Nonlinear wave excitations by orbiting charged space debris objects

Space debris collision probability analysis for proposed global broadband constellations

This Technical Memorandum covers revolutionary ideas for space radiation shielding that would mitigate mission costs while limiting human exposure, as studied in a workshop held at Marshall Space Flight Center at the request of NASA Headquarters. None of the revolutionary new ideas examined for the .rst time in this workshop showed clear promise. The workshop attendees felt that some previously examined concepts were de.nitely useful and should be pursued. The workshop attendees also concluded that several of the new concepts warranted further investigation to clarify their value.

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Revolutionary Concepts of Radiation Shielding for Human Exploration of Space

The natural space environment is characterized by many complex and subtle phenomena hostile to spacecraft. The effects of these phenomena impact spacecraft design, development, and operations. Space systems become increasingly susceptible to the space environment as use of composite materials and smaller, faster electronics increases. This trend makes an understanding of the natural space environment essential to accomplish overall mission objectives, especially in the current climate of better/cheaper/faster. Meteoroids are naturally occurring phenomena in the natural space environment. Orbital debris is manmade space litter accumulated in Earth orbit from the exploration of space. Descriptions are presented of orbital debris source, distribution, size, lifetime, and mitigation measures. This primer is one in a series of NASA Reference Publications currently being developed by the Electromagnetics and Aerospace Environments Branch, Systems Analysis and Integration Laboratory, Marshall Space Flight Center, National Aeronautics and Space Administration.

Meteoroids and Orbital Debris: Effects on Spacecraft

This paper investigates the relationship between archaeological stratigraphy (in archaeology) and artificial ground (in geology) and considers their wider application to the investigation and characterization of the Anthropocene. Evidence from two archaeological case studies is used to illuminate key points. The first case study examines stratigraphic sequences from beneath the city of Leicester, UK; the second looks at stratified deposits within the prehistoric settlement mound of Abu Hureyra, Syria. Earthworks, riverworks and cultivation soils are also considered. Archaeological and geological perspectives are combined to develop a unified view of anthropogenic deposits that cover large parts of the surface of the Earth. Archaeology and geology are related disciplines, sharing common roots in intellectual developments of the eighteenth and nineteenth centuries. The publication of Charles Lyell’s Principles of Geology (Lyell 1830) was a significant moment in the development of both subjects. Largely as a result of Lyell’s book, Nicholas Steno’s earlier law of superposition of sedimentary layers and related geological principals were introduced into archaeological thinking. Other major formative influences on archaeology were James Hutton’s work on the geological cycle (Hutton 1795) and William Smith’s work on the correlation of strata (Smith 1816). Such works opened up the time depth necessary for emergence of archaeology as a modern discipline, and provided key conceptual tools for understanding material evidence encountered in excavation, especially with regard to interpretation of stratigraphy and relative dating of deposits. Detailed analysis of the early historical links between geology and archaeology is not attempted here but excellent accounts are available elsewhere (Daniel 1976; Daniel & Renfrew 1987; Harris 1989). Despite such common sources and early connections, however, development of stratigraphical analysis in archaeology and geology has to some extent followed divergent paths. This is partly due to increasing academic specialization and division of labour, splitting respective subject matters along disciplinary lines. Although there are areas of overlap and collaboration (such as Holocene studies and geoarchaeology), archaeologists generally work with shallow surface deposits and shallow time depth, leaving the study of underlying rock formations and deep time for geologists. Likewise, geologists have until recently mostly left the study of anthropogenic deposits, and the relatively recent periods associated with their formation, for archaeologists to study. The emergence of the concept of artificial ground within geology brings the two subjects back onto a potentially convergent path again. Artificial ground started to be shown on geological maps in the 1960s, but it was only in the 1990s that geological mapping of such deposits became standard. At first, investigation of it was mainly concerned with assessing stability and contamination of land for development. More recently – especially in relation to discussion of the Anthropocene as a proposed new geological epoch (Zalasiewicz et al. 2008, 2011) – artificial ground has come to be of interest to geologists in its own right (Price et al. 2011; Ford et al. 2013). There are important differences in how the two disciplines characterize the evidence, but deposits that geologists call artificial ground are broadly similar in principal to those that archaeologists call archaeological stratigraphy. Some consideration of how these different characterizations of the same material evidence might be related or integrated is required. It is sometimes assumed that most artificial ground was formed in the two hundred years from the onset of the industrial age to the present, and this tends to be supported by examples drawn from once heavily industrialized areas of countries like Great Britain. Thick layers or dumps of ironworks slag, furnace ash and colliery waste, or large quarries containing landfill, might be thought of as typical scenarios. Although taking stock of the accelerated rate of formation of artificial ground in parts of the industrialized world over the last two centuries is important, however, this should not lead to an underestimation of the amount of materials moved or modified by humans in preceding centuries or even millenia, sometimes in the same From: Waters, C. N., Zalasiewicz, J. A., Williams, M., Ellis, M. A. & Snelling, A. M. (eds) A Stratigraphical Basis for the Anthropocene. Geological Society, London, Special Publications, 395, http://dx.doi.org/10.1144/SP395.3 # The Geological Society of London 2013. Publishing disclaimer: www.geolsoc.org.uk/pub_ethics locations. There is a danger that, if artificial ground is identified with the Anthropocene, and the start of the Anthropocene dated to commencement of the industrial period (Steffen et al. 2007), other parts of artificial ground (and the context of industrial deposits within broader sequences of archaeological stratigraphy) would be overlooked. It is therefore valuable to examine anthropogenic deposits in a range of locations and from different periods. As well as places associated with extensive mining and processing in the industrial period, for example, long established cities such as Leicester, which were important centres of commerce and light industry, might also be considered. Well-known instances of the build-up of anthropogenic deposits in urban contexts from pre-industrial times include the 8 m deep Viking occupation deposits in York (Hall & Hunter-Mann 2003), which formed part of the bid for World Heritage status for the city. However, it cannot be assumed that such processes were confined to historic times. Accumulation of occupation debris is also characteristic of much older sites, such as prehistoric settlement mounds in Syria and other parts of the Middle East.

The relationship between archaeological stratigraphy and artificial ground and its significance in the Anthropocene

To acquire an unbiased technical assessment of (1) the research needed to better understand the debris environment, (2) the necessity and means of protecting spacecraft against the debris environment, and (3) potential methods of reducing the future debris hazard, NASA asked the National Research Council to form an international committee to examine the orbital debris issue. The committee was asked to draw upon available data and analyses to: characterize the current debris environment, project how this environment might change in the absence of new measures to alleviate debris proliferation, examine ongoing alleviation activities, explore measures to address the problem, and develop recommendations on technical methods to address the problems of debris proliferation.

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Susumu Toda

Papers

Orbital debris: A technical assessment

European Space Launch Failures