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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Space mechanisms needs for future NASA long duration space missions

Future NASA long duration missions will require high performance, reliable, long lived mechanical moving systems. In order to develop these systems, high technology components such as bearings, gears, seals, lubricants, etc., will need to be utilized. There has been concern in the NASA community that the current technology level in these mechanical component/tribology areas may not be adequate to meet the goals of long duration NASA mission such as Space Exploration Initiative (SEI). To resolve this concern, NASA-Lewis sent a questionnaire to government and industry workers (who have been involved in space mechanism research, design, and implementation) to ask their opinion if the current space mechanisms technology (mechanical components/tribology) is adequate to meet future NASA Mission needs and goals. In addition, a working group consisting of members from each NASA Center, DoD, and DOE was established to study the technology status. The results of the survey and conclusions of the working group are summarized.

Fusaro, Robert L.↗
NASA NTRS2012

Advanced Prototype Fan Operating Experience, Post Test Evaluation, and Refurbishment for PLSS 2.0 Test Use

NASA s plans for Extravehicular Activity (EVA) portable life support systems for future exploration missions result in different design requirements than those which led to the combined fan / pump / separator in the current ISS Extravehicular Mobility Unit (EMU). To meet these new requirements, NASA contracted with Hamilton Sundstrand to provide two new prototype fans designed to meet anticipated future system requirements. Based on design trade studies, a high speed fan with mechanical bearing support of the rotating elements and a novel non-metallic barrier canned motor design was developed and implemented in the deliverable prototypes. The prototypes, which used two different bearing lubricants, have been extensively tested in both stand-alone and integrated system tests in NASA laboratories and proven to meet the anticipated performance requirements. Subsequently, they have been subjected to post test inspection and analysis in Hamilton Sundstrand laboratories to assess the effects of integrated operation and resultant exposure to vent loop contaminants. Results have confirmed expectations that one of the lubricants would be superior in this application and the prototype fans have been reassembled with new bearings with the superior lubricant. They have now been returned to the Johnson Space Center for further testing and maturation as part of NASA s PLSS 2.0 integrated test effort. This paper will discuss the test history of these units, resulting test data, the results of post test evaluation, and plans for further testing in the near future.

Hodgson, Edward↗
NASA NTRS2007

Increased Water Storage at Ice-stream Onsets: A Critical Mechanism?

The interdependence of rapid ice flow, surface topography and the spatial distribution of subglacial water are examined by linking existing theories. The motivation is to investigate whether the acceleration of an ice-stream tributary contains a positive feedback that encourages the retention of subglacial water that leads to faster flow. Periodically varying surface and bed topographies are related through a linear ice-flow perturbation theory for various values of mean surface slope, perturbation amplitude and basal sliding speeds. The topographic variations lead to a periodic variation in hydraulic potential that is used to infer the tendency for subglacial water to be retained in local hydraulic potential minima. If water retention leads to enhanced basal sliding, a positive feedback loop is closed that could explain the transition from slower tributary flow to faster-streaming flow and the sustained downstream acceleration along the tributary-ice-stream system. A sensitivity study illustrates that the same range of topographic wavelengths most effectively transmitted from the bed to the surface also strongly influences the behavior of subglacial water. A lubrication index is defined to qualitatively measure the heterogeneity of the subglacial hydrologic system. Application of this index to field data shows that the transition from tributary to ice stream closely agrees with the location where subglacial water may be first stored.

Bindschadler, Robert↗
NASA NTRS2013

Oil-Free Turbomachinery Technologies for Long-Life, Maintenance-Free Power Generation Applications

