Weight optimization of an aerobrake structural concept for a lunar transfer vehicle

An aerobrake structural concept for a lunar transfer vehicle was weight optimized through the use of the Taguchi design method, finite element analyses, and element sizing routines. Six design parameters were chosen to represent the aerobrake structural configuration. The design parameters included honeycomb core thickness, diameter-depth ratio, shape, material, number of concentric ring frames, and number of radial frames. Each parameter was assigned three levels. The aerobrake structural configuration with the minimum weight was 44 percent less than the average weight of all the remaining satisfactory experimental configurations. In addition, the results of this study have served to bolster the advocacy of the Taguchi method for aerospace vehicle design. Both reduced analysis time and an optimized design demonstrated the applicability of the Taguchi method to aerospace vehicle design

Ideas and Perspectives: A Strategic Assessment of Methane and Nitrous Oxide Measurements In the Marine Environment

In the current era of rapid climate change, accurate characterization of climate-relevant gas dynamics-namely production, consumption, and net emissions-is required for all biomes, especially those ecosystems most susceptible to the impact of change. Marine environments include regions that act as net sources or sinks for numerous climateactive trace gases including methane (CH4) and nitrous oxide (N2O). The temporal and spatial distributions of CH4 and N2O are controlled by the interaction of complex biogeochemical and physical processes. To evaluate and quantify how these mechanisms affect marine CH4 and N2O cycling requires a combination of traditional scientific disciplines including oceanography, microbiology, and numerical modeling. Fundamental to these efforts is ensuring that the datasets produced by independent scientists are comparable and interoperable. Equally critical is transparent communication within the research community about the technical improvements required to increase our collective understanding of marine CH4 and N2O. A workshop sponsored by Ocean Carbon and Biogeochemistry (OCB) was organized to enhance dialogue and collaborations pertaining to marine CH4 and N2O. Here, we summarize the outcomes from the workshop to describe the challenges and opportunities for near-future CH4 and N2O research in the marine environment

From Blockhouse To Hog House: The Historical Dendroarchaeology Of The Swaggerty Blockhouse, Cocke County, Tennessee, U.S.A.

The Swaggerty Blockhouse has historical and cultural significance for Tennessee because it is believed to be the only remaining 18th Century blockhouse in the state. We incorporated analyses of artifacts obtained from archaeological excavations coupled with tree-ring dating techniques to determine the possible year of construction of the structure. A nearby reference tree-ring chronology from Norris Dam anchored the Swaggerty Blockhouse tree-ring chronology from 1674 to 1859. The assemblages of artifacts (nails, ceramics, and window glass) recovered from the site corroborated the construction date and provided a clear understanding of the structure’s use as a barn for storage and hog processing. Based on our analyses, the historic Swaggerty ‘‘Blockhouse,’’ originally believed to have been built by James Swaggerty in 1787, is instead a small cantilever barn built by Jacob Stephens in 1860 and used for hog farming.This item is part of the Tree-Ring Research (formerly Tree-Ring Bulletin) archive. For more information about this peer-reviewed scholarly journal, please email the Editor of Tree-Ring Research at [email protected]