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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 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Location of unidentified weak X-ray sources by the HEAO-1 scanning modulation collimator

Four weak sources for which precise positions have been obtained from the HEAO-1 Scanning Modulation Collimator (MC) experiment are discussed. One source (4U 0446+44) with the center of the cluster of galaxies containing 3C129 and 3C129.1 has been identified, and its angular size has been measured. One source with a galactic star is identified, although it is at galactic latitude b = 51 deg. The other two sources, 2A 0526-328 and 2A 0922-317, remain unidentified.

Schwartz, D. A.↗
NASA NTRS1978

Evaporative water loss in man in a gravity-free environment

Daily evaporative water losses (EWL) during the three Skylab missions were measured indirectly using mass and water-balance techniques. The mean daily values of EWL for the nine crew members who averaged 1 hr of daily exercise were: preflight 1,750 + or - 37 (SE) ml or 970 + or - 20 ml/sq m and inflight 1,560 + or - 26 ml or 860 + or - 14 ml/sq m. Although it was expected the EWL would increase in the hypobaric environment of Skylab, an average decrease from preflight sea-level conditions of 11% was measured. The results suggest that weightlessness decreased sweat losses during exercise and possibly reduced insensible skin losses. The weightlessness environment apparently promotes the formation of an observed sweat film on the skin surface during exercise by reducing convective flow and sweat drippage, resulting in high levels of skin wettedness that favor sweat suppression.

Leach, C. S.↗
NASA NTRS1978

A review of the consequences of fluid and electrolyte shifts in weightlessness

This review describes the renal-endocrine mechanisms related to the early losses of fluid-electrolytes from the body during weightlessness as well as their contribution to longer term adaptation of fluid-electrolyte balance. The hypotheses presented were generated by a systematic analysis of body fluid and renal dynamics observed under conditions of actual and simulated spaceflight. These have increased our understanding of the effects of acute headward fluid shifts on renal excretion, the factors promoting excess sodium excretion and the regulation of extracellular fluid composition.

Leach, C. S.↗
NASA NTRS1979

Parameter estimation in X-ray astronomy using maximum likelihood

Methods of estimation of parameter values and confidence regions by maximum likelihood and Fisher efficient scores starting from Poisson probabilities are developed for the nonlinear spectral functions commonly encountered in X-ray astronomy. It is argued that these methods offer significant advantages over the commonly used alternatives called minimum chi-squared because they rely on less pervasive statistical approximations and so may be expected to remain valid for data of poorer quality. Extensive numerical simulations of the maximum likelihood method are reported which verify that the best-fit parameter value and confidence region calculations are correct over a wide range of input spectra.

Wachter, K.↗
NASA NTRS1978

Abiotic synthesis of fatty acids

The formation of fatty acids by Fischer-Tropsch-type synthesis was investigated with ferric oxide, ammonium carbonate, potassium carbonate, powdered Pueblito de Allende carbonaceous chondrite, and filings from the Canyon Diablo meteorite used as catalysts. Products were separated and identified by gas chromatography and mass spectrometry. Iron oxide, Pueblito de Allende chondrite, and Canyon Diablo filings in an oxidized catalyst form yielded no fatty acids. Canyon Diablo filings heated overnight at 500 C while undergoing slow purging by deuterium produced fatty acids only when potassium carbonate was admixed; potassium carbonate alone also produced these compounds. The active catalytic combinations gave relatively high yields of aliphatic and aromatic hydrocarbons; substantial amounts of n-alkenes were almost invariably observed when fatty acids were produced; the latter were in the range C6 to C18, with maximum yield in C9 or 10.

Leach, W. W.↗
NASA NTRS1980

Spacecraft radiators for advanced mission requirements

Design requirements for spacecraft heat rejection systems are identified, and their impact on the construction of conventional pumped fluid and hybrid heat pipe/pumped fluid radiators is evaluated. Heat rejection systems to improve the performance or reduce the cost of the spacecraft are proposed. Heat rejection requirements which are large compared to those of existing systems and mission durations which are relatively long, are discussed.

