Stability of rectangular flexible plates made from nonlinearly elastic materials
Critical stresses and deformation pattern after buckling for flexible rectangular plates of nonlinearly elastic materials
PLASTIC DEFORMATION↗
SEARCH · Engineering Papers
Results for “Critical materials”
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.
Advanced Materials for the Lunar Surface: Multiscale Computational Design of Refractory Alloys and Carbides
Emerging operational environments, such as the lunar surface, present novel challenges for NASA and drive the need for advanced materials in applications like fission surface power systems. To address these demands, computational materials science is rapidly evolving to augment or replace costly and hazardous empirical testing. Although materials selection at NASA remains predominantly experimentally driven, advanced simulation methodologies are being steadily integrated into the engineering lifecycle. This work details the application of multiscale simulation techniques—including first-principles calculations, CALPHAD, dislocation dynamics, and molecular dynamics—at NASA's Ames Research Center to evaluate advanced materials for extreme environments. First, we present contributions to the Space Nuclear Propulsion Project. Be-cause propellant channel coatings in nuclear thermal rockets must withstand high-pressure, high-temperature hydro-gen, optimizing these materials is critical. First-principles calculations were employed to establish a rigorous quantitative and qualitative understanding of the behavior of the refractory carbides ZrC, NbC, and their mixtures in high-enthalpy hydrogen environments. This necessitated the generation of high-fidelity thermodynamic models for both stoichiometric and carbon-depleted carbides, both with and without the presence of hydrogen. Furthermore, we highlight efforts under the Refractory Alloy Additive Manufacturing Build Optimization (RAAMBO) project, where existing and novel alloy compositions were assessed for additive manufacturing printability and subsequent performance in applications such as heat pipes and rocket nozzle extensions. This was accomplished through a comprehensive multiscale simulation framework that bridged the gap from the nanometer to the millimeter scale. Across both initiatives, rigorous validation against empirical data was prioritized. By systematically employing a verified and validated computational frame-work, we demonstrate how simulation effectively supports multidisciplinary engineering efforts, builds project-wide confidence, and drives critical materials development.
computational materials↗
Simple technique determines ac properties of hard superconductive materials
Critical current density of neodymium-titanium alloy samples is analyzed from magnetization curves to determine the ac properties of hard semiconductive materials. A complete family of magnetization curves is obtained, each curve representing performance at a different temperature.
Harper, C. M.↗
Construction of power supplies for operation in the critical region
Materials and techniques used in construction of power supplies for high voltage equipment operating in critical region
Clark, J. P.↗
Research study to determine critical optical/mechanical properties of materials considered for selection as substrates for the primary mirror on a large telescope
An investigation was conducted to evaluate the stability of a specific low expansion glass-ceramic material relative to its use as a large, lightweight mirror substrate for diffraction-limited spaceborne optical applications. These evaluations were made on a segment (0.44 meter diameter by 0.31 meter thick) of a 2 to 3 meter diameter mirror blank. The dimensional stability of this mirror was measured interferometrically before and after lightweighting, as a function of rough machining, etching, thermal environment, and support configuration. A special computer analysis program was used to plot the coefficients corresponding to aberrations with sixfold symmetry (caused by the mirror's self-weight deflection on a three point support). The objective was to enhance the test sensitivity. Results indicate that any such effects due to self-weight deflection are of the order of 0.015 lambda rms. The rms and peak-to-peak figure changes associated with each processing operation are summarized.
Slomba, A. F.↗
Solar Absorptance and Thermal Emittance of Some Common Spacecraft Thermal-Control Coatings
Solar absorptance and thermal emittance of spacecraft materials are critical parameters in determining spacecraft temperature control. Because thickness, surface preparation, coatings formulation, manufacturing techniques, etc. affect these parameters, it is usually necessary to measure the absorptance and emittance of materials before they are used. Absorptance and emittance data for many common types of thermal control coatings, are together with some sample spectral data curves of absorptance. In some cases for which ultraviolet and particle radiation data are available, the degraded absorptance and emittance values are also listed.
