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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 1,153 records · Page 64
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Small Scale Trace Contaminant Testing of SA9T at Ambient and Reduced Pressure Conditions

A principle concern for air revitalization technology in a closed loop system is the capability to control carbon dioxide (CO2) and humidity (H2O). An amine based sorbent technology, SA9T, has long been evaluated for use in this application and several programs are evaluating it for use in both a cabin as well as space suit applications. While the CO2 and H2O performance of the sorbent has been tested extensively, the question of how trace contaminants impact performance requires further evaluation. This paper presents experimental results of small scale SA9T testing that was performed over a variety of test conditions and with a variety of trace contaminants. Testing evaluated the ability of SA9T media to sufficiently remove CO2 and H2O after exposure to a fully saturated trace contaminant at ambient conditions. Testing also evaluated the impact of CO2 and H2O removal performance at suit loop pressures during cyclic operation with a constant inlet contaminant load. In addition, testing evaluated the performance of SA9T at ambient conditions in a continuous 30-day test with a mixed trace contaminant stream.

Broerman, Craig↗
NASA NTRS2011

Increased Mechanical Properties Through the Addition of Zr to GRCop-84

GRCop-84 (Cu-8 at.% Cr-4 at.% Nb) has shown exceptional mechanical properties above 932 F (773 K). However, its properties below 932 F (773 K) are inferior to precipitation strengthened alloys such as Cu-Cr, Cu-Zr and Cu-Cr-Zr when they are in the fully aged, hard-drawn condition. It has been noted that the addition of small amounts of Zr, typically 0.1 wt.% to 0.5 wt.%, can greatly enhance the mechanical properties of copper-based alloys. Limited testing was conducted upon GRCop-84 with an addition of 0.4 wt.% Zr to determine its tensile, creep and low cycle fatigue (LCF) properties. Very large increases in strength (up to 68%) and ductility (up to 123%) were observed at both room temperature and 932 F (773 K). Creep properties at 932 F (773 K) demonstrated more than an order of magnitude decrease in the creep rate relative to unmodified GRCop-84 with a corresponding order of magnitude increase in creep life. Limited LCF testing showed that the modified alloy had a comparable LCF life at room temperature, but it was capable of sustaining a much higher load. While more testing and composition optimization are required, the addition of Zr to GRCop-84 has shown clear benefits to mechanical properties.

Ellis, David L.↗
DOE OSTI2020

On the fatigue crack growth behavior of Ti–10V–2Fe–3Al in gaseous hydrogen

Here, the fatigue crack growth behavior of Ti–10V–2Fe–3Al in gaseous hydrogen (H 2 ) was assessed through comparative experiments conducted in laboratory air and 8.3 MPa H 2 . The measured fatigue crack growth rate (da/dN) versus applied stress intensity factor range (ΔK) relationships and observed fracture morphologies for laboratory air and H 2 were comparable up to ΔK ≈ 6.9 MPa√m, when tested at a load ratio of 0.1 and frequency of 10 Hz. At higher ΔK values, significant crack deflection and subsequent catastrophic failure occurred in the specimen tested in H 2 . This degradation was not observed in a specimen pre-exposed to 8.3 MPa H 2 for 96 h and then immediately tested in laboratory air. X-ray diffraction of the failed H 2 -tested specimen revealed that the material remnants were predominantly composed of TiH 2 , suggesting that hydride formation was the catalyst for catastrophic failure in H 2 . The mechanistic implications of these results and their impact on current material compatibility assessments for Ti alloys in hydrogen service are then discussed.

08 HYDROGEN↗
NASA NTRS1978

Radiative, actively cooled panel tests results

The radiative, actively cooled panel designed to withstand a uniform incident heat flux of 136 kW/sq m to a 444 K surface temperature was evaluated. The test program consisted of preliminary static thermal mechanical loading and aerothermal flow tests. Test results are briefly discussed.

