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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Dynamically controlled crystal growth system

Crystal growth can be initiated and controlled by dynamically controlled vapor diffusion or temperature change. In one aspect, the present invention uses a precisely controlled vapor diffusion approach to monitor and control protein crystal growth. The system utilizes a humidity sensor and various interfaces under computer control to effect virtually any evaporation rate from a number of different growth solutions simultaneously by means of an evaporative gas flow. A static laser light scattering sensor can be used to detect aggregation events and trigger a change in the evaporation rate for a growth solution. A control/follower configuration can be used to actively monitor one chamber and accurately control replicate chambers relative to the control chamber. In a second aspect, the invention exploits the varying solubility of proteins versus temperature to control the growth of protein crystals. This system contains miniature thermoelectric devices under microcomputer control that change temperature as needed to grow crystals of a given protein. Complex temperature ramps are possible using this approach. A static laser light scattering probe also can be used in this system as a non-invasive probe for detection of aggregation events. The automated dynamic control system provides systematic and predictable responses with regard to crystal size. These systems can be used for microgravity crystallization projects, for example in a space shuttle, and for crystallization work under terrestial conditions. The present invention is particularly useful for macromolecular crystallization, e.g. for proteins, polypeptides, nucleic acids, viruses and virus particles.

Bray, Terry L.↗
NASA NTRS1984

Radially-Graduated Turbine-Temperature Profile

Proposed scheme to change temperature distribution in gas-turbine flame increases radially instead of remaining spatially uniform offers important advantages. Radially increasing temperature allows higher mean gas temperature, greater power output, higher rotational speed and longer life for blades. Principle suitable for axial-flow gas turbine directly in line with cylindrical combustor. Included in category many rocket, aircraft, stationary, and shipboard turbines.

Wagner, W. R.↗
NASA NTRS1989

Remote sensing of the thermal forcing on the tropical Pacific

Monthly fields of shortwave radiation (SR) and latent heat flux (LE) over the central and eastern tropical Pacific between 1980 and 1983 have been computed using satellite data. They are the dominant variable components of surface thermal forcing on the ocean in this time scale. During the 1982-1983 ENSO episode, surface-wind convergence and cloudiness associated with the displacement of equatorial organized convection caused a reduction in both the SR into the ocean and the LE out of the ocean. The lag-correlation coefficients between the forcing (SR-LE) and the sea surface temperature are found to be significantly high outside the equatorial region, showing that surface thermal forcing is the dominant factor in sea surface temperature change. In the narrow equatorial wave guide, ocean dynamics play a more important role, and surface heat flux is a consequence rather than the cause of sea surface temperature change.

Liu, W. Timothy↗
NASA NTRS1988

Antarctic springtime ozone depletion computed from temperature observations

An observationally based, mechanistic dynamical model is used to simulate the decline of total ozone during September and October for the years 1979 through 1986. Vertical velocities derived from observed stratospheric temperature changes and computed radiative heating rates are used to advect an ozone mixing ratio profile during the Antarctic spring period. An early August 1982 Syowa balloonsonde ozone profile is used to initialize the computations. The model reasonably simulates the September and October changes in total ozone, considering the uncertainties in the observed data and the radiative heating. The simulated decline is found to be very sensitive to the choice of initial ozone profile and to small changes in the radiative heating. The results of this study suggest that the dynamical hypothesis of the Antarctic ozone depletion is both quantitatively credible and consistent with the observed temperature changes.

