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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 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

An evaluation of coding methodologies for potential use in the Alabama Resource Information System (ARIS)-transportation study for the state of Alabama

Procedures developed for digitizing the transportation arteries, airports, and dock facilities of Alabama and placing them in a computerized format compatible with the Alabama Resource Information System are described. The time required to digitize by the following methods: (a) manual, (b) Telereadex 29 with film reading and digitizing system, and (c) digitizing tablets was evaluated. A method for digitizing and storing information from the U. T. M. grid cell base which was compatible with the system was developed and tested. The highways, navigable waterways, railroads, airports, and docks in the study area were digitized and the data stored. The manual method of digitizing was shown to be best for small amounts of data, while the graphic input from the digitizing tablets would be the best approach for entering the large amounts of data required for an entire state.

Montgomery, O. L.↗
NASA NTRS1977

Mathematical modelling of a human external respiratory system

A closed system of algebraic and common differential equations solved by computer is investigated. It includes equations which describe the activity pattern of the respiratory center, the phrenic nerve, the thrust produced by the diaphragm as a function of the lung volume and discharge frequency of the phrenic nerve, as well as certain relations of the lung stretch receptors and chemoreceptors on various lung and blood characteristics, equations for lung biomechanics, pulmonary blood flow, alveolar gas exchange and capillary blood composition equations to determine various air and blood flow and gas exchange parameters, and various gas mixing and arterial and venous blood composition equations, to determine other blood, air and gas mixing characteristics. Data are presented by means of graphs and tables, and some advantages of this model over others are demonstrated by test results.

Source record↗
NASA NTRS1977

Specialized physiological studies in support of manned space flight

Breath-by-breath measurements of pulmonary capillary O2 transfer and ventilation with a box-balloon spirometer and mass spectrometer were made on 3 subjects before, during and after 10 min of lower body negative pressure (LBNP) at -20, -40 and -60 Torr with arterial samples at -60 Torr. Deficits in blood O2 stores (O2B) were noted during LBNP with repayment of O2B during recovery being related to the intensity of LBNP stress. Concurrent calf volume, measured with a Hg strain gauge, decreased towards baseline well before the peak rise in pulmonary capillary O2 transfer after the release of LBNP which signified that O2B changes were related to blood volume shifts. The return of O2-depleted pooled blood to the central circulation during the first min. of recovery caused significant stress-related hyperpnea which peaked near 30 sec. and returned to near baseline after the first min. Three-compartment lung model analyses indicated an increase in the ventilated unperfused lung fraction from 0.09 to 0.17 with the effective compartment decreasing from 0.83 to 0.77. It appears that the 30% increase in ventilation equivalent was primarily the result of less effective lung perfusion during the LBNP.

Source record↗
NASA NTRS1977

Performance of the 12 GHz, 200 watt Transmitter Experiment Package for the Hermes Satellite

Performance characteristics from on-orbit tests of the Transmitter Experiment Package (TEP) for the Hermes Satellite are presented. The tests were conducted from February 8, 1976 through August 8, 1977. The TEP consists of a Power Processing System (PPS), an Output Stage Tube (OST) and a Variable Conductance Heat Pipe System (VCHPS), all of which are described. The OST is a coupled-cavity traveling wave tube with a multistage depressed collector and a stepped velocity-tapered slow wave structure for efficiency enhancement. It has an RF output power of 233 W and overall efficiency of 50.75% at a center band frequency of 12.080 GHz. The PPS provides the required operating voltages, regulation, control and protection for the OST. The VCHPS consists of a fin radiator and three dual-artery stainless steel heat pipes using methanol and a mixture of inert gases. Test results presented include efficiencies, RF output power and body current. A discussion of thermal anomalies which occurred is presented.

Alexovich, R. E.↗
NASA NTRS1978

Extent of utilization of the Frank-Starling mechanism in conscious dogs

The left ventricular end-diastolic pressure-dimension relationships in conscious dogs were studied; the ventricle was stressed to its limit in terms of myocardial preload in order to assess the extent of use of the Frank-Starling mechanism under these conditions. The preload was increased through volume loading with saline infusions, the provocation of global myocardial ischemia by constriction of the left main coronary artery, and infusion of methoxamine. While left ventricular end-diastolic pressure increased substantially in the reclining conscious animals, the left ventricular end-diastolic diameter did not increase, suggesting a minimum role for the Frank-Starling mechanism in this case.