Leach, J. W.↗
NASA NTRS1979

Optimum design of spacecraft radiators for large capacity or long duration mission applications

Results of trade studies comparing optimum pumped fluid and hybrid heat pipe/pumped fluid radiator designs are presented. Design variables considered in the system optimization analyses include transport fluid properties and Reynolds number, pump loop component reliabilities, micrometeoroid protection, heat pipe spacing, manifolding and flow routing in pumped fluid designs, transport tubing spacing and diameters, and radiator fin parameters. Criteria for evaluating candidate radiator system designs include mass, radiator area, and overall system reliability. The studies show advantages in constructing large systems from small independent subsystems with oversizing to account for subsystem failures. The optimum size and survivability of the subsystems are identified as a function of the radiator construction, the system heat rejection requirements, the mission duration, and the system reliability requirements.

Leach, J. W.↗
NASA NTRS1979

A study of metabolic balance in crewmembers of Skylab IV

A metabolic balance study was conducted on the three crewmembers of the 84-day Skylab IV earth orbital mission. Dietary intake was controlled, monitored, and kept very nearly constant for a period commencing 21 days prior to flight, throughout flight, and for a period of 18 days postflight. Within the first 30 days of flight urine calcium rose to a level approx. 100% above preflight levels and remained elevated for the remainder of the flight. Fecal calcium excretion increased more slowly but continued to accelerate throughout the flight and did not return to baseline levels during the postflight period. Urinary nitrogen increased to 25-30% above preflight levels within one month following launch and thereafter gradually subsided toward control values. The overall losses of calcium averaged approx. 200 mg per day throughout the mission while nitrogen losses averaged 590 mg. Various other indices of musculoskeletal deterioration are discussed and correlated. The parallelism between the effects of weightlessness and bed rest is reviewed. It is noted, that no evidence is yet available as to the identity of the initial biological response to the absence of gravity.

Rambaut, P. C.↗
NASA NTRS1979

Amino aciduria in weightlessness

Urinary excretion of amino acids by the 9 Skylab crewmen was studied as an indicator of the metabolic effects caused by exposure to the space flight environment. Intake was consistent in quality and quantity throughout the 28, 59 and 84-day flights for each of the crewmen and complete collections were accomplished. The results indicated an increased excretion in most amino acids during the first month of flight which remained elevated in the second and third months but to a lesser extent. Additional indications of change in muscle and skeletal metabolism were observed. These results point to the desirability of obtaining additional indices of alterations in protein synthetic processes in conjunction with future space flights.

Leach, C. S.↗
NASA NTRS1980

Threshold windspeeds for sand on Mars - Wind tunnel simulations

Wind friction threshold speeds for particle movement were determined in a wind tunnel operating at martian surface pressure with a 95 percent CO2 and 5 percent air atmosphere. The relationship between friction speed and free-stream velocity is extended to the critical case for Mars of momentum thickness Reynolds numbers between 425 and 2000. It is determined that the dynamic pressure required to initiate saltation is nearly constant for pressures between 1 bar and 4 mb for atmospheres of both air and CO2.

Greeley, R.↗
NASA NTRS1980

Is the weight loss of hyperbaric habitation a disorder of osmoregulation

To examine the weight loss of hyperbaric helium-oxygen habitation, the exchange of liquids and calories was measured in six men who lived in this atmosphere for 32 d. The maximum pressure was 49.5 ATA. The men lost 3.7-10.1 kg, in spite of warm ambient (31-32 C) temperatures and adequate calories (2,737 kcal/d) provided for the sedentary ways of chamber living. Weight loss and a calculated fluid deficit were accompanied by significant hemoconcentration, shown by increases in serum proteins. These changes were followed by a rise in urinary aldosterone and vasopressin, but not thirst. Weight loss in hyperbaric atmospheres is probably multifactorial, but the data suggests an uncoupling of normal osmoregulation may have occured in the present set of subjects. This may have been due to altered lung mechanics, increased catecholamines, or effects of high pressure on cellular responses to vasopressin.

