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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 325 records · Page 18

All sources NASA NTRS DOE OSTI

NASA NTRS1980

LSA field test

After almost four years of endurance testing of photovoltaic modules, no fundamental life-limiting mechanisms were identified that could prevent the twenty-year life goal from being met. The endure data show a continual decline in the failure rate with each new large-scale procurement. Cracked cells and broken interconnects continue to be the principal causes of failure. Although the modules are more adversely affected physically by hot, humid environments than by cool or dry environments there are insufficient data to correlate failure with environment. There is little connection between the outward physical condition of a module and changes in its electrical performance.

Jaffe, P.↗

NASA NTRS1981

Analytical study of the cruise performance of a class of remotely piloted, microwave-powered, high-altitude airplane platforms

Each cycle of the flight profile consists of climb while the vehicle is tracked and powered by a microwave beam, followed by gliding flight back to a minimum altitude. Parameter variations were used to define the effects of changes in the characteristics of the airplane aerodynamics, the power transmission systems, the propulsion system, and winds. Results show that wind effects limit the reduction of wing loading and increase the lift coefficient, two effective ways to obtain longer range and endurance for each flight cycle. Calculated climb performance showed strong sensitivity to some power and propulsion parameters. A simplified method of computing gliding endurance was developed.

Morris, C. E. K., Jr.↗

NASA NTRS1980

Cardiovascular responses to static exercise in distance runners and weight lifters

Three groups of athletes including long-distance runners, competitive and amateur weight lifters, and age- and sex-matched control subjects have been studied by hemodynamic and echocardiographic methods in order to determine the effect of the training programs on the cardiovascular response to static exercise. Blood pressure, heart rate, and double product data at rest and at fatigue suggest that competitive endurance (dynamic exercise) training alters the cardiovascular response to static exercise. In contrast to endurance exercise, weight lifting (static exercise) training does not alter the cardiovascular response to static exercise: weight lifters responded to static exercise in a manner very similar to that of the control subjects.

Longhurst, J. C.↗

NASA NTRS1981

Parametric study of microwave-powered high-altitude airplane platforms designed for linear flight

The performance of a class of remotely piloted, microwave powered, high altitude airplane platforms is studied. The first part of each cycle of the flight profile consists of climb while the vehicle is tracked and powered by a microwave beam; this is followed by gliding flight back to a minimum altitude above a microwave station and initiation of another cycle. Parametric variations were used to define the effects of changes in the characteristics of the airplane aerodynamics, the energy transmission systems, the propulsion system, and winds. Results show that wind effects limit the reduction of wing loading and the increase of lift coefficient, two effective ways to obtain longer range and endurance for each flight cycle. Calculated climb performance showed strong sensitivity to some power and propulsion parameters. A simplified method of computing gliding endurance was developed.

Morris, C. E. K., Jr.↗

NASA NTRS1982

Evaluation of candidate stirling engine heater tube alloys at 820 deg and 860 deg C

Seven commercial alloys were evaluated in Stirling simulator materials rigs. Five iron base alloys (N-155, A-286, Incoloy 800, 19-9DL, and 316 stainless steel), one nickel base alloy (Inconel 718), and one cobalt base alloy (HS-188) were tested in the form of thin wall tubing in a diesel fuel fired test rig. Tubes filled with hydrogen or helium at gas pressure of 21.6 MPa and temperatures of 820 and 860 C were endurance tested for 1000 and 535 hours, respectively. Results showed that under these conditions hydrogen permeated rapidly through the tube walls, thus requiring refilling during each five hour cycle. Helium was readily contained, exhibiting no measurable loss by permeation. Helium filled tubes tested at 860 C all exhibited creep-rupture failures within the 535 hour endurance test. Subsequent tensile test evaluation after removal from the rig indicated reduced room temperature ductility for some hydrogen-filled tubes compared to helium-filled tubes, suggesting possible hydrogen embrittlement in these alloys.

