SEARCH · Engineering Papers
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Manufacturing process produces molybdenum foil 0.002 cm thick and 305 m long, and forms foil into high-strength, thin-walled tubing which can be flattened for storage on a spool. Desirable metal properties include high thermal conductivity stiffness, yield and tensile stress, and low thermal expansion coeffecient.
NASA computer program for dynamic structural analysis in stress and thermal deformation problems
Pressure-induced absorption in planetary atmospheres from hydrogen-methane collisions, stressing resulting thermal opacity
The alloys Nimonic 90, IN 100, coated IN 100, B 1900, coated B 1900, MAR M200, and MAR M200DS (directionally solidified) were studied. Maximum temperatures ranged from 770 C to 1120 C (1420 F to 2050 F). Specimen geometries included tapered disks, double-edged wedges, and cambered airfoils. The disks and wedges were heated and cooled in fluidized beds. The airfoil specimens were heated by a Mach 1 natural gas burner and rapid-air-cooled, with and without spanwise loading. Life calculations included two distinct failure modes: conventional low cycle fatigue and cyclic creep. Required material properties were limited to conventional thermal, tensile, and creep rupture data. The complete life calculation system included the calculation of transient temperature distributions, thermal strains, stresses, creep damage, fatigue damage, and cycles to first crack. Calculated lives were within a factor of two for 76 of the 86 data points analyzed. Cyclic creep accounted for 81% of all the calculated damage.
Alloys investigated were Nimonic 90, IN 100, coated IN 100, B 1900, coated B 1900, MAR M200, and MAR M200DS (directionally solidified). Maximum temperatures ranged from 770 to 1120 C. Specimen geometries included tapered disks, double-edged wedges, and cambered airfoils. The disks and wedges were heated and cooled in fluidized beds. The airfoil specimens were heated by a Mach 1 natural gas burner and rapid-air cooled, with and without spanwise loading. Life calculations included two distinct failure modes: conventional low-cycle fatigue and cyclic creep. The complete life calculation system included the calculation of transient temperature distributions, thermal strains, stresses, creep damage, fatigue damage, and finally cycles to first crack. Calculated lives were within a factor of two for 76 of the 86 data points analyzed.
A preliminary design study of flight-type dc conduction-permanent magnetic, ac helical induction, and ac linear induction pumps for circulating 883 K (1130 F) NaK at 9.1 kg/sec (20 lb/sec) is described. Various electromagnetic pump geometrics are evaluated against hydraulic performance, and the effects of multiple windings and numbers of pumps per assembly on overall reliability were determined. The methods used in the electrical-hydraulic, stress, and thermal analysis are discussed, and the high temperature electrical materials selected for the application are listed.
A solid propellant rocket motor containing 60.9 Kg (134-lb) of propellant was successfully static fired after being subjected to eight heat sterilization cycles (three 54-hour cycles plus five 40-hour cycles) at 125 C (257 F). The test motor, a modified SVM-3 chamber, incorporated a flexible grain retention system of EPR rubber to relieve thermal shrinkage stresses. The propellant used in the motor was ANB-3438, and 84 wt% solids system (18 wt% aluminum) containing 66 wt% stabilized ammonium perchlorate oxidizer and a saturated hydroxylterminated polybutadiene binder. Bonding of the propellant to the EPR insulation (GenGard V-4030) was provided by the use of SD-886, an epoxy urethane restriction.
The design and fabrication of a flight gas generator for the space shuttle were investigated. Critical performance parameters and stability criteria were evaluated as well as a scaling laws that could be applied in designing the flight gas generator. A test program to provide the necessary design information was included. A structural design, including thermal and stress analysis, and two gas generators were fabricated based on the results. Conclusions are presented.
The requirements, conceptual design, tradeoffs, procedures, and techniques for orbital assembly of the support structure of the microwave power transmission system and the radio astronomy telescope are described. Thermal and stress analyses, packaging, alignment, and subsystems requirements are included along with manned vs. automated and transportation tradeoffs. Technical and operational concepts for the manned and automated maintenance of satellites were investigated and further developed results are presented.
Differential thermal expansion has been shown to be responsible for many observed failures in ceramic chip capacitors mounted on alumina substrates. The present work has shown that the mounting techniques used in bonding the capacitors have a marked effect upon the thermally induced mechanical stress and thus the failure rate. A mathematical analysis of a composite model of the capacitor-substrate system to predict the magnitude of thermally induced stresses have been conducted. It has been experimentally observed that the stresses in more compliant bonding systems such as soft lead/tin and indium solders are significantly lower than those in hard solder and epoxy systems. From the data obtained, several recommendations are made concerning the optimum bonding system for the achievement of maximum reliability.
