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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Analytical and experimental investigation of aircraft metal structures reinforced with filamentary composites. Phase 3: Major component development

Analytical and experimental investigations, performed to establish the feasibility of reinforcing metal aircraft structures with advanced filamentary composites, are reported. Aluminum-boron-epoxy and titanium-boron-epoxy were used in the design and manufacture of three major structural components. The components were representative of subsonic aircraft fuselage and window belt panels and supersonic aircraft compression panels. Both unidirectional and multidirectional reinforcement concepts were employed. Blade penetration, axial compression, and inplane shear tests were conducted. Composite reinforced structural components designed to realistic airframe structural criteria demonstrated the potential for significant weight savings while maintaining strength, stability, and damage containment properties of all metal components designed to meet the same criteria.

Bryson, L. L.↗
NASA NTRS1973

Delta's inexpensive, reliable, and versatile third generation upper stage

The need for larger diameter fairings to encapsulate spacecraft designed to use Delta's increased lifting capabilities resulted in hammer-head design configurations that would have unaccepably degraded vehicle flight characteristics. This situation led to the development of the Straight Eight configuration. The towed mode arrangement for the second stage negated the requirement for the engine compartment structure, thus establishing the potential for an improved packaging of the hydraulic and pneumatic systems. Therefore, with cost reduction and reliability improvement objectives, a second stage propulsion system improvement program was initiated. The paper will describe these improvements and their system benefits.

Bonnett, E. W.↗
NASA NTRS1974

Preliminary nondestructive evaluation manual for the space shuttle

Nondestructive evaluation (NDE) requirements are presented for some 134 potential fracture-critical structural areas identified, for the entire space shuttle vehicle system, as those possibly needing inspection during refurbishment/turnaround and prelaunch operations. The requirements include critical area and defect descriptions, access factors, recommended NDE techniques, and descriptive artwork. Requirements discussed include: Orbiter structure, external tank, solid rocket booster, and thermal protection system (development area).

Pless, W. M.↗
NASA NTRS1978

A review of electron bombardment thruster systems/spacecraft field and particle interfaces

Information on the field and particle interfaces of electron bombardment ion thruster systems was summarized. Major areas discussed were the nonpropellant particles, neutral propellant, ion beam, low energy plasma, and fields. Spacecraft functions and subsystems reviewed were solar arrays, thermal control systems, optical sensors, communications, science, structures and materials, and potential control.

Byers, D. C.↗
NASA NTRS1978

A review of electron bombardment thruster systems/spacecraft field and particle interfaces

This paper collates and summarizes information on the field and particle interfaces of electron bombardment ion thruster systems. Major areas discussed are the nonpropellant particles, neutral propellant, ion beam, low energy plasma, and fields. Spacecraft functions and subsystems reviewed are solar arrays, thermal control systems, optical sensors, communications, science, structures and materials, and potential control. An appendix is included to facilitate identification of specific interaction areas.

Byers, D. C.↗
NASA NTRS1979

Ab initio studies of the electronic structure of UF6, UF6/+/, and UF6/-/ using relativistic effective core potentials

The paper presents ab initio calculations performed on the electronic states of UF6, UF6(+), and UF6(-) using a relativistic effective core potential (ECP) for uranium and a nonrelativistic ECP for fluorine. In most of the calculations 56 valence electrons are treated explicitly using a contracted (3s 3p 2d 2f/2s2p) Gaussian basis. It is noted that various ECP's were explored, but all yield an overall charge density of U(+2.4)/F(-0.4)/6. In addition, the bonding in the ground state of UF6 is discussed. SCF and CI calculations on UF6(+) are compared with the experimental photoelectron spectrum and with previous scattered wave calculations. Further, the role of spin-orbit coupling in the states of UF6(+) and UF6(-) is covered. Finally, it is concluded that the calculated electron affinity of UF6 (7.1 eV) is considerably larger than in current experimental estimates, but the relative energies of the states of UF6(-) are in agreement (0.1-0.2 eV) with those of the experiment.

Hay, P. J.↗
NASA NTRS1978

Characterization and properties of controlled nucleation thermochemical deposited (CNTD) silicon carbide

The microstructure of controlled nucleation thermochemical deposition (CNTD) - SiC material was studied and the room temperature and high temperature bend strength and oxidation resistance was evaluated. Utilizing the CNTD process, ultrafine grained (0.01-0.1 mm) SiC was deposited on W - wires (0.5 mm diameter by 20 cm long) as substrates. The deposited SiC rods had superior surface smoothness and were without any macrocolumnar growth commonly found in conventional CVD material. At both room and high temperature (1200 - 1380 C), the CNTD - SiC exhibited bend strength approximately 200,000 psi (1380 MPa), several times higher than that of hot pressed, sintered, or CVD SiC. The excellent retention of strength at high temperature was attributed to the high purity and fine grain size of the SiC deposit and the apparent absence of grain growth at elevated temperatures. The rates of weight change for CNTD - SiC during oxidation were lower than for NC-203 (hot pressed SiC), higher than for GE's CVD - SiC, and considerably below those for HS-130 (hot pressed Si3N4). The high purity, fully dense, and stable grain size CNTD - SiC material shows potential for high temperature structural applications; however problem areas might include: scaling the process to make larger parts, deposition on removable substrates, and the possible residual tensile stress.