Misencik, J. A.↗

NASA NTRS1982

JT90 Ceramic Outer Air Seal System Refinement Program, Phase 2

The sprayed ceramic gas turbine outer air seal system was tested in two JT9D engines to substantiate the abradability and durability of the seals. Of particular significance was that one of the tests, a 150 hour 1000 cycle endurance program at nominal JT9D operating conditions, was completed with minimal effect on the seals and received Federal Aviation Administration cognizance with respect to potential field service use by the airlines. The other engine test completed 1825 endurance cycles at severe operating conditions and no burn through or other serious defects in the structural integrity of a seal segment was observed. These test results combined with other Pratt and Whitney Aircraft engine tests substantiate the potential of the ceramic outer air seal system to attain the durability goal of 50000 hour engine operating capability. Both engine tests subjected the seals to intentional blade rubs and demonstrated good abradability with volume wear ratios greater than 100, far exceeding the design goal of 10. The improved volume wear ratio will allow the turbine tip clearance to be reduced, thereby resulting in an estimated thrust specific fuel consumption improvement of 0.3 percent.

Shiembob, L. T.↗

NASA NTRS1983

High frequency, high power capacitor development

A program to develop a special high energy density, high power transfer capacitor to operate at frequency of 40 kHz, 600 V rms at 125 A rms plus 600 V dc bias for space operation. The program included material evaluation and selection, a capacitor design was prepared, a thermal analysis performed on the design. Fifty capacitors were manufactured for testing at 10 kHz and 40 kHz for 50 hours at Industrial Electric Heating Co. of Columbus, Ohio. The vacuum endurance test used on environmental chamber and temperature plate furnished by Maxwell. The capacitors were energized with a special power conditioning apparatus developed by Industrial Electric Heating Co. Temperature conditions of the capacitors were monitored by IEHCo test equipment. Successful completion of the vacuum endurance test series confirmed achievement of the main goal of producing a capacitor or reliable operation at high frequency in an environment normally not hospitable to electrical and electronic components. The capacitor developed compared to a typical commercial capacitor at the 40 kHz level represents a decrease in size and weight by a factor of seven.

White, C. W.↗

NASA NTRS1983

Electrochemical carbon dioxide concentrator subsystem development

The fabrication of a one-person Electrochemical Depolarized Carbon Dioxide Concentrator subsystem incorporating advanced electrochemical, mechanical, and control and monitor instrumentation concepts is discussed. This subsystem included an advanced liquid cooled unitized core composite cell module and integrated electromechanical components. Over 1800 hours with the subsystem with removal efficiencies between 90%. and 100%; endurance tests with a Fluid Control Assembly which integrates 11 gas handling components of the subsystem; and endurance testing of a coolant control assembly which integrates a coolant pump, diverter valve and a liquid accumulator were completed.

Heppner, D. B.↗

NASA NTRS1984

Evaluation of candidate Stirling engine heater tube alloys after 3500 hours exposure to high pressure doped hydrogen or helium

The heater head tubes of current prototype automotive Stirling engines are fabricated from alloy N-155, an alloy which contains 20 percent cobalt. Because the United States imports over 90 percent of the cobalt used in this country and resource supplies could not meet the demand imposed by automotive applications of cobalt in the heater head (tubes plus cylinders and regenerator housings), it is imperative that substitute alloys free of cobalt be identified. The research described herein focused on the heater head tubes. Sixteen alloys (15 potential substitutes plus the 20 percent Co N-155 alloy) were evaluated in the form of thin wall tubing in the NASA Lewis Research Center Stirling simulator materials diesel fuel fired test rigs. Tubes filled with either hydrogen doped with 1 percent CO2 or with helium at a gas pressure of 15 MPa and a temperature of 820 C were cyclic endurance tested for times up to 3500 hr. Results showed that two iron-nickel base superalloys, CG-27 and Pyromet 901 survived the 3500 hr endurance test. The remaining alloys failed by creep-rupture at times less than 3000 hr, however, several other alloys had superior lives to N-155. Results further showed that doping the hydrogen working fluid with 1 vol % CO2 is an effective means of reducing hydrogen permeability through all the alloy tubes investigated.

