Keywords: space station; health; space crews; rescue operations; medical equipment; medical sciences; medicine; medical personnel; medical services
Abstract: In developing a permanently crewed space station, the importance of medical care has been continually reaffirmed; and the health maintenance facility (HMF) is an integral component. It has diagnostic, therapeutic, monitoring, and information management capability. It is designed to allow supportive care for non-life-threatening illnesses, moderate to severe, possibly life-threatening illnesses; and severe, incapacitating, life-threatening illnesses. Since the HMF will not have a general surgical capability, the need for emergency escape and recovery methods has been studied. Medical risk assessments have determined that it is impossible to accurately predict the incidence of cremember illness or injury. A best estimate is 1:3 per work-year, with 1 percent of those needing an ACRV. For an eight-person crew, this means that one ACRV will be used every 4 to 12 years. The ACRV would serve atleast three basic objectives as a crew return if the Shuttle is unavailable; an escape vehicle from a major time-critical space station emergency; and a full or partial crew return vehicle for a medical emergency. The focus of this paper is the third objective for the ACRV.
Keywords: fuel, solid fuel, diffusion flame, extinction, gas-phase radiation, kinetics, surface radiation
Abstract: This is the first attempt to analyze both radiation and detailed kinetics on the burning and extinction of a solid fuel in a stagnation-point diffusion flame. We present a detailed and comparatively accurate computation model of a solid fuel flame along with a quantitative study of the kinetics mechanism, radiation interactions, and the extinction limits of the flame. A detailed kinetics model for the burning of solid trioxane (a trimer of formaldehyde) is coupled with a narrowband radiation model with carbon dioxide, carbon monoxide, and water vapor as the gas-phase participating media. The solution of the solid trioxane diffusion flame over the flammable regime is presented in some detail, as this is the first solution of a heterogeneous trioxane flame. We then compare the adiabatic solution to solutions that include the surface radiation only and gas-phase and surface radiation using a black surface model. The analysis includes discussion of detailed flame chemistry over the flammable regime and, in particular, at the low stretch extinction limit. We emphasize the low stretch regime of the radiatively participating flame, since this is the region representative of microgravity flames. When only surface radiation is included, two extinction limits exist, and the burning rate and maximum flame temperatures are lower, as expected. With the inclusion of surface and gas-phase radiation, results show that, while flame temperatures are lower, the burning rate of the trioxane diffusion flame may actually increase at low stretch rate due to radiative feedback from the flame to the surface.
Keywords: pressure reduction; decompression sickness; hypobaric atmospheres; altitude chamber; tissue ratio; extravehicular activity
Abstract: It is important to understand the risk of serious hypobaric decompression sickness (DCS) to develop procedures and treatment responses to mitigate the risk. Since it is not ethical to conduct prospective tests about serious DCS with humans, the necessary information was gathered from 73 published reports. We hypothesize that a 4-hr 100% oxygen (O2) prebreathe results in a very low risk of serious DCS, and test this through analysis. We evaluated 258 tests containing information from 79,366 exposures in altitude chambers. Serious DCS was documented in 918 men during the tests. A risk function analysis with maximum likelihood optimization was performed to identify significant explanatory variables, and to create a predictive model for the probability of serious DCS. Useful variables were Tissue Ratio, the planned time spent at altitude, and whether or not repetitive exercise was performed at altitude. A prebreathe and decompression profile Shuttle astronauts use for extravehicular activity (EVA) includes a 4-hr prebreathe with 100% O2, an ascent to P2 = 4.3 lb per sq. in. absolute, and a Talt = 6 hr. Given 100 Shuttle EVAs to date and no report of serious DCS, the true risk is less than 0.03 with 95% confidence. It is problematic to estimate the risk of serious DCS since it appears infrequently, even if the estimate is based on thousands of altitude chamber exposures. The true risk to astronauts may lie between the extremes of the confidence intervals since the contribution of other factors, particularly exercise, to the risk of serious DCS during EVA is unknown. A simple model that only accounts for four important variables in retrospective data is still helpful to increase our understanding about the risk of serious DCS.
Keywords: Vlasov-Maxwell Equation; equations; Vlasov Equations; Maxwell Equations; electron distribution; Jacobi Equation; hypergeometric functions
Abstract: A spectral method algorithm is developed for the numerical solution of the full six-dimensional Vlasov-Maxwell system of equations. Here, the focus is on the electron distribution function, with positive ions providing a constant background. The algorithm consists of a Jacobi polynomial-spherical harmonic formulation in velocity space and a trigonometric formulation in position space. A transform procedure is used to evaluate nonlinear terms. The algorithm is suitable for performing moderate resolution simulations on currently available supercomputers for both scientific and engineering applications.
