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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 1,171 records · Page 65
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Intramuscular pressure: A better tool than EMG to optimize exercise for long-duration space flight

A serious problem experienced by astronauts during long-duration space flight is muscle atrophy. In order to develop countermeasures for this problem, a simple method for monitoring in vivo function of specific muscles is needed. Previous studies document that both intramuscular pressure (IMP) and electromyography (EMG) provide quantitative indices of muscle contraction force during isometric exercise. However, at present there are no data available concerning the usefulness of IMP versus EMG during dynamic exercise. Methods: IMP (Myopress catheter) and surface EMG activity were measured continuously and simultaneously in the tibalis anterior (TA) and soleus (SOL) muscles of 9 normal male volunteers (28-54 years). These parameters were recorded during both concentric and eccentric exercises which consisted of plantarflexon and dorsiflexon of the ankle joint. A Lido Active Isokinetic Dynamometer concurrently recorded ankle joint torque and position. Results: Intramuscular pressure correlated linearly with contraction force for both SOL (r exp 2 = 0.037) and TA (R exp 2 = 0.716 and r exp 2 = 0.802, respectively). During eccentric exercises, SOL and TA IMP also correlated linearly with contraction force (r(exp 2) = 0.883 and r(exp 2) = 0.904 respectively), but SOL and TA EMG correlated poorly with force (r(exp 2) = 0.489 and r(exp 2) = 0.702 respectively). Conclusion: IMP measurement provides a better index of muscle contraction force than EMG during concentric and eccentric exercise. IMP reflects intrinsic mechanical properties of individual muscles, such as length tension relationships. Although invasive, IMP provides a more powerful tool and EMG for developing exercise hardware and protocols for astronauts exposed to long-duration space flight.

Hargens, A. R.↗
NASA NTRS1995

Advanced transportation system studies. Technical area 2: Heavy lift launch vehicle development: Technical Results - Volume 2

Sections 10 to 13 of the Advanced Transportation System Studies final report are included in this volume. Section 10 contains a copy of an executive summary that was prepared by Lockheed Space Operations Company (LSOC) to document their support to the TA-2 contract during the first-year period of performance of the contract, May 1992 through May 1993. LSOC participated on the TA-2 contract as part of the concurrent engineering launch system definition team, and provided outstanding heavy lift launch vehicle (HLLV) ground operations requirements and concept assessments for Lockheed Missiles and Space Company (LMSC) through an intercompany work transfer as well as providing specific HLLV ground operations assessments at the direction of NASA KSC through KSC funding that was routed to the TA-2 contract. Section 11 contains a copy of a vehicle-independent, launch system health management requirements assessment. The purpose of the assessment was to define both health management requirements and the associated interfaces between a generic advanced transportation system launch vehicle and all related elements of the entire transportation system, including the ground segment. Section 12 presents the major TA-2 presentations provided to summarize the significant results and conclusions that were developed over the course of the contract. Finally, Section 13 presents the design and assessment report on the first lunar outpost heavy lift launch vehicle.

Source record↗
NASA NTRS1993

Heart Imaging System

Johnson Space Flight Center's device to test astronauts' heart function in microgravity has led to the MultiWire Gamma Camera, which images heart conditions six times faster than conventional devices. Dr. Jeffrey Lacy, who developed the technology as a NASA researcher, later formed Proportional Technologies, Inc. to develop a commercially viable process that would enable use of Tantalum-178 (Ta-178), a radio-pharmaceutical. His company supplies the generator for the radioactive Ta-178 to Xenos Medical Systems, which markets the camera. Ta-178 can only be optimally imaged with the camera. Because the body is subjected to it for only nine minutes, the radiation dose is significantly reduced and the technique can be used more frequently. Ta-178 also enables the camera to be used on pediatric patients who are rarely studied with conventional isotopes because of the high radiation dosage.

Source record↗
NASA NTRS1988

Core temperature is regulated, although at a lower temperature, in rats exposed to hypergravic fields

1. In rats acclimated to 23 degrees C (RT rats) or 5 degrees C (CA rats), core temperature (Tc), tail temperature (Tt) and oxygen consumption (VO2) were measured during exposure to a hypergravic field. 2. Rats were exposed for 5.5 h to a 3 g field while ambient temperature (Ta) was varied. For the first 2 h, Ta was 25 degrees C; then Ta was raised to 34 degrees C for 1.5 h. During this period of warm exposure, Tc increased 4 degrees C in both RT and CA rats. Finally, Ta was returned to 25 degrees C for 2 h, and Tc decreased toward the levels measured prior to warm exposure. 3. In a second experiment at 3 g, RT and CA rats were exposed to cold (12 degrees C) after two hours at 25 degrees C. During the one hour cold exposure, Tc fell 1.5 degrees C in RT and 0.5 degree C in CA rats. After cold exposure, when ambient temperature was again 25 degrees C, Tc of RT and CA rats returned toward the levels measured prior to the thermal disturbance. 4. Rats appear to regulate their temperature, albeit at a lower level, in a 3 g field.