John H Henninger↗
A Coaxial Flow Reactor - A Gaseous Nuclear-Rocket Concept
Aspects of a new gaseous nuclear-rocket concept are considered. The principle of this type of cavity reactor is one of maintaining the separation of two coaxial streams - fuel within propellant - rather than attaining the separation of fuel propellant gases within the cavity. An acceptably low uranium consumption rate is possible if the fuel stream can be maintained at an axial velocity which is 1/100 to 1/1000 of the propellant velocity. An elementary hydrodynamic analysis for laminar incompressible flow indicates that the average uranium core velocity may only reach 2 to 11 times the initial core velocity for a typical reactor. The results of a 1-D criticality analysis for a D2O/(235)U system show that the effect of shrinking the fuel region within the reactor cavity is not serious; the effects of moderator heating and structural materials on critical mass are also shown. Overall rocket performance calculations are made for reasonable operating conditions; these results indicate that thrusts from 25,000 to 50,000 pounds and accelerations from 10(exp -1) to 3 g are possible.
Robert G Ragsdale↗
SOLID CRYOGENIC REFRIGERATION OF SPACECRAFT COMPONENTS
Design of a refrigeration system based on the sublimation of a solid cryogenic material for critical spacecraft components
CRYOGENIC EQUIPMENT↗
Evaluation of mechanisms returned from Surveyor 3
The mechanisms of the TV camera and surface sampler retrieved from the Surveyor 3 spacecraft during the Apollo 12 mission are discussed. Data are presented showing the performance of these mechanisms before and after operation for one lunar day and storage for 2-1/2 years on the surface of the moon. An analysis of the critical component materials is also given.
Jones, J. R.↗
Critical appraisal and research opportunities - The materials research viewpoint
Critique of friction and wear from materials research viewpoint
Lawless, K. R.↗
Saturn S-2 quality assurance techniques, critical process control. Volume 7: Metallic materials
The special skills developed during the Saturn S-2 Program are documented to enable qualified personnel to carry out efficient operations in future S-2 production. Skills covered include: acceptance testing of fusion-welding equipment, weld operators and inspector certification, machine certification, preweld operations, and repair weld certification.
Ross, W. D., Jr.↗
Continuous magnetic flux pump
A method and means for altering the intensity of a magnetic field by transposing flux from one location to the location desired fro the magnetic field are examined. The device described includes a pair of communicating cavities formed in a block of superconducting material, is dimensioned to be insertable into one of the cavities and to substantially fill the cavity. Magnetic flux is first trapped in the cavities by establishing a magnetic field while the superconducting material is above the critical temperature at which it goes superconducting. Thereafter, the temperature of the material is reduced below the critical value, and then the exciting magnetic field may be removed. By varying the ratios of the areas of the two cavities, it is possible to produce a field having much greater flux density in the second, smaller cavity, into which the flux transposed.
Hildebrandt, A. F.↗
Gaseous-fueled cavity reactors - Criticality calculations and analysis
Computer calculation of material, temperature, and dimensional variables on criticality and size of gaseous fueled cavity reactor for nuclear rocket propulsion
REACTOR TECHNOLOGY↗
Effects of insulator ablation on the operation of a quasi-steady MPD arc
Multimegawatt operation of quasi-steady MPD arcjets can involve serious ablation of the insulator surfaces within the arc discharge chamber. Various degrees of insulator ablation manifest themselves by significantly perturbing the voltage-current characteristics and the exhaust velocity profiles. Voltage-current characteristics for two different insulator materials, Plexiglas and boron nitride, are interpreted in terms of an empirical Ohm's law. Use of the refractory insulator material eliminates the ablation-dominated nature of the terminal voltage, but the exhaust stream is still disturbed by insulator material. An Alfven critical velocity model can be applied to this influence of insulator ablation on exhaust velocity. Appropriate changes in the propellant injection geometry eliminate this influence and result in arcjet operation which is independent of insulator material. A particular combination of propellant injection geometries reduces the terminal voltage for a given current and mass flow while maintaining insulator-independent operation, thus implying an improvement in the overall efficiency of the device.
