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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 1,477 records · Page 82
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Kilometric radiation power flux dependence on area of discrete aurora

Kilometer wavelength radiation, measured from distant positions over the North Pole and over the Earth's equator, was compared to the area of discrete aurora imaged by several low-altitude spacecraft. Through correlative studies of auroral kilometric radiation (AKR) with about two thousand auroral images, a stereoscopic view of the average auroral acceleration region was obtained. A major result is that the total AKR power increases as the area of the discrete auroral oval increases. The implications are that the regions of parallel potentials or the auroral plasma cavities, in which AKR is generated, must possess the following attributes: (1) they are shallow in altitude and their radial position depends on wavelength, (2) they thread flux tubes of small cross section, (3) the generation mechanism in them reaches a saturation limit rapidly, and (4) their distribution over the discrete auroral oval is nearly uniform. The above statistical results are true for large samples collected over a long period of time (about six months). In the short term, AKR frequently exhibits temporal variations with scales as short as three minutes (the resolution of the averaged data used). These fluctuations are explainable by rapid quenchings as well as fast starts of the electron cyclotron maser mechanism. There were times when AKR was present at substantial power levels while optical emissions were below instrument thresholds. A recent theoretical result may account for this set of observations by predicting that suprathermal electrons, of energies as low as several hundred eV, can generate second harmonic AKR. The indirect observations of second harmonic AKR require that these electrons have mirror points high above the atmosphere so as to minimize auroral light emissions. The results provide evidence supporting the electron cyclotron maser mechanism.

Saflekos, N. A.↗
NASA NTRS1988

Automated seed manipulation and planting

The Mechanical Division fabricated three seed separators utilizing pressure gradients to move and separate wheat seeds. These separators are called minnow buckets and use air, water, or a combination of both to generate the pressure gradient. Electrostatic fields were employed in the seed separator constructed by the Electrical Division. This separator operates by forcing a temporary electric dipole on the wheat seeds and using charged electrodes to attract and move the seeds. Seed delivery to the hydroponic growth tray is accomplished by the seed cassette. The cassette is compatible with all the seed separators, and it consists of a plastic tube threaded with millipore filter paper. During planting operations, the seeds are placed in an empty cassette. The loaded cassette is then placed in the growth tray and nutrient solution provided. The solution wets the filter paper and capillary action draws the nutrients up to feed the seeds. These seeding systems were tested and showed encouraging results. Seeds were effectively separated and the cassette can support the growth of wheat plants. Problems remaining to be investigated include improving the success of delivering the seeds to the cassette and providing adequate spacing between seeds for the electric separator.

Garcia, Ray↗
NASA NTRS1988

Cut-and-connect of two antiparallel vortex tubes

Motivated by an early conjecture that vortex cut-and-connect plays a key role in mixing and production of turbulence, helicity and aerodynamic noise, the cross-linking of two antiparallel viscous vortex tubes via direct numerical simulation is studied. The Navier-Stokes equations are solved by a dealiased pseudo-spectral method with 64 cubed grid points in a periodic domain for initial Reynolds numbers Re up to 1000. The vortex tubes are given an initial sinusoidal perturbation to induce a collision and keep the two tubes pressed against each other as annihilation continues. Cross-sectional and wire plots of various properties depict three stages of evolution: (1) Inviscid induction causing vortex cores to first approach and form a contact zone with a dipole cross-section, and then to flatten and stretch; (2) Vorticity annihilation in the contact zone accompanied by bridging between the two vortices at both ends of the contact zone due to a collection of cross-linked vortex lines, now orthogonal to the initial vortex tubes. The direction of dipole advection in the contact zone reverses; and (3) Threading of the remnants of the original vortices in between the bridges as they pull apart. The crucial stage 2 is shown to be a simple consequence of vorticity annihilation in the contact zone, link-up of the un-annihilated parts of vortex lines, and stretching and advection by the vortex tube swirl of the cross-linked lines, which accumulate at stagnation points in front of the annihilating vortex dipole. It is claimed that bridging is the essence of any vorticity cross-linking and that annihilation is sustained by stretching of the dipole by the bridges. Vortex reconnection details are found to be insensitive to asymmetry. Modeling of the reconnection process is briefly examined. The 3D spatial details of scalar transport (at unity Schmidt number), enstrophy production, dissipation and helicity are also examined.