Rosenfield, Joan E.↗
NASA NTRS1978

A numerical simulation of seasonal stratospheric climate. I - Zonal temperatures and winds

Two numerical experiments were designed to isolate the effects of seasonal and latitudinal variations in longwave radiative transfer processes. The first experiment aimed at computing the rate of temperature change in the stratosphere due to longwave radiative transfer by CO2, H2O and O3 from Ramanathan's (1976) radiative-convective model applied to the troposphere-stratosphere circulation. The second experiment employs the Newtonian cooling approximation in which the rate of temperature change in the stratosphere by longwave radiative transfer is set equal to the product of the Newtonian cooling coefficient 'h' and the departure of the local temperature from a reference temperature. It is shown that the latitudinal temperature distribution of the lower stratosphere is maintained by the combined effects of dynamics, O3 solar heating and the longwave radiative coupling between troposphere and stratosphere. The latitudinal gradient in the troposphere-stratosphere longwave radiative coupling is maximum during winter and spring. The radiative response time (1/h) of the middle and upper stratosphere undergoes significant latitudinal and seasonal variations, largely due to the temperature dependence of h.

Ramanathan, V.↗
NASA NTRS1979

Investigation of medium and high temperature phase change materials

A detailed description of the programs for acquisition and analysis of the test results is given. Basically it concerns three programs. The TEST program controls the recording of the test data. With the THELLI program it is possible to follow the temperature curve recorded for each individual thermoelement during the test. With the AUSW program the test data can be analyzed, to determine, for example, the melting point and the start of melting. The first results of the service life tests are discussed. From these it is attempted to draw inferences for the subsequent tests. An attempt is made to focus on the determination of the area-related mass loss, the reduction in thickness and the corrosion rate as well as optical and scanning electron microscope evaluation.

Heine, D.↗
NASA NTRS1977

Cooling of a sunspot

The question of whether a perturbed photospheric area can grow into a region of reduced temperature resembling a sunspot is investigated by considering whether instabilities exist that can lead to a growing temperature change and corresponding magnetic-field concentration in some region of the photosphere. After showing that Alfven cooling can lead to these instabilities, the effect of a heat sink on the temperature development of a perturbed portion of the photosphere is studied. A simple form of Alfven-wave cooling is postulated, and computations are performed to determine whether growing modes exist for physically relevant boundary conditions. The results indicate that simple inhibition of convection does not give growing modes, but Alfven-wave production can result in cooling that leads to growing field concentration. It is concluded that since growing instabilities can occur with strong enough cooling, it is quite possible that energy loss through Alfven waves gives rise to a self-generating temperature change and sunspot formation.

Boruta, N.↗
NASA NTRS2003

Leak Location and Classification in the Space Shuttle Main Engine Nozzle by Infrared Testing

The Space Shuttle Main Engine (SSME) is composed of cooling tubes brazed to the inside of a conical structural jacket. Because of the geometry there are regions that can't be inspected for leaks using the bubble solution and low-pressure method. The temperature change due escaping gas is detectable on the surface of the nozzle under the correct conditions. The methods and results presented in this summary address the thermographic identification of leaks in the Space Shuttle Main Engine nozzles. A highly sensitive digital infrared camera is used to record the minute temperature change associated with a leak source, such as a crack or pinhole, hidden within the nozzle wall by observing the inner "hot wall" surface as the nozzle is pressurized. These images are enhanced by digitally subtracting a thermal reference image taken before pressurization, greatly diminishing background noise. The method provides a nonintrusive way of localizing the tube that is leaking and the exact leak source position to within a very small axial distance. Many of the factors that influence the inspectability of the nozzle are addressed; including pressure rate, peak pressure, gas type, ambient temperature and surface preparation.

Russell, Samuel S.↗
NASA NTRS1993

Temperature effects in the modal phase shift of a weakly guiding fiber

Temperature may be determined by monitoring the modal phase shift of an optical fiber. We present the results of a numerical model that has been developed to calculate the phase shift of a weakly guiding optical fiber due to thermal strain. Whenever an optical fiber is subjected to temperature changes, the optical path length, the index of refraction and the propagation constants of each fiber mode change. In consequence, the modal phase term, beta(ln)L, of the fields is also modified. A relationship for the modal phase shift is presented. This relation is applied to both single mode and two-mode fibers in order to determine the sensitivity characteristics of fibers that are subjected to temperature changes.

