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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Elevated central venous pressure: a consequence of exercise training-induced hypervolemia?

Resting blood volumes and arterial and central venous pressures (CVP) were measured in 14 men before and after exercise training to determine whether training-induced hypervolemia is accompanied by a change in total vascular capacitance. In addition, resting levels of plasma arginine vasopressin (AVP), atrial natriuretic peptide (ANP), aldosterone (Ald), and norepinephrine (NE) were measured. The same measurements were conducted in seven subjects who did not undergo exercise and acted as controls. Exercise training consisted of 10 wk of controlled cycle exercise for 30 min/day, 4 days/wk at 75-80% of maximal O2 uptake (VO2max). A training effect was verified by a 20% increase in VO2max, a resting bradycardia, and a 9% increase in blood volume. Mean arterial blood pressure was unaltered by exercise training, but resting CVP increased by 16% (P less than 0.05). The percent change in blood volume from before to after training was linearly related to the percent change in CVP (r = 0.903, P less than 0.05). As a consequence of elevations in both blood volume and CVP, the volume-to-pressure ratio was unchanged after exercise training. Plasma AVP, ANP, Ald, and NE were unaltered. Our results indicate that elevated CVP is a consequence of training-induced hypervolemia without alteration in total effective venous capacitance.

NASA Program Space Physiology and Countermeasures↗
NASA NTRS2005

Structural and energetic consequences of mutations in a solvated hydrophobic cavity

The structural and energetic consequences of modifications to the hydrophobic cavity of interleukin 1-beta (IL-1beta) are described. Previous reports demonstrated that the entirely hydrophobic cavity of IL-1beta contains positionally disordered water. To gain a better understanding of the nature of this cavity and the water therein, a number of mutant proteins were constructed by site-directed mutagenesis, designed to result in altered hydrophobicity of the cavity. These mutations involve the replacement of specific phenylalanine residues, which circumscribe the cavity, with tyrosine, tryptophan, leucine and isoleucine. Using differential scanning calorimetry to determine the relative stabilities of the wild-type and mutant proteins, we found all of the mutants to be destabilizing. X-ray crystallography was used to identify the structural consequences of the mutations. No clear correlation between the hydrophobicities of the specific side-chains introduced and the resulting stabilities was found.

Solvents/chemistry↗
NASA NTRS2004

The Decompression Sickness and Venous Gas Emboli Consequences of Air Breaks During 100% Oxygen Prebreathe

Not enough is known about the increased risk of hypobaric decompression sickness (DCS) and production of venous (VGE) and arterial (AGE) gas emboli following an air break in an otherwise normal 100% resting oxygen (O2) prebreathe (PB), and certainly a break in PB when exercise is used to accelerate nitrogen (N2) elimination from the tissues. Current Aeromedical Flight Rules at the Johnson Space Center about additional PB payback times are untested, possibly too conservative, and therefore not optimized for operational use. A 10 min air break at 90 min into a 120 min PB that includes initial dual-cycle ergometry for 10 min will show a measurable increase in the risk of DCS and VGE after ascent to 4.3 psia compared to a 10 min break at 15 min into the PB, or when there is no break in PB. Data collection with humans begins in 2005, but here we first evaluate the hypothesis using three models of tissue N2 kinetics: Model I is a simple single half-time compartment exponential model, Model II is a three compartment half-time exponential model, and Model III is a variable half-time compartment model where the percentage of maximum O2 consumption for the subject during dual-cycle ergometry exercise defines the half-time compartment. Model I with large rate constants to simulate an exercise effect always showed a late break in PB had the greatest consequence. Model II showed an early break had the greatest consequence. Model III showed there was no difference between early or late break in exercise PB. Only one of these outcomes will be observed when humans are tested. Our results will favor one of these models, and so advance our understanding of tissue N2 kinetics, and of altitude DCS after an air break in PB.

Conkin, J.↗
NASA NTRS2006

Selected Systems Engineering Process Deficiencies and Their Consequences

The systems engineering process is well established and well understood. While this statement could be argued in the light of the many systems engineering guidelines and that have been developed, comparative review of these respective descriptions reveal that they differ primarily in the number of discrete steps or other nuances, and are at their core essentially common. Likewise, the systems engineering textbooks differ primarily in the context for application of systems engineering or in the utilization of evolved tools and techniques, not in the basic method. Thus, failures in systems engineering cannot credibly be attributed to implementation of the wrong systems engineering process among alternatives. However, numerous systems failures can be attributed to deficient implementation of the systems engineering process. What may clearly be perceived as a system engineering deficiency in retrospect can appear to be a well considered system engineering efficiency in real time - an efficiency taken to reduce cost or meet a schedule, or more often both. Typically these efficiencies are grounded on apparently solid rationale, such as reuse of heritage hardware or software. Over time, unintended consequences of a systems engineering process deficiency may begin to be realized, and unfortunately often the consequence is system failure. This paper describes several actual cases of system failures that resulted from deficiencies in their systems engineering process implementation, including the Ariane 5 and the Hubble Space Telescope.

