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At least 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Improving the breed - Shuttle development

An evaluation is made of design improvements that have been made to the Space Shuttle System, and the performance gains obtained; the most important of these stem from efforts to refine procedures for rendezvous with stricken satellites, in order to repair them. Ascent performance has been improved through Space Shuttle Main Engine thrust improvements and external tank weight reductions. On-orbit living convenience has been enhanced by the addition of small sleeping compartments and a galley. Greater flexibility has been obtained for reentry and landing maneuvers. Attention is given to problems which continue to be posed by the thermal protection tiles.

Brand, V.↗
NASA NTRS1985

Space Shuttle main engine product improvement

The current design of the Space Shuttle Main Engine has passed 11 certification cycles, amassed approximately a quarter million seconds of engine test time in 1200 tests and successfully launched the Space Shuttle 17 times of 51 engine launches through May 1985. Building on this extensive background, two development programs are underway at Rocketdyne to improve the flow of hot gas through the powerhead and evaluate the changes to increase the performance margins in the engine. These two programs, called Phase II+ and Technology Test Bed Precursor program are described. Phase II+ develops a two-tube hot-gas manifold that improves the component environment. The Precursor program will evaluate a larger throat main combustion chamber, conduct combustion stability testing of a baffleless main injector, fabricate an experimental weld-free heat exchanger tube, fabricate and test a high pressure oxidizer turbopump with an improved inlet, and develop and test methods for reducing temperature transients at start and shutdown.

Lucci, A. D.↗
NASA NTRS1985

Properties of autoclaved Gr/PI composites made from improved tack PMR-15 prepreg

Autoclave processing studies were conducted, using improved tack PMR-15 prepreg, to determine the effect of tack enhancing PMR resin modifications on composite processability and mechanical properties. Improved tack graphite fiber reinforced PMR-15 prepregs were prepared and exposed to ambient conditions for various times and then autoclave molded into composites. Composite specimens were prepared and tested for flexural and interlaminar shear strengths at room temperature and 316 C. The retention of flexural and interlaminar shear strength as a function of exposure in air at 316 C was also determined. The results show that the modified PMR resin solutions provide prepreg with improved tack and drape retention characteristics without adversely affecting processability or mechanical properties of autoclave molded graphite fiber reinforced PMR-15 composites.

Vannucci, R. D.↗
NASA NTRS1985

Productivity improvement in engineering at Rocketdyne

The Rocketdyne Division of Rockwell International has embarked on a productivity improvement program in engineering. This effort included participation in the White Collar Productivity Improvement (WCPI) project sponsored by the American Productivity Center. A number of things have been learned through this project. It seems that any productivity improvement project should be employee driven. The Rocketdyne project was essentially started as a result of a grassroots effort to remove some particular hindrances, and employee enthusiasm was a prime factor in the continuing progress of the effort. A significant result was that awareness of problems at all levels increased. Many issues surfaced in the diagnostic phase, and were then noted and discussed. This process added legitimacy to issues that had previously been merely unspoken concerns. The initial feelings of many members of the pilot group was that significant changes would occur relatively quickly. It is now recognized that this will have to be an ongoing, long-term effort.

Nordlund, R. M.↗
NASA NTRS1985

Improving engineering effectiveness

Methodologies to improve engineering productivity were investigated. The rocky road to improving engineering effectiveness is reviewed utilizing a specific semiconductor engineering organization as a case study. The organization had a performance problem regarding new product introductions. With the help of this consultant as a change agent the engineering team used a systems approach to through variables that were effecting their output significantly. Critical factors for improving this engineering organization's effectiveness and the roles/responsibilities of management, the individual engineers and the internal consultant are discussed.

Fiero, J. D.↗
NASA NTRS1985

Actions for productivity improvement in crew training

Improvement of the productivity of astronaut crew instructors in the Space Shuttle program and beyond is proposed. It is suggested that instructor certification plans should be established to shorten the time required for trainers to develop their skills and improve their ability to convey those skills. Members of the training cadre should be thoroughly cross trained in their task. This provides better understanding of the overall task and greater flexibility in instructor utilization. Improved facility access will give instructors the benefit of practical application experience. Former crews should be integrated into the training of upcoming crews to bridge some of the gap between simulated conditions and the real world. The information contained in lengthy and complex training manuals can be presented more clearly and efficiently as computer lessons. The illustration, animation and interactive capabilities of the computer combine an effective means of explanation.