Keywords: carbon nanotubes, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffractometry, thermogravimetric analysis
Abstract: This report summarizes the comparison of a variety of procedures used to purify carbon nanotubes. Carbon nanotube material is produced by the arc process and laser over process. Most of the procedures are tested using laser-grown, single-wall nanotube material. The material is characterized at each step of the purification procedures by using different techniques including a scanning electron microscope, energy-dispersive X-ray spectroscopy, a transmission electron microscopy, Raman, X-ray diffractometry, a thermogravimetric analysis, nuclear magnetic resonance, and high-performance liquid chromatography. The identified impurities are amorphous and grphitic carbon, catalyst particle aggregates, fullerenes, and hydrocarbons. Solvent extraction and low-temperature annealing are used to reduce the amount of volatile hydrocarbons and dissolve fullerenes. Metal catalysts and amorphous as well as graphitic carbon are oxidized by reflux in acids including HCl, HNO3 and HF and other oxidizers such as H2O2. High-temperature annealing in vacuum and in inert atmosphere helps to improve the quality of single-wall nanotubes by increasing crystallinity and reducing intercalation.
Keywords: International Space Station; Space Shuttle; Mir; cleaning; cleanliness; zero gravity; showers; human body
Abstract: Note: This document was originally published in 1997 as an International Space University Master of Space Studies student's project. While the specifics may be a little dated, the results gleaned are still relevant and valid. Johnson Space Center is now abuzz with preparations for the International Space Station. The work on various systems for the U.S. Habitation module will begin in 1998. As a prelude, the Flight Crew Support Division perceived the need to take a closer, more critical look at planning the Whole Body Cleansing function for ISS. This report is an attempt to retrieve all data available on whole body cleansing mechanisms used, past and present, by the Russians and the Americans, analyze it and create design concepts for products for zero-g cleansing on ISS. This report takes a close look at the Skylab collapsible shower, the Mir shower/sauna, the full body cleansing methods currently in use on board the Shuttle and Mir, and at the whole body shower designed and tested for Space Station Freedom. It attempts to "listen" carefully to what Mir astronauts have to say about their personal hygiene experiences during their recent stays on Mir. The findings in the report call for a change in paradigm. What is good for Earth conditions is not necessarily good for zero-g! It concludes that a shower is not a good idea for ISS. The final concept that is proposed reflects very strongly what the Mir astronauts would like to have and to use on a station like ISS. The report concludes with directions of how to take the "idea" further and realize it in the form of a product system for whole body cleansing on board ISS.
Keywords: manned spaceflight; histories; manned Mars missions; Mars probes; Mars environment; strategy; mission planning; Viking Mars Program
Abstract: The history of human Mars mission planning from the early 1950s through the 1960s is examined. For centuries, Mars has been an object of fascination and, since the 1800s, science fiction authors have imagined what it would be like for humans to travel to that planet. Space enthusiasts have shared this dream and as early as the 1950s were presenting feasible proposals for human missions to Mars. Since the creation of NASA, the Agency has maintained the idea of human Mars missions as an important long-term goal. Throughout its history, NASA has conducted studies aimed at landing an astronaut on Mars. NASA's current strategic plan still includes this goal. Therefore, it is important to look at previous planning efforts to see what work has been accomplished and to discover lessons that future planners can apply to their programs.
Keywords: decompression sickness; doses, biological effects; altitude sickness; decompression; altitude simulation; exercise physiology; extravehicular activity
Abstract: Decompression sickness (DCS) is a complex, multivariable problem. A mathematical description or model of the likelihood of DCS requires a large amount of quality research data, ideas on how to define a decompression dose using physical and physiological variables, and an appropriate analytical approach. It also requires a high-performance computer with specialized software. I have used published DCS data to develop my decompression doses, which are variants of equilibrium expressions for evolved gas plus other explanatory variables. My analytical approach is survival analysis, where the time of DCS occurrence is modeled. My conclusions can be applied to simple hypobaric decompressions - ascents lasting from 5 to 30 minutes - and, after minutes to hours, to denitrogenation (prebreathing). They are also applicable to long or short exposures, and can be used whether the sufferer of DCS is at rest or exercising at altitude. Ultimately I would like my models to be applied to astronauts to reduce the risk of DCS during spacewalks, as well as to future spaceflight crews on the Moon and Mars.
Keywords: Mars; manned Mars missions; Mars surface; mission planning; exploration; space
Abstract: This document describes current expectations for the activities of human and robotic crews, and the associated support equipment, that will occur as they explore the surface of Mars. These descriptions, made at a functional level, were prepared assuming a split-mission architecture. It should be noted that these descriptions can, in general, be used in conjunction with other mission approaches. The Mars Surface Reference Mission is a tool used by the Exploration Team and the exploration community to compare and evaluate approaches to surface activities. Intended to identify and clarify system drivers, or significant sources of cost, performance, risk, and schedule variation, it does not represent a final or recommended approach. The Exploration Team is currently studying alternative scenarios, including technical approaches to solving mission and technology challenges, and human exploration missions to the Moon, asteroids, or other targets beyond Earth orbit. Comparing alternative approaches in this way provides the basis for continual improvement to technology investment plans and a general understanding of future human exploration missions. This document has been divided into several major sections. The first provides an overview of the split-mission approach, to provide a framework for the surface mission. The remainder is devoted to a series of vignettes describing key activities or functions that will be a part of the surface mission. This document represents a “snapshot” of work in progress in support of planning through October 1998 for future human exploration of the Martian surface. Publications of revisions to this document are planned.
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