Thomas, Lawrence Dale↗
NASA NTRS2008

Anticipating Cycle 24 Minimum and its Consequences: An Update

This Technical Publication updates estimates for cycle 24 minimum and discusses consequences associated with cycle 23 being a longer than average period cycle and cycle 24 having parametric minimum values smaller (or larger for the case of spotless days) than long term medians. Through December 2007, cycle 23 has persisted 140 mo from its 12-mo moving average (12-mma) minimum monthly mean sunspot number occurrence date (May 1996). Longer than average period cycles of the modern era (since cycle 12) have minimum-to-minimum periods of about 139.0+/-6.3 mo (the 90-percent prediction interval), inferring that cycle 24 s minimum monthly mean sunspot number should be expected before July 2008. The major consequence of this is that, unless cycle 24 is a statistical outlier (like cycle 21), its maximum amplitude (RM) likely will be smaller than previously forecast. If, however, in the course of its rise cycle 24 s 12-mma of the weighted mean latitude (L) of spot groups exceeds 24 deg, then one expects RM >131, and if its 12-mma of highest latitude (H) spot groups exceeds 38 deg, then one expects RM >127. High-latitude new cycle spot groups, while first reported in January 2008, have not, as yet, become the dominant form of spot groups. Minimum values in L and H were observed in mid 2007 and values are now slowly increasing, a precondition for the imminent onset of the new sunspot cycle.

Wilson, Robert M.↗
NASA NTRS2011

Coronal Mass Ejections and Their Heliospheric Consequences

Coronal mass ejections (CMEs) have been recognized as the most energetic phenomenon in the heliosphere, deriving their energy from the stressed magnetic fields on the Sun. The Solar and Heliospheric Observatory (SOHO) mission has accumulated a wealth of information on CMEs with unprecedented extent, clarity, and uniformity. The CME data base has been useful in confirming results from past missions and obtaining a number of new results on the initiation, propagation, and heliospheric consequences of CMEs. This paper highlights some of the recent results on the morphological, physical, and kinematic properties of CMEs observed during solar cycle 23. White-light signatures of CMEs and their utility in inferring coronal magnetic fields near the Sun will be discussed. Presence of coronal holes near eruption regions have been shown to significantly modify the trajectories of CMEs. New results on the interaction of CMEs with large-scale structures such as coronal holes and other CMEs will be presented. Finally, the CME consequences in the heliosphere such as interplanetary shocks, type II radio bursts, energetic particles, geomagnetic storms, and cosmic ray modulation will be discussed

Gopalswamy, Nat↗
NASA NTRS2012

System Safety and the Unintended Consequence

The analysis and identification of risks often result in design changes or modification of operational steps. This paper identifies the potential of unintended consequences as an over-looked result of these changes. Examples of societal changes such as prohibition, regulatory changes including mandating lifeboats on passenger ships, and engineering proposals or design changes to automobiles and spaceflight hardware are used to demonstrate that the System Safety Engineer must be cognizant of the potential for unintended consequences as a result of an analysis. Conclusions of the report indicate the need for additional foresight and consideration of the potential effects of analysis-driven design, processing changes, and/or operational modifications.

Watson, Clifford↗
NASA NTRS2019

An Operational Algorithm for Evaluating Satellite Collision Consequence

Risk is properly considered as the combination of likelihood and consequence; but conjunction assessment has usually limited itself to the consideration of only collision likelihood. When considered from an orbital regime protection perspective, the focus shifts to the question of the amount of debris that a collision might produce (the “consequence”). The present paper presents an operational algorithm for determining the expected amount of debris production should a conjunction result in a collision, and an assessment of the algorithm’s fidelity against a database of characterized objects.

Lechtenberg, Travis↗
NASA NTRS2019

An Operational Algorithm for Evaluating Satellite Collision Consequence

Risk is properly considered as the combination of likelihood and consequence; but conjunction assessment has usually limited itself to the consideration of only collision likelihood. When considered from an orbital regime protection perspective, the focus shifts to the question of the amount of debris that a collision might produce (the “consequence”). The present paper presents an operational algorithm for determining the expected amount of debris production should a conjunction result in a collision, and an assessment of the algorithm’s fidelity against a database of characterized objects.

