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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 1,261 records · Page 70

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NASA NTRS1987

Nonlinear dynamics, chaos and complex cardiac arrhythmias

Periodic stimulation of a nonlinear cardiac oscillator in vitro gives rise to complex dynamics that is well described by one-dimensional finite difference equations. As stimulation parameters are varied, a large number of different phase-locked and chaotic rhythms is observed. Similar rhythms can be observed in the intact human heart when there is interaction between two pacemaker sites. Simplified models are analyzed, which show some correspondence to clinical observations.

Glass, L.↗

NASA NTRS1987

Gas release and ordering of carbon in the Allende meteorite

An attempt is made to ascertain whether the inert gas atoms leave their carrier phases by volume diffusion, with intact internal phase frameworks, or are instead expelled from the solids as a results of substantial rearrangement, during release from samples of the Allende carbonaceous meteorite. Gas release over the 300-1100 C range was followed by Raman spectroscopic studies in the 1360 and 1580/cm wavelength bands of carbon. The results obtained indicate that the gas release at high temperatures is causally related to the ordering of carbon.

Heymann, D.↗

NASA NTRS1987

Specific immunization of mice against Leishmania mexicana amazonensis using solubilized promastigotes

In this work, it was demonstrated that mice (BALB/c strain) highly susceptible to Leishmania mexicana amazonensis can be protected against infection by this parasite by being preimmunized with whole solubilized (in a buffer that contained EDTA, NP-40, and SDS) promastigotes; the use of adjuvant or intact inactivated parasite cells is shown to be not necessary. The best immunization schedule consisted of three intravenous injections of 5 x 10 to the 7th parasite equivalents, administered one to eight weeks before infection. Immunized mice exhibited a marked inhibition of primary lesion development, reduced numbers of parasites in the spleen, and reduced death rate.

Barral-Netto, M.↗

NASA NTRS1988

Shuttle performance enhancement using an uprated OMS engine

The NASA Space Shuttle's Orbital Maneuvering Engine (OME) has been investigated as the basis for an enhancement of Shuttle operational flexibility. The Johnson Space Center has given attention to an upgrading of the OME through the use of a gas generator-driven turbopump to raise engine specific impulse. Hardware tests have demonstrated the projected performance gains, which will yield an enhanced, intact ascent-abort capability, as well an an improved on-orbit payload and altitude capability. Attention is given to the application of these capabilities to the Hubble Space Telescope's deployment.

Mallini, Charles J.↗

NASA NTRS1988

The breakup of the Southern Hemisphere spring polar ozone and temperature minimums from 1979 to 1987

The purpose of this study is to quantify the observations of the polar vortex breakup. The data used in this study consist of Total Ozone Mapping Spectrometer (TOMS) data, and National Meteorological Center (NMC) analyses. The final warming is diagnosed using the difference between zonal means at 80 degrees and 50 degrees S for temperature, ozone, and layer mean temperature. The polar vortex breakup can also be diagnosed by the onset of weak zonal mean zonal winds (i.e., u, overbar denotes a zonal average) at 60 degrees S. Computations of the polar vortex breakdown date using NMC meteorological data and TOMS total ozone data indicate that the breakdown is occurring later in the spring in the lowest portion of the stratosphere. At altitudes above 100 mb, the large interannual variance of the breakdown date renders any trend determination of the breakdown date difficult. Individual plots of TOMS total ozone indicate that the total ozone minimum remains intact for a longer period of time than is observed in earlier years.

Newman, Paul A.↗

NASA NTRS1987

Cosmic dust collection with a sub satellite tethered to a Space Station

The number concentration and density of 1 micron and submicron sized grains in interplanetary space, as well as their relation to the larger zodical dust particles, and the importance of the beta meteoroid phenomenon are currently being questioned. The best approach to collecting large numbers of intact micron and submicron sized cosmic dust particles in real time while avoiding terrestrial and man made contamination would be to employ a tethered subsatellite from a space station down into the earth's atmosphere. Such a subsatellite tied to the space shuttle by a 100 km long tether is being developed. It is also possible that a permanent space station would allow the use of a tether even longer than 100 km. It should be noted that the same tethered collectors could also be employed to study the composition and flux of man made earth orbiting debris in any direction within 100 km or so of the space station.