Miller, G. E.↗
NASA NTRS1986

Improvement of the second- and third-moment modeling of turbulence: A study of Reynolds-stress closure model

Four parts of the Reynolds-stress closure modeling are reported: (1) improvement of the k and epsilon equaitons; (2) development of the third-moment transport equation; (3) formulation of the diffusion coefficient of the momentum equation by using the algebraic-stress model of turbulence; and (4) the application of the Reynolds-stress model to a heat exchanger problem. It was demonstrated that the third-moment transport model improved the prediction of the triple-velocity products in the recirculating and reattaching flow regions in comparison with the existing algebraic models for the triple-velocity products. Optimum values for empirical coefficients are obtained for the prediction of the backward-facing step flows. A functional expression is derived for the coefficient of the momentum diffusion by employing the algebraic-stress model. The second-moment closure is applied to a heat transfer problem. The computations for the flow in a corrugated-wall channel show that the second-moment closure improves the prediction of the heat transfer rates by 30% over the k - epsilon model.

Amano, R. S.↗
NASA NTRS1986

Improved Skin Friction Interferometer

An improved system for measuring aerodynamic skin friction which uses a dual-laser-beam oil-film interferometer was developed. Improvements in the optical hardware provided equal signal characteristics for each beam and reduced the cost and complexity of the system by replacing polarization rotation by a mirrored prism for separation of the two signals. An automated, objective, data-reduction procedure was implemented to eliminate tedious manual manipulation of the interferometry data records. The present system was intended for use in two-dimensional, incompressible flows over a smooth, level surface without pressure gradient, but the improvements discussed are not limited to this application.

Westphal, R. V.↗
NASA NTRS1985

Operational life improvement of SSME high-pressure turbopumps

The current Space Shuttle Main Engine (SSME) Phase I engine demonstrated excellent flight performance but showed limited operational life of the high-pressure fuel turbopumps (HPFTP). Design improvements, supporting analyses, and test results of the SSME Phase II development program are presented. The HPFTP improvements include reduction of turbine operating temperature by 110 to 130 R by reconstructing the seals and the flow contours; modifications of the first- and second-stage turbine blades by recontouring the shank, shotpeening the shank surface, and applying a multilayered, plasma-spray coating to the shank on the downstream side to reduce the effect of the disk coolant; and reduction of the tendency for thermal cracks in the turbine by changing weld configuration to avoid the concentration of stresses in local areas. The high-pressure oxidizer turbopump has been also modified to improve bearing life and to eliminate subsynchronous whirl.

Hale, J. R.↗
NASA NTRS1985

Utilization of satellite-derived cloud cover to improve the estimation of latent heat release in a winter extratropical cyclone

A simple scheme for utilizing satellite cloud pattern information to improve the estimation of parameterized stable and convective latent heat release is proposed and tested for an extratropical cyclone occurring over the United States during January 9-11, 1975. Calculations are done over the standard North American rawinsonde data region and over a sparse data region simulated by ignoring one-third of the original rawinsonde stations. Results indicate 15 percent and 30 percent improvements in latent heating estimates derived from the total and sparse data sets, respectively. A larger improvement was found using the sparse data set because the parameterized latent heat release estimates obtained using these data were poorer than those obtained using the total data set.

Lin, S.-J.↗
NASA NTRS1986

Voyager engineering improvements for Uranus encounter

Engineering changes made on the Voyager spacecraft during their explorations of the outer solar system are discussed. A recovery from a scan actuator fault, achieved by ground testing, in flight capability enhancement and testing, conservation of actuator usage and a set of contingency plans to substitute roll motion of the spacecraft for motion of the scan platform in the AZ direction, is discussed. General engineering improvements made are addressed, including a scan platform anticreep patch modification, an improvement of dynamic performance during maneuvers, and adaptive control of the attitude control deadband. Changes made in the power management are described. Finally, engineering improvements made in order to enhance scientific findings at the Uranus encounter are reviewed in detail. The two most important were the increased gyro drift turn rate capability to accommodate image motion compensation for the close fly-by of Miranda and the reduction in spacecraft rates to accommodate increased imaging exposure times without incurring excessive image smear.

