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At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Critical Current Stability of 2G REBCO Tape for Space-Flight HTS Leads

High reliability is an essential requirement for all spaceflight hardware. XRISM, a follow-on mission to the Hitomi x-ray observatory, also uses 2G REBCO tapes as current leads for the superconducting magnets that are a key component of the Adiabatic Demagnetization Refrigerator (ADR) that cools the detector array. While the Hitomi Soft X-ray Spectrometer (SXS) worked flawlessly in orbit, during its development there were indications that the critical current of its specialized REBCO tapes could degrade over time when exposed to normal-humidity air. To demonstrate that the updates to the XRISM HTS lead assemblies had mitigated this risk, a series of tests were carried out to measure the stability of Ic of dozens of samples over a period greater than the flight assemblies were exposed to air during integration and test. The test rig allowed not only the measurement of the sample Ic, but also the localization of the voltage rise as the current approached Ic. We will discuss the trends in the critical current of the samples, as well as localization of lower Ic regions.

Edgar R. Canavan↗
NASA NTRSDate not supplied

Advancement of Metal Additive Manufacturing Processes and Alloys for Rocket Propulsion Applications

NASA has been involved in the development and maturation of metal additive manufacturing (AM) for space applications since the 2000’s. Several efforts have focused on the understanding of AM processes through material characterization and testing, standards development, component fabrication, and infusion into development and flight applications. While many common aerospace alloys have been and continue to be a focus of ongoing development, the need for custom-alloy developments for high performance applications enabled by various AM processes has been realized. The applications being targeted are liquid rocket engines with high heat fluxes, high pressure, and that utilize propellants such as hydrogen, which can degrade the alloy. NASA has recently focused on the development and advancement of novel alloy advancement using AM for use in these harsh environments, such as GRCop-42, GRCop-84, NASA HR-1, and JBK-75. These alloys have been evaluated using powder bed fusion (PBF), directed energy deposition (DED), and solid-state AM processes. The results from these processes have demonstrated that AM can enable rapid development of new alloy systems that can yield higher performances across various metal AM processes. These alloys have undergone the fundamental metallurgical evaluations, heat treatment study, and microstructure characterization and mechanical testing campaign. This, combined with direct application-specific component fabrication and hot-fire testing, enabled the increase of the Technology Readiness Level (TRL). This presentation will provide a background and overview of various AM-enabled novel alloys, a comparison across the AM processes, and development including metallurgical and mechanical property studies. It will also cover the latest advancement in the parallel component development and testing and future developments. The goal of these alloy development and use of various AM processes is to allow for technology infusion into NASA and commercial spaceflight missions as well as to establish and sustain the needed commercial AM supply chain.

Additive Manufacturing↗
NASA NTRSDate not supplied

Metal Additive Manufacturing Developments for Propulsion Applications

NASA has been involved in the development and maturation of metal additive manufacturing (AM) for space applications since the 2000’s. Several efforts have focused on the understanding of AM processes through material characterization and testing, standards development, component fabrication, and infusion into development and flight applications. While many common aerospace alloys have been and continue to be a focus of ongoing development, the need for custom-alloy developments for high performance applications enabled by various AM processes has been realized. The applications being targeted are liquid rocket engines with high heat fluxes, high pressure, and that utilize propellants such as hydrogen, which can degrade the alloy. NASA has recently focused on the development and advancement of novel alloy advancement using AM for use in these harsh environments, such as GRCop-42, GRCop-84, NASA HR-1, and JBK-75. These alloys have been evaluated using powder bed fusion (PBF), directed energy deposition (DED), and solid-state AM processes. The results from these processes have demonstrated that AM can enable rapid development of new alloy systems that can yield higher performances across various metal AM processes. These alloys have undergone the fundamental metallurgical evaluations, heat treatment study, and microstructure characterization and mechanical testing campaign. This, combined with direct application-specific component fabrication and hot-fire testing, enabled the increase of the Technology Readiness Level (TRL). This presentation will provide a background and overview of various AM-enabled novel alloys, a comparison across the AM processes, and development including metallurgical and mechanical property studies. It will also cover the latest advancement in the parallel component development and testing and future developments. The goal of these alloy development and use of various AM processes is to allow for technology infusion into NASA and commercial spaceflight missions as well as to establish and sustain the needed commercial AM supply chain.