Lechtenberg, Travis↗
NASA NTRSDate not supplied

Miserable Risk Estimation: “Managing” Low-Probability, High-Consequence Risks

As with all bold endeavors, NASA missions must identify and manage their risks. While estimating the consequences of these risks is typically straightforward, it can be challenging to estimate their likelihood. This is especially true for low-probability risks, due both to the lack of operational data and the cognitive biases humans bring to risk estimation. In this talk, I will present both a tongue-in-cheek and “Management Science” approach to estimating low-probability, high-consequence risks. I then summon my Human Factors colleagues to provide NASA mission managers with the gentle guidance needed to avoid common errors in risk assessment

Mary K Kaiser↗
NASA NTRSDate not supplied

Neuro-behavioral Consequences of Low Dose Radiation Social Isolation and Sex Differences in the Longevity MCAT Mouse Model

The physiological responses to spaceflight elicit wide-ranging consequences and resemble aspects of aging on Earth. Previous studies have shown that oxidative damage via reactive oxygen species (ROS), contributes to aging-related pathologies. Our study uses 1-year old C57BL/6NJ male and female mice (astronaut-relevant age) that underwent exposure to 0.5 gray of gamma radiation together with social isolation and were euthanized 12 weeks after. We used the longevity MCAT mouse model in which human catalase is overexpressed in the mitochondria, for ROS quenching. We aimed to determine whether in older mice quenching ROS, will mitigate the neuro-behavioral consequences of low dose ionizing radiation and/or social isolation and whether the outcomes will differ in males and females. We have performed five mission relevant behavioral tests which focused on performance, memory, physical stance, and stress. We have detected both sex and radiation effects; the older females look physically better are faster and perform better almost in all behavioral tests compared to their male counterparts. On the other hand, they are more sensitive to low dose radiation in many cases, in some cases this effect was indeed mitigated in the MCAT mice, pointing out to the importance of ROS in response to radiation stress and social isolation. We have measured plasma (7- and 90-days post radiation), cytokines, corticosterone and hippocampal cytokine and microglial activation at the end of the experiment. We saw significant changes in the plasma markers due to radiation, sex, and genotype in both short and long post radiation period and detected long term sex and radiation effects in the brain. Our focus is now on applying advanced statistical modeling to corelate the behavioral tests with our recent molecular findings to look for specific biomarkers that could predict behavioral deficits.

radiation↗
NASA NTRS1972

Longer term consequences of the Short Take-Off and Landing (STOL) aircraft system

An assessment of the STOL aircraft and the various means of employing it are discussed in the light of a research study to evaluate the efficacy of such analyses. It was determined that current approaches to assessment are generally inadequate for investigating the full social consequences of implementing a new technology. It is stated that a meaningful methodology of technology assessment must reflect mechanisms underlying the relationship of technology to social change. Interrelated methods which are discussed are: (1) gaming and simulation as heurisitic approaches in analysis and inquiry, (2) long range planning and questions of the future, (3) planning theory as a background for critical analysis of policy planning, and (4) social theory, with particular emphasis on social change and systems theories.

Laporte, T. R.↗
NASA NTRS1975

The non-homogeneous accumulation model for terrestrial planet formation and the consequences for the atmosphere of Venus

The nonhomogeneous-accumulation model for the formation of the terrestrial planets is described, and its consequences for the formation of the Venusian atmosphere are assayed in the context of our knowledge of the composition of the earth and carbonaceous chondrites. The relative abundances of the low-temperature condensibles in the reservoirs at the earth's surface are applied to Venus. Although carbonaceous chondrites show similar properties for the chemically bound elements, they show large deficiencies for the rare gases. The major gases on Venus, by volume, are predicted to be 98.12% CO2, 1.86% N2 and 0.02% Ar-40.

Turekian, K. K.↗
NASA NTRS1977

Electrostatically unstable heat flow during solar flares and its consequences

This paper examines some of the consequences of an electrostatically unstable return current associated with heat conduction during a solar flare. It is noted that an electrostatically unstable return current will lead to strong hydrodynamic effects and more rapid magnetic-field thermalization if reconnection is the source of primary energy release during a solar flare.

Spicer, D. S.↗
NASA NTRS1978

Orbital topography and other astrophysical consequences of Rosen's bimetric theory of gravity

Since Rosen's bimetric theory of gravity provides at present a worthy devil's advocate for the black hole hypothesis, it is important for eventual observational work to elaborate the astrophysical consequences and possibilities peculiar to it. This work is begun by deriving the orbital topography of the spherically symmetric solution to Rosen's field equations - which is relevant to the behavior of relativistic axisymmetric accretion flows - and calculating predicted accretion disk efficiencies, which can be as much as 2.5 times higher than for a disk in Schwarzschild. Thereafter, a brief treatment of the shortest kinematic time scale and the time dilations for in-falling material is given. Finally it is shown that Birkhoff's theorem does not hold in Rosen's theory, and, therefore, that genuine gravitational monopole radiation is possible. The energy it carries, however, is not positive definite.

Stoeger, W. R.↗