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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Variability in the high energy gamma ray emission from Cyg X-3 over a two-year period (1983 - 1984) at E 4 x 10(11) eV

Cygnus X-3 is observed to emit gamma rays with energies in excess of 4 x 10 to the 11th power eV during two out of 9 observational categories over an 18 month time span. The emissions are observed at the 0.6 phase of the characteristic 4.8 hr light curve for this binary system. We estimate a peak flux at phase 0.6 of 5 x 10 to the minus 10th power photons cm-2s-1 at a software threshold of 8 x 10 to the 11th power eV for Oct/Nov 1983. A flux for the June 84 effect cannot be reliably calculated at present due to lack of Monte Carlo simulations for the energy range and spectral region. For the other 7 observational categories the observations are consistent with zero source emission. The light curve would appear to be variable on a time scale of a couple of weeks at these categories. Selection of compact images in accordance with Monte Carlo simulations combined with empirical optimization techniques have led to an enriched gamma ray light curve for the Oct/Nov 1983 data. Selection on the basis of shower orientation, however, has not led to any notable enhancement of the gamma ray content. Individual Cherenko images can be reliably sorted on an event by event basis into either proton-induced or photon-induced showers.

Cawley, M. F.↗
NASA NTRS1983

Fiber optic temperature sensor

A temperature sensor has been developed that utilizes the temperature dependent absorption of a rare earth doped optical fiber. The temperature measurement is localized at a remote position by splicing a short section of the rare earth fiber into a loop of commercial data communication fiber that sends and returns an optical probe signal to the temperature sensitive section of fiber. The optical probe signal is generated from two different wavelength filtered LED sources. A four port fiber optic coupler combines the two separate wavelength signals into the fiber sensing loop. Time multiplexing is used so that each signal wavelength is present at a different time. A reference signal level measurement is also made from the LED sources and a ratio taken with the sensor signal to produce a transmission measurement of the fiber loop. The transmission is affected differently at each wavelength by the rare earth temperature sensitive fiber. The temperature is determined from a ratio of the two transmission measurements. This method eliminates any ambiguity with respect to changes in signal level in the fiber loop such as mating and unmating optical connectors. The temperature range of the sensor is limited to about 800 C by the temperature limit fo the feed fibers.

Morey, W. W.↗
NASA NTRS1986

Photoelectronic Monitor of Motion Sickness

Instrument includes gallium arsenide light-emitting diode (LED) and silicon phototransistor with infrared filter, all cast in single plastic housing. Housing attached to subject's face with transparent doublesided adhesive tape. LED directs pulses of infrared light to skin, which reflects them to phototransistor. Phototransistor produces signal that is processed by external circuits to yield plot of infrared reflectance with time. External circuits temperature-compensated and respond only to pulsed component of detector output, rejecting those components caused by stray light. Circuits also extract blood-volume pulse amplitude and heart rate.

Oman, C. M.↗
NASA NTRS1985

A view of software management issues

The Software Development Environment (SDE) Panel addressed key programmatic, scope, and structural issues raised by its members and the general audience regarding the proposed software development environment for the Space Station program. The general team approach taken by this group led to a consensus on 18 recommendations to NASA mangament regarding the acquisition and definition of the SDE. This approach was keyed by the initial issues presentation given to the general audience. Additional issues (for a total of 23) were developed by the panelists in their first closed session from which key areas were selected and discussed in open session. These discussions led to key recommendations which are summarized and described.

Manley, J. H.↗
NASA NTRS1985

The Space Flight Participant Program - Taking the teacher and classroom into space

NASA established the Space Flight Participant Program as a means to offer periodic opportunities for private citizens to fly on Space Shuttle missions. With the purpose of communicating the mission experience with the general public, it is expected that Space Flight Participants will be included on the crews of two to three Shuttle missions per year. This paper discusses the first flight opportunity - the NASA Teacher in Space Project - provided under this new initiative. Included in the discussion is a review of the events that led to the establishment of the Space Flight Participant Program, a review of the process that led to the selection of Christa McAuliffe as the first Space Flight Participant, a summary of the training activities to prepare a participant for a mission, and an outline of educational activities that will be offered by NASA in conjunction with Shuttle mission 51-L in January 1986 on which Ms. McAuliffe will fly.

Ladwig, A.↗
NASA NTRS1987

Phased array antenna for space shuttle orbiter

The National Aeronautics and Space Administration is developing a distributed phased array antenna at the Lyndon B. Johnson Space Center as a possible upgrade for the Space Shuttle Orbiter S-band phase modulation communications system. The antenna consists of an eight-element transmit section, eight-element receive section, and a single L-band receive element. The antenna design is constrained by the existing Orbiter system and space environment. The solution to the interface design problems led to an antenna system which provides improved link margins and yet supports previous operational configurations. This paper describes the system development, antenna hardware, and the interface consideration which led to the final design.