Misencik, J. A.↗

NASA NTRS1983

Alkaline fuel cells for the regenerative fuel cell energy storage system

The development of the alkaline Regenerative Fuel Cell System, whose fuel cell module would be a derivative of the 12-kW fuel cell power plant currently being produced for the Space Shuttle Orbiter, is reviewed. Long-term endurance testing of full-size fuel cell modules has demonstrated: (1) the extended endurance capability of potassium titanate matrix cells, (2) the long-term performance stability of the anode catalyst, and (3) the suitability of a lightweight graphite structure for use at the anode. These approaches, developed in the NASA-sponsored fuel cell technology advancement program, would also reduce cell weight by nearly one half.

Martin, R. E.↗

NASA NTRS1984

Cardiovascular responses during orthostasis - Effect of an increase in maximal O2 uptake

A study is described which tests the hypothesis that changes in aerobic activity (increases in maximum oxygen uptake) will reduce the effectiveness of cardiovascular reflexes to regulate blood pressure during orthostasis. The hypothesis was tested by measuring heart rate, blood pressure and blood volume responses in eight healthy male subjects before and after an eight-day endurance regimen. The results of the study suggest that the physiologic responses to orthostasis are dependent upon the rate of plasma volume loss and pooling, and are associated with training-induced hypervolemia. It is indicated that endurance type exercise training enhances cardiovascular adjustments during tilt. The implications of these results for the use of exercise training as a countermeasure and/or therapeutic method for the prevention of cardiovascular instability during orthostatic stress are discussed.

Convertino, V. A.↗

NASA NTRS1982

Advanced blade tip seal system, volume 2

The results of the endurance and performance engine tests conducted on monocrystal/abrasive-tipped CF6-50 Stage 1 HPT blades fabricated in Task VII of MATE Project 3 are presented. Two engine tests are conducted. The endurance engine test is conducted for 1000 C cycles. The performance engine test is conducted on a variable cycle core engine. Posttest evaluation and analyses of the blades and shrouds included visual, dimensional, and destructive evaluations.

Zelahy, J. W.↗

NASA NTRS1985

Long-life high performance fuel cell program

A multihundred kilowatt Regenerative Fuel Cell for use in a space station is envisioned. Three 0.508 sq ft (471.9 cm) active area multicell stacks were assembled and endurance tested. The long term performance stability of the platinum on carbon catalyst configuration suitability of the lightweight graphite electrolyte reservoir plate, the stability of the free standing butyl bonded potassium titanate matrix structure, and the long life potential of a hybrid polysulfone cell edge frame construction were demonstrated. A 18,000 hour demonstration test of multicell stack to a continuous cyclical load profile was conducted. A total of 12,000 cycles was completed, confirming the ability of the alkaline fuel cell to operate to a load profile simulating Regenerative Fuel Cell operation. An orbiter production hydrogen recirculation pump employed in support of the cyclical load profile test completed 13,000 hours of maintenance free operation. Laboratory endurance tests demonstrated the suitability of the butyl bonded potassium matrix, perforated nickel foil electrode substrates, and carbon ribbed substrate anode for use in the alkaline fuel cell. Corrosion testing of materials at 250 F (121.1 C) in 42% wgt. potassium identified ceria, zirconia, strontium titanate, strontium zirconate and lithium cobaltate as candidate matrix materials.

Martin, R. E.↗

NASA NTRS1985

Surface fatigue life and failure characteristics of EX-53, CBS 1000M, and AISI 9310 gear materials

Spur gear endurance tests and rolling-element surface fatigue tests are conducted to investigate EX-53 and CBS 1000M steels for use as advanced application gear materials, to determine their endurance characteristics, and to compare the results with the standard AISI 9310 gear material. The gear pitch diameter is 8.89 cm (3.50 in). Gear test conditions are an oil inlet temperature of 320 K (116 F), an oil outlet temperature of 350 K (170 F), a maximum Hertz stress of 1.71 GPa (248 ksi), and a speed of 10,000 rpm. Bench-type rolling-element fatigue tests are conducted at ambient temperature with a bar specimen speed of 12,500 rpm and a maximum Hertz stress of 4.83 GPa (700 ksi). The EX-53 test gears have a surface fatigue life of twice that of the AISI 9310 spur gears. The CBS 1000M test gears have a surface fatigue life of more than twice that of the AISI 9310 spur gears. However, the CBS 1000M gears experience a 30-percent tooth fracture failure which limits its use as a gear material. The rolling-contact fatigue lines of RC bar specimens of EX-53 and ASISI 9310 are approximately equal. However, the CBS 1000M RC specimens have a surface fatigue life of about 50 percent that of the AISI 9310.