Egalon, Claudio O.↗
NASA NTRS1987

Global trends of measured surface air temperature

The paper presents the results of surface air temperature measurements from available meteorological stations for the period of 1880-1985. It is shown that the network of meteorological stations is sufficient to yield reliable long-term, decadal, and interannual temperature changes for both the Northern Hemisphere and the Southern Hemisphere, despite the fact that most stations are located on the continents. The results indicate a global warming of about 0.5-0.7 C in the past century, with warming of similar magnitude in both hemispheres. A strong warming trend between 1965 and 1980 raised the global mean temperature in 1980 and 1981 to the highest level in the period of instrumental records. Selected graphs of the temperature change in each of the eight latitude zones are included.

Hansen, James↗
NASA NTRS2000

Core Temperature Measurement During Submaximal Exercise: Esophageal, Rectal, and Intestinal Temperatures

The purpose of this study was to determine if intestinal temperature (Tin) might be in acceptable alternative to esophageal (Tes) and rectal temperature (Trec) to assess thermoregulation during supine exercise. We hypothesized that Tin would have values similar to Tes and a response time similar to Trec, but the rate of temperature change across time would not be different between measurement sites. Seven subjects completed a continuous supine protocol of 20 min of rest, 20 min of cycle exercise at 40% peak oxygen consumption (VO2pk), 20 min of cycle exercise at 65% V02pk, and 20 min of recovery. Tes, Trec, and Tin were recorded each min throughout the test. Temperatures were not different after 20 min of rest, but Trec was less than the Tes and Tin at the end of the 40% and 65% VO2pk stages. After 20 min of recovery, Tes was less than either Trec or Tin, which were not different from each other. Time to threshold for increased temperature from rest was greater for Trec than Tes but not different from Tin. Time to reach peak temperature was greater for Tin and Trec than Tes. Similarly, time to a decrease in temperature after exercise was greater for Trec than Tes, but not different from Tin. The rate of temperature change from threshold to the end of the 40% VO2pk stage was not different between measurement sites. However, the rate of change during recovery was more negative for Tes than Tin and Trec, which were different from each other. Measurement of Tin may he an acceptable alternative to Tes and Trec with an understanding of its limitations.

Lee, Stuart M. C.↗
NASA NTRS1974

Spectral variation in the microwave emissivity of the roughened seas

Recently acquired microwave data obtained from the NASA CV 990 research aircraft have yielded variation of sea surface emissivity as a function of various parameters. Data acquired at a wavelength of 1.5 cm, horizontal polarization, agree with data obtained earlier by Nordberg et al. and Hollinger at nadir and 50 deg viewing angles respectively; the ratio of brightness temperature change to wind speed change was found to be approximately 1 K per meter per second over a wind speed range of 5 to 26 meters per second. Combining these recent measurements with the earlier measurements, it is evident that microwave radiometry can be used as a remote-sensing anemometer over all wind speed ranges of interest. Data analysis revealed that for nadir-viewing instruments, the ratio of brightness temperature change to wind speed change was approximately constant for the 0.8-2.8 cm wavelength range, about three-quarters of that value at 6 cm, and nearly zero at 21 cm. A model is proposed that is consistent with observations.

Gloersen, P.↗
NASA NTRS1975

Program to design, fabricate, test, and deliver a thermal control-mixing control device, phase 1

The development of a sensor capable of detecting temperature changes as a function of viscosity changes, was completed. This type of sensor, consisting of an orifice bridge circuit, resulted in a device with a threshold above internally generated noise of 0.8C (1.5F). Data were obtained using a noise free Freon source provided by an air pressurized bladder. Tests conducted to operate the sensor from a typical Freon centrifugal pump system employing an air bubble accumulator for noise attentuation disclosed the sensor could be used only to sense temperature changes greater than 3.3C (6F) because of the excessively noisy output. This is attributed to the high frequency-pressure fluctuations in the Freon supply to the sensor.

