 tables, 5 figures, 2 photo-illustrated appendices)

A study of the effectiveness of thermoradiation sterilization

Effectiveness of thermoradiation sterilization of spacecraft hardwar

Plasmonic Cloaking of Cylinders: Finite Length, Oblique Illumination and Cross-Polarization Coupling

Metamaterial cloaking has been proposed and studied in recent years following several interesting approaches. One of them, the scattering-cancellation technique, or plasmonic cloaking, exploits the plasmonic effects of suitably designed thin homogeneous metamaterial covers to drastically suppress the scattering of moderately sized objects within specific frequency ranges of interest. Besides its inherent simplicity, this technique also holds the promise of isotropic response and weak polarization dependence. Its theory has been applied extensively to symmetrical geometries and canonical 3D shapes, but its application to elongated objects has not been explored with the same level of detail. We derive here closed-form theoretical formulas for infinite cylinders under arbitrary wave incidence, and validate their performance with full-wave numerical simulations, also considering the effects of finite lengths and truncation effects in cylindrical objects. In particular, we find that a single isotropic (idealized) cloaking layer may successfully suppress the dominant scattering coefficients of moderately thin elongated objects, even for finite lengths comparable with the incident wavelength, providing a weak dependence on the incidence angle. These results may pave the way for application of plasmonic cloaking in a variety of practical scenarios of interest.Comment: 17 pages, 11 figures, 2 table

Does Updating Natural Hazard Maps to Reflect Best Practices Increase Viewer Comprehension of Risk?

In this study, we examine whether updating an interactive hazard map using recommendations from the literature improves user map comprehension. Analyses of experimental data collected from 75 university students revealed that map comprehension scores were not significantly better for those who viewed a “best practices” map compared to those who viewed an existing version. This may be because the existing map was itself better than most other interactive maps. Additionally, we found map comprehension levels to have significant positive relationships with objective tests, but not self-reported measures of spatial ability. Moreover, self-reported spatial ability had statistically significant, but only moderately strong, correlations with objective tests. These results indicate that spatial ability should be measured objectively rather than through self-reported methods in research on map comprehension. Further research is needed to examine the cognitive processes involved in hazard map comprehension, especially using a broader range of map characteristics and population segments with more diverse cognitive abilities

Test and Analysis of a Hyper-X Carbon-Carbon Leading Edge Chine

During parts production for the X43A Mach 10 hypersonic vehicle nondestructive evaluation (NDE) of a leading edge chine detected on imbedded delamination near the lower surface of the part. An ultimate proof test was conducted to verify the ultimate strength of this leading edge chine part. The ultimate proof test setup used a pressure bladder design to impose a uniform distributed pressure field over the bi-planar surface of the chine test article. A detailed description of the chine test article and experimental test setup is presented. Analysis results from a linear status model of the test article are also presented and discussed. Post-test inspection of the specimen revealed no visible failures or areas of delamination

Exposure Path Perceptions and Protective Actions in Biological Water Contamination Emergencies

This study extends the Protective Action Decision Model, developed to address disaster warning responses in the context of natural hazards, to “boil water” advisories. The study examined 110 Boston residents’ and 203 Texas students’ expectations of getting sick through different exposure paths for contact with contaminated water. In addition, the study assessed respondents’ actual implementation (for residents) or behavioral expectations (for students) of three different protective actions – bottled water, boiled water, and personally chlorinated water – as well as their demo-graphic characteristics and previous experience with water contamination. The results indicate that people distinguish among the exposure paths, but the differences are small (one-third to one-half of the response scale). Nonetheless, the perceived risk from the exposure paths helps to explain why people are expected to consume (or actually consumed) bottled water rather than boiled or personally chlorinated water. Overall, these results indicate that local authorities should take care to communicate the relative risks of different exposure paths and should expect that people will respond to a boil water order primarily by consuming bottled water. Thus, they should make special efforts to increase supplies of bottled water in their communities during water contamination emergencies