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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS2024

Risk of Bone Fracture due to Spaceflight-induced Changes to Bone

The Human Research Program (HRP) is taking a biomechanical approach to assessing subsequent fracture risk in active astronauts as a consequence of spaceflight exposure. Triennial testing of active and retired astronauts continues as Space Medicine monitors for a premature diagnosis of primary osteoporosis, which is associated with age-related bone loss and skeletal fragility. This updated 2023 Fracture Evidence Report has expanded the description of skeletal changes to capture the full effects of spaceflight on bone: • Recent analysis of fractures from health records of the full astronaut cohort, suggests an increased incidence rate of hip and spine fractures in astronauts following longer spaceflight duration flights compared to incident rates found in shorter duration flights. • Routine preflight-to-postflight surveillance by DXA (dual-energy x-ray absorptiometry) does not provide the full detection of loss and recovery in the long-duration (LD) astronaut nor the full recovery of hip trabecular bone. • The inclusion of hip quantitative computed tomography (QCT) in flight studies delineates effects of spaceflight, of countermeasures, and of post-flight recovery on cortical and trabecular bone parameters—some of which are verified predictors of hip fracture in the aged. • QCT detects and compares the distinct countermeasure effects of the pharmaceutical alendronate and of resistive exercise (on the Advanced Resistive Exercise Device, ARED) in specific cortical and trabecular bone sub-regions during spaceflight. • A published comparison of QCT-determined loss rates of hip trabecular bone in LD astronauts compared to terrestrial cohorts suggest that accelerated loss rates in trabecular volumetric BMD (vBMD) during spaceflight might be analogous to skeletal effects of accelerated loss rates in females due to menopause, potentially leading to disruptions in trabecular microarchitecture. • A dataset of finite element (FE) estimates of hip bone strength in aging terrestrial cohorts (spanning astronaut age-range) provides comparative context for changes in the FE of hip bone strength in LD astronauts, including comparison (force unit of newton) to percentiles (50th, 75th, and 100th) of sex-matched aged humans with hip fractures. • Risk of fracture, due to the mechanical overloading of bones, is being updated with IMPACT, the next-generation tool suite for probabilistic risk assessment (PRA) for exploration missions being created by the Exploration and Medical Capability Element (ExMC) at NASA. IMPACT is currently in development and will not be included in this 2024 update. The risk for fracture necessitates understanding the relationship between applied loads to bone and the biomechanical competence of bone. The Risk for Early Onset Osteoporosis focuses on the weakened condition of bone (including development of new technologies, measurements of novel skeletal attributes, translation of multiple measures to an index of bone fragility, and interpretations of data used to reflect a weakened bone), while the Risk for Fracture assesses factors that influence the probability an astronaut would encounter applied loads exceeding the biomechanical competence of bones, resulting in fracture. This Evidence Report combines the research gaps and tasks associated with both risks.