Dutta, S.↗
NASA NTRS1979

Preliminary Report: Issues in selection and training for long duration space flight

Based on previous experience with crew selection, three important avenues of consideration for future missions are discussed: technical qualifications and expertise; medical fitness and ability to tolerate the various conditions of space; and psychological considerations including personality structure, motivation, intelligence, leadership potential, group compatibility, etc. Primary emphasis was given to the psychological considerations.

Akins, F. R.↗
NASA NTRS1982

High temperature deformation of NiAl and CoAl

The high temperature mechanical properties of the aluminides are reviewed with respect to their potential as high temperature structural materials. It is shown that NiAl and CoAl are substantially stronger than the pure metals Ni and Co at high temperatures and approach the strength of some superalloys, particularly when those superalloys are tested in "weak" directions. The factors that limit and control the high temperature strengths of NiAl and CoAl are examined to provide a basis for the development of intermetallic alloys of this type.

Nix, W. D.↗
NASA NTRS1983

Noise transmission through sidewall treatments applicable to twin-engine turboprop aircraft

The noise transmission loss characteristics of the sidewall treatment in the propeller plane of a twin-engine turboprop aircraft are experimentally investigated in the NASA Langley Research Center Transmission Loss Facility. The sound attenuation properties of the individual elements of this treatment are evaluated showing least noise transmission loss in the low frequencies (below 500 Hz) where the excitation levels at the propeller blade passage frequency and the first few harmonics are highest. It is shown that single and double wall resonances play an important role in the noise transmission loss values of the treatment at these low frequencies suggesting that a limp mass with a very low resonance frequency serves better as a trim panel than a trim panel having a high structural stiffness. It is indicated that the window structures might be a potential noise control problem.

Grosveld, F. W.↗
NASA NTRS1983

Use of MAGSAT anomaly data for crustal structure and mineral resources in the US midcontinent

Magnetic field data acquired by NASA's MAGSAT satellite is used to construct a long-wavelength magnetic anomaly map for the U.S. midcontinent. This aids in interpretation of gross crustal geology (structure, lithologic composition, resource potential) of the region. Magnetic properties of minerals and rocks are investigated and assessed, to help in evaluation and modelling of crustal magnetization sources and depth to the Curie-temperature isotherm.

Carmichael, R. S.↗
NASA NTRS1985

Ion beam sputter deposited zinc telluride films

Zinc telluride is of interest as a potential electronic device material, particularly as one component in an amorphous superlattice, which is a new class of interesting and potentially useful materials. Some structural and electronic properties of ZnTe films deposited by argon ion beam sputter depoairion are described. Films (up to 3000 angstroms thick) were deposited from a ZnTe target. A beam energy of 1000 eV and a current density of 4 mA/sq. cm. resulted in deposition rates of approximately 70 angstroms/min. The optical band gap was found to be approximately 1.1 eV, indicating an amorphous structure, as compared to a literature value of 2.26 eV for crystalline material. Intrinsic stress measurements showed a thickness dependence, varying from tensile for thicknesses below 850 angstroms to compressive for larger thicknesses. Room temperature conductivity measurement also showed a thickness dependence, with values ranging from 1.86 x to to the -6/ohm. cm. for 300 angstrom film to 2.56 x 10 to the -1/ohm. cm. for a 2600 angstrom film. Measurement of the temperature dependence of the conductivity for these films showed complicated behavior which was thickness dependent. Thinner films showed at least two distinct temperature dependent conductivity mechanisms, as described by a Mott-type model. Thicker films showed only one principal conductivity mechanism, similar to what might be expected for a material with more crystalline character.

Gulino, D. A.↗
NASA NTRS1985

Microbial mats and modern stromatolites in Shark Bay, Western Australia

Distribution, external morphology, texture, and microbial composition of microbial mats in Hamelin Pool, Shark Bay, Western Australia, have been studied and reviewed along a composite representative profile starting from the permanently submerged zone, across the zones of periodic flooding, toward permanently emerged land and coastal dunes. The following nine types of algal mats have been recognized: colloform, gelatinous, smooth, pincushion, tufted, mamillate, film, reticulate, and blister. Solar ponds represent a particular environment. The mat types represent microbial communities that are characterized by one or more dominant microorganisms. The colonization and stabilization of loose sediment is carried out by a microbial assemblage of generalists that prepare the ground for later replacement and succession by specialized microflora. Lithification of microbial mats takes place periodically, mainly during the austral summer. This process is destructive for the microbial community but increases the preservation potential of the stromatolitic structures.

