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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Energetic solar particle events

Studies of the arrival directions of energetic solar particles during ground level enhancements (CLE's) observed by neutron monitors have shown that, in general, in the first hour of the event most of the particles arrive with a distribution of pitch angles peaked about the garden hose field direction in the vicinity of Earth. During the first hour some of the particles arrive from the antisolar direction, while in later stages of the event the intensity becomes more nearly isotropic as a result of scattering of particles in interplanetary space. An attempt is made to determine the arrival directions of the particles during the early stages of the GLE of 16 February 1984 using the data currently available from high latitude neutron monitors near sea level where the cut off is essentially atmospheric (approx. LGV).

Fenton, K. B.↗
NASA NTRS1985

Magnetopause merging site asymmetries

Regions where a draped model magnetosheath magnetic field is nearly antiparallel to a model geomagnetic field are shown to be asymmetric for an interplanetary magnetic field (IMF) at the garden hose angle, as suggested by Heelis. When the IMF has a southward component, the asymmetry favors the dawn region for both IMF polarities. The dusk region is favored when the IMF has a northward component. If the regions of antiparallel fields are assumed to be sites of maximum magnetic merging, then the asymmetry is consistent with observed seasonal variations of geomagnetic activity and with dawn-displaced magnetospheric phenomena. In the alternate merging geometry of a line passing through the subsolar region, the asymmetry is predominantly north-south rather than dawn-dusk. Merging line geometry is consistent with the seasonal variations but not with the dawn-displaced phenomena.

Crooker, N. U.↗
NASA NTRS1985

Electromagnetic electron temperature anisotropy instabilities

This paper considers electromagnetic Vlasov instabilities driven by electron temperature anisotropies in a homogeneous, nonrelativistic magnetized plasma. Numerical solutions of the full linear dispersion equation for bi-Maxwellian distribution functions and instabilities propagating parallel to the magnetic field are presented. Parametric dependences of the maximum growth rates of the electron fire hose and whistler anisotropy instabilities are given.

Gary, S. P.↗
NASA NTRS1986

Detection of Machining Chips by Pressure Reversal

Inaccessible interior spaces inspected acoustically. In acoustic inspection, inlet and outlet ports of component connected to pneumatic hoses of apparatus that rapidly reverses induced pressure differential. If loose particles inside this component, they will generate noise detected by series of contact microphones attached to component. Noise indicates general location of contaminants, and its characteristic helps in identifying particles from their acoustic signatures.

Wyett, L. M.↗
NASA NTRS1987

Cotton-Fiber-Filled Rubber Insulation

Carbonization of fibers at high temperatures improves strength and erosion resistance. Cotton linters tested as replacement for asbestos filler currently used in rubber insulation in solid rocket motors. Cotton-filled rubber insulation has industrial uses; in some kinds of chemical- or metal-processing equipment, hoses, and protective clothing.

Anderson, Floyd A.↗
NASA NTRS1987

Inverse problems in the modeling of vibrations of flexible beams

The formulation and solution of inverse problems for the estimation of parameters which describe damping and other dynamic properties in distributed models for the vibration of flexible structures is considered. Motivated by a slewing beam experiment, the identification of a nonlinear velocity dependent term which models air drag damping in the Euler-Bernoulli equation is investigated. Galerkin techniques are used to generate finite dimensional approximations. Convergence estimates and numerical results are given. The modeling of, and related inverse problems for the dynamics of a high pressure hose line feeding a gas thruster actuator at the tip of a cantilevered beam are then considered. Approximation and convergence are discussed and numerical results involving experimental data are presented.

Banks, H. T.↗
NASA NTRS1988

Heat Exchanger For Rotating Modular Structures

Heat exchanger transfers heat from one structure to another while accommodating rotary motion of structures. Flat-panel heat exchanger passes heat from fluid in middle panel to fluid in outer panels. Diaphragm-like outer panels swell to conform to surfaces of middle panel, ensuring thermal contact. Rotary fluid coupling provides connection for both supply fluid and return fluid. Flexible hoses carrying fluid to and from coupling accommodate tilt of one structure with respect to other. Adapted to transfer of fluids and heat across joints of machine tools and robot arms and to flow of coolant through portable electronic equipment.