Davidson, Shayla E.↗
NASA NTRS1986

Role of glucocorticoids in the response of rat leg muscles to reduced activity

Adrenalectomy did not prevent atrophy of rat soleus muscle during 6 days of tail cast suspension. Cortisol treatment enhanced the atrophy and caused atrophy of the weight-bearing soleus and both extensor digitorum longus (EDL) muscles. Unloading led to increased sarcoplasmic protein concentration in the soleus but cortisol administration increased the myhofibrillar (+stromal) protein concentration in both muscles. Suspension of hindlimbs of adrenalectomized animals led to faster protein degradation, slower sarcoplasmic protein degradation, and faster myofibrillar protein synthesis in the isolated soleus, whereas with cortisol-treated animals, the difference in synthesis of myofibrillar proteins was enhanced and that of sarcoplasmic proteins was abolished. Both soleus and EDL of suspended, cortisol-treated animals showed faster protein degradation. It is unlikely that any elevation in circulating glucocorticoids was solely responsible for atrophy of the soleus in this model, but catabolic amounts of glucocorticoids could alter the response of muscle to unloading.

Jaspers, Stephen R.↗
NASA NTRS1987

On the development of the theory of the QBO

The events that led to the discovery of the quasi-biennial oscillation (QBO) of the equatorial stratosphere are described together with the development of current QBO theory. Three independent areas of inquiry led to this theory: (1) the observational and theoretical studies of equatorial waves, (2) the theoretical study of the behavior of mountain waves at critical levels where the mean flow speed went to zero, and (3) the semiempirical study of the momentum budget of the QBO. The efforts in each of these three areas are discussed.

Lindzen, Richard S.↗
NASA NTRS1987

The solar wind interaction with comets: A post encounter view

The recent spacecraft encounters with comets Giacobini-Zinner and Halley have led to an enormous increase in our knowledge of comets, including their dust, neutral gas, plasma, and magnetic field environments. The latter has in turn led to better understanding of the nature of the solar wind interaction with the well developed atmosphere of a comet. The post-encounter understanding of this interaction is reviewed, underscoring the differences with pre-encounter reasoning. The problems outstanding in this area are emphasized.

Mendis, D. A.↗
NASA NTRS1987

Space vehicle approach velocity judgments under simulated visual space conditions

Thirty-five volunteers responded when they first perceived an increase in apparent size of a collimated, 2-D image of an Orbiter vehicle. The test variables of interest included the presence of a fixed angular reticle within the field of view (FOV); three initial Orbiter distances; three constant Orbiter approach velocities corresponding to 1.6, 0.8, and 0.4 percent of the initial distance per second; and two background starfield velocities. It was found that: (1) at each initial range, increasing approach velocity led to a larger distance between the eye and Orbiter image at threshold; (2) including the fixed reticle in the FOV produced a smaller distance between the eye and Orbiter image at threshold; and (3) increasing background star velocity during this judgment led to a smaller distance between the eye and Orbiter image at threshold. The last two findings suggest that other detail within the FOV may compete for available attention which otherwise would be available for judging image expansion; thus, the target has to approach the observer nearer than otherwise if these details were present. These findings are discussed in relation to previous research and possible underlying mechanisms.

Haines, Richard F.↗
NASA NTRS1987

NASA small civil airplane research

NASA-Langley's ongoing research programs on behalf of performance, safety, and utility enhancements for small civil aircraft have over the last decade introduced important advancements in natural laminar flow inducement and stall/spin recovery and prevention. The achievability and maintainability of natural laminar flow has led to performance improvements of as much as 25 percent. Recent research has improved predictive techniques for aircraft stall/spin characteristics, and also led to the development of a wing leading edge design for enhanced spin resistance.

Stough, H. Paul, III↗
NASA NTRS1987

Space vehicle approach velocity judgments under simulated visual space conditions

Thirty-five volunteers responded when they first perceived an increase in apparent size of a collimated, 2-D image of an Orbiter vehicle. The test variables of interest included the presence of a fixed angular reticle within the field of view (FOV); three initial Orbiter distances; three constant Orbiter approach velocities corresponding to 1.6, 0.8, and 0.4 percent of the initial distance per second; and two background starfield velocities. It was found that: (1) at each initial range, increasing approach velocity led to a larger distance between the eye and Orbiter image at threshold; (2) including the fixed reticle in the FOV produced a smaller distance between the eye and Orbiter image at threshold; and (3) increasing background star velocity during this judgment led to a smaller distance between the eye and Orbiter image at threshold. The last two findings suggest that other detail within the FOV may compete for available attention which otherwise would be available for judging image expansion; thus, the target has to approach the observer nearer than otherwise if these details were present. These findings are discussed in relation to previous research and possible underlying mechanisms.

