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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 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Composite structural materials

The use of filamentary composite materials in the design and construction of primary aircraft structures is considered with emphasis on efforts to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, and reliability and life prediction. The redesign of a main spar/rib region on the Boeing 727 elevator near its actuator attachment point is discussed. A composite fabrication and test facility is described as well as the use of minicomputers for computer aided design. Other topics covered include (1) advanced structural analysis methids for composites; (2) ultrasonic nondestructive testing of composite structures; (3) optimum combination of hardeners in the cure of epoxy; (4) fatigue in composite materials; (5) resin matrix characterization and properties; (6) postbuckling analysis of curved laminate composite panels; and (7) acoustic emission testing of composite tensile specimens.

Ansell, G. S.↗
NASA NTRS1980

Investigation of the fuel feed line failures on the Space Shuttle main engine

The Space Shuttle Main Engine (SSME) development program experienced two similar appearing fuel feed line failures during the shutdown portion of two engine tests. Failure investigations into each incident showed that a few cycles of high-amplitude transient strain occurring during the start and cutoff portions of each test could have either accumulated damage and led to a fatigue failure after 46 tests, or caused rupture in a low-strength weld joint. The cause of the high strain was traced to a period of unsteady flow separation during the start and cutoff of each test coincident with the oblique shock approaching the nozzle exit. Since elimination of the flow separation was impractical, the steps taken to allow engine development and flight preparations to continue were: (1) establish the safe operating life of the nozzle, (2) reinforce all low-strength welds, and (3) eliminate the use of thin-wall fuel feed lines. In parallel, the feed line was redesigned and fabrication was initiated on units to be incorporated into the development program.

Larson, E. W.↗
NASA NTRS1980

CF6 fan performance improvement

A significant portion of the NASA-sponsored Performance Improvement Program for the CF6 engine was the development of an improved fan concept. This involved aerodynamic redesign of the CF6 fan blade to increase fan efficiency while retaining the mechanical integrity, operability, and acoustic characteristics of the existing blade. A further improvement in performance was obtained by adding a fan case stiffener ring to decouple blade-case vibrational characteristics, permitting a significant reduction in running tip clearance. Engine testing was performed to establish the performance, mechanical and acoustic properties of the new design relative to the current fan, and to establish power management characteristics for the CF6-50C2/E2 engine. A significant improvement in cruise power SFC of 1.8 percent was demonstrated in Sea Level testing projected to altitude flight conditions.

Patt, R. F.↗
NASA NTRS1980

Sensitivity of the optimal preliminary design of a transport to operational constraints and performance index

Constrained parameter optimization was used to perform the optimal preliminary design of a medium range transport configuration. The impact of choosing a performance index was studied and the required fare for a 15 percent return-on-investment was proposed as a figure-of-merit. A number of design constants and constraint functions were systematically varied to document the sensitivities of the optimal design to a variety of economic and technological assumptions. Additionally, a comparison is made for each of the parameter variations between the baseline configuration and the optimally redesigned configuration.

Sliwa, S. M.↗
NASA NTRS1980

Real-time operating system for selected Intel processors

The rationale for system development is given along with reasons for not using vendor supplied operating systems. Although many system design and performance goals were dictated by problems with vendor supplied systems, other goals surfaced as a result of a design for a custom system able to span multiple projects. System development and management problems and areas that required redesign or major code changes for system implementation are examined as well as the relative successes of the initial projects. A generic description of the actual project is provided and the ongoing support requirements and future plans are discussed.