Thurston, T. S.↗
NASA NTRS2011

Seasonal Changes in Titan's Surface Temperatures

Seasonal changes in Titan's surface brightness temperatures have been observed by Cassini in the thermal infrared. The Composite Infrared Spectrometer (CIRS) measured surface radiances at 19 micron in two time periods: one in late northern winter (Ls = 335d eg) and another centered on northern spring equinox (Ls = 0 deg). In both periods we constructed pole-to-pole maps of zonally averaged brightness temperatures corrected for effects of the atmosphere. Between late northern winter and northern spring equinox a shift occurred in the temperature distribution, characterized by a warming of approximately 0.5 K in the north and a cooling by about the same amount in the south. At equinox the polar surface temperatures were both near 91 K and the equator was 93.4 K. We measured a seasonal lag of delta Ls approximately 9 in the meridional surface temperature distribution, consistent with the post-equinox results of Voyager 1 as well as with predictions from general circulation modeling. A slightly elevated temperature is observed at 65 deg S in the relatively cloud-free zone between the mid-latitude and southern cloud regions.

Jennins, Donald E.↗
NASA NTRS1984

High stability buffered phase comparator

A low noise RF signal phase comparator comprised of two high stability driver buffer amplifiers driving a double balanced mixer which operate to generate a beat frequency between the two RF input signals coupled to the amplifiers from the RF sources is described. The beat frequency output from the mixer is applied to a low noise zero crossing detector which is the phase difference between the two RF inputs. Temperature stability is provided by mounting the amplifiers and mixer on a common circuit board with the active circuit elements located on one side of a circuit board and the passive circuit elements located on the opposite side. A common heat sink is located adjacent the circuit board. The active circuit elements are embedded into the bores of the heat sink which slows the effect of ambient temperature changes and reduces the temperature gradients between the active circuit elements, thus improving the cancellation of temperature effects. The two amplifiers include individual voltage regulators, which increases RF isolation.

Adams, W. A.↗
NASA NTRS1984

Optimization of thermal systems with sensitive optics, electronics, and structures

A strategy was investigated by which thermal designers for spacecraft could devise an optimal thermal control system to maintain the required temperatures, temperature differences, changes in temperature, and changes in temperature differences for specified equipment and elements of the spacecraft's structure. Thermal control is to be maintained by the coating pattern chosen for the external surfaces and heaters chosen to supplement the coatings. The approach is to minimize the thermal control power, thereby minimizing the weight of the thermal control system. Because there are so many complex computations involved in determining the optimal coating design a computerized approach was contemplated. An optimization strategy including all the elements considered by the thermal designer for use in the early stages of design, where impact on the mission is greatest, and a plan for implementing the strategy were successfully developed. How the optimization process may be used to optimize the design of the Space Telescope as a test case is demonstrated.

Bettini, R. G.↗
NASA NTRS1929

Investigation of damping liquids for aircraft instruments

This report covers the results of an investigation carried on at the Bureau of Standards under a research authorization from, and with the financial assistance of, the National Advisory Committee for Aeronautics. The choice of a damping liquid for aircraft instruments is difficult owing to the range of temperature at which aircraft operate. Temperature changes affect the viscosity tremendously. The investigation was undertaken with the object of finding liquids of various viscosities otherwise suitable which had a minimum change in viscosity with temperature. The new data relate largely to solutions. The effect of temperature on the kinematic viscosity of the following liquids and solutions was determined in the temperature interval -18 degrees to +30 degrees C. (1) solutions of animal and vegetable oils in xylene. These were poppy-seed oil, two samples of neat's-foot oils, castor oil, and linseed oil. (2) solutions of mineral oil in xylene. These were Squibb's petrolatum of naphthene base and transformer oil. (3) glycerine solutions in ethyl alcohol and in mixture of 50-50 ethyl alcohol and water. (4) mixtures of normal butyl alcohol with methyl alcohol. (5) individual liquids, kerosene, mineral spirits, xylene, recoil oil. The apparatus consisted of four capillary-tube viscometers, which were immersed in a liquid bath in order to secure temperature control. The method of calibration and the related experimental data are presented.

Keulegan, G H↗