Raymond, L. W.↗
NASA NTRS1981

Impulsive phase of solar flares. 1: Characteristics of high energy electrons

The variation along a magnetic field line of the energy and pitch angle distribution of high energy electrons injected into a cold hydrogen plasma containing either an open or closed magnetic field structure was investigated. The problem is formulated as a time independent Fokker-Planck Equation for the electron number distribution as a function of the electron energy, electron pitch angle, and the structure of the global magnetic field. Simple analytic solution valid in the small pitch angle regime and for slowly varying magnetic field is presented. For the more general situation a numerical code for solving the Fokker-Planck Equation was used and it was found that the analytic expression agrees well with the numerical results to values of the pitch angle much larger than expected. For most practical applications, one many confidently use the analytic expression instead of having to resort to lengthy numerical computations. These results are useful in the study of the nonthermal models of the impulsive phase of solar flares.

Leach, J.↗
NASA NTRS1981

The influence of space flight on erythrokinetics in man

An experiment is described the purpose of which is to measure specific factors relative to the control of erythrokinetics in man which might be altered during the first seven days of exposure to the weightless environment of space flight. It is anticipated that these data will provide information relative to the mechanism by which the red cell mass is reduced during space flight. Specifically, the experiment is designed to establish: (1) if there is a significant change in red cell mass and plasma volume during the initial period of exposure to weightlessness; (2) if the plasma concentration of erythropoietin is reduced; (3) if there is an increase in the plasma concentration of erythropoietin inhibitors; (4) if there is a change in the effectiveness of erythropoiesis; and (5) if the number and age distribution of reticulocytes are altered.

Leach, C. S.↗
NASA NTRS1982

Correlation of hard X-ray and type 3 bursts in solar flares

Correlations between X-ray and type 3 radio emission of solar bursts are described through a bivariate distribution function. Procedures for determining the form of this distribution are described. A model is constructed to explain the correlation between the X-ray spectral index and the ratio of X-ray to radio intensities. Implications of the model are discussed.

Petrosian, V.↗
NASA NTRS1982

Energy efficient engine: Turbine transition duct model technology report

The Low-Pressure Turbine Transition Duct Model Technology Program was directed toward substantiating the aerodynamic definition of a turbine transition duct for the Energy Efficient Engine. This effort was successful in demonstrating an aerodynamically viable compact duct geometry and the performance benefits associated with a low camber low-pressure turbine inlet guide vane. The transition duct design for the flight propulsion system was tested and the pressure loss goal of 0.7 percent was verified. Also, strut fairing pressure distributions, as well as wall pressure coefficients, were in close agreement with analytical predictions. Duct modifications for the integrated core/low spool were also evaluated. The total pressure loss was 1.59 percent. Although the increase in exit area in this design produced higher wall loadings, reflecting a more aggressive aerodynamic design, pressure profiles showed no evidence of flow separation. Overall, the results acquired have provided pertinent design and diagnostic information for the design of a turbine transition duct for both the flight propulsion system and the integrated core/low spool.

Leach, K.↗
NASA NTRS1982

The impulsive phase of solar flares. 2: Characteristics of the hard X-rays

The results of an investigation into the electron distribution in the general non-thermal models of solar flares were used to calculate the characteristics of the impulsive hard X-rays. The height distribution, the spectrum, the polarization, and directivity of the X-rays were observed and how these X-ray characteristics are affected by the parameters defining the model was investigated. An expression is obtained for the X-ray intensity as a function of source height which is an excellent fit under certain constraints. Some available data with spatial resolution are examined and it is shown that it is possible to reproduce these data adequately with the non-thermal model and to determine the values of the parameters describing the flares.

Leach, J.↗