Townsend, D. P.↗

NASA NTRS1985

Experimental assessment of advanced Stirling component concepts

The results of an experimental assessment of some advanced Stirling engine component concepts are presented. High performance piston rings, reciprocating oil scrapers and heat pipes with getters and with mechanical couplings were tested. The tests yielded the following results: (1) Bonded, split, pumping piston rings, in preliminary testing, proved a promising concept, exhibiting low leakage and friction losses. Solid piston rings proved impractical in view of their sensitivity to the operating temperature; (2) A babbit oil scraper in a compliant housing performed well in atmospheric endurance testing. In pressurized tests the scraper did not perform well as a containment seal. The latter tests suggest modifications which may adapt Ti successfully to that application; and (3) Heat pipe endurance tests indicated the adequacy of simple, inexpensive fabrication and filling procedures. Getters were provided to increase the tolerance of the heat pipes to the presence of air and commercially available couplings were demonstrated to be suitable for heat pipe application. In addition to the above tests, the program also included a design effort for a split shaft applicable to a swashplate driven engine with a pressurized crank-case. The design is aimed, and does accomplish, an increase in component life to more than 10,000 hours.

Ziph, B.↗

NASA NTRS1986

Surface fatigue and failure characteristics of hot forged powder metal AISI 4620, AISI 4640, and machined AISI 4340 steel spur gears

Spur gear surface fatigue endurance tests were conducted to investigate hot forged powder metal AISI 4620 and 4640 steel for use as a gear material, to determine endurance characteristics and to compare the results with machined AISI 4340 and 9310 steel gear materials. The as-forged and unground SISI 4620 gear exhibited a 10 percent fatigue life that was approximately one-fourth of that for AISI 9310 and less than one-half that for the AISI 4340 gears. The forged and finish ground AISI 4620 gears exhibited a 10 percent life, approximately 70 percent that of AISI 9310 and slightly better than that of AISI 4340. The AISI 4640 hot forged gears had less fracture toughness and slightly less fatigue life than the AISI 4620 test gears.

Townsend, D. P.↗

NASA NTRS1986

Fatigue delamination behavior of PEEK thermoplastic composite laminates

The delamination resistance of graphite-reinforced PEEK composites was quantified by conducting static and cyclic edge delamination tests on (35n/-35n/0n/90n)s AS4/PEEK laminates, where n = 1, 2. The experimentally determined mechanical delamination onset strains were used to calculate the critical strain-energy release rate for delamination onset as a function of fatigue cycle. The delamination onset strains decreased dramatically with fatigue cycles and then began to level off to an endurance limit at 1 million cycles. Although the static interlaminar fracture toughness of the AS4/PEEK composite is much greater than the toughness of graphite epoxy composites, the delamination fatigue threshold, calculated from the cyclic strain endurance limit at 1 million cycles, was only slightly greater than the threshold for graphite epoxy composites. The contribution of residual thermal stresses to delamination in the AS4/PEEK is substantial due to the large temperature range between the manufacture and the room temperatures.

O'Brien, T. K.↗

NASA NTRS1987

Surface fatigue and failure characteristics of hot-forged powder metal AISI 4620, AISI 4640, and machined AISI 4340 steel spur gears

Spur gear surface fatigue endurance tests were conducted to investigate hot forged powder metal AISI 4620 and 4640 steel for use as a gear material, to determine endurance characteristics and to compare the results with machined AISI 4340 and 9310 steel gear materials. The as-forged and unground AISI 4620 gear exhibited a 10 percent fatigue life that was approximately one-fourth of that for AISI 9310 and less than one-half that for the AISI 4340 gears. The forged and finish ground AISI 4620 gears exhibited a 10 percent life, approximately 70 percent that of AISI 9310 and slightly better than that of AISI 4340. The AISI 4640 hot forged gears had less fracture toughness and slightly less fatigue life than the AISI 4620 test gears.

Townsend, Dennis P.↗