Radiative cooler for spacecraft

The design, construction, and testing of a passive radiative cooler that provides solutions to the design problems of withstanding mechanical stress, achieving the required thermal isolation, and maintaining optical alinement, cleanliness, and integration with the spacecraft are described

Apollo command module land impact tests

Full-scale-model and actual spacecraft were impact tested to define the emergency land-landing capability of the Apollo command module. Structural accelerations and strains were recorded on analog instrumentation, and a summary to these data is included. The landing kinematics were obtained from high-speed photography. Photographs of the structural damage caused during the tests are included. Even though extensive damage can be expected, the crew will receive nothing more than minor injuries during the majority of the probable landing conditions

Centrifuge Modeling of Pile-Supported Wharves for Seismic Hazards

Recent earthquakes have highlighted many seismic hazard concerns for western U.S. ports. Port waterfront structures are commonly constructed utilizing pile-supported wharves in combination with rock dike structures retaining a hydraulically placed backfill. Seismic damage is generally attributed to weak soils that are often prevalent in the marine environment (e.g. liquefiable sands, sensitive cohesive soils). In response to past damage, many ports are instigating soil improvement strategies to eliminate or minimize potential occurrences of liquefaction and to increase the strength of cohesive soils. The design of a seismically resilient wharf requires an understanding of its performance during design level earthquakes. Due to the complex nature of pile-supported wharves, state-of-the-art centrifuge modeling techniques are being used to better understand their seismic performance. The authors used the large-scale centrifuge facility at the University of California at Davis. This paper presents details on the construction, instrumentation, and testing of the models. Results from the tests are also included, such as the seismic pile behavior, effect of soil improvement, and the overall behavior

Failure of vaccination to prevent outbreaks of foot-and-mouth disease

Outbreaks of foot-and-mouth disease persist in dairy cattle herds in Saudi Arabia despite revaccination at intervals of 4-6 months. Vaccine trials provide data on antibody responses following vaccination. Using this information we developed a mathematical model of the decay of protective antibodies with which we estimated the fraction of susceptible animals at a given time after vaccination. The model describes the data well, suggesting over 95% take with an antibody half-life of 43 days. Farm records provided data on the time course of five outbreaks. We applied a 'SLIR' epidemiological model to these data, fitting a single parameter representing disease transmission rate. The analysis provides estimates of the basic reproduction number R(0), which may exceed 70 in some cases. We conclude that the critical intervaccination interval which would provide herd immunity against FMDV is unrealistically short, especially for heterologous challenge. We suggest that it may not be possible to prevent foot-and-mouth disease outbreaks on these farms using currently available vaccines

Defining forgiveness: Christian clergy and general population perspectives.

The lack of any consensual definition of forgiveness is a serious weakness in the research literature (McCullough, Pargament &amp; Thoresen, 2000). As forgiveness is at the core of Christianity, this study returns to the Christian source of the concept to explore the meaning of forgiveness for practicing Christian clergy. Comparisons are made with a general population sample and social science definitions of forgiveness to ensure that a shared meaning of forgiveness is articulated. Anglican and Roman Catholic clergy (N = 209) and a general population sample (N = 159) completed a postal questionnaire about forgiveness. There is agreement on the existence of individual differences in forgiveness. Clergy and the general population perceive reconciliation as necessary for forgiveness while there is no consensus within psychology. The clergy suggests that forgiveness is limitless and that repentance is unnecessary while the general population suggests that there are limits and that repentance is necessary. Psychological definitions do not conceptualize repentance as necessary for forgiveness and the question of limits has not been addressed although within therapy the implicit assumption is that forgiveness is limitless.</p

Contamination control engineering design guidelines for the aerospace community

Thermal control surfaces, solar arrays, and optical devices may be adversely affected by a small quantity of molecular and/or particulate contamination. What is rarely discussed is how one: (1) quantifies the level of contamination that must be maintained in order for the system to function properly, and (2) enforces contamination control to ensure compliance with requirements. This document is designed to address these specific issues and is intended to serve as a handbook on contamination control for the reader, illustrating process and methodology while providing direction to more detailed references when needed. The effects of molecular contamination on reflecting and transmitting surfaces are examined and quantified in accordance with MIL STD 1246C. The generation, transportation, and deposition of molecular contamination is reviewed and specific examples are worked to illustrate the process a design engineer can use to estimate end of life cleanliness levels required by solar arrays, thermal control surfaces, and optical surfaces. A similar process is used to describe the effect of particulate contamination as related to percent area coverage (PAC) and bi-directional reflectance distribution function (BRDF). Relationships between PAC and surface cleanliness, which include the effects of submicron sized particles, are developed and BRDF is related to specific sensor design parameters such as Point Source Transmittance (PST). The pros and cons of various methods of preventing, monitoring, and cleaning surfaces are examined and discussed

The Nature and Origin of Molecular Knots in Planetary Nebulae

doi:10.1063/1.2146252Planetary Nebulae (PNe) are major contributors to the enrichment of the interstellar medium (ISM). Knots and filaments in the ionized gas images of PNe are common, if not ubiquitous. Additionally, it has been shown that molecular gas exists inside dense condensations within the ionized regions. The origins of these clumps are not known, though the suggested formation mechanisms fall into two main scenarios: (1) they form during the AGB phase; (2) they form as a result of the onset of the PN phase as the fast wind ploughs into the slower moving AGB wind. The currently favored model is that the knots are formed by the onset of the PN phase and then sculpted as the ionizing radiation penetrates deeper into the circumstellar envelope. We present preliminary results of a study which compares the morphologies of molecular and ionized gas emission in several PNe, covering a range of ages.This work was supported by several funding agencies: SE and AS were supported by HST-AR- 10686, and by the Research Council of University of Missouri - Columbia. MM and PM were supported in part by HST-GO-01041 and by the internal STScI funds, DDRFD0001.82319. Support for Program numbers HST-AR-10686 and HST-GO-01041 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555