Fracture↗
NASA NTRS2024

Modeling Impacts of Dust Mineralogy on Fast Climate Response

Mineralogical composition drives dust impacts on Earth's climate systems. However, most climate models still use homogeneous dust, without accounting for the temporal and spatial variation in mineralogy. To quantify the radiative impact of resolving dust mineralogy on Earth's climate, we implement and simulate the distribution of dust minerals (i.e., illite, kaolinite, smectite, hematite, calcite, feldspar, quartz, and gypsum) from Claquin et al. (1999) (C1999) and activate their interaction with radiation in the GFDL AM4.0 model. Resolving mineralogy reduces dust absorption compared to the homogeneous dust used in the standard GFDL AM4.0 model that assumes a globally uniform hematite volume content of 2.7 % (HD27). The reduction in dust absorption results in improved agreement with observation-based single-scattering albedo (SSA), radiative fluxes from CERES (the Clouds and the Earth's Radiant Energy System), and land surface temperature from the CRU (Climatic Research Unit) compared to the baseline HD27 model version. It also results in distinct radiative impacts on Earth's climate over North Africa. Over the 19-year (from 2001 to 2019) modeled period during JJA (June–July–August), the reduction in dust absorption in AM4.0 leads to a reduction of over 50 % in net downward radiation across the Sahara and approximately 20 % over the Sahel at the top of the atmosphere (TOA) compared to the baseline HD27 model version. The reduced dust absorption weakens the atmospheric warming effect of dust aerosols and leads to an alteration in land surface temperature, resulting in a decrease of 0.66 K over the Sahara and an increase of 0.7 K over the Sahel. The less warming in the atmosphere suppresses ascent and weakens the monsoon inflow from the Gulf of Guinea. This brings less moisture to the Sahel, which combined with decreased ascent induces a reduction of precipitation. To isolate the effect of reduced absorption compared to resolving spatial and temporal mineralogy, we carry out a simulation where the hematite volume content of homogeneous dust is reduced from 2.7 % to 0.9 % (HD09). The dust absorption (e.g., single-scattering albedo) of HD09 is comparable to that of the mineralogically speciated model on a global mean scale, albeit with a lower spatial variation that arises solely from particle size. Comparison of the two models indicates that the spatial inhomogeneity in dust absorption resulting from resolving mineralogy does not have significant impacts on Earth's radiation and climate, provided there is a similar level of dust absorption on a global mean scale before and after resolving dust mineralogy. However, uncertainties related to emission and distribution of minerals may blur the advantages of resolving minerals to study their impact on radiation, cloud properties, ocean biogeochemistry, air quality, and photochemistry. On the other hand, lumping together clay minerals (i.e., illite, kaolinite, and smectite), but excluding externally mixed hematite and gypsum, appears to provide both computational efficiency and relative accuracy. Nevertheless, for specific research, it may be necessary to fully resolve mineralogy to achieve accuracy.

Soil dust↗
NASA NTRS1967

Welding, bonding, and sealing of refractory metals by vapor deposition

Plating process welds, bonds, and seals refractory metals without weakening or changing the structure of the base metals. A metal halide compound in the vapor phase is decomposed to deposit filler metal on the base metal. The resulting bond is a true metal-to-metal bond.

Source record↗
NASA NTRS1972

Stimulus control in pigeons after extended discriminative training

The effects of amount of training on conditioned inhibition and on the degree of stimulus control were studied using pigeons. The ability of an S- associated with non-reinforcement of suppress positive reinforced behavior was acquired very rapidly during discriminative training. Increased S+, S- training appeared to weaken this conditioned inhibitory effect while at the same time more S+ training apparently increased the amount of external inhibition (non-conditioned inhibition) of positively reinforced behavior by a novel stimulus. Behavioral contrast and incremental generalization gradients along the S- dimension (inhibitory dimensional control) were absent at all stages of training. Behavioral contrast and inhibitory dimensional control are therefore not necessary concomitants of conditioned inhibition by an S-. A new method of assessing the suppressive effects of stimuli during generalization tests was described.

Yarczower, M.↗
NASA NTRS1972

A comparison of reliability and conventional estimation of safe fatigue life and safe inspection intervals

Both the conventional and reliability analyses for determining safe fatigue life are predicted on a population having a specified (usually log normal) distribution of life to collapse under a fatigue test load. Under a random service load spectrum, random occurrences of load larger than the fatigue test load may confront and cause collapse of structures which are weakened, though not yet to the fatigue test load. These collapses are included in reliability but excluded in conventional analysis. The theory of risk determination by each method is given, and several reasonably typical examples have been worked out, in which it transpires that if one excludes collapse through exceedance of the uncracked strength, the reliability and conventional analyses gave virtually identical probabilities of failure or survival.