Boyle, M. J.↗
Development and Validation of a High-Vacuum Thermal Conductivity Testbed for Aerospace Interface Materials
Thermal Interface Materials (TIMs) are critical components in spacecraft thermal management systems, where thermal performance is strongly influenced by vacuum conditions, interface contact resistance, and layered metallic joint behavior. However, manufacturer-reported thermal conductivity values are often derived under idealized conditions and may not accurately represent performance within operational aerospace applications. To address this limitation, the Testbed for Advanced Interface Materials in Vacuum (TAIMV) was developed as a modular vacuum-compatible thermal conductivity characterization platform capable of evaluating aerospace-relevant TIM configurations under both ambient and high-vacuum environments. The testbed was derived from the ASTM C1044-16 guarded hot plate methodology and incorporates interchangeable layers of stainless steel coupon geometries, independently controlled main and guard heaters, embedded resistance temperature detectors (RTDs), thermocouples, multi-layer insulation (MLI), and a temperature-controlled cold plate to characterize through-thickness thermal gradients across layered interfaces. In the current configuration, interface compression is limited to the nominal contact pressure generated by the experimental stack assembly. Initial experimental campaigns were conducted at ambient pressure and below 1×10-5 torr for vacuum cases using multiple interface materials including Braycote 601EF and Krytox-based greases across a range of thermal operating conditions. In parallel, a coupled numerical Python thermal model was developed to predict temperature distribution throughout the stack while accounting for conduction, radiation, and parasitic heat transfer pathways and effective interface resistance effects. Experimental measurements and numerical predictions showed consistent thermal trends across multiple operating conditions and environmental states. Results also revealed measurable differences between ambient and vacuum thermal behavior, demonstrating the importance of interface resistance, parasitic heat transfer mechanisms, and stack geometry in determining effective thermal performance within layered thermal interfaces. The presented work establishes a foundation for future thermal model correlation efforts and expanded characterization of aerospace thermal interface materials under representative environmental conditions. Future work will focus on the integration of a load cell system to enable controlled pressure-dependent characterization of thermal interface materials under compressive loading. This capability will allow investigation of the influence of contact pressure on effective thermal conductivity, interface resistance, and thermal performance within layered aerospace thermal interfaces under representative operational conditions.
Thermal Development Testing↗
Measurement of Thermal Radiation Properties of Solids
The overall objectives of the Symposium were to afford (1) an opportunity for workers in the field to describe the equipment and procedures currently in use for measuring thermal radiation properties of solids, (2) an opportunity for constructive criticism of the material presented, and (3) an open forum for discussion of mutual problems. It was also the hope of the sponsors that the published proceedings of the Symposium would serve as a valuable reference on measurement techniques for evaluating thermal radiation properties of solids, partic.ularly for those with limited experience in the field. Because of the strong dependence of emitted flux upon temperature, the program committee thought it advisable to devote the first session to a discussion of the problems of temperature measurement. All of the papers in Session I were presented at the request of and upon topics suggested by the Committee. Because of time and space limitations, it, was impossible to consider all temperature measurement problems that might arise--the objective was rather to call to the attention of the reader some of the problems that might be encountered, and to provide references that might provide solutions.
EMISSION↗
Plastic shoe facilitates ultrasonic inspection of thin wall metal tubing
Plastic shoe aids inspection of thin walled stainless steel welded tubing to locate voids or other material defects in critical component equipment. Incorporated in available ultrasonic inspection equipment, it couples the transducer to the tube at desired incident angles.
Lambermeyer, D. J.↗
Polymeric materials for unusual service conditions; Proceedings of the Conference, Moffett Field, Calif., November 29-December 1, 1972
Polymers for aircraft and spacecraft structures are considered, giving attention to novel foams and porous structures, aircraft nacelle composite structure technology, properties and processing of polyimidazoquinazoline composites, and the processing of organic matrices into structural composites. Other subjects discussed are related to high temperature resins and composites, elastomers for high temperature applications, fire retardant materials, polymers for critical pollution control, and polymers for critical medical use. Individual items are announced in this issue.
Golub, M. A.↗