Additive Manufacturing↗
NASA NTRS1978

Organic geochemical studies on kerogen precursors in recently deposited algal mats and oozes

The same kerogen-like residue from the algal mats and oozes at Laguna Mormona, Baja California, is examined following degradation by saponification, alkaline KMnO4 oxidation, and HBr treatment. For comparison, pyrolytic degradation is performed for the residue and five others, two of which are obtained from algal mats at Baffin Bay, Texas. Major conclusions are that (1) Saponification of a residue specimen from the algal-ooze residue results in minor amounts of components bonded to it as esters; (2) Alkaline KMnO4 oxidation reveals that the same residue consists of a cross-linked aliphatic nucleus with additional components attached to it as esters; (3) the major products from pyrolysis of the residue include phytenes, pristenes, sterenes, and triterpenes; and (4) the HBr treatment yielded only one product, indicating the absence of a large number of ether-linkages readily cleaved by HBr.

Philp, R. P.↗
NASA NTRS1982

Mass-Loss Buttons Monitor Material Degradation

Small button-sized samples attached to parent materials are simple way of monitoring degradation of parent in harsh environments. Samples determine effects of multiple exposures to environmental extremes without disturbing fit or function of parent. They are less costly and more convenient than complex instrumentation normally required to measure complete temperature/pressure time history of parent component.

Webster, C. N.↗
NASA NTRS1983

A case study of the sensitivity of forecast skill to data and data analysis techniques

A series of experiments have been conducted to examine the sensitivity of forecast skill to various data and data analysis techniques for the 0000 GMT case of January 21, 1979. These include the individual components of the FGGE observing system, the temperatures obtained with different satellite retrieval methods, and the method of vertical interpolation between the mandatory pressure analysis levels and the model sigma levels. It is found that NESS TIROS-N infrared retrievals seriously degrade a rawinsonde-only analysis over land, resulting in a poorer forecast over North America. Less degradation in the 72-hr forecast skill at sea level and some improvement at 500 mb is noted, relative to the control with TIROS-N retrievals produced with a physical inversion method which utilizes a 6-hr forecast first guess. NESS VTPR oceanic retrievals lead to an improved forecast over North America when added to the control.

Baker, W. E.↗
NASA NTRS1992

Demonstration of a flight capable system for plume spectroscopy

A small, rugged, high-speed/resolution Fabry-Perot interferometer (FPI) based spectrometer has been developed for detecting the spectral signatures of eroding rocket engine components during ground tests and/or flight operations, with a view to use in future rocket engine health-management systems (HMSs). A flight-capable HMS will furnish prognoses and responses to incipient engine failures, as well as diagnoses of wear and degradation during maintenance. Attention is given to the development of a prototype FPI spectrometer for demonstration and validation testing at NASA-Marshall.

Bickford, R. L.↗
NASA NTRS1992

Technology planning for long range utilization of Space Station Freedom

A system is described with specific examples for identifying and selecting advanced technologies for use with the Space Station Freedom (SSF) that positively impact capabilities and costs. Emerging advanced technologies should be compared with SSF technological needs and selected according to an optimal combination of readiness, development risks/costs, performance requirements, and crew safety. The selected technologies should be planned to the extent that the technology continues advancing to the point of readiness in a manner consistent with the objectives and timeframe of the SSF program. An SSF Advanced Studies component is described that worked to advance critical emergent technologies including advanced heat rejection, closed air-loops, high-efficiency space-power systems, and advanced power storage. The efforts can lead to the identification of crucial parameters such as performance degradation, lifetime, growth, and area that are relevant to the SSF overall objectives.