Melander, Mogens V.↗
NASA NTRS1989

Technical Evaluation Motor 3 (TEM-3)

A primary objective of the technical evaluation motor program is to recover the case, igniter and nozzle hardware for use on the redesigned solid rocket motor flight program. Two qualification objectives were addressed and met on TEM-3. The Nylok thread locking device of the 1U100269-03 leak check port plug and the 1U52295-04 safe and arm utilizing Krytox grease on the barrier-booster shaft O-rings were both certified. All inspection and instrumentation data indicate that the TEM-3 static test firing conducted 23 May 1989 was successful. The test was conducted at ambient conditions with the exception of the field joints (set point of 121 F, with a minimum of 87 F at the sensors), igniter joint (set point at 122 F with a minimum of 87 F at sensors) and case-to-nozzle joint (set point at 114 F with a minimum of 87 F at sensors). Ballistics performance values were within specification requirements. Nozzle performance was nominal with typical erosion. The nozzle and the case joint temperatures were maintained at the heaters controlling set points while electrical power was supplied. The water and the CO2 quench systems prevented damage to the metal hardware. All other test equipment performed as planned, contributing to a successful motor firing. All indications are that the test was a success, and all expected hardware will be refurbished for the RSRM program.

Garecht, Diane↗
NASA NTRS1988

The magnetic geometry and structure of the giant post-flare arch of 21-22 May, 1980

The photospheric line-of-sight magnetic field distribution of a giant post-flare arch observed on May 21-22, 1980 is used to determine the three-dimensional topology of the coronal field above the flare site. It is proposed that the arch is the by-poduct of magnetic reconnection occurring far above the flare site. The field lines undergoing reconnection link more distant parts of the active region and are topologically distinct from those which thread the underlying post-flare loops.

Poletto, G.↗
NASA NTRS1988

Commercialization of space

Space-commercialization activities are grouped into five categories: private sector development from existing technology for private sector use; pure privatization; private sector development for U.S. government use; private sector development from novel technology for private sector use; and, finally, full commercialization. The commercialization of space categories is defined, and the key issues in each are highlighted. A description of key NASA actions is included for each category. It is concluded that NASA and other government agency involvement is a common thread across the spectrum of space commercialization activities.

Rose, James T.↗
NASA NTRS1989

Cyclotron line features from neutron star atmospheres

Cyclotron line features from the polar cap plasmas of accreting magnetized neutron stars are modeled. The polar cap environment is modeled by a homogeneous isothermal plane-parallel slab threaded by a uniform superstrong magnetic field oriented orthogonal to the slab. Two physical cyclotron photon source functions are used. For conventional stopping depths, the emergent line spectra are fairly independent of the source functions. For hot atmospheres the details of the line transfer using relativistic kinematics differ substantially from those using nonrelativistic kinematics. Aside from finite recoil, both a finite natural linewidth and conventional stopping depths suppress the escape of photons blueward of line center and potential line features tend to be smeared out into the low-energy continuum. The formation of a line features is most favorable in low-field high-temperature atmospheres where cyclotron photon production is confined to a layer of small column density.

Wang, John C. L.↗
NASA NTRS1989

An adiabatic demagnetization refrigerator for SIRTF

An adiabatic demagnetization refrigerator (ADR) has been proposed to cool bolometric infrared detectors on the multiband imaging photometer of the Space Infrared Telescope Facility (SIRTF). One such refrigerator has been built which uses a ferric ammonium alum salt pill suspended by nylon threads in a 3-T solenoid. The resonant modes of this suspension are above 100 Hz. The heat leak to the salt pill is less than 0.5 microW. The system has a hold time at 0.1K of more than 12 h. The cold stage temperature is regulated with a feedback loop that controls the magnetic field. A second, similar refrigerator is being built at a SIRTF prototype to fly on a ballon-borne telescope. It will use a ferromagnetic shield. The possibility of using a high-Tc solenoid-actuated heat switch is also discussed.

Timbie, P. T.↗
NASA NTRS1990

Impact Wire Dislodges Obstructions

Snakelike tool loosens trapped debris obstructing narrow passages in normally inaccessible locations. Flexible tool threaded into obstructed channel, much like common plumbing snake. Wire fed along inner tube of tool until tip reaches obstruction. Delivers impact from impact tool to obstruction. Designed for use in narrow, intricate coolant channels of rocket engine. Lends itself readily to modification for use in engine blocks, heat exchangers, general plumbing, and like.

Ricklefs, Steven K.↗
NASA NTRS1990

High-Pressure Promoted-Combustion Chamber

Proposed combustion-testing chamber burns specimens of materials in fully contained, high-pressure oxygen atmosphere. Test operator uses handles on threaded retaining rings to attach or remove top or bottom plates sealing combustion chamber. Tests conducted in static or flowing oxygen. Oxygen inlet and outlet far enough above burning specimen, little danger of entrainment of burning fragments in oxygen flowing out.

Rucker, Michelle A.↗
NASA NTRS1990

Mechanized Fluid Connector And Assembly Tool

In new tool-and-connector system, necessary to have access to only one side of pipe, access offset from centerline. Connections made or broken in confined spaces and with small external forces. Tool turns spur gear on externally threaded retainer on left member of connector. Retainer engages nut on right member of connector. Intended for assembly of pipes in proposed Space Station, tool and fitting used on Earth to make or break plumbing connections in crowded utility runs or other confined spaces where wrenches cannot be turned, where forces exerted by wrenches might cause damage, or where lack of good grip prevents technician from exerting sufficient torque on connector.