NASA Discipline Number 40-30↗
NASA NTRS1992

A new animal model for modulating myosin isoform expression by altered mechanical activity

The purpose of this study was to develop a new rodent model that is capable of delineating the importance of mechanical loading on myosin heavy chain (MHC) isoform expression of the plantar and dorsi flexor muscles of the ankle. The essential components of this system include 1) stimulating electrodes that are chronically implanted into a muscle, allowing for the control of the activation pattern of the target muscle(s); 2) a training apparatus that translates the moment of the ankle into a linear force; and 3) a computer-controlled Cambridge 310 ergometer. The isovelocity profile of the ergometer ensured that the medial gastrocnemius (MG) produced forces that were > 90% of maximal isometric force (Po), and the eccentric contractions of the tibialis anterior (TA) were typically 120% of Po. Both the concentric and eccentric training programs produced statistically significant increases in the muscle mass of the MG (approximately 15%) and TA (approximately 7%) as well as a decrease in myofibrillar adenosinetriphosphatase activity. Both the white and red regions of the MG and TA exhibited significant increases in the relative content of the type IIa MHC and concomitant decreases in type IIb MHC expression. Although the red regions of the MG and red TA contained approximately 10% type I MHC, the training programs did not affect this isoform. It appears that when a fast-twitch muscle is stimulated at a high frequency (100 Hz) and required to contract either concentrically or eccentrically under high loading conditions, the expression of the type IIa MHC isoform will be upregulated, whereas that of the type IIb MHC will be concomitantly downregulated.

NASA Discipline Musculoskeletal↗
NASA NTRS2011

Effect of Reverse Bias Stress on Leakage Currents and Breakdown Voltages of Solid Tantalum Capacitors

The majority of solid tantalum capacitors are produced by high-temperature sintering of a fine tantalum powder around a tantalum wire followed by electrolytic anodization that forms a thin amorphous Ta2O5 dielectric layer and pyrolysis of manganese nitrite on the oxide to create a conductive manganese dioxide electrode. A contact to tantalum wire is used as anode terminal and to the manganese layer as a cathode terminal of the device. This process results in formation of an asymmetric Ta -- Ta2O5 -- MnO2 capacitor that has different characteristics at forward (positive bias applied to tantalum) and reverse (positive bias applied to manganese cathode) voltages. Reverse bias currents might be several orders of magnitude larger than forward leakage currents so I-V characteristics of tantalum capacitors resemble characteristics of semiconductor rectifiers. Asymmetric I-V characteristics of Ta -- anodic Ta2O5 systems have been observed at different top electrode materials including metals, electrolytes, conductive polymers, and manganese oxide thus indicating that this phenomenon is likely related to the specifics of the Ta -- Ta2O5 interface. There have been multiple attempts to explain rectifying characteristics of capacitors employing anodic tantalum pentoxide dielectrics. A brief review of works related to reverse bias (RB) behavior of tantalum capacitors shows that the mechanism of conduction in Ta -- Ta2O5 systems is still not clear and more testing and analysis is necessary to understand the processes involved. If tantalum capacitors behave just as rectifiers, then the assessment of the safe reverse bias operating conditions would be a relatively simple task. Unfortunately, these parts can degrade with time under reverse bias significantly, and this further complicates analysis of the I-V characteristics and establishing safe operating areas of the parts. On other hand, time dependence of reverse currents might provide additional information for investigation of the processes under reverse bias conditions. In practice, there were instances when, due to unforeseen events, the system operated at conditions when capacitors experience periodically a relatively small reverse bias for some time followed by normal, forward bias conditions. In such a case an assessment should be made on the degree to which these capacitors are degraded by application of low-voltage reverse bias, and whether this degradation can be reversed by normal operating conditions. In this study, reverse currents in different types of tantalum capacitors were monitored at different reverse voltages below 15%VR and temperatures in the range from room to 145 C for up to 150 hours to get better understanding of the degradation process and determine conditions favorable to the unstable mode of operation. The reversibility of RB degradation has been evaluated after operation of the capacitors at forward bias conditions. The effect of reverse bias stress (RBS) on reliability at normal operating conditions was evaluated using highly accelerated life testing at voltages of 1.5VR and 2 VR and by analysis of changes in distributions of breakdown voltages. Possible mechanisms of RB degradation are discussed.