Clark, William E.↗
NASA NTRS1988

Rotary Fluid Coupling

Rotary coupling for heat-transfer fluid contains four lines for vapor and four corresponding liquid-return lines. This one allows unlimited rotation and does not have to be rewound to prevent damage to hoses. Fluid coupled with minimal leakage between stationary housing and inner rotating shaft.

Zentner, Ron↗
NASA NTRS1989

Lightweight Restraint For Coupling Flanges

End flanges of flexible coupling system restrained against excessive rotation or axial separation by inexpensive, lightweight mechanism based on cables and pulleys. Restraining mechanism adapted to cable, duct, hose, or passageway couplings between vehicles, or to other applications in which angular and positional misalignments must be restricted to moderate specified values. Total misalignment of two end flanges limited to amount of slack available in cable-and-pulley mechanism. When cable taut, further axial separation of flange centers restrained, but small tilts accommodated by running of cable through pulleys.

Whitaker, Willie D.↗
NASA NTRS1989

Compact Right-Angle Connector

New right-angle connector between hose and "quick-disconnect" coupler smaller and simpler than its predecessor. Employs fewer parts and therefore cheaper and less likely to leak. Connector consists of only two major parts.

Barajas, Salvador L.↗
NASA NTRS1989

Vacuum Head Checks Foam/Substrate Bonds

Electromechanical inspection system quickly gives measurements indicating adhesion, or lack thereof, between rigid polyurethane foam and aluminum substrate. Does not damage inspected article, easy to operate, and used to perform "go/no-go" evaluations or as supplement to conventional destructive pull-plug testing. Applies vacuum to small area of foam panel and measures distance through which foam pulled into vacuum. Probe head applied to specimen and evacuated through hose to controller/monitor unit. Digital voltmeter in unit reads deflection of LVDT probe head.

Lloyd, James F.↗
NASA NTRS1988

Monocoque structure for the SKITTER three-legged walker

The SKITTER 2 design is a monocoque version of the proposed lunar three-legged walker. By the definition of monocoque, the body and legs are a shell with no internal ribbing or supports added for absorbing stresses. The purpose of the monocoque is to encase the elements used for power transmission, power supply, and control of the motion. The material for the structure is a vinyl ester resin, Derakane 8084. This material is easily formable and locally obtainable. The body consists of a hexagonally shaped cylinder with truncated hexagonal pyramids on the top and botton. The legs are eight inch diameter cylinders. The legs are comprised of a tibia section and a femur section. The SKITTER 2 is powered by six actuators which provide linear forces that are transformed into rotary torques by a series of chains and sprockets. The joints connect the femur to the body and the tibia to the femur. Surrounding the joints are flexible rubber hoses that fully encase the chains and sprockets. The SKITTER 2 is capable of walking upside down, righting itself after being overturned, and has the ability to perform in many environments. Applications for this walker include lunar transport or drilling, undersea exploration, and operation in severe surroundings such as arctic temperatures or high radiation.

Bansek, Robert N.↗
NASA NTRS1989

Thermodynamic and fluid mechanic analysis of rapid pressurization in a dead-end tube

Three models have been applied to very rapid compression of oxygen in a dead-ended tube. Pressures as high as 41 MPa (6000 psi) leading to peak temperatures of 1400 K are predicted. These temperatures are well in excess of the autoignition temperature (750 K) of teflon, a frequently used material for lining hoses employed in oxygen service. These findings are in accord with experiments that have resulted in ignition and combustion of the teflon, leading to the combustion of the stainless steel braiding and catastrophic failure. The system analyzed was representative of a capped off-high-pressure oxygen line, which could be part of a larger system. Pressurization of the larger system would lead to compression in the dead-end line, and possible ignition of the teflon liner. The model consists of a large plenum containing oxygen at the desired pressure (500 to 6000 psi). The plenum is connected via a fast acting valve to a stainless steel tube 2 cm inside diameter. Opening times are on the order of 15 ms. Downstream of the valve is an orifice sized to increase filling times to around 100 ms. The total length from the valve to the dead-end is 150 cm. The distance from the valve to the orifice is 95 cm. The models describe the fluid mechanics and thermodynamics of the flow, and do not include any combustion phenomena. A purely thermodynamic model assumes filling to be complete upstream of the orifice before any gas passes through the orifice. This simplification is reasonable based on experiment and computer modeling. Results show that peak temperatures as high as 4800 K can result from recompression of the gas after expanding through the orifice. An approximate transient model without an orifice was developed assuming an isentropic compression process. An analytical solution was obtained. Results indicated that fill times can be considerably shorter than valve opening times. The third model was a finite difference, 1-D transient compressible flow model. Results from the code show the recompression effect but predict much lower peak temperatures than the thermodynamic model.