Ahlf, P.↗
NASA NTRS2011

Interfaces - Weak Links, Yet Great Opportunities

Inadequate turbomachine interface design can rapidly degrade system performance, yet provide great opportunity for improvements. Engineered coatings of seals and bearing interfaces are major issues in the operational life of power systems. Coatings, films, and combined use of both metals and ceramics play a major role in maintaining component life. Interface coatings, like lubricants, are sacrificial for the benefit of the component. Bearing and sealing surfaces are routinely protected by tribologically paired coatings such as silicon diamond like coatings (SiDLC) in combination with an oil lubricated wave bearing that prolongs bearing operational life. Likewise, of several methods used or researched for detecting interface failures, dopants within coatings show failures in functionally graded ceramic coatings. The Bozzolo-Ferrante-Smith (BFS) materials models and quantum mechanical tools, employed in interface design, are discussed.

Hendricks, Robert C.↗
NASA NTRS2015

Creep, Fatigue and Fracture Behavior of Environmental Barrier Coating and SiC-SiC Ceramic Matrix Composite Systems: The Role of Environment Effects

Advanced environmental barrier coating (EBC) systems for low emission SiCSiC CMC combustors and turbine airfoils have been developed to meet next generation engine emission and performance goals. This presentation will highlight the developments of NASAs current EBC system technologies for SiC-SiC ceramic matrix composite combustors and turbine airfoils, their performance evaluation and modeling progress towards improving the engine SiCSiC component temperature capability and long-term durability. Our emphasis has also been placed on the fundamental aspects of the EBC-CMC creep and fatigue behaviors, and their interactions with turbine engine oxidizing and moisture environments. The EBC-CMC environmental degradation and failure modes, under various simulated engine testing environments, in particular involving high heat flux, high pressure, high velocity combustion conditions, will be discussed aiming at quantifying the protective coating functions, performance and durability, and in conjunction with damage mechanics and fracture mechanics approaches.

Environmental Barrier Coatings↗
NASA NTRS2016

Environmental Barrier Coating Development for SiC/SiC Ceramic Matrix Composites: Recent Advances and Future Directions

This presentation briefly reviews the SiC/SiC major environmental and environment-fatigue degradations encountered in simulated turbine combustion environments, and thus NASA environmental barrier coating system evolution for protecting the SiC/SiC Ceramic Matrix Composites for meeting the engine performance requirements. The presentation will review several generations of NASA EBC materials systems, EBC-CMC component system technologies for SiC/SiC ceramic matrix composite combustors and turbine airfoils, highlighting the temperature capability and durability improvements in simulated engine high heat flux, high pressure, high velocity, and with mechanical creep and fatigue loading conditions. This paper will also focus on the performance requirements and design considerations of environmental barrier coatings for next generation turbine engine applications. The current development emphasis is placed on advanced NASA candidate environmental barrier coating systems for SiC/SiC CMCs, their performance benefits and design limitations in long-term operation and combustion environments. The efforts have been also directed to developing prime-reliant, self-healing 2700F EBC bond coat; and high stability, lower thermal conductivity, and durable EBC top coats. Major technical barriers in developing environmental barrier coating systems, the coating integrations with next generation CMCs having the improved environmental stability, erosion-impact resistance, and long-term fatigue-environment system durability performance will be described. The research and development opportunities for turbine engine environmental barrier coating systems by utilizing improved compositions, state-of-the-art processing methods, and simulated environment testing and durability modeling will be briefly discussed.

Environmental Barrier Coatings↗
NASA NTRS1995

Identification And Survival Of Bacteriohopanepolyol In A Hot Spring Microbial Mat