Turbines have long been used to convert thermal energy to shaft work for power generation. Conventional turbines rely upon oil-lubricated rotor supports (bearings, seals, etc.) to achieve low wear, high efficiency and reliability. Emerging Oil-Free technologies such as gas foil bearings and magnetic bearings offer a path for reduced weight and complexity and truly maintenance free systems. Oil-Free gas turbines, using gaseous and liquid fuels are commercially available in power outputs to at least 250kWe and are gaining acceptance for remote power generation where maintenance is a challenge. Closed Brayton Cycle (CBC) turbines are an approach to power generation that is well suited for long life space missions. In these systems, a recirculating gas is heated by nuclear, solar or other heat energy source then fed into a high-speed turbine that drives an electrical generator. For closed cycle systems such as these, the working fluid also passes through the bearing compartments thus serving as a lubricant and bearing coolant. Compliant surface foil gas bearings are well suited for the rotor support systems of these advanced turbines. Foil bearings develop a thin hydrodynamic gas film that separates the rotating shaft from the bearing preventing wear. During start-up and shut down when speeds are low, rubbing occurs. Solid lubricants are used to reduce starting torque and minimize wear. Other emerging technologies such as magnetic bearings can also contribute to robust and reliable Oil-Free turbomachinery. In this presentation, Oil-Free technologies for advanced rotor support systems will be reviewed as will the integration and development processes recommended for implementation.

turbomachinery↗
NASA NTRS2007

Wear of Spur Gears Having a Dithering Motion and Lubricated with a Perfluorinated Polyether Grease

Gear contact surface wear is one of the important failure modes for gear systems. Dedicated experiments are required to enable precise evaluations of gear wear for a particular application. The application of interest for this study required evaluation of wear of gears lubricated with a grade 2 perfluorinated polyether grease and having a dithering (rotation reversal) motion. Experiments were conducted using spur gears made from AISI 9310 steel. Wear was measured using a profilometer at test intervals encompassing 10,000 to 80,000 cycles of dithering motion. The test load level was 1.1 GPa maximum Hertz contact stress at the pitch-line. The trend of total wear as a function of test cycles was linear, and the wear depth rate was approximately 1.2 nm maximum wear depth per gear dithering cycle. The observed wear rate was about 600 times greater than the wear rate for the same gears operated at high speed and lubricated with oil.

Krantz, Timothy↗
NASA NTRS2017

Hybrid Gear Performance Under Loss-of-Lubrication Conditions

Hybrid composite gear technology is being investigated to increase power density in rotorcraft drive systems. These gears differ from conventional steel gears in that the structural web material is replaced with a lightweight carbon fiber composite. Past studies have focused on performance of this technology under normal operating conditions, however, for this technology to be viable it must also withstand adverse conditions. The study presented here evaluates the performance of hybrid gears under loss-of-lubrication conditions in NASA Glenn Research Centers Contact Fatigue Test Facility. Two experiments are presented using small-scale 3.5 inch (8.9 cm) pitch diameter hybrid gears and compared to a baseline steel gear pair. Results of these tests show that there are limitations to the use of a hexagonal interlock pattern between the steel and composite. There is also evidence that the presence of polymer in the gear during an oil out event has a potential to increase time to failure. Further studies are planned to expand on these initial findings.

Gearbox↗
NASA NTRS2017

Hybrid Gear Performance Under Loss-of-Lubrication Conditions

Hybrid composite gear technology is being investigated to increase power density in rotorcraft drive systems. These gears differ from conventional steel gears in that the structural web material is replaced with a lightweight carbon fiber composite. Past studies have focused on performance of this technology under normal operating conditions, however, for this technology to be viable it must also withstand adverse conditions. The study presented here evaluates the performance of hybrid gears under loss-of-lubrication conditions in NASA Glenn Research Centers Contact Fatigue Test Facility. Two experiments are presented using small-scale 3.5 inch (8.9 cm) pitch diameter hybrid gears and compared to a baseline steel gear pair. Results of these tests show that there are limitations to the use of a hexagonal interlock pattern between the steel and composite. There is also evidence that the presence of polymer in the gear during an oil out event has a potential to increase time to failure. Further studies are planned to expand on these initial findings.