Hooke, F. H.↗
NASA NTRS1972

Technology Development of a Biowaste Resistojet, Volume 2

The thruster development effort of the biowaste resistojet program is reported. Under this program, several variations of the concentric tube resistojet were built and tested. Because of the corrosive nature of the biowaste gases available for propellants, thruster effort was concentrated on the use of noble metals (platinum and its alloys) for the critical center tube heating element. This tube must operate at high temperatures. Initially the biowaste gases were projected to be CO2, CH4, H2O or H2 with only very small amounts of O2 or N2. However, during 1971, results from experimental life support tests indicated that the oxygen content would probably be in the range from 0.5 to 1.0%. To achieve the desired high specific impulses, metal temperatures as high as 1700 K (3060 R) were considered desirable goals. The first thruster, designated Mark 1, employed the alloy platinum-rhodium for the center tube. Although this material was oxidation resistant and had high strength relative to pure platinum, experimental materials tests showed that this alloy suffered from carbonyl reactions when tested on pure CO2. These reactions resulted in a depletion of rhodium and significantly weakened the tubes. The next series of thrusters were designated Mark 2 and employed platinum-iridium for the center tubes.

Phillips, D. G.↗
NASA NTRS1971

Application of space benefits to education.

Information is given on the conduct of a summer teacher workshop designed to strengthen a weakened public interest in the benefits of space programs to various aspects of life. The workshop is part of an educational program for teachers based on the NASA Marshall Space Flight Center industrial facilities and displays at the Alabama Space and Rocket Center.

Dannenberg, K. K.↗
NASA NTRS1972

Photoelectric line profiles in umbral spectra.

Umbral line profiles of H-alpha, NaD2 and HeI 10830 have been observed photoelectrically with a pressure scanning spectrometer. The H-alpha line profile shows, in a medium-sized spot, a pronounced weakening in the wings but a persistence of the line core in agreement with the results of Fricke and Elsaesser (1965). The profile of the HeI 10830 line shows an unexpected strengthening over the umbra of the two spots which have been observed. The NaD2 line profile together with continuum observations at 4260, 5890, and 6530 A have been accounted for with an empirical (T, tau) relation by one of us (Yun, 1971). The wavelength dependence and the absolute values from 4000 to 14,000 A of the intensity curve generated by this relation shows very good agreement with the intensities observed by Woehl et al. (1970) in a spot of similar diameter.

Fay, T. D.↗
NASA NTRS1973

A photometric perturbation of the counterglow.

An example of photometric variability of a counterglow region in the antisolar direction is discussed. A speculative interpretation of its significance leads to the suggestion that the weakened radiance of the counterglow may in this case be due to a dust cloud of scattering material in the general region of the earth-moon system.

Roach, F. E.↗
NASA NTRS1974

Proposed geomagnetic control of semiannual waves in the mesospheric zonal wind

The polar semiannual oscillation in zonal wind can explain midwinter weakening of the polar vortex and the relatively short stratospheric and mesospheric summar easterlies. The phase of the wind oscillation is equinoctial, as is the phase of the semiannual component in magnetic storm activity. For a given altitude, the contours of amplitude of the semiannual wind oscillation have less variability in geomagnetic than in geographic coordinates. It is suggested that polar wind oscillations are caused by the semiannual maxima in magnetic storm activity which lead to electron dissociation of O2 into O, in turn increasing ozone more rapidly than the dissociation of N2 destroys ozone, and thereby inducing a semiannual variation in the thermal and wind fields. This implies that geomagnetic processes may cause or affect the development of sudden warmings. As the tropical semiannual wind oscillation is symmetric about the geomagnetic equator, the same processes may also influence the location of the tropical wind wave.

Belmont, A. D.↗
NASA NTRS1974

A concise history of Hawaii

The review outlines the early migration of Polynesian settlers from the Marquesa and Society Islands, develops the ancient societal hierachy, reports on the historic visits of Captain Cook, and describes the gradual weakening of the native culture and population by increased foreign trade and the final annexation of the islands by the United States of America.

Greeley, C. R.↗