Teverovsky, Alexander A.↗
NASA NTRS2018

NEPP Evaluation of Automotive Grade Tantalum Chip Capacitors

Automotive grade tantalum (Ta) chip capacitors are available at lower cost with smaller physical size and higher volumetric efficiency compared to military/space grade capacitors. Designers of high reliability aerospace and military systems would like to take advantage of these attributes while maintaining the high standards for long-term reliable operation they are accustomed to when selecting military-qualified established reliability tantalum chip capacitors (e.g., MIL-PRF-55365). The objective for this evaluation was to assess the long-term performance of off-the-shelf automotive grade Ta chip capacitors (i.e., manufacturer self-qualified per AEC Q-200). Two (2) lots of case size D manganese dioxide (MnO2) cathode Ta chip capacitors from 1 manufacturer were evaluated. The evaluation consisted of construction analysis, basic electrical parameter characterization, extended long-term (2000 hours) life testing and some accelerated stress testing. Tests and acceptance criteria were based upon manufacturer datasheets and the Automotive Electronics Council's AEC Q-200 qualification specification for passive electronic components. As-received a few capacitors were marginally above the specified tolerance for capacitance and ESR. X-ray inspection found that the anodes for some devices may not be properly aligned within the molded encapsulation leaving less than 1 mil thickness of the encapsulation. This evaluation found that the long-term life performance of automotive grade Ta chip capacitors is generally within specification limits suggesting these capacitors may be suitable for some space applications.

Automotive↗
NASA NTRS2024

StarNAV: An Architecture for Autonomous Spacecraft Navigation by the Relativistic Perturbation of Starlight

Exploration missions to the outer Solar System (e.g., Neptune, Kuiper belt objects) or to the interstellar medium present several challenges for conventional spacecraft designs. One of the greatest challenges is a means for navigation, as Earth-based tracking with the Deep Space Network (DSN) becomes less desirable due to high cost, decreased performance at long ranges, and long light-time delays. Indeed, light time delays at Neptune are over four hours (one way), making control of spacecraft during critical events nearly impossible—and this problem only becomes worse as we move to the Kuiper belt or to interstellar space. The need for autonomous spacecraft navigation is well established and is prominently featured in the 2015 NASA Technology Roadmap (e.g., TA 5.4.2.6 & 5.4.2.8). This has led to investment in various technologies to accomplish this task, with the majority of recent work focusing on optical navigation (OPNAV; TA 5.4.4.1) [1], X-ray pulsar navigation (XNAV; TA 5.6.1) [2], or DSN one-way ranging with the Deep Space Atomic Clock (DSAC; TA 5.4.1.1) [3]. This NIAC study suggests a new (and completely different) way of autonomously navigating a spacecraft anywhere in the Solar System or beyond. We call this new technique StarNAV.

NIAC Phase I↗
DOE OSTI2025

Emergence of Local Magnetic Moment in Ternary TaWSe 2 Single Crystal via Atomic Clustering

Ternary transition metal dichalcogenides (TMDs) provide a versatile platform to explore novel electronic and magnetic ground states via compositional substitution and local structural modulations. Using a combination of scanning tunneling microscopy and spectroscopy (STM/S), magnetic property measurements, and density functional theory (DFT) calculations, the emergence of local magnetic moments driven by the clustering of Ta atoms in ternary TaWSe 2 single crystals is analyzed. STM topography reveals triangular clusters of Ta atoms embedded within W-rich regions of TaWSe 2 . These clusters exhibit a consistent shape and an orderly arrangement throughout the surfaces. DFT calculations show that these Ta clusters induce local strain, giving rise to localized magnetic moments. The magnetic behavior is further corroborated by temperature-dependent magnetization measurements, which exhibit a magnetic anomaly at ∼50 K. In conclusion, this study offers a pathway to engineer magnetism in TMD systems with potential applications in spintronic and quantum materials.

DFT↗
DOE OSTI2020

Materials Data on Ta2N by Materials Project

Ta2N is trigonal omega structured and crystallizes in the trigonal P-3m1 space group. The structure is two-dimensional and consists of one Ta2N sheet oriented in the (0, 0, 1) direction. Ta is bonded in a distorted T-shaped geometry to three equivalent N atoms. All Ta–N bond lengths are 2.18 Å. N is bonded to six equivalent Ta atoms to form edge-sharing NTa6 octahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaRh3 by Materials Project