Golubic, S.↗
NASA NTRS1986

Ion beam sputter deposited zinc telluride films

Zinc telluride is of interest as a potential electronic device material, particularly as one component in an amorphous superlattice, which is a new class of interesting and potentially useful materials. Some structural and electronic properties of ZnTe films deposited by argon ion beam sputter deposition are described. Films (up to 3000 angstroms thick) were deposited from a ZnTe target. A beam energy of 1000 eV and a current density of 4 mA/sq cm resulted in deposition rates of approximately 70 angstroms/min. The optical band gap was found to be approximately 1.1 eV, indicating an amorphous structure, as compared to a literature value of 2.26 eV for crystalline material. Intrinsic stress measurements showed a thickness dependence, varying from tensile for thicknesses below 850 angstroms to compressive for larger thicknesses. Room temperature conductivity measurement also showed a thickness dependence, with values ranging from 1.86 x 10 to the -6th/ohm cm for 300 angstrom film to 2.56 x 10 to the -1/ohm cm for a 2600 angstrom film. Measurement of the temperature dependence of the conductivity for these films showed complicated behavior which was thickness dependent. Thinner films showed at least two distinct temperature dependent conductivity mechanisms, as described by a Mott-type model. Thicker films showed only one principal conductivity mechanism, similar to what might be expected for a material with more crystalline character.

Gulino, D. A.↗
NASA NTRS1986

Surface generation and detection of coupled fiber-matrix mode acoustic wave propagation in fiber-reinforced composites

A technique is described that makes it possible to transmit and receive bulk ultrasonic waves launched from the same surface of a composite sheet by means of transducers mounted on variable angle blocks. A straightforward approach to measure the velocity and attenuation of this wave is presented. A bulk compressional wave of 930,000 cm/sec velocity was launched and received in this manner in an 8-ply unidirectional T-300-5208 epoxy composite. Preliminary results indicate that parameters associated with this wave might be sensitive to accumulated damage in a composite; thus, the technique has a potential for NDE in structures made from composite materials.

Yost, W. T.↗
NASA NTRS1988

Polyquinoxalines

This paper reviews the properties of different substituted and unsubstituted polyquinoxalines (PQs) and polyphenylquinoxalines (PPQs), a family of high-performance high-temperature polymers that exhibit high potential for functional and structural applications, and discusses the synthesis of these polymers. Tables are presented of data on the apparent glass-transition temperatures of various PQs and PPQs and on their mechanical properties. Particular consideration is given to the laminate properties of PQ and PPQ composites with glass, boron, and carbon-graphite fibers. Also discussed are the structures and the properties of ladder- and step-ladder-type polymers.

Hergenrother, Paul↗
NASA NTRS1990

Genetic algorithm based fuzzy control of spacecraft autonomous rendezvous

The U.S. Bureau of Mines is currently investigating ways to combine the control capabilities of fuzzy logic with the learning capabilities of genetic algorithms. Fuzzy logic allows for the uncertainty inherent in most control problems to be incorporated into conventional expert systems. Although fuzzy logic based expert systems have been used successfully for controlling a number of physical systems, the selection of acceptable fuzzy membership functions has generally been a subjective decision. High performance fuzzy membership functions for a fuzzy logic controller that manipulates a mathematical model simulating the autonomous rendezvous of spacecraft are learned using a genetic algorithm, a search technique based on the mechanics of natural genetics. The membership functions learned by the genetic algorithm provide for a more efficient fuzzy logic controller than membership functions selected by the authors for the rendezvous problem. Thus, genetic algorithms are potentially an effective and structured approach for learning fuzzy membership functions.

Karr, C. L.↗
NASA NTRS1990

Ballooning instability of the earth's plasma sheet region in the presence of parallel flow

Stability of the plasma sheet and plasma sheet boundary layer against the ballooning mode instability is investigated. The equilibrium state of a two-dimensional plasma sheet configuration with parallel sheared flow is modeled. This equilibrium is shown to be ballooning unstable when delta-W is not positive definite, where delta-W is the potential energy. The eigenmode structure of the ballooning mode is found by imposing the boundary conditions that the waves are totally reflected from the ionosphere, and that no waves are coming in from infinity. The eigenmode structure of the unstable balloning modes is highly oscillatory, extending beyond about 100 R(E). The ballooning modes are thus a possible candidate for explaining the MHD waves and other dynamical events observed in the magnetotail by ISEE 3 and other spacecraft.

Lakhina, G. S.↗