Keywords: charged coupled devices; debris; space debris; telescopes; Earth orbital environments; geosynchronous orbits; Schmidt cameras; Schmidt telescope
Abstract: NASA has been using the charged coupled device (CCD) debris telescope (CDT)—a transportable 32-cm Schmidt telescope located near Cloudcroft, New Mexico—to help characterize the debris environment in geosynchronous Earth orbit (GEO). The CDT is equipped with a SITe 512 x 512 CCD camera whose 24 m2 (12.5 arc sec) pixels produce a 1.7 x 1.7-deg field of view. The CDT system can therefore detect 17th-magnitude objects in a 20-sec integration corresponding to an ~0.6-m diameter, 0.20 albedo object at 36,000 km. The telescope pointing and CCD operation are computer controlled to collect data automatically for an entire night. The CDT has collected more than 1500 hrs of data since November 1997. This report describes the collection and analysis of 58 nights (~420 hrs) of data acquired in 1998.
Keywords: plasma control; magnetohydrodynamics; plasma turbulence; plasmas (physics); Fourier transformation; Liouville theorem; pseudoscalars; ergodic process
Abstract: Plasmas, such as those found in the space environment or in plasma confinement devices, are often modeled as electrically conducting fluids. When fluids and plasmas are energetically stirred, regions of highly nonlinear, chaotic behavior known as turbulence arise. Understanding the fundamental nature of turbulence is a long-standing theoretical challenge. The present work describes a statistical theory concerning a certain class of nonlinear, finite dimensional, dynamical models of turbulence. These models arise when the partial differential equations describing incompressible, ideal (i.e., non-dissipative) homogeneous fluid and magnetofluid (i.e., plasma) turbulence are Fourier transformed into a very large set of ordinary differential equations. These equations define a divergenceless flow in a high-dimensional phase space, which allows for the existence of a Liouville theorem, guaranteeing a distribution function based on constants of the motion (integral invariants). The novelty of these particular dynamical systems is that there are integral invariants other than the energy, and that some of these invariants behave like pseudoscalars under two of the discrete symmetry transformations of physics, parity and charge conjugation. In this work the "rugged invariants" of ideal homogeneous turbulence are shown to be the only significant scalar and pseudoscalar invariants. The discovery that pseudoscalar invariants cause symmetries of the original equations to be dynamically broken and induce a nonergodic structure on the associated phase space is the primary result presented here. Applicability of this result to dissipative turbulence is also discussed.
Keywords: metamorphism (geology); beds (geology); geology; geomorphology; geophysics;
Abstract: We collected ~ 400 rock chips in continuous vertical profile at Meteor Crater, Arizona, representing - from bottom to top - the Coconino, Toroweap, Kaibab, and Moenkopi Formations to support ongoing compositional analyses of the impact melts and their stratigraphic source depth(s) and other studies at Meteor Crater that depend on the composition of the target rocks. These rock chips were subsequently pooled into 23 samples for compositional analysis by XRF methods, each sample reflecting a specific stratigraphic “subsection” ~ 5-10 m thick. We determined the modal abundance of quartz, dolomite, and calcite for the entire Kaibab Formation at vertical resolutions of 1-2 meters. The Coconino Formation composes the lower half of the crater cavity. It is an exceptionally pure sandstone. The Toroweap is only 2 m thick and compositionally similar to Coconino; therefore, it is not a good compositional marker horizon. The Kaibab Formation is ~ 80 m thick. XRD studies show that the Kaibab Formation is dominated by dolomite and quartz, albeit in highly variable proportions; calcite is a minor phase at best. The Kaibab at Meteor Crater is therefore a sandy dolomite rather than a limestone, consistent with pronounced facies changes in the Permian of SE Arizona over short vertical and horizontal distances. The Moenkopi forms the 12 m thick cap rock and has the highest Al2O3 and FeO concentrations of all target rocks. With several examples, we illustrate how this systematic compositional and modal characterization of the target ideologies may contribute to an understanding of Meteor Crater, such as the depth of its melt zone, and to impact cratering in general, such as the liberation of CO2 from shocked carbonates.
Keywords: biostimulation; photbiology; laser therapy; nanotechnology; nanobacteria; biomineralization; biofilm; biological systems; molecular; biology
Abstract: The International NASA/DARPA Photobiology Conference held at the Johnson Space Center in Houston/TX demonstrated where low level laser therapy (LLLT), respectively low intensity light activated biostimulation (LILAB) and nanotechnological applications employing photobiomodulation techniques will presumably go in the next ten years. The conference was a continuation of the 1st International Conference on Nearfield Optical Analysis organized by Andrei Sommer (ENSOMA Lab, University of Ulm, Germany) in November 2000 at Castle Reisensburg, Germany, which started with a group of ten scientists from eight different countries. The 2nd conference was co-sponsored by DARPA, NASA-JSC and the Medical College of Wisconsin. The 2nd conference hosted 40 international experts from universities, research institutes, agencies and industry. Materials published here are expected to become milestones forming a novel platform in biomedical photobiology. The multidisciplinary group of researchers focused on LLLT/LILAB-applications under extreme conditions expected to have beneficial effects particularly in space, on submarines, and under severe battlefield conditions. The group also focused on novel technologies with possibilities allowing investigating the interaction of light with biological systems, molecular mechanisms of wound healing, bone regeneration, nerve regeneration, pain modulation, as well as biomineralization and biofilm formation processes induced by nanobacteria. The proceedings of the 2nd NOA, together with the proceedings of the previous meeting held in Germany (Journal of Clinical Laser Medicine & Surgery, 2001, 19, 109-112) demonstrated the synergistic interplay and complementary output of a coherent approach to interrelated scientific questions of excessive clinical relevance, offering results beyond any previous expectation. The 3rd NOA is scheduled for 2002, in Brazil.