Shore, C. P.↗
NASA NTRS1984

Antiwear Additive Mechanisms in Sliding Contacts

The possible mechanisms associated with wear in a sliding contact and how an oil and antiwear additive can mitigate wear or prevent catastropic seizure of the contacting parts was examined. The various load and temperature regimes are examined and the mechanisms which are predominant under these conditions are determined. The critical mechanism(s) depend on the test parameters, particularly load and temperature, although sliding speed is also a factor. Different ways to improve the efficiency of antiwear additives are suggested.

Baldwin, B. A.↗
NASA NTRS1985

Small centrifugal pumps for low thrust rockets

This paper presents the results of a combined analytical and experimental investigation of low specific speed pumps for potential use as components of propellant feed systems for low thrust rocket engines. Shrouded impellers and open face impellers were tested in volute type and vaned diffuser type pumps. Full- and partial-emission diffusers and full- and partial-admission impellers were tested. Axial and radial loads, head and efficiency versus flow, and cavitation tests were conducted. Predicted performance of two pumps are compared when pumping water and liquid hydrogen. Detailed pressure loss and parasitic power values are presented for two pump configurations. Partial-emission diffusers were found to permit use of larger impeller and diffuser passages with a minimal performance penalty. Normal manufacturing tolerances were found to result in substantial power requirement variation with only a small pressure rise change. Impeller wear ring leakage was found to reduce pump pressure rise to an increasing degree as the pump flowrate was decreased.

Gulbrandsen, N. C.↗
NASA NTRS2005

Space Shuttle Body Flap Actuator Bearing Testing For NASA Return to Flight

The Space Shuttle body flap is located beneath the main engine nozzles and is required for proper aerodynamic control during orbital descent. Routine inspection of one of four body flap actuatols found one of the actuator bearings had degraded and blackened balls. A test program was initiated to demonstrate that it is acceptable to operate bearings which are degraded from operation over several flights. This test exposed the bearing to predicted flight axial loads, speeds and temperatures. Testing has been completed, and results indicate the previously flown bearings are acceptable for up to 12 additional missions.

Jett, Timothy R.↗
NASA NTRS2006

Space Shuttle Body Flap Actuator Bearing Testing for NASA Return to Flight

The Space Shuttle body flap is located beneath the main engine nozzles and is required for proper aerodynamic control during orbital descent. Routine inspection of one of four body flap actuators found one of the actuator bearings had degraded and blackened balls. A test program was initiated to demonstrate that it is acceptable to operate bearings which are degraded from operation over several flights. This test exposed the bearing to predicted flight axial loads, speeds and temperatures. Testing at 140 F has been completed, and results indicate the previously flown bearings are acceptable for up to 12 additional missions. Additional testing is underway to determine the lubricant life at various temperatures and stresses and to further understand the mechanism that caused the blacken balls. Initial results of this testing indicates that bearing life is shorten at room temperature possibly due fact that higher temperature (140 F) accelerates the flow of grease and oil into the wear surface

Jett, Timothy R.↗
NASA NTRS2012

Transient Side Load Analysis of Out-of-Round Film-Cooled Nozzle Extensions

There was interest in understanding the impact of out-of-round nozzle extension on the nozzle side load during transient startup operations. The out-of-round nozzle extension could be the result of asymmetric internal stresses, deformation induced by previous tests, and asymmetric loads induced by hardware attached to the nozzle. The objective of this study was therefore to computationally investigate the effect of out-of-round nozzle extension on the nozzle side loads during an engine startup transient. The rocket engine studied encompasses a regeneratively cooled chamber and nozzle, along with a film cooled nozzle extension. The computational methodology is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, and transient inlet boundary flow properties derived from an engine system simulation. Six three-dimensional cases were performed with the out-of-roundness achieved by three different degrees of ovalization, elongated on lateral y and z axes: one slightly out-of-round, one more out-of-round, and one significantly out-of-round. The results show that the separation line jump was the primary source of the peak side loads. Comparing to the peak side load of the perfectly round nozzle, the peak side loads increased for the slightly and more ovalized nozzle extensions, and either increased or decreased for the two significantly ovalized nozzle extensions. A theory based on the counteraction of the flow destabilizing effect of an exacerbated asymmetrical flow caused by a lower degree of ovalization, and the flow stabilizing effect of a more symmetrical flow, created also by ovalization, is presented to explain the observations obtained in this effort.