Rh3Ta is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Ta is bonded to twelve equivalent Rh atoms to form TaRh12 cuboctahedra that share corners with twelve equivalent TaRh12 cuboctahedra, edges with twenty-four equivalent RhTa4Rh8 cuboctahedra, faces with six equivalent TaRh12 cuboctahedra, and faces with twelve equivalent RhTa4Rh8 cuboctahedra. All Ta–Rh bond lengths are 2.76 Å. Rh is bonded to four equivalent Ta and eight equivalent Rh atoms to form distorted RhTa4Rh8 cuboctahedra that share corners with twelve equivalent RhTa4Rh8 cuboctahedra, edges with eight equivalent TaRh12 cuboctahedra, edges with sixteen equivalent RhTa4Rh8 cuboctahedra, faces with four equivalent TaRh12 cuboctahedra, and faces with fourteen equivalent RhTa4Rh8 cuboctahedra. All Rh–Rh bond lengths are 2.76 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaB2 by Materials Project

TaB2 is hexagonal omega structure structured and crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Ta is bonded to twelve equivalent B atoms to form a mixture of edge and face-sharing TaB12 cuboctahedra. All Ta–B bond lengths are 2.45 Å. B is bonded in a 9-coordinate geometry to six equivalent Ta and three equivalent B atoms. All B–B bond lengths are 1.79 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaSi2 by Materials Project

TaSi2 is Titanium Disilicide-like structured and crystallizes in the hexagonal P6_422 space group. The structure is three-dimensional. Ta is bonded in a distorted q6 geometry to ten equivalent Si atoms. There are a spread of Ta–Si bond distances ranging from 2.62–2.84 Å. Si is bonded in a 10-coordinate geometry to five equivalent Ta and five equivalent Si atoms. There are a spread of Si–Si bond distances ranging from 2.57–2.84 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaCo3 by Materials Project

Co3Ta is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Ta is bonded to twelve equivalent Co atoms to form TaCo12 cuboctahedra that share corners with twelve equivalent TaCo12 cuboctahedra, edges with twenty-four equivalent CoTa4Co8 cuboctahedra, faces with six equivalent TaCo12 cuboctahedra, and faces with twelve equivalent CoTa4Co8 cuboctahedra. All Ta–Co bond lengths are 2.57 Å. Co is bonded to four equivalent Ta and eight equivalent Co atoms to form CoTa4Co8 cuboctahedra that share corners with twelve equivalent CoTa4Co8 cuboctahedra, edges with eight equivalent TaCo12 cuboctahedra, edges with sixteen equivalent CoTa4Co8 cuboctahedra, faces with four equivalent TaCo12 cuboctahedra, and faces with fourteen equivalent CoTa4Co8 cuboctahedra. All Co–Co bond lengths are 2.57 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaNi2 by Materials Project

Ni2Ta is Titanium Disilicide-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ta is bonded in a distorted q6 geometry to ten equivalent Ni atoms. There are eight shorter (2.60 Å) and two longer (2.63 Å) Ta–Ni bond lengths. Ni is bonded in a 10-coordinate geometry to five equivalent Ta and five equivalent Ni atoms. There are four shorter (2.60 Å) and one longer (2.62 Å) Ni–Ni bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaRu by Materials Project

RuTa is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Ta is bonded in a body-centered cubic geometry to eight equivalent Ru atoms. All Ta–Ru bond lengths are 2.75 Å. Ru is bonded in a body-centered cubic geometry to eight equivalent Ta atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca2Ta2O6F by Materials Project

Ca2Ta2O6F crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Ca2+ is bonded in a distorted body-centered cubic geometry to six equivalent O2- and two equivalent F1- atoms. All Ca–O bond lengths are 2.52 Å. Both Ca–F bond lengths are 2.25 Å. Ta+4.50+ is bonded to six equivalent O2- atoms to form corner-sharing TaO6 octahedra. The corner-sharing octahedral tilt angles are 51°. All Ta–O bond lengths are 2.04 Å. O2- is bonded to two equivalent Ca2+ and two equivalent Ta+4.50+ atoms to form distorted OCa2Ta2 tetrahedra that share corners with two equivalent FCa4 tetrahedra, corners with twelve equivalent OCa2Ta2 tetrahedra, an edgeedge with one FCa4 tetrahedra, and edges with four equivalent OCa2Ta2 tetrahedra. F1- is bonded to four equivalent Ca2+ atoms to form FCa4 tetrahedra that share corners with four equivalent FCa4 tetrahedra, corners with twelve equivalent OCa2Ta2 tetrahedra, and edges with six equivalent OCa2Ta2 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on TaRu by Materials Project

RuTa is Tetraauricupride structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Ta is bonded in a body-centered cubic geometry to eight equivalent Ru atoms. All Ta–Ru bond lengths are 2.76 Å. Ru is bonded in a body-centered cubic geometry to eight equivalent Ta atoms.

36 MATERIALS SCIENCE↗