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  • 1
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    Ground operation of robotics on Space Station Freedom (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: This paper reflects work carried out on Ground Operated Telerobotics (GOT) in 1992 to refine further the ideas, procedures, and technologies needed to test the procedures in a high latency environment, and to integrate GOT into Space Station Freedom operations. Space Station Freedom (SSF) will be in operation for 30 years, and will depend on robots to carry out a significant part of the assembly, maintenance, and utilization workload. Current plans call for on-orbit robotics to be operated by on-board crew members. This approach implies that on-orbit robotics operations use up considerable crew time, and that these operations cannot be carried out when SSF is unmanned. GOT will allow robotic operations to be operated from the ground, with on-orbit crew interventions only when absolutely required. The paper reviews how GOT would be implemented, how GOT operations would be planned and supported, and reviews GOT issues, critical success factors, and benefits.
    Keywords: MECHANICAL ENGINEERING
    Type: JPL, SpaceOps 1992: Proceedings of the Second International Symposium on Ground Data Systems for Space Mission Operations; p 51-55
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  • 2
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    Development of a full-scale transmission testing procedure to evaluate advanced lubricants (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Experimental tests were performed on the OH-58A helicopter main rotor transmission in the NASA Lewis 500-hp Helicopter Transmission Test Stand. The testing was part of a joint Navy/NASA/Army lubrication program. The objective of the program was to develop a separate lubricant for gearboxes and demonstrate an improved performance in life and load-carrying capacity. The goal of the experiments was to develop a testing procedure to fail certain transmission components using a MIL-L-23699 base reference oil, then run identical tests with improved lubricants and demonstrate performance. The tests were directed at failing components that the Navy has had problems with due to marginal lubrication. These failures included mast shaft bearing micropitting, sun gear and planet bearing fatigue, and spiral bevel gear scoring. A variety of tests were performed and over 900 hours of total run time accumulated for these tests. Some success was achieved in developing a testing procedure to produce sun gear and planet bearing fatigue failures. Only marginal success was achieved in producing mast shaft bearing micropitting and spiral bevel gear scoring.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TP-3265 , E-6531 , NAS 1.60:3265 , AVSCOM-TR-91-C-026 , AD-A257204
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  • 3
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    Vibration characteristics of OH-58A helicopter main rotor transmission (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Experimental vibration tests covering a range of torque and speed conditions were performed on the OH-58A helicopter main rotor transmission at the NASA Lewis Research Center. Signals from accelerometers located on the transmission housing were analyzed by using Fourier spectra, power spectral density functions, and averaging techniques. Most peaks of the Fourier spectra occurred at the spiral bevel and planetary gear mesh harmonics. The highest level of vibration occurred at the spiral bevel meshing frequency. Transmission speed and vibration measurement location had a significant effect on measured vibration; transmission torque and measurement direction had a small effect.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TP-2705 , E-3368 , NAS 1.60:2705 , AVSCOM-TR-86-C-42 , AD-A180364
    Format: application/pdf
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  • 4
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    Helicopter transmission testing at NASA Lewis Research Center (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The helicopter has evolved into a highly valuable air mobile vehicle for both military and civilian needs. The helicopter transmission requires advanced studies to develop a technology base for future rotorcraft advances. A joint helicopter transmission research program between the NASA Lewis Research Center and the U.S. Army Aviation Systems Command has existed since 1970. Program goals are to reduce weight and noise and to increase life and reliability. The current experimental activities at Lewis consist of full-scale helicopter transmission testing, a base effort in gearing technology, and a future effort in noise reduction technology. The experimental facilities at Lewis for helicopter transmission testing are described. A description of each of the rigs is presented along with some significant results and near-term plans.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-89912 , E-3603 , NAS 1.15:89912 , AVSCOM-TR-87-C-10
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  • 5
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    Predicted effect of dynamic load on pitting fatigue life for low-contact-ratio spur gears (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: How dynamic load affects the surface pitting fatigue life of external spur gears was predicted by using the NASA computer program TELSGE. Parametric studies were performed over a range of various gear parameters modeling low-contact-ratio involute spur gears. In general, gear life predictions based on dynamic loads differed significantly from those based on static loads, with the predictions being strongly influenced by the maximum dynamic load during contact. Gear mesh operating speed strongly affected predicted dynamic load and life. Meshes operating at a resonant speed or one-half the resonant speed had significantly shorter lives. Dynamic life factors for gear surface pitting fatigue were developed on the basis of the parametric studies. In general, meshes with higher contact ratios had higher dynamic life factors than meshes with lower contact ratios. A design chart was developed for hand calculations of dynamic life factors.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TP-2610 , E-2989 , NAS 1.60:2610 , AD-A170906 , AVSCOM-TR-86-C-21