Wang, Ten-See↗
NASA NTRSDate not supplied

Development of a Full-Scale Finite Element Model of the Fokker F28 Fellowship Aircraft and Crash Simulation Predictions

In June 2019, a full-scale crash test of a Fokker F28 Fellowship aircraft was conducted as part of a joint National Aeronautics and Space Administration/Federal Aviation Administration (NASA/FAA) project to investigate the performance of transport aircraft under realistic crash conditions. The test objectives were to provide data for assessment of transport aircraft crashworthiness under realistic impact conditions and to generate test data for model validation. The test article was loaded with transport aircraft seats in a 3+2 configuration. A total of 24 instrumented ATDs were placed in the seats and restrained. The test article weighed 33,306-lb. (15,107.3-kg) and, during the crash test, impacted a 2-ft. (0.61-m) high soil bed at 65.3-ft/s (19.9-m/s) forward and 31.8-ft/s (9.7-m/s) vertical velocity. The full-scale aircraft crash test was simulated using the commercial nonlinear explicit transient dynamic finite element code, LS-DYNA. This paper will provide a description of the test article and the crash test conditions, document the F28 full-scale model development, and present test-analysis comparisons. The test-analysis comparisons include inertial properties, kinematic responses, structural acceleration responses, and structural deformation and failure.

Karen E Jackson↗
NASA NTRS1988

Effects of subcritical crack growth on fracture toughness of ceramics assessed in chevron-notched three-point bend tests

A numerical computational study was carried out to assess the effects of subcritical crack growth on crack stability in the chevron-notched three-point bend specimens. A power-law relationship between the subcritical crack velocity and the applied stress intensity were used along with compliance and stress-intensity relationships for the chevron-notched bend specimen to calculate the load response under fixed deflection rate and a machine compliance. The results indicate that the maximum load during the test occurs at the same crack length for all the deflection rates; the maximum load, however, is dependent on the deflection rate for rates below the critical rate. The resulting dependence of the apparent fracture toughness on the deflection rate is compared to experimental results on soda-lime glass and polycrystalline alumina.

Chao, L. Y.↗
NASA NTRS1997

Performance and Vibratory Loads Data From a Wind-Tunnel Test of a Model Helicopter Main-Rotor Blade With a Paddle-Type Tip

An investigation was conducted in the Langley Transonic Dynamics Tunnel to obtain data to permit evaluation of paddle-type tip technology for possible use in future U.S. advanced rotor designs. Data was obtained for both a baseline main-rotor blade and a main-rotor blade with a paddle-type tip. The baseline and paddle-type tip blades were compared with regard to rotor performance, oscillatory pitch-link loads, and 4-per-rev vertical fixed-system loads. Data was obtained in hover and forward flight over a nominal range of advance ratios from 0.15 to 0.425. Results indicate that the paddle-type tip offers no performance improvements in either hover or forward flight. Pitch-link oscillatory loads for the paddle-type tip are higher than for the baseline blade, whereas 4-per-rev vertical fixed-system loads are generally lower.