Impact energy absorbing layers (EALs) comprised of partially densified silicon carbide were formed in situ on fully sinterable silicon carbide substrates. After final sintering, duplex silicon carbide structures resulted which were comprised of a fully sintered, high density silicon carbide substrate or core, overlayed with an EAL of partially sintered silicon carbide integrally bonded to its core member. Thermal cycling tests proved such structures to be moderately resistant to oxidation and highly resistant to thermal shock stresses. The strength of the developed structures in some cases exceeded but essentially it remained the same as the fully sintered silicon carbide without the EAL. Ballistic impact tests indicated that substantial improvements in the toughness of sintered silicon carbide were achieved by the use of the partially densified silicon carbide EALs.
Techniques for monitoring changes in preparation of solar sail materials resulting from space radiation simulation, stressing (e.g., thermal, mechanical) and exposure to terrestrial environments are developed. The properties of interest are: metallic coating deterioration, polymeric film deterioration, interfacial debonding and possible metallic coating diffusion into the polymeric film. Four accelerated tests were devised to simulate the possible degradation processes mentioned above. These four tests are: a thermal shock test to simulate the wide variation of temperature expected in space (260 C to -100 C), a cyclic temperature test to stimulate the 6 minute temperature cycle anticipated in space, a mechanical vibration test to simulate mechanical bonding, folding and handling, and a humidity test to simulate terrestrial environment effects. The techniques for monitoring property changes are: visual and microscopic examination, ellipsometry, surface potential difference (SPD), photoelectron emission (PEE), and water contact angles.
Two approximation concepts for combined thermal/structural design are evaluated. The first concept is an approximate thermal analysis based on the first derivatives of structural temperatures with respect to design variables. Two commonly used first-order Taylor series expansions are examined. The direct and reciprocal expansions are special members of a general family of approximations, and for some conditions other members of that family of approximations are more accurate. Several examples are used to compare the accuracy of the different expansions. The second approximation concept is the use of critical time points for combined thermal and stress analyses of structures with transient loading conditions. Significant time savings are realized by identifying critical time points and performing the stress analysis for those points only. The design of an insulated panel which is exposed to transient heating conditions is discussed.
Silicon dendritic web, ribbon form of silicon and capable of fabrication into solar cells with greater than 15% AMl conversion efficiency, was produced from the melt without die shaping. Improvements were made both in the width of the web ribbons grown and in the techniques to replenish the liquid silicon as it is transformed to web. Through means of improved thermal shielding stress was reduced sufficiently so that web crystals nearly 4.5 cm wide were grown. The development of two subsystems, a silicon feeder and a melt level sensor, necessary to achieve an operational melt replenishment system, is described. A gas flow management technique is discussed and a laser reflection method to sense and control the melt level as silicon is replenished is examined.
The design and development of a modular solar thermal power system for application in the 1 to 10 MWe range is described. The system consists of five subsystems: the collector, power conversion, energy transport, energy storage, and the plant control subsystem. The collector subsystem consists of concentrator, receiver, and tower assemblies. The energy transport subsystem uses a mixture of salts with a low melting temperature to transport thermal energy. A steam generator drives a steam Rankine cycle turbine which drives an electrical generator to produce electricity. Thermal and stress analysis tests are performed on each subsystem in order to determine the operational reliability, the minimum risk of failure, and the maintenance and repair characteristics.
The development and design of a modular solar thermal power system for application in the 1 to 10 MWe range is described. The system is used in remote utility applications, small communities, rural areas, and for industrial uses. Thermal and stress analyses are performed on the collector subsystem, energy storage subsystem, energy transport subsystem, the power conversion subsystem, and the plant control subsystem.
The construction and mounting of mirrors for an infrared telescope are described. Tests conducted to determine the thermal and stress characteristics of various types of mounting for main and collection mirrors are also discussed.
The repetitive Q-switched performances of an x-axis neodymium-doped lanthanum beryllate (Nd:BeL) laser and the current state-of-the-art Nd:YAG laser are compared. Output beam pulse energy, peak power, pulse width, beam divergence and mode pattern were measured for a gold-plated single elliptical cavity using a xenon flashlamp for excitation. The output of the Nd:BeL laser is found to exceed that of the Nd:YAG laser by a factor of two at Q-switched repetition rates on the order of 1 Hz, due to the smaller stimulated emission cross section of the x-axis Nd:BeL. When the repetition rate is increased to 10 Hz, the Nd:BeL output falls to a level three fifths lower than its low-rate value, while Nd:YAG output remained essentially constant. Analysis reveals that the decrease in output may be attributed to a depolarization loss due to thermally induced stress birefringence.