Marderness, H. P.↗
NASA NTRS1987

Traveling-wave-tube efficiency improvement by a low-cost technique for deposition of carbon on multistage depressed collector

A simple method of improving the traveling-wave-tube (TWT) and multistage depressed collector (MDC) efficiency has been demonstrated. The efficiency improvement was produced by the application of a thin layer of carbon to the copper electrodes of the MDC by means of a rapid, low-cost technique involving the pyrolysis of hydrocarbon oil in electric arc discharges. Experimental results with a representative TWT and MDC showed an 11 percent improvement in both the TWT and MDC efficiencies as compared to those of the same TWT and MDC efficiencies with bare copper electrode surfaces. An extended test with a 500-W, continuous wave (CW) TWT and small-sized MDC indicated good stability of the carbon coated electrode surfaces after a relatively small initial degradation in TWT overall and apparent MDC efficiencies.

Ebihara, Ben T.↗
NASA NTRS1987

TWT efficiency improvement by a low-cost technique for deposition of carbon on MDC electrodes

A simple method of improving the TWT and multistage depressed collector (MDC) efficiency has been demonstrated. The efficiency improvement was produced by the application of a thin layer of carbon to the copper electrodes of the MDC by means of a rapid low-cost technique involving the pyrolysis of hydrocarbon oil in electric arc discharges. Experimental results with a representative TWT and MDC showed an 11 percent improvement in both the TWT and MDC efficiencies as compared to those of the same TWT and MDC with machined copper electrode surfaces. An extended test with a 550-W CW TWT indicated good durability of the carbon-coated electrode surfaces.

Ebihara, Ben T.↗
NASA NTRS1986

Recent Space Shuttle crew compartment design improvements

Significant design changes to the Space Shuttle waste management system (WMS) and its related personal hygiene support provisions (PHSP) have been made recently to improve overall operational performance and human factors interfaces. The WMS design improvements involve increased urinal flow, individual urinals, and provisions for manually compacting feces and cleanup materials to ensure adequate mission capacity. The basic arrangement and stowage of the PHSP used during waste management operations were extensively changed to better serve habitability concerns and operations needs, and to improve the hygiene of WMS operations. This paper describes these changes and the design, development, and flight test evaluation. In addition, provisions for an eighth crewmember and a new four-tier sleep station are described.

Goodman, Jerry R.↗
NASA NTRS1986

Shuttle waste management system design improvements and flight evaluation

The Space Shuttle waste management system has undergone a variety of design changes to improve performance and man-machine interface. These design improvements have resulted in more reliable operation and hygienic usage. Design enhancements include individual urinals, increased urine collection airflows, increased solids storage capacity, easier access to personal hygiene items, and additional wet trash stowage. The development and flight evaluation of these improvements are described herein. The Space Shuttle Orbiter has proved to be an invaluable test bed for development and in-flight evaluation of life support and habitability concepts which involve transport or separation of solids, liquids, and gases in a zero-g environment.

Winkler, H. Eugene↗
NASA NTRS1988

Improved Consolidation Of Silicon Carbide

Colloidal techniques used to improve dispersion and suspension of SiC in water. In combination with slurry pressing, resulted in increase in strength of sintered SiC by 87 percent over SiC sintered after dry pressing. Improvement due to reduced porosity and reflected in improved densities of "green" and sintered specimens. Smaller sizes of pores, and reduced sizes of critical flaws contributed to increase in strength. Useful for making parts from particulate-, transformation-, and whisker-toughened ceramics and monolithic ceramics. Provides avenue for study of variables contributing to reliability of current structural ceramics.

Freedman, Marc R.↗
NASA NTRS1988

Modification of a successive corrections objective analysis for improved higher order calculations

The use of objectively analyzed fields of meteorological data for the initialization of numerical prediction models and for complex diagnostic studies places the requirements upon the objective method that derivatives of the gridded fields be accurate and free from interpolation error. A modification was proposed for an objective analysis developed by Barnes that provides improvements in analysis of both the field and its derivatives. Theoretical comparisons, comparisons between analyses of analytical monochromatic waves, and comparisons between analyses of actual weather data are used to show the potential of the new method. The new method restores more of the amplitudes of desired wavelengths while simultaneously filtering more of the amplitudes of undesired wavelengths. These results also hold for the first and second derivatives calculated from the gridded fields. Greatest improvements were for the Laplacian of the height field; the new method reduced the variance of undesirable very short wavelengths by 72 percent. Other improvements were found in the divergence of the gridded wind field and near the boundaries of the field of data.

Achtemeier, Gary L.↗