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  • 6
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    Suppression of Subsynchronous Vibration in the SSME HPFTP (1991)
    In:  CASI
    Details
    Publication Date: 2014-09-24
    Description: Space Shuttle Main Engine (SSME) High Pressure Fuel Turbopump (HPFTP) hot-fire dynamic data evaluation and rotordynamic analysis both confirm that two of the most significant turbopump attributes in determining susceptibility to subsynchronous vibration are impeller interstage seal configuration and rotor sideload resulting from turbine turnaround duct configuration and hot gas manifold. Recent hot-fire testing has provided promising indications that the incorporation of roughened damping seals at the impeller interstages may further increase the stability margin of this machine. A summary of the analysis which led to the conclusion that roughened seals would enhance the stability margin is presented along with a correlation of the analysis with recent test data.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center, Rotordynamic Instability Problems in High-Performance Turbomachinery, 1990; p 191-202
    Format: application/pdf
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  • 7
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    Fault detection of helicopter gearboxes using the multi-valued influence matrix method (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: In this paper we investigate the effectiveness of a pattern classifying fault detection system that is designed to cope with the variability of fault signatures inherent in helicopter gearboxes. For detection, the measurements are monitored on-line and flagged upon the detection of abnormalities, so that they can be attributed to a faulty or normal case. As such, the detection system is composed of two components, a quantization matrix to flag the measurements, and a multi-valued influence matrix (MVIM) that represents the behavior of measurements during normal operation and at fault instances. Both the quantization matrix and influence matrix are tuned during a training session so as to minimize the error in detection. To demonstrate the effectiveness of this detection system, it was applied to vibration measurements collected from a helicopter gearbox during normal operation and at various fault instances. The results indicate that the MVIM method provides excellent results when the full range of faults effects on the measurements are included in the training set.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-106100 , E-7742 , NAS 1.15:106100 , AVSCOM-TR-92-C-015
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  • 8
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    Evaluation of an oil-debris monitoring device for use in helicopter transmissions (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Experimental tests were performed on an OH-58A helicopter main-rotor transmission to evaluate an oil-debris monitoring device (ODMD). The tests were performed in the NASA 500-hp Helicopter Transmission Test Stand. Five endurance tests were run as part of a U.S. Navy/NASA/Army advanced lubricants program. The tests were run at 100 percent design speed, 117-percent design torque, and 121 C (250 F) oil inlet temperature. Each test lasted between 29 and 122 hr. The oils that were used conformed to MIL-L-23699 and DOD-L-85734 specifications. One test produced a massive sun-gear fatigue failure; another test produced a small spall on one sun-gear tooth; and a third test produced a catastrophic planet-bearing cage failure. The ODMD results were compared with oil spectroscopy results. The capability of the ODMD to detect transmission component failures was not demonstrated. Two of the five tests produced large amounts of debris. For these two tests, two separate ODMD sensors failed, possibly because of prolonged exposure to relatively high oil temperatures. One test produced a small amount of debris and was not detected by the ODMD or by oil spectroscopy. In general, the ODMD results matched the oil spectroscopy results. The ODMD results were extremely sensitive to oil temperature and flow rate.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-105830 , E-7265 , NAS 1.15:105830 , AVSCOM-TR-92-C-007 , AD-A262479
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  • 9
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    Limiting critical speed response on the SSME Alternate High Pressure Fuel Turbopump (ATD HPFTP) with bearing deadband (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Yammamoto (1954) described the influence of bearing deadband on the critical speed response of a rotor-bearing system. Practical application of these concepts to limit critical speed response of turbopump rotors is described. Nonlinear rotordynamic analyses are used to define the effect of bearing deadband and rotor unbalance on the Space Shuttle Main Engine Alternate High Pressure Fuel Turbopump. Analysis results are used with hot fire test data to verify the presence of a lightly damped critical speed within the operating speed range. With the proper control of rotor unbalance and bearing deadband, the response of this critical speed is reduced to acceptable levels without major design modifications or additional sources of damping.
    Keywords: MECHANICAL ENGINEERING
    Type: AIAA PAPER 92-3402
    Format: text
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  • 10
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    Helicopter transmission research at NASA Lewis Research Center (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A joint helicopter transmission research program between NASA Lewis Research Center and the U.S. Army Aviation Systems Command has existed since 1970. Program goals are to reduce weight and noise and to increase life and reliability. Reviewed are significant advances in technology for gears and transmissions and the experimental facilities at NASA Lewis for helicopter transmission testing are described. A description of each of the rigs is presented along with some significant results from the experiments.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-100962 , E-4181 , AVSCOM-TM-88-C-003 , NAS 1.15:100962 , AD-A242220
    Format: application/pdf
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