Leslie, Ian H.↗
NASA NTRS1991

Open-Section Composite Structural Elements

Report describes investigation of manufacture and mechanical properties of graphite-fiber/aluminum-matrix open-section structural elements; e.g., channels and angle bars. Conducted with view toward using such elements to build lightweight, thermally stable truss structures in outer space. Other applications transport to, and assembly at, remote or otherwise uninviting locations. Advantages include shapes permitting high packing density during shipment, convenient paths for routing tubes, hoses, and cables; accessibility of both inner and outer surfaces for repair; and ease of attachment of additional hardware. Easier and require less equipment to fabricate, and more amenable to automated fabrication and assembly at remote site. Disadvantages, not as resistant to some kinds of deformation under load.

Loftin, T. A.↗
NASA NTRS1991

Servo Reduces Friction In Flexure Bearing

Proposed servocontrol device reduces such resistive torques as stiction, friction, ripple, and cogging in flexure bearing described in LAR-14348, "Flexure Bearing Reduces Startup Friction". Reduces frictional "bump" torque encountered when bearing ball runs into buildup of grease on bearing race. Also used as cable follower to reduce torque caused by cable and hoses when they bend because of motion of bearing. New device includes torquer across ball race. Torquer controlled by servo striving to keep flexure at null, removing torque to outer ring. In effect, device is inner control loop reducing friction, but does not control platforms or any outer-control-loop functions.

Clingman, W. Dean↗
NASA NTRS1991

Localized corrosion of high performance metal alloys in an acid/salt environment

Various vacuum jacketed cryogenic supply lines at the Space Shuttle launch site at Kennedy Space Center use convoluted flexible expansion joints. The atmosphere at the launch site has a very high salt content, and during a launch, fuel combustion products include hydrochloric acid. This extremely corrosive environment has caused pitting corrosion failure in the thin walled 304L stainless steel flex hoses. A search was done to find a more corrosion resistant replacement material. The study focussed on 19 metal alloys. Tests which were performed include electrochemical corrosion testing, accelerated corrosion testing in a salt fog chamber, and long term exposure at a beach corrosion testing site. Based on the results of these tests, several nickel based alloys were found to have very high resistance to this corrosive environment. Also, there was excellent agreement between the electrochemical tests and the actual beach exposure tests. This suggests that electrochemical testing may be useful for narrowing the field of potential candidate alloys before subjecting samples to long term beach exposure.

Macdowell, L. G.↗
NASA NTRS1989

Flammability and sensitivity of materials in oxygen-enriched atmospheres; Proceedings of the Fourth International Symposium, Las Cruces, NM, Apr. 11-13, 1989. Volume 4

The present volume discusses the ignition of nonmetallic materials by the impact of high-pressure oxygen, the promoted combustion of nine structural metals in high-pressure gaseous oxygen, the oxygen sensitivity/compatibility ranking of several materials by different test methods, the ignition behavior of silicon greases in oxygen atmospheres, fire spread rates along cylindrical metal rods in high-pressure oxygen, and the design of an ignition-resistant, high pressure/temperature oxygen valve. Also discussed are the promoted ignition of oxygen regulators, the ignition of PTFE-lined flexible hoses by rapid pressurization with oxygen, evolving nonswelling elastomers for high-pressure oxygen environments, the evaluation of systems for oxygen service through the use of the quantitative fault-tree analysis, and oxygen-enriched fires during surgery of the head and neck.

Stoltzfus, Joel M.↗
NASA NTRS1992

Significance of modeling internal damping in the control of structures

Several simple systems are examined to illustrate the importance of the estimation of damping parameters in closed-loop system performance and stability. The negative effects of unmodeled damping are particularly pronounced in systems that do not use collocated sensors and actuators. An example is considered for which even the actuators (a tip jet nozzle and flexible hose) for a simple beam produce significant damping which, if ignored, results in a model that cannot yield a reasonable time response using physically meaningful parameter values. It is concluded that correct damping modeling is essential in structure control.

Banks, H. T.↗