Pool, W. R.↗
NASA NTRS1981

Steering law for parallel mounted double-gimbaled control moment gyros. Revision A

Mounting of double-gimbaled control moment gyros (CMG's) of unlimited outer gimbal angle freedom with all their outer gimbal axes parallel allows drastic simplification of the CMG steering law development hardware. The advantages of the parallel mounting for the CMG steering law development are such that a law could be developed which is applicable to any number of CMG's with arbitrary angular momentum. Parallel mounting of the CMG's in conjunction with the steering law can therefore be considered a CMG kit suitable for many missions of differing momentum requirements. It also means that increasing momentum demands during the design phase of a space vehicle can be easily met by the addition of one or more CMG's of the original momentum capacity rather than a redesign to a larger momentum capacity. Another advantage of the parallel mounting is that the failure of any CMG can be treated like any other, i.e., only one failure mode is possible. The CMG steering law distributes the CMG momentum vectors such that all inner gimbal angles are equal which reduces the rate requirements on the outer gimbal axes. The steering law also spreads the outer gimbals which ensures avoidance of singularities internal to the angular momentum envelope.

Kennel, H. F.↗
NASA NTRS1980

Use of constrained optimization in the conceptual design of a medium-range subsonic transport

Constrained parameter optimization was used to perform the optimal conceptual design of a medium range transport configuration. The impact of choosing a given performance index was studied, and the required income for a 15 percent return on investment was proposed as a figure of merit. A number of design constants and constraint functions were systematically varied to document the sensitivities of the optimal design to a variety of economic and technological assumptions. A comparison was made for each of the parameter variations between the baseline configuration and the optimally redesigned configuration.

Sliwa, S. M.↗
NASA NTRS1981

Offset wrap rib antenna concept development

A program to demonstrate large diameter offset reflector technology readiness through the development of ground testable, flight representative full size hardware also aims to provide a basis of data to allow confirmation of cost, performance, and size growth projections for the offset wrap ribe antenna design. An overview of the antenna system is presented and the operational deployment sequence examined. The ability to manufacture multiple segment ribs is assured and tooling for rib manufacture was redesigned to reduce cost. The selected mast design permits adequate stiffness and minimum stowed volume. Reflector and mast concerns and the program plan are summarized.

Woods, A. A., Jr.↗
NASA NTRS1981

Description of recent changes in the Langley 6- by 28-inch transonic tunnel

Calibrations were obtained in the Langley 6 by 28-inch transonic tunnel with newly installed controllable reentry flaps and test section floor and ceiling. Using available theory, the top and bottom slotted walls were redesigned for minimum wind tunnel interference errors of blockage and stream-line curvature. To minimize Mach number gradients along the tunnel axis downstream of the model, controllable flaps were installed to regulate the flow reentering the test section through the slotted walls. The flap setting is independent of stagnation pressure and varies only with Mach number. The freestream Mach number is determined from the pressrue measured at a station 66.04 cm upstream of the model station. The model has no significant influence on the vertical Mach number distribution at this station. This method of Mach number determination appears to be more accurate than one using the plenum pressure.

Sewall, W. G.↗
NASA NTRS1981

Process Development for Automated Solar Cell and Module Production. Task 4: Automated Array Assembly

The Automated Lamination Station is mechanically complete and is currently undergoing final wiring. The high current driver and isolator boards have been completed and installed, and the main interface board is under construction. The automated vacuum chamber has had a minor redesign to increase stiffness and improve the cover open/close mechanism. Design of the Final Assembly Station has been completed and construction is underway.

Hagerty, J. J.↗
NASA NTRS1981

Development of a polysilicon process based on chemical vapor deposition, phase 1

The development of a dichlorosilane-based reductive chemical vapor deposition process for the production of polycrystalline silicon is discussed. Experimental data indicate that the ease of ignition and explosion severity of dichlorosilane (DCS)/air mixtures is substantially attenuated if the DCS is diluted with hydrogen. Redesign of the process development unit to accommodate safety related information is described. Several different sources of trichlorosilane were used to generate a mixture of redistributed chlorosilanes via Dowex ion exchange resin. The unseparated mixtures were then fed to an experimental reactor in which silicon was deposited and the deposited silicon analyzed for electrically active impurities. At least one trichlorosilane source provided material of requisite purity. Silicon grown in the experimental reactor was converted to single crystal material and solar cells fabricated and tested.