Boettcher, D. H.↗
NASA NTRS1978

Investigation of a cryogenic thermal diode

This paper describes a series of parametric investigations to determine the effect of various fluid charges on the performance of a 0.635-cm-diameter spiral-artery, liquid-trap diode in both the forward and reverse modes. Specific parameters such as forward- and reverse-mode conductances, shutdown times and energies, and recovery to forward-mode operation, are evaluated for ethane as a working fluid in the temperature range 170 K to 220 K. Results indicate that the heat pipe will not reliably start up in the forward mode. However, startup can be initiated when preceded by a diode reversal. Also concluded are data which show the susceptibility of the diode to fluid charge and tilt. The optimum fluid charge was found to be 2.67 g, and transport capability at this charge was in excess of 1200 W-cm at 200 K. The diode in the reverse mode exhibited a rapid shutdown (within 9 min) with a shutdown energy of 1150 J (0.32 Wh).

Williams, R. J.↗
NASA NTRS1978

High temperature heat pipe research at NASA Lewis Research Center

In the course of studies of thermionic power plants for space applications, high-temperature refractory metal heat pipes have been designed and built for alkali metal working fluids. Fabrication of tungsten wire-reinforced tantalum pipes by chemical vapor deposition is discussed; the development of reinforced pipes with integral arteries produced by chemical vapor deposition is also mentioned. The feasibility of using lithium, sodium, potassium, cesium or mercury as the working fluid in the heat pipes is also reviewed. Operation of a lithium-filled heat pipe of about 3-kW capacity for several thousand hours is reported.

Tower, L. K.↗
NASA NTRS1979

Thermal anomalies of the transmitter experiment package on the communications technology satellite

The causes of four temporary thermal-control-system malfunctions that gave rise to unexpected temperature excursions in the 12-gigahertz, 200-watt transmitter experiment package (TEP) on the Communications Technology Satellite were investigated. The TEP consists of a nominal 200-watt output stage tube (OST), a supporting power-processing system (PPS), and a variable-conductance heat-pipe system (VCHPS). The VCHPS, which uses three heat pipes to conduct heat from the body of the OST to a radiator fin, was designed to maintain the TEP at safe operating temperatures at all operating conditions. On four occasions during 1977, all near the spring and fall equinoxes, the OST body temperature and related temperatures displayed sudden, rapid, and unexpected rises above normal levels while the TEP was operating at essentially constant, normal conditions. The temperature excursions were terminated without TEP damage by reducing the radio frequency (RF) output power of the OST. Between the anomalies and since the fourth, the thermal control system has apparently functioned as designed. The results indicate the most probable cause of the temperature anomalies is depriming of the arteries in the variable-conductance heat pipes. A mode was identified in which the TEP, as presently configured, may operate with stable temperatures and with minimum change in performance level.

Alexovich, R. E.↗
NASA NTRS1978

CTS-type variable conductance heat pipes for SEP FM/PPU

The development effort for, and the fabrication and testing of, six CTS-type variable conductance heat pipes is described. The heat pipes are constructed of stainless steel, use methanol as a working fluid, and a nitrogen/helium mixture as the control gas. The wicking structure consists of interior wall grooves, a metal-felt diametral slab wick, and two wire-mesh arteries. The heat pipes are used to cool two Functional Model/Power Processing Units in a Solar Electric Propulsion prototype BIMOD thruster subsystem assembly. The Power Processing Units convert the electric power from a spacecraft solar array system to the voltages required to operate the electric thrusters which are part of the BIMOD assembly.

Antoniuk, D.↗
NASA NTRS1979

Medical science in Siberia: Oxygen exchange in the Far North

Differences in oxygen conditions between the native and migrant Siberian population were studied in relation to respiratory function, arterial and venous blood indicators and acid-base indicators. Significant adaptation differences were ascertained between the two populations.

Kulikov, V.↗
NASA NTRS1974

Evaluation of exercise-respiratory system modifications and preliminary respiratory-circulatory system integration scheme

The respiratory control system, functioning as an independent system, is presented with modifications of the exercise subroutine. These modifications illustrate an improved control of ventilation rates and arterial and compartmental gas tensions. A very elementary approach to describing the interactions of the respiratory and circulatory system is presented.

Gallagher, R. R.↗
NASA NTRS1978

User's instructions for the erythropoiesis regulatory model

The purpose of the model provides a method to analyze some of the events that could account for the decrease in red cell mass observed in crewmen returning from space missions. The model is based on the premise that erythrocyte production is governed by the balance between oxygen supply and demand at a renal sensing site. Oxygen supply is taken to be a function of arterial oxygen tension, mean corpuscular hemoglobin concentration, oxy-hemoglobin carrying capacity, hematocrit, and blood flow. Erythrocyte destruction is based on the law of mass action. The instantaneous hematocrit value is derived by integrating changes in production and destruction rates and accounting for the degree of plasma dilution.