Zentner, Ronald C.↗
NASA NTRS1990

Transducer-Mounting Fixture

Transducer-mounting fixture holds transducer securely against stud. Projects only slightly beyond stud after installation. Flanged transducer fits into fixture when hinged halves open. When halves reclosed, fixture tightened onto threaded stud until stud makes contact with transducer. Knurled area on fixture aids in tightening fixture on stud.

Spiegel, Kirk W.↗
NASA NTRS1990

Scaled Ellipses For Computer-Aided Design

An addition to CAD-PACK, computer-aided design program, speeds preparation of iosmetric drawings, particularly cutaway views showing bores and threads. Consists of set of 50 scaled ellipses on detail pages of program. Designer selects ellipse, rotates it, and draws feature. Then erases reference lines on video screen.

Schembri, Anthony J.↗
NASA NTRS1989

Composite multilayer insulations for thermal protection of aerospace vehicles

Composite flexible multilayer insulation systems (MLI), consisting of alternating layers of metal foil and scrim cloth or insulation quilted together using ceramic thread, were evaluated for thermal performance and compared with a silica fibrous (baseline) insulation system. The systems studied included: (1) alternating layers of aluminoborosilicate (ABS) scrim cloth and stainless steel foil, with silica, ABS, or alumina insulation; (2) alternating layers of scrim cloth and aluminum foil, with silica or ABS insulation; (3) alternating layers of alumininum foil and silica or ABS insulation; and (4) alternating layers of aluminum-coated polyimide placed on the bottom of the silica insulation. The MLIs containing aluminum were the most efficient, measuring as little as half the backface temperature increase of the baseline system.

Kourtides, D. A.↗
NASA NTRS1989

Recommendations for the future

The workshop explored four major areas of concern to solar-terrestrial science. Looking across the discipline reports given previously, it is possible to find common threads that can contribute to the development of NASA's programmatic strategy for the solar-terrestrial sciences. The following areas are outlined: scientific balance; previously gathered information; imaging; impact of the space station and related platforms; vitality and relevance; and future studies.

Source record↗
NASA NTRS1990

Fastener Design Manual

This manual was written for design engineers to enable them to choose appropriate fasteners for their designs. Subject matter includes fastener material selection, platings, lubricants, corrosion, locking methods, washers, inserts, thread types and classes, fatigue loading, and fastener torque. A section on design criteria covers the derivation of torque formulas, loads on a fastener group, combining simultaneous shear and tension loads, pullout load for tapped holes, grip length, head styles, and fastener strengths. The second half of this manual presents general guidelines and selection criteria for rivets and lockbolts.

Barrett, Richard T.↗
NASA NTRS1990

Unique failure behavior of metal/composite aircraft structural components under crash type loads

Failure behavior results are presented on some of the crash dynamics research conducted with concepts of aircraft elements and substructure which have not necessarily been designed or optimized for energy absorption or crash loading considerations. To achieve desired new designs which incorporate improved energy absorption capabilities often requires an understanding of how more conventional designs behave under crash type loadings. Experimental and analytical data are presented which indicate some general trends in the failure behavior of a class of composite structures which include individual fuselage frames, skeleton subfloors with stringers and floor beams but without skin covering, and subfloors with skin added to the frame-stringer arrangement. Although the behavior is complex, a strong similarity in the static/dynamic failure behavior among these structures is illustrated through photographs of the experimental results and through analytical data of generic composite structural models. It is believed that the thread of similarity in behavior is telling the designer and dynamists a great deal about what to expect in the crash behavior of these structures and can guide designs for improving the energy absorption and crash behavior of such structures.

Carden, Huey D.↗
NASA NTRS1989

Composite multilayer insulations for thermal protection of aerospace vehicles

Composite flexible multilayer insulation systems (MLI), consisting of alternating layers of metal foil and scrim cloth or insulation quilted together using ceramic thread, were evaluated for thermal performance and compared with a silica fibrous (baseline) insulation system. The systems studied included: (1) alternating layers of aluminoborosilicate (ABS) scrim cloth and stainless steel foil, with silica, ABS, or alumina insulation; (2) alternating layers of scrim cloth and aluminum foil, with silica or ABS insulation; (3) alternating layers of aluminum foil and silica or ABS insulation; and (4) alternating layers of aluminum-coated polyimide placed on the bottom of the silica insulation. The MLIs containing aluminum were the most efficient, measuring as little as half the backface temperature increase of the baseline system.

Kourtides, Demetrius A.↗