Keywords: composite materials; pressure vessel design; pressure vessels; impact damage; materials
Abstract: This document represents efforts accomplished at the NASA Johnson Space Center White Sands Test Facility in support of the Enhanced Technology for Composite Overwrapped Pressure Vessels Program, a joint research and technology effort among the U.S. Air Force, NASA, and the Aerospace Corporation.WSTF performed testing for several facects of the program. Testing that contributed to the Task 3.0 COPV database extension objective included baseline structural strength, failure mode and safe-life, impact damage tolerance, sustained load/impact effect, and materials compatibility. WSTF was also responsible for establishing impact protection and control requirements under Task 8.0 of the program. This included developing a methodology for establishing an impact control plan.Seven test reports detail the work done at WSTF. As such, this document contributes to the database of information regarding COPV behavior that will ensure performance benefits and safety are maintained throughout vessel service life.
Keywords: plants (botany); plant roots; plant stress; microgravity; porous materials; porosity; microporosity
Abstract: This NASA Technical Memorandum is a compilation of presentations and discussions in the form of minutes from a workshop entitled Plant Production Systems for Microgravity: Critical Issues in Water, Air, and Solute Transport Through Unsaturated Porous Media held at NASA’s Johnson Space Center, July 24-25, 2000. This workshop arose from the growing belief within NASA’s Advanced Life Support Program that further advances and improvements in plant production systems for microgravity would benefit from additional knowledge of fundamental processes occurring in the root zone. The objective of the workshop was to bring together individuals who had expertise in various areas of fluid physics, soil physics, plant physiology, hardware development, and flight tests to identify, discuss, and prioritize critical issues of water and air flow through porous media in microgravity. Participants of the workshop included representatives from private companies involved in flight hardware development and scientists from universities and NASA Centers with expertise in plant flight tests, plant physiology, fluid physics, and soil physics.
Keywords: space missions, anomalies, memory (computers), computer storage devices, integrated
Abstract: This paper describes a Web-based system to support the temporary Anomaly Response Team formed from distributed subteams in Space Shuttle and International Space Station missions. The system was designed for easy and flexible creation of small collections of files and links associated with work on a particular anomaly. The system supports privacy and levels of formality for the subteams. First we describe the supported groups and an anomaly response scenario. Then we describe the support system prototype, the Anomaly Response Tracking and Integration System (ARTIS). Finally, we describe our evaluation approach and the results of the evaluation.
Keywords: aviator decompression sickness, skin mottling, skin bends, bubbles, skin lesion, cutaneous circulation
Abstract: There is disagreement about the pathophysiology, classification, and treatment of cutis marmorata (CM), so there is disagreement about the disposition and medical status of a person that had CM. CM is rare, associated with stressful decompressions, and may be associated with serious signs and symptoms of decompression sickness (DCS). CM presents as purple or bluish-red skin mottling, often in the pectoral region, shoulders, chest, or upper abdomen. It is unethical to induce CM in humans so all information comes from retrospective analysis of case reports, or from animal models. A literature search, seven recent case reports from the Johnson Space Center and Brooks Air Force Base Hypobaric DCS Databases, interviews with DCS treatment experts, and responses to surveys provided the factual information used to arrive at our conclusions and recommendations. The weight of evidence indicates that CM is a local, not centrally mediated or systemic response to bubbles. It is unclear whether obstruction of arterial or venous blood flow is the primary insult since the lesion is reported under either condition. Any neurological or cardiovascular involvements are coincidental, developing along the same time course. The skin could be the source of the bubbles due to its mass, the associated layer of fat, and the variable nature of skin blood flow. CM should not be categorized as Type II DCS, should be included with other skin manifestations in a category called cutaneous DCS, and hyperbaric treatment is only needed if ground level oxygen is ineffective in the case of altitude-induced CM.
Keywords: Antarctic regions, space exploration, Mars surface, planetary environments
Abstract: Four Antarctic explorers were invited to a workshop at Johnson Space Center (JSC) to provide expert assessments of NASA's current understanding of future human exploration missions beyond low Earth orbit. These explorers had been on relatively sophisticated, extensive Antarctic expeditions with sparse or nonexistent support infrastructure in the period following World War II through the end of the International Geophysical Year. Their experience was similar to that predicted for early Mars or other planetary exploration missions. For example: one Antarctic expedition lasted 2 years with only one planned resupply mission and contingency plans for no resupply missions should sea ice prevent a ship from reaching them; several traverses across Antarctica measured more than 1000 total miles, required several months to complete, and were made without maps (because they did not exist) and with only a few aerial photos of the route; and the crews of 6 to 15 were often international in composition. At JSC, the explorers were given tours of development, training, and scientific facilities, as well as documentation of operational scenarios for future planetary exploration. This report records their observations about these facilities and plans in answers to a series of questions provided to them before the workshop.