The polar lipids of a hot spring microbial mat located in Yellowstone National Park were examined for the presence of bacteriohopanepolvols (BHP). BHP are a group of molecules consisting of a hopanoid (peotacyclic triterpene) linked via a n-alkyl polyhydroxylated chain to a variety of polar end groups. BHP have been isolated in varying amounts from phylogenetically diverse eubacterial groups including cyanobacteria, methanotrophs and the Rhodospirillaceae. The hopanoids are excellent biomarkers and have been detected in sedimentary rocks as old as 1.7 bya. In order to interpret the ancient organic record, it is important to understand the abundance, source and fate of such biomarker compounds in microbial mats. A 40 sq cm mat section was taken from a 52 to 55 C site in the effluent channel of Octopus Spring and was sampled vertically over approximately 16 mm. The first 5-6 mm was sectioned into a top green layer (310 mg dry weight) and several subjacent, deep orange layers (240 and 250 mg, respectively). The lower 10 mm of the mat was sectioned into two gelatinous orange layers containing a siliceous gritty material (260 and 440 mg) which increased with depth, and a bottom layer composed almost exclusively of siliceous sinter (4.1 g). The progressive decrease in total organic carbon from 45% in the top green layer to only 4% in the bottom layer reflects the observed increase in siliceous deposition. GC-MS analysis of the phospholipid and glycolipid fatty acids yielded predominantly saturated normal chain acids, n-15 to n-18, and iso-branched acids, i-15 to i-17. Small amounts of unsaturated fatty acids (16:1, two positional isomers of 18:1, and two cyclopropyl acids, C(sub 17) and C(sub 19)) were present mainly in the top layer. Esterified fatty acid which is a good index for intact cellular membrane, i.e. viable organisms, was highest in the top two layers (203 and 231 micro g/mg total lipid, respectively) and gradually decreased to 66 micro g/mg total lipid in the bottom layer. Small amounts of BHP were present in all six layers, however in this case, BHP was lowest in the top green and subjacent deep-orange layers (118 and 172 micro g/mg total lipid, respectively) and increased with depth reaching almost 400 micro g/mg in the bottom two layers. This data suggest that BHP are survivina the initial phase of mat degradation and may be preferentially enriched in any organic record of such thermal environments. The relatively low level of BHP in the top layer also suggests that cyanobacteria may not be the major source of BHP in this mat. Since Chloroflexus a major component of the deep-orange layer has been reported to lack BHP, this material may prove a valuable biomarker for some other mat inhabitant. Further isotopic characterization of this BHP should help resolve this finding.

Janke, Linda L.↗
NASA NTRS1978

Environmental effects on composites for aircraft

A number of ongoing, long-term environmental effects programs for composite materials are evaluated. The flight service experience was evaluated for 142 composite aircraft components after more than 5 years and 1 million successful component flight hours. Ground-based outdoor exposures of composite material coupons after 3 years of exposure at 5 sites have reached equilibrium levels of moisture pickup which are predictable. Solar ultraviolet-induced material loss is discussed for these same exposures. No significant degradation was observed in residual strength for either stressed or unstressed specimens, or for exposures to aviation fuels and fluids.

Pride, R. A.↗
NASA NTRS1978

Interim results of long-term environmental exposures of advanced composites for aircraft applications

Interim results from a number of ongoing, long-term environmental effects programs for composite materials are reported. The flight service experience is evaluated for 142 composite aircraft components after more than five years and one million successful component flight hours. Ground-based outdoor exposures of composite material coupons after 3 years of exposure at five sites have reached equilibrium levels of moisture pickup which are predictable. Solar ultraviolet-induced material loss is discussed for these same exposures. No significant degradation has been observed in residual strength for either stressed or unstressed specimens, or for exposures to aviation fuels and fluids.

Pride, R. A.↗
NASA NTRS1992

Comparative evaluation of optical waveguides as alternative interconnections for high performance packaging

A detailed comparison between optical and electrical interconnections is presented, with emphasis on advantages and drawbacks of optical link utilization. The impact of attenuation, dispersive degradation, and fan out on signal integrity is discussed. Reflections from discontinuities are taken into account in the section on fan out. According to our results, there is no obvious advantage of using optical interconnections for the distribution of digital signals containing significant frequency components in excess of 10 GHz, unless substantial distances are involved, for which low dispersion optical waveguides could provide a solution. The implementation of a polyimide optical waveguide in the MCNC package is discussed.