Gearbox↗
NASA NTRS2015

An Overview of 2014 SBIR Phase I and Phase II Materials Structures for Extreme Environments

NASA's Small Business Innovation Research (SBIR) program focuses on technological innovation by investing in development of innovative concepts and technologies to help NASA mission directorates address critical research needs for Agency programs. This report highlights nine of the innovative SBIR 2014 Phase I and Phase II projects that emphasize one of NASA Glenn Research Center's six core competencies-Materials and Structures for Extreme Environments. The technologies cover a wide spectrum of applications such as high temperature environmental barrier coating systems, deployable space structures, solid oxide fuel cells, and self-lubricating hard coatings for extreme temperatures. Each featured technology describes an innovation, technical objective, and highlights NASA commercial and industrial applications. This report provides an opportunity for NASA engineers, researchers, and program managers to learn how NASA SBIR technologies could help their programs and projects, and lead to collaborations and partnerships between the small SBIR companies and NASA that would benefit both.

barrier coating system; deployable space structure↗
NASA NTRS1970

Small hydraulic turbine drives

Turbine, driven by the fluid being pumped, requires no external controls, is completely integrated into the flow system, and has bearings which utilize the main fluid for lubrication and cooling. Torque capabilities compare favorably with those developed by positive displacement hydraulic motors.

Rostafinski, W. A.↗
NASA NTRS1973

Momentum wheel with magnetic bearings

An engineering model of a momentum wheel is described that is suspended by magnetic bearings. It consists of a mechanical assembly on the right, and associated electronics on the left. The momentum wheel is mounted at the center of the rotor shaft and the magnetic bearings are on each end. The rotor is magnetically suspended so there is no physical contact between the rotor and the support structure. The system, therefore, can operate directly in the vacuum environment without lubrication; and it has virtually unlimited operating lifetime, independent of speed.

Veillette, L. J.↗
NASA NTRS1973

KSC lubricant testing program

A program was conducted to evaluate the performance of various lubricants in use and considered for use at Kennedy Space Center (KSC). The overall objectives of the program were to: (1) determine the lubrication characteristics and relative corrosion resistance of lubricants in use and proposed for use at KSC; (2) identify materials which may be equivalent to or better than KELF-90 and Krytox 240 AC greases; and (3) identify or develop an improved lubricating oil suitable for use in liquid oxygen (LOX) pumps at KSC. It was concluded that: (1) earth gel thickened greases are very poor corrosion preventive materials in the KSC environment; (2) Halocarbon 25-5S and Braycote 656 were suitable substiutes for KELF-90 and Krytox 240 AC respectively; and (3) none of the oils evaluated possessed the necessary inertness, lubricity, and corrosion prevention characteristics for the KSC LOX pumping systems in their present configuration.

Lockhart, B. J.↗
NASA NTRS1989

Graphite Fluoride Fiber Composites For Heat Sinking

Graphite fluoride fiber/polymer composite materials consist of graphite fluoride fibers in epoxy, polytetrafluoroethylene, or polyimide resin. Combines high electrical resistivity with high thermal conductivity and solves heat-transfer problems of many electrical systems. Commercially available in powder form, for use as dry lubricant or cathode material in lithium batteries. Produced by direct fluorination of graphite powder at temperature of 400 to 650 degree C. Applications include printed-circuit boards for high-density power electronics, insulators for magnetic-field cores like those found in alternators and transformers, substrates for thin-film resistors, and electrical-protection layers in aircraft de-icers.

Hung, Ching-Cheh↗
NASA NTRS1992

New results from FRECOPA analysis

Given Long Duration Exposure Facility (LDEF) new situation (5.8 years mission), CNES decided to set up a team to analyze FRECOPA systems (AO 138). We studied the kinematic system first. We observed damage on the DELRIN gears and lubricant ageing. The results are based on comparative appraisals between components after flight and those stored on ground in laboratory conditions. We observed also the aluminum surface treatment in the exposed areas and we measured the thermo-optical properties changes. Now, with all the results stored, we try to give a ruling on the use of FRECOPA materials in space environment.