Mccormick, J.↗
NASA NTRS1981

Energy absorption studied to reduce aircraft crash forces

The NASA/FAA aircraft safety reseach programs for general aviation aircraft are discussed. Energy absorption of aircraft subflooring and redesign of interior flooring are being studied. The testing of energy absorbing configurations is described. The three NASA advanced concepts performed at neary the maximum possible amount of energy absorption, and one of two minimum modifications concepts performed well. Planned full scale tests are described. Airplane seat concepts are being considered.

Source record↗
NASA NTRS1981

Qualification testing of secondary sterilizable silver-zinc cells for use in the Jupiter atmospheric entry probe

A series of qualification tests were run on the secondary, sterilizable silver oxide - zinc cell developed at the NASA Lewis Research Center to determine if the cell was capable of providing mission power requirements for the Jupiter atmospheric entry probe. The cells were tested for their ability to survive radiation at the levels predicted for the Jovian atmosphere with no loss of performance. Cell performance was evaluated under various temperature and loading conditions, and the cells were tested under various environmental conditions related to launch and to deceleration into the Jovian atmosphere. The cell performed acceptably except under the required loading at low temperatures. The cell was redesigned to improve low-temperature performance and energy density. The modified cells improved performance at all temperatures. Results of testing cells of both the original and modified designs are discussed.

Manzo, M. A.↗
NASA NTRS1981

Coal/rock interface detection by sensitized pick, part A

In order to increase the operating margins of the detector for safe, reliable operation under difficult in-mine conditions the transmitted signal strength was increased to provide additional signal margin for in-mine conditions and the transmitter section was redesigned to reduce frequency pulling of the transmitter frequency with variations in antenna load. The linearity of the pick load SCO signal with true pick load was increased, and hysteresis effects were minimized. The sensitized pick hardware was ruggedized for rough inmine use. The sensitized pick and telemetry system provided excellent, high quality signals proportional to cutting load under all conditions experienced during testing.

Wu, P. T. K.↗
NASA NTRS1981

The millimeter wave super-Schottky diode detector

The 31 and 92 GHz measurements of the superconductor-Schottky diode extended to millimeter wavelengths by a redesign of the semiconductor interface are reported. Diodes were fabricated by pulse electroplating Pb on 2 x 10 to the 19th/cu cm p-Ga-As etched with HCl; a thin Au overplate is deposited to protect the Pb film from degradation and to improve its lifetime. The noise performance was almost ideal at 31 and 92 GHz; it was concluded that this diode is a quantum-limited-detector at 31 GHz, with excessive parasitic losses at 92 GHz.

Silver, A. H.↗
NASA NTRS1980

SPS design with solid-state transmitter

The replacement of the klystrons in the microwave transmitter in the SPS leads to major redesign considerations. Several curves are presented which show the interrelations of the major design features, the power level and the transmitting and receiving dimensions.

Ettenberg, M.↗
NASA NTRS1981

Computation of wind tunnel model deflections

The experimental deflections for a transport type solid wing model were measured for several single point load conditions. These deflections were compared with those obtained by structural modeling of the wing by using plate and solid elements of Structural Performance Analysis and Redesign (SPAR) program. The solid element representation of the wing showed better agreement with the experimental deflections than the plate representation. The difference between the measured and calculated deflections is about 5 percent.

Mehrotra, S. C.↗
NASA NTRS1983

Barrier for Continuous-Crystal-Growth Crucible

Properly designed openings permit free flow of melt while restraining pellets. Redesigned partition between growth region and melt-replenishment region of crystal-growth crucible makes it less likely crucible will run out of feed material in middle of cycle. Supply of molten silicon is maintained by addition of silicon pellets to compartment at one end of heated crucible, and partition or barrier is required to hold pellets while allowing melted silicon to flow from compartment.

Skutch, M. E.↗