Schacham, S. E.↗
NASA NTRS1992

Development of advanced seal verification

The purpose of this research is to develop a technique to monitor and insure seal integrity with a sensor that has no active elements to burn-out during a long duration activity, such as a leakage test or especially during a mission in space. The original concept proposed is that by implementing fiber optic sensors, changes in the integrity of a seal can be monitored in real time and at no time should the optical fiber sensor fail. The electrical components which provide optical excitation and detection through the fiber are not part of the seal; hence, if these electrical components fail, they can be easily changed without breaking the seal. The optical connections required for the concept to work does present a functional problem to work out. The utility of the optical fiber sensor for seal monitoring should be general enough that the degradation of a seal can be determined before catastrophic failure occurs and appropriate action taken. Two parallel efforts were performed in determining the feasibility of using optical fiber sensors for seal verification. In one study, research on interferometric measurements of the mechanical response of the optical fiber sensors to seal integrity was studied. In a second study, the implementation of the optical fiber to a typical vacuum chamber was implemented and feasibility studies on microbend experiments in the vacuum chamber were performed. Also, an attempt was made to quantify the amount of pressure actually being applied to the optical fiber using finite element analysis software by Algor.

Workman, Gary L.↗
NASA NTRS2000

SAVANT: Solar Array Verification and Analysis Tool Demonstrated

The photovoltaics (PV) industry is now being held to strict specifications, such as end-oflife power requirements, that force them to overengineer their products to avoid contractual penalties. Such overengineering has been the only reliable way to meet such specifications. Unfortunately, it also results in a more costly process than is probably necessary. In our conversations with the PV industry, the issue of cost has been raised again and again. Consequently, the Photovoltaics and Space Environment Effects branch at the NASA Glenn Research Center at Lewis Field has been developing a software tool to address this problem. SAVANT, Glenn's tool for solar array verification and analysis is in the technology demonstration phase. Ongoing work has proven that more efficient and less costly PV designs should be possible by using SAVANT to predict the on-orbit life-cycle performance. The ultimate goal of the SAVANT project is to provide a user-friendly computer tool to predict PV on-orbit life-cycle performance. This should greatly simplify the tasks of scaling and designing the PV power component of any given flight or mission. By being able to predict how a particular PV article will perform, designers will be able to balance mission power requirements (both beginning-of-life and end-of-life) with survivability concerns such as power degradation due to radiation and/or contamination. Recent comparisons with actual flight data from the Photovoltaic Array Space Power Plus Diagnostics (PASP Plus) mission validate this approach.

Chock, Ricaurte↗
NASA NTRS2003

Pulsed Plasma Thruster (PPT) Technology: Earth Observing-1 PPT Operational and Advanced Components Being Developed

In 2002 the pulsed plasma thruster (PPT) mounted on the Earth Observing-1 spacecraft was operated successfully in orbit. The two-axis thruster system is fully incorporated in the attitude determination and control system and is being used to automatically counteract disturbances in the pitch axis of the spacecraft. The first tests conducted in space demonstrated the full range of PPT operation, followed by calibration of control torques from the PPT in the attitude control system. Then the spacecraft was placed in PPT control mode. To date, it has operated for about 30 hr. The PPT successfully controlled pitch momentum during wheel de-spin, solar array acceleration and deceleration during array rewind, and environmental torques in nominal operating conditions. Images collected with the Advanced Landsat Imager during PPT operation have demonstrated that there was no degradation in comparison to full momentum wheel control. In addition, other experiments have been performed to interrogate the effects of PPT operation on communication packages and light reflection from spacecraft surfaces. Future experiments will investigate the possibility of orbit-raising maneuvers, spacecraft roll, and concurrent operation with the Hyperion imager. Future applications envisioned for pulsed plasma thrusters include longer life, higher precision, multiaxis thruster configurations for three-axis attitude control systems or high-precision, formationflying systems. Advanced components, such as a "dry" mica-foil capacitor, a wear-resistant spark plug, and a multichannel power processing unit have been developed under contract with Unison Industries, General Dynamics, and C.U. Aerospace. Over the last year, evaluation tests have been conducted to determine power processing unit efficiency, atmospheric functionality, vacuum functionality, thruster performance evaluation, thermal performance, and component life.

Pencil, Eric J.↗