Haines, Richard F.↗
NASA NTRS1989

High accuracy thermal conductivity measurements near the lambda transition of helium with very high temperature resolution

Over the past few years extensive thermal conductivity measurements near the lambda point of helium were made. The original goal of measuring the thermal conductivity with a resolution of t = T/T sub lambda -1 of 3 x 10(-8) was reached, but with somewhat less accuracy than was hoped. Subtle effects in the apparatus near the transition were observed which reduced the ability to interpret the results. Nevertheless, for resolution of t is greater than or equal to 10(-7) reliable data was obtained, extending previous measurements by more than an order of magnitude. Deviations from theoretical predictions were observed for t is less than or equal to 3 x 10(-6) leading to the question of the validity of the present renormalization group analysis of transport properties, at least for the case of helium. This anomaly led to closer examination of the boundary effects in the measurements. During the experiments a totally unexpected effect in the very dilute He-3 - He-4 mixtures was observed which led to the explanation of the anomalous results. The concentration dependence of the thermal conductivity near T sub lambda in the superfluid phase was found to deviate strongly from the predictions. The results gave an independent verification of this behavior and caused reanalysis of the Khalatnikov theory of hydrodynamics of the mixtures. An alternative solution was found which is in better agreement with the experiment.

Fairbank, William M.↗
NASA NTRS1988

A miniature, infrared pressure telemetry system

A miniature, single-channel, infrared telemetry system designed for making base pressure measurements on a wind tunnel model has been developed for the 13-inch magnetic suspension and balance system (MSBS) at Langley Research Center. The system consists of a transmitter installed in the wind tunnel model and a receiver station located outside of the test section. The onboard transmitter package includes a miniature pressure transducer, a signal conditioning circuit, and IR LED and a hearing-aid battery package. The IR LED, which is mounted flush with the model's surface, serves as the transmitter. The system is automatically activated in a magnetic field and has low power requirements. The system has been successfully employed to make low speed base pressure measurements at the 13-inch MSBS. The battery powered telemetry transmitter has a demonstrated one-hour operating life and an overall precision of better than 1/2 percent full scale.

Tcheng, Ping↗
NASA NTRS1989

The fragmentation of proto-globular clusters. I - Thermal instabilities

The metal abundances among the stars within a typical globular cluster are remarkably homogeneous. This indicates that star formation in these systems was a globally coordinated event which occurred over a time span less than or comparable to the collapse time scale of the cluster. This issue is addressed by assuming that the fragmentation of a proto-globular cluster cloud proceeded in two steps. In the first step, thermal instability led to the rapid growth of initial fluctuations. This led to a large contrast in the dynamical time scales between the perturbations and the parent cloud, and the perturbations then underwent gravitational instabilities on short time scales. This process is modeled using one-dimensional hydrodynamic simulations of clouds both with and without external heat sources and self-gravity. The models include the effects of a non-equilibrium H2 abundance. The results indicate that fragmentation can occur on time scales significantly less than the dynamical time scale of the parent cloud.

Murray, Stephen D.↗
NASA NTRS1989

Structural and metabolic characteristics of human skeletal muscle following 30 days of simulated microgravity

The effects of simulated microgravity (30 days of continuous 6-deg headdown bedrest, BR) on the structural and metabolic characteristics of human skeletal muscle were determined. Percutaneous needle biopsy samples obtained from the vastus lateralis and soleus muscles before and after the headdown BR were analyzed for histochemical, biochemical and ultrastructual changes. It was found that headdown BR led to decreases in both fast-twitch and slow-twitch fiber areas in both muscles, and there was evidence of remodeling of the ultrastructure in both muscles. The activities of beta-hydroxyacyl-CoA dehydrogenase and citrate synthase were reduced during BR, but phosphofructokinase and lactate dehydrogenase activities did not change. The results indicate that 30-d exposure to simulated microgravity decreased the capacity for aerobic energy supply of human skeletal muscle and led to a disorganization of the contractile machinery.

Hikida, Robert S.↗
NASA NTRS1990

Welding-Current Indicator

Light flashes on to indicate high current. Simple, inexpensive display circuit indicates when 3,000-A welding current flows in welding gun. Onset of welding current induces voltage and current in 1,000-turn, 28-gauge copper-wire coil. Single-transistor amplifier amplifies induced current, energizing light-emitting diode (LED) connected to collector of transistor. Light from LED gives simple, direct indication of welding current.

Hensley, Milton C.↗
NASA NTRS1990

Control Circuit For Two Stepping Motors

Control circuit operates two independent stepping motors, one at a time. Provides following operating features: After selected motor stepped to chosen position, power turned off to reduce dissipation; Includes two up/down counters that remember at which one of eight steps each motor set. For selected motor, step indicated by illumination of one of eight light-emitting diodes (LED's) in ring; Selected motor advanced one step at time or repeatedly at rate controlled; Motor current - 30 mA at 90 degree positions, 60 mA at 45 degree positions - indicated by high or low intensity of LED that serves as motor-current monitor; Power-on reset feature provides trouble-free starts; To maintain synchronism between control circuit and motors, stepping of counters inhibited when motor power turned off.

Ratliff, Roger↗