Durin, Christian↗
NASA NTRS2010

Effects of Hydrocarbon-Based Grease on Rapid Prototype Material Used for Grease Retention Shrouds

Effects of hydrocarbon-based greases on specific rapid prototype (RP) materials used to fabricate grease retention shrouds (GRS) were explored in this study. Grease retention shrouds are being considered as a way to maintain adequate grease lubrication at the gear mesh in a prototype research transmission system. Due to their design and manufacturing flexibility, rapid prototype materials were chosen for the grease retention shrouds. In order to gain a better understanding of the short and long term effects grease pose on RP materials, research was conducted on the interaction of hydrocarbon-based grease with RP materials. The materials used in this study were durable polyamide (nylon), acrylonitrile butadiene styrene (ABS), and WaterClear 10120. Testing was conducted using Mobilgrease 28 and Syn-Tech 3913G grease (gear coupling grease). These greases were selected due to their regular use with mechanical components. To investigate the effect that grease has on RP materials, the following methods were used to obtain qualitative and quantitative data: Fourier transform infrared spectroscopy (FT-IR), interference profilometer measurements, digital camera imaging, physical shape measurement, and visual observations. To record the changes in the RP materials due to contact with the grease, data was taken before and after the grease application. Results showed that the WaterClear 10120 RP material provided the best resistance to grease penetration as compared to nylon and ABS RP materials. The manufacturing process, and thus resulting surface conditions of the RP material, played a key role in the grease penetration properties and resilience of these materials.

Zakrajsek, Andrew J.↗
NASA NTRS2011

Oil-Free Shaft Support System Rotordynamics: Past, Present, and Future Challenges and Opportunities

Recent breakthroughs in Oil-Free technologies have enabled new high-speed rotor systems and turbomachinery. Such technologies can include compliant-surface gas bearings, magnetic bearings, and advanced solid lubricants and tribo-materials. This presentation briefly reviews critical technology developments and the current state-of-the-art, emerging Oil-Free rotor systems and discusses obstacles preventing more widespread use. Key examples of "best practices" for deploying Oil-Free technologies will be presented and remaining major technical questions surrounding Oil-Free technologies will be brought forward.

DellaCorte, Christopher↗
NASA NTRS1982

Stability evaluation of rotor/bearing system

A stability study of rotor/bearing systems is presented. Even though it was limited to study of a fully lubricated bearing subject to oil whirl, and further limited to low eccentricity region for linearity and with only one type of lubricant, it can be seen that the perturbation methodology, together with the sorting of the impedance terms into direct and quadrature with respect to input force can be very useful to the general study of stability. Further, the concept of active feedback should assist to increase knowledge in rotor system stability. While there remains a large amount of study to be accomplished, perhaps some more tools are available to assist this field of analysis.

Bently, D. E.↗
NASA NTRS2009

Intermetallic Nickel-Titanium Alloys for Oil-Lubricated Bearing Applications

An intermetallic nickel-titanium alloy, NITINOL 60 (60NiTi), containing 60 wt% nickel and 40 wt% titanium, is shown to be a promising candidate material for oil-lubricated rolling and sliding contact applications such as bearings and gears. NiTi alloys are well known and normally exploited for their shape memory behavior. When properly processed, however, NITINOL 60 exhibits excellent dimensional stability and useful structural properties. Processed via high temperature, high-pressure powder metallurgy techniques or other means, NITINOL 60 offers a broad combination of physical properties that make it unique among bearing materials. NITINOL 60 is hard, electrically conductive, highly corrosion resistant, less dense than steel, readily machined prior to final heat treatment, nongalling and nonmagnetic. No other bearing alloy, metallic or ceramic encompasses all of these attributes. Further, NITINOL 60 has shown remarkable tribological performance when compared to other aerospace bearing alloys under oil-lubricated conditions. Spiral orbit tribometer (SOT) tests were conducted in vacuum using NITINOL 60 balls loaded between rotating 440C stainless steel disks, lubricated with synthetic hydrocarbon oil. Under conditions considered representative of precision bearings, the performance (life and friction) equaled or exceeded that observed with silicon nitride or titanium carbide coated 440C bearing balls. Based upon this preliminary data, it appears that NITINOL 60, despite its high titanium content, is a promising candidate alloy for advanced mechanical systems requiring superior and intrinsic corrosion resistance, electrical conductivity and nonmagnetic behavior under lubricated contacting conditions.

DellaCorte, C.↗