Corso, George J.↗

NASA NTRS1987

New techniques for the detection and capture of micrometeoroids

In order to understand the origin and distribution of the biogenic elements and their compounds in the solar system, it will be necessary to study materials from many classes of objects. Chemical, elemental, and isotopic measurements of returned samples of comets, asteroids, and possibly extra-solar system dust clouds would provide information on a particularly important class: primitive objects. Extraterrestrial micron-sized particles in the vicinity of Earth are one source of such materials that might otherwise be inaccessible. The Space Station appears to be an eminently suitable platform from which to collect and detect these various particles. The primary challenge, however, is to collect intact, uncontaminated particles which will be encountered at tens of kilometers per seconds. A concept for a micrometeoroid detector that could be deployed from the Space Station was developed which uses a large area detector plate implanted with acoustic transducers. When an impact event occurs, the resulting signal is subjected to spectral analysis providing positive detection, momentum information, and angle of incidence. The primary advantage of this detector is the large area which increases the probability of measuring events. A concept of a nondestuctive micrometeoroid collector for use from a Space Station was also developed. The collector utilizes input port charging of the incoming particle followed by staged high voltage deceleration for nondestructive capture. Low velocity particles (local contamination) would be rejected due to insufficient energy and only uncontaminated micrometeoroids would be collected.

Wolfe, J. H.↗

NASA NTRS1989

Undercutting of defects in thin film protective coatings on polymer surfaces exposed to atomic oxygen

Protection for polymeric surfaces is needed to make them durable in the low Earth orbital environment, where oxidation by atomic oxygen is the predominant failure mechanism. Thin film coatings of oxides such as silicon dioxide are viable candidates to provide this protection, but concern has been voiced over the ability of these coatings to protect when defects are present in the coating due to surface anomalies occurring during the deposition process, handling, or micrometeoroid and debris bombardment in low Earth orbit. When a defected coating protecting a polymer substrate is exposed to atomic oxygen, the defect provides a pathway to the underlying polymer allowing oxidation and subsequent undercutting to occur. Defect undercutting was studied for sputter deposited coatings of silicon dioxide on polyimide Kapton. Preliminary results indicate that undercutting may be limited as long as the coating remains intact with the substrate. Therefore, coatings may not need to be defect free to give protection to the underlying surface.

Rutledge, Sharon K.↗

NASA NTRS1989

The reusable reentry satellite - A mission and system description and operational concept

A significant need exists for a system which will provide the life science experimenter with relatively frequent and inexpensive access to the space environment. To fulfill this need, a project and spacecraft system described as the Reusable Reentry Satellite (RRS) or LifeSat has been proposed by NASA. The RRS provides a relatively inexpensive method of access to space for extended periods of time and eventual intact recovery of the experiments on the earth's surface. The payload support requirements, flight operations concept are reviewed and the mission and system of the RRS are described in detail.

Swenson, Byron L.↗

NASA NTRS1988

Astrophysical implications of presolar grains

The widely accepted hypothesis that presolar materials survive intact in meteorites and can be studied in our laboratories is of great potential astrophysical significance. Two first-order conclusions have been drawn from the evidence supporting this hypothesis: graphitic grains are rare in the interstellar medium and grain lifetimes are considerably longer than 100 million yr. Both conclusions are in conflict with currently accepted astrophysical models, but might still be consistent with astronomical observations. Many more astrophysical revelations could be concealed within the meteorites, but until astronomers are again given some training in meteoritics, only the meteoritics community has the tools necessary to decipher the message.

Nuth, Joseph A., III↗

NASA NTRS1989

Martian tension fractures and the formation of grabens and collapse features at Valles Marineris

Simple models of the Martian crust are summarized that predict extensional deformation style on the basis of depth, material friction and strength, and hydraulic conditions appropriate to the planet. These models indicate that tension fractures may be common features on Mars, given adequate differential stress conditions. Examples of tension fractures on Mars inferred from morphological criteria are examined based on the probable geologic conditions in which they formed and on model constraints. It is proposed that the grabens and collapse features of Valles Marineris are controlled by tension fractures in intact basement rocks that lie below impact ejecta.