Yeager, William T., Jr.↗
DOE OSTI2020

Tensile testing and fracture mechanism analysis of polyvinyl alcohol nanofibrous webs

Abstract A tensile properties testing study was conducted to understand the influence of thickness, cross‐head speed (speed of testing), gauge length (GL; specimen test length), and sample shape on important tensile properties of polyvinyl alcohol (PVA) nanofiber webs. The effects of each testing parameter on load at break, extension at break, Young's modulus, and tensile stress–strain curve of PVA nanofiber webs are analyzed. The Welch two sample t ‐tests show the significant difference among tested data. Using interaction plots, two‐way analysis of variance, and margin mean plots, the interaction effects among testing parameters have been analyzed. Of all the factors, cross‐head speed, the interaction among GL, and sample thickness (GL: Thickness) and the interaction among GL, testing speed and sample thickness (GL: Speed: Thickness) have significant influence on the tensile properties of PVA nanofiber webs. Moreover, the hypothesized model of mechanism of tensile strain–stress curve of PVA nanofiber webs has been proposed. Based on the model, the tensile strain–stress curve can be split into three stages: linear elastic, partial break up, and complete breakage. This study will provide a better understanding of tensile testing parameters' effects and their interaction effects on the tensile properties of nanowebs.

Lou, Lihua↗
NASA NTRS1978

Mini-BRU/BIPS foil bearing development

The analysis revealed the failure agent to be a combination of poor teflon coating adhesion, a decrease in bearing sway space and, possibly, lack of flushing flow through the bearing. A change in Teflon coating vendors provided substantially improved coating quality and surface finish. The sway space was increased and the cooling bleed flow was adjusted to flush the bearing. These changes were included in a test conducted in the WHL from 6 April to 22 May 1978 which resulted in the completion of 1006.9 hours of operation at temperature and load. Post-test inspection revealed the bearings to be in excellent condition and capable of completing a much longer test.

Dobler, F. X.↗
NASA NTRS1986

Measurement of Centaur/Orbiter multiple reaction forces in a full-scale test rig

A multiple component load cell for measuring load is described, and its capability and reliability are evaluated by utilizing it to measure the reaction forces between the Centaur and Centaur Support Structure. The system employs 11 six-component balances in a single test rig to react a combination of loads. The vehicle and balance loads, procedures for fabricating each balance, and the assembly of the balances are discussed. The calibration and testing of the balances are examined. It is noted that the multiple component load cell system is a cost-effective method for obtaining an accurate measurement of friction effects and primary loads.

Mole, Philip J.↗
NASA NTRS1974

Miniature load cell instrumentation for finite deformation biaxial testing of elastomers

Accuracy of biaxial test equipment to examine the nonlinear mechanical behavior of thin sheet specimens of elastomeric materials has been hampered by lack of precise determination of the force distribution along the sides of the specimen. It has been necessary to use an effective width established by approximate means to obtain the stress from the overall force applied along the edges. To avoid this experimental difficulty, individual miniature proof-ring load cells utilizing semiconductor strain gages have been developed and applied to the support hooks for the thin sheet specimens. Typical results are shown for time-dependent stress distributions for all degrees of biaxiality. An accurate evaluation of the effective specimen width is now possible.

Arenz, R. J.↗
DOE OSTI2023

Drop C: The Drop-In, Ring-of-Power Heliostat (Final Report)

This report summarizes the work performed within the Drop-C: The Drop-In, Ring-of-Power Heliostat project. The Drop-C project aimed to develop a novel heliostat with an installed cost of $\$50$/m 2 ($\$2015$) which is a drastic cost reduction compared to the state-of-the-art. The resulting 27m 2 SunRing TM heliostat’s relative small size necessitates the parallel development of a wireless solar field network and a rapid calibration system. The SunRing heliostat is an evolution of the Ring-of-Power (ROP) design from Abengoa Solar LLC which had a reported installed cost of $114/m 2 . Cost savings relative to the ROP were sought by increasing the mirror area, improving the structural efficiency, a more accurate assessment of wind loads, and an improved assembly and installation procedure. The project spanned three Budget Periods (BP) where a digital heliostat was developed in BP1 using wind tunnel testing to define load conditions.

14 SOLAR ENERGY↗