Keywords: flight control; spacecraft control; reentry vehicles; dynamics; equations of motion; nonlinear equations; control systems design
Abstract: This report addresses issues in developing a flight control design for vehicles operating across a broad flight regime and with highly nonlinear physical descriptions of motion. Specifically it addresses the need for reentry vehicles that could operate through reentry from space to controlled touchdown on Earth. The latter part of controlled descent is achieved by parachute or paraglider or by an automatic or a human-controlled landing similar to that of the Orbiter. Since this report addresses the specific needs of human-carrying (not necessarily piloted) reentry vehicles, it deals with highly nonlinear equations of motion, and their generated control systems must be robust across a very wide range of physics. Thus, this report deals almost exclusively with some form of dynamic inversion (DI). Two vital aspects of control theory noninteracting control laws and the transformation of nonlinear systems into equivalent linear systems are embodied in DI. Though there is no doubt that the mathematical tools and underlying theory are widely available, there are open issues as to the practicality of using DI as the only or primary design approach for reentry vehicles. This report provides a set of guidelines that can be used to determine the practical usefulness of the technique.
Keywords: venous gas emobli; bubbles; decompression sickness; bends; extravehicular activity; goodness of fit; accuracy, predictive; random effects; distribution, lognormal
Abstract: Venous gas emboli (VGE) (gas bubbles in venous blood) are associated with an increased risk of decompression sickness (DCS) in hypobaric environments. A high grade of VGE can be a precursor to serious DCS. In this paper, we model time to Grade IV VGE considering a subset of individuals assumed to be immune from experiencing VGE. Our data contain monitoring test results from subjects undergoing up to 13 denitrogenation test procedures prior to exposure to a hypobaric environment. The onset time of Grade IV VGE is recorded as contained within certain time intervals. We fit a parametric (lognormal) mixture survival model to the interval- and right-censored data to account for the possibility of a subset of cured individuals who are immune to the event. Our model contains random subject effects to account for correlations between repeated measurements on a single individual. Model assessments and cross-validation indicate that this limited failure population mixture model is an improvement over a model that does not account for the potential of a fraction of cured individuals. We also evaluated some alternative mixture models. Predictions from the best fitted mixture model indicate that the actual process is reasonably approximated by a limited failure population model.
Keywords: Radiation Hazards, Planetary Environments, Cancer, Space Exploration, Risk
Abstract: In this paper we discuss expected lifetime excess cancer risks for astronauts returning from exploration class missions. For the first time we make a quantitative assessment of uncertainties in cancer risk projections for space radiation exposures. Late effects from the high charge and energy (HZE) ions present in the galactic cosmic rays including cancer and the poorly undersood risks to the central nervous system constitute the major risks. Methods used to project risk in low Earth orbit are seen as hightly uncertain for projecting risks on exploration missions because of the limted radiobiology data available for estimating HZE ion risks. Cancer risk projections are described as a product of many biological and physical factors, each of which has a differential range of uncertainty due to lack of data and knowledge. Monte-Carlo sampling from subjective error distributions represents the lack of knowledge in each factor to quantify risk projection overall uncertainty. Cancer risk analysis is applied to several exploration mission scenarios. At solar minimum, the number of days in space where career risk of less than the limiting 3% excess cancer mortality can be asssured at a 95% confidence level is found to be only of the order of 100 days.
Keywords: computer programming; computer modeling; orbital debris; space debris; population modeling; low Earth orbit; collision risk; risk assessment
Abstract: The NASA Orbital Debris Program Office at Johnson Space Center has developed a new computer-based orbital debris engineering model, ORDEM2000, which describes the orbital debris environment in the low Earth orbit region between 200 and 2000 km altitude. The model is appropriate for those engineering solutions requiring knowledge and estimates of the orbital debris environment (debris spatial density, flux, etc.). ORDEM2000 can also be used as a benchmark for ground-based debris measurements and observations. We incorporated a large set of observational data, covering the object size range from 10 mm to 10 m, into the ORDEM2000 debris database, utilizing a maximum likelihood estimator to convert observations into debris population probability distribution functions. These functions then form the basis of debris populations. We developed a finite element model to process the debris populations to form the debris environment. A more capable input and output structure and a user-friendly graphical user interface are also implemented in the model. ORDEM2000 has been subjected to a significant verification and validation effort.This document describes ORDEM2000, which supersedes the previous model, ORDEM96. The availability of new sensor and in situ data, as well as new analytical techniques, has enabled the construction of this new model. Section 1 describes the general requirements and scope of an engineering model. Data analyses and the theoretical formulation of the model are described in Sections 2 and 3. Section 4 describes the verification and validation effort and the sensitivity and uncertainty analyses. Finally, Section 5 describes the graphical user interface, software installation, and test cases for the user.
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