Tanaka, K. L.↗

NASA NTRS1987

Independent Orbiter Assessment (IOA): Analysis of the electrical power distribution and control subsystem, volume 1

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. This report documents the independent analysis results corresponding to the Orbiter Electrical Power Distribution and Control (EPD and C) hardware. The EPD and C hardware performs the functions of distributing, sensing, and controlling 28 volt DC power and of inverting, distributing, sensing, and controlling 117 volt 400 Hz AC power to all Orbiter subsystems from the three fuel cells in the Electrical Power Generation (EPG) subsystem. Each level of hardware was evaluated and analyzed for possible failure modes and effects. Criticality was assigned based upon the severity of the effect for each failure mode. Of the 1671 failure modes analyzed, 9 single failures were determined to result in loss of crew or vehicle. Three single failures unique to intact abort were determined to result in possible loss of the crew or vehicle. A possible loss of mission could result if any of 136 single failures occurred. Six of the criticality 1/1 failures are in two rotary and two pushbutton switches that control External Tank and Solid Rocket Booster separation. The other 6 criticality 1/1 failures are fuses, one each per Aft Power Control Assembly (APCA) 4, 5, and 6 and one each per Forward Power Control Assembly (FPCA) 1, 2, and 3, that supply power to certain Main Propulsion System (MPS) valves and Forward Reaction Control System (RCS) circuits.

Schmeckpeper, K. R.↗

NASA NTRS1989

Safety and rescue during STS operations

The space shuttle means, provided to the crew, of abort/escape for noncatastrophic mishap scenaries, during Space Transportation Systems (STS) operations, are discussed. From vehicle ingress until launch, the crew can escape the launch pad by use of slidewire baskets. For various emergencies during ascent, the crew can fly an intact abort. Such aborts include return to launch site, transoceanic abort landing, abort once around, and abort to orbit. The crew can fly the orbiter to an emergency airfield, or to an over ocean bailout for more serious ascent or on-orbit emergencies. For failures during landing, the crew can quickly egress the orbiter from the overhead hatch, or by use of an inflatable slide mounted at the side hatch.

Oconnor, Bryan↗

NASA NTRS1989

Space shuttle Production Verification Motor 1 (PV-1) static fire

All inspection and instrumentation data indicate that the PV-1 static test firing conducted 18 Aug. 1988 was successful. With the exception of the intentionally flawed joints and static test modifications, PV-1 was flight configuration. Fail-safe flaws guaranteeing pressure to test the sealing capability of primary O-rings were included in the aft field joint, case-to-nozzle joint, and nozzle internal Joint 5. The test was conducted at ambient conditions, with the exception of the field joints and case/nozzle joints which were maintained at a minimum of 75 F. Ballistics performance values were within specification requirements. The PV-1 motor exhibited chamber pressure oscillations similar to previously tested Space Shuttle redesigned solid rocket motors, particularly QM-7. The first longitudinal mode oscillations experienced by PV-1 were the strongest ever measured in a Space Shuttle motor. Investigation into this observation is being conducted. Joint insulation performed as designed with no evidence of gas flow within unflawed forward field joints. The intentionally flawed center and aft case field joint insulation performance was excellent. There was no evidence of hot gas past the center field joint capture feature O-ring, the case-to-nozzle joint primary O-ring, or the aft field joint primary O-ring. O-ring seals and barriers with assured pressure at the flaws showed erosion and heat effect, but all sealed against passage of hot gases with the exception of the aft field joint capture feature O-ring. There was no evidence of erosion, heat effect, or blowby on any O-ring seals or barriers at the unflawed joints. Nozzle performance was nominal with typical erosion. Post-test examination revealed that the forward nose ring was of the old high performance motor design configuration with the 150-deg ply angle. All nozzle components remained intact for post-test evaluation. The thrust vector control system operated correctly. The water deluge system, CO2 quench, and other test equipment performed as planned during all required test operations.