Source record↗
NASA NTRS1974

Evaluation of exercise-respiratory system modifications and integration schemes for physiological systems

Exercise subroutine modifications are implemented in an exercise-respiratory system model yielding improvement of system response to exercise forcings. A more physiologically desirable respiratory ventilation rate in addition to an improved regulation of arterial gas tensions and cerebral blood flow is observed. A respiratory frequency expression is proposed which would be appropriate as an interfacing element of the respiratory-pulsatile cardiovascular system. Presentation of a circulatory-respiratory system integration scheme along with its computer program listing is given. The integrated system responds to exercise stimulation for both nonstressed and stressed physiological states. Other integration possibilities are discussed with respect to the respiratory, pulsatile cardiovascular, thermoregulatory, and the long-term circulatory systems.

Gallagher, R. R.↗
NASA NTRS1978

Lithium and potassium heat pipes for thermionic converters

A prototypic heat pipe system for an out-of-core thermionic reactor has been built and tested. The emitter of the concentric thermionic converter consists of the condenser of a tungsten heat pipe utilizing a lithium working fluid. The evaporator section of the emitter heat pipe is radiation heated to simulate the thermal input from the nuclear reactor. The emitter heat pipe thermal transport is matched to the thermionic converter input requirement. The collector heat pipe of niobium, 1%-zirconium alloy uses potassium as the working fluid. The thermionic collector is coupled to the heat pipe by a tapered conical joint designed to minimize the temperature drop. The area ratio of the evaporator to condenser is 16:1, which increases the radiation area. The composite wick structure consists of seven arteries and cylindrical wraps. The collector heat flux matches the design requirements of the thermionic converter.

Miskolczy, G.↗
NASA NTRS1978

Telemetry of intracranial pressure

A completely implantable epidural pressure telemetry system designed for accurate measurement of intracranial pressure (ICP) is described. The implant device is batteryless, providing unlimited operating life. The described system uses a capacitive pressure transducer with excellent long-term stability. Once detected with the transducer and converted to a frequency with the oscillator electronics, the pressure signal is digitized. It is then telemetered without the possibility of further degradation. After detection with the small external module, the data can be retransmitted by a radio link for complete patient mobility or the energizer signal pickup module can be wired to a bedside readout unit. Continuous data are available from the system so that the dynamic ICP changes reflecting arterial blood pressure can be observed and used for diagnosis.

Fryer, T. B.↗
NASA NTRS1979

Effects of regional hemoconcentration during LBNP on plasma volume determinations

Blood samples were obtained from forearm vein or artery with indwelling cannula (1) before, (2) during the last min, and (3) about 2 min after lower body negative pressure (LBNP) in 16 experiments to determine whether plasma volume (PV) estimates were affected by regional hemoconcentration in the lower body. Total hemoglobin (THb) was estimated with the CO method prior to LBNP. Hemoglobin (Hb) and hematocrit (Hct) values from (2) gave only a 3% (87 ml) loss in PV due to LBNP, assuming no change in THb. However, Hb and Hct values from (3) showed an 11% loss in PV (313 ml). This 72% underestimation of PV loss with (2) must have resulted from the sequestration of blood and subsequent hemoconcentration in the lower body during LBNP. The effects of LBNP on PV should be estimated 1-3 min after exposure, after mixing but before extravascular fluid returns to the circulation.

Loeppky, J. A.↗
NASA NTRS1979

Cardiopulmonary readjustments in passive tilt

The readjustment of cardiopulmonary variables in human volunteers at various tilt angles on a tilt board is studied. Five healthy subjects (18-31 yr) with thorough knowledge of the experimental protocol are tested, passively tilted from the supine to the upright position in 15-deg increments in random sequence. The parameters measured are cardiac output (Q), heart rate (HR), stroke volume (SV), minute and alveolar ventilation /V(E) and V(A)/, functional residual capacity (FRC), and arterial-end-tidal P(CO2) pressure difference. It is found that changes in Q and FRC are linearly related to the sine of the tilt angle, indicating that either reflexes are absent or their net effect is proportional to the effects of gravity. This is clearly not the case for other variables /HR, SV, V(E), V(A)/, where it is possible to demonstrate threshold values for the appearance of secondary changes.

Matalon, S. V.↗
NASA NTRS1978

Computer quantitation of coronary angiograms

A computer technique is being developed at the Jet Propulsion Laboratory to automate the measurement of coronary stenosis. A Vanguard 35mm film transport is optically coupled to a Spatial Data System vidicon/digitizer which in turn is controlled by a DEC PDP 11/55 computer. Programs have been developed to track the edges of the arterial shadow, to locate normal and atherosclerotic vessel sections and to measure percent stenosis. Multiple frame analysis techniques are being investigated that involve on the one hand, averaging stenosis measurements from adjacent frames, and on the other hand, averaging adjacent frame images directly and then measuring stenosis from the averaged image. For the latter case, geometric transformations are used to force registration of vessel images whose spatial orientation changes.

Ledbetter, D. C.↗