Source record↗

NASA NTRS1989

Direction of movement effects under transformed visual/motor mappings

Performance in a discrete aiming task was compared under several transformed visual/motor mappings: rotations by 45, 90, 135, and 180 deg and reflections about the horizontal and the vertical midlines. Eight aiming targets were used, corresponding to eight directions of movement: up, down, right, left, up-right, down-left, up-left, and down-right. Direction of movements were characterized in terms of separable visual and motor components, and two kinds of direction of movement effects were considered. First, a direction of movement effect paralleling that seen in rapid aiming under the usual nontransformed mapping. Second, because rotations, but not reflections, are physically realizable 2-D transformations, a visual/motor control system which is sensitive to physical constraints should perform reflections, but not rotations, in a piecemeal fashion. Results supported the hypothesis that a motor factor having to do with complexity of limb movement accounts for differences in movement accuracy between right and left oblique directions. Direction of movement effects were more evident in reflections than in rotations, and were consistent with the hypothesis that the visual/motor-control system seeks a physically realizable 2-D rotation solution to reflections. Results also suggested that reversal of two orthogonal basis dimensions is far less difficult than reversing only one and leaving the other intact.

Cunningham, H. A.↗

NASA NTRS1990

The challenge of assembling a space station in orbit

Assembly of a space station in orbit is a challenging and complicated task. If mankind is to exploit the knowledge already gained from space flight and continue to advance the frontiers of space exploration, then space stations in orbit must be part of the overall space infrastructure. Space stations, like the Freedom, having relatively large mass which greatly exceeds the lifting capability of their transportation system, are candidates for on-orbit assembly. However, when a large wide-body booster is available, there are significant advantages to having a deployable space station assembled on Earth and transported into orbit intact or in a few large pieces. The United States will build the Space Station Freedom by the assembly method. Freedom's assembly is feasible, but a significant challenge, and it will absorb much of NASA's effort in the next 8 years. The Space Station Freedom is an international program which will be the centerpiece of the free world's space activities in the late 1990's. Scientific information and products from the Space Station Freedom and its use as a transportation depot will advance technology and facilitate the anticipated manned space exploration surge to the Moon and Mars early in the 21st century.

Brand, Vance D.↗

NASA NTRS1990

Inhomogeneities of stratocumulus liquid water

There is a growing body of observational evidence on inhomogeneous cloud structure, most recently from the extensive measurements of the FIRE field program. Knowledge of cloud structure is important because it strongly influences the cloud radiative properties, one of the major factors in determining the global energy balance. Current atmospheric circulation models use plane-parallel radiation, so that the liquid water in each gridbox is assumed to be uniform, which gives an unrealistically large albedo. In reality cloud liquid water occupies only a subset of each gridbox, greatly reducing the mean albedo. If future climate models are to treat the hydrological cycle in a manner consistent with energy balance, a better treatment of cloud liquid is needed. FIRE concentrated upon two cloud types of special interest: cirrus and marine stratocumulus. Cirrus tend to be high and optically thin, thus reducing the effective radiative temperature without increasing the albedo significantly, leading to an enhanced greenhouse heating. In contrast, marine stratocumulus are low and optically thick, thus producing a large increase in reflected radiation with a small change in emitted radiation, giving a net cooling which could potentially mitigate the expected greenhouse warming. The FIRE measurements in California stratocumulus during June and July of 1987 show variations in cloud liquid water on all scales. Such variations are associated with inhomogeneous entrainment, in which entrained dry air, rather than mixing uniformly with cloudy air, remains intact in blobs of all sizes, which decay only slowly by invasion of cloudy air. Two important stratocumulus observations are described, followed by a simple fractal model which reproduces these properties, and finally, the model radiative properties are discussed.

Cahalan, Robert F.↗

NASA NTRS1989

1200 to 1400 K slow strain rate compressive properties of NiAl/Ni2AlTi-base materials

An attempt to apply the Martin Marietta Corporation's XD technology to the fabrication of NiAl-Ni2AlTi materials with improved creep properties is presented. Composite materials, containing from 0 to 30 vol pct of nominally 1-micron-diameter TiB2 particles in the intermetallic matrix have been produced by the XD process and compacted by hot pressing. Such composites demonstrated significant strength increases, approaching 3-fold for the 20 vol pct materials, in comparison to the unreinforced aluminide. This behavior was accomplished without deleterious side effects as the grain boundaries and particle-matrix interfaces were intact after compressive deformation to 10 percent or more strain. Typical true compressive stress-strain diagrams for materials tested in air between 1200 and 1400 K at approximate strain rates of 1.7 x 10 to the -6th/sec are presented.

Whittenberger, J. Daniel↗