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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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The amount of solar radiation incident on a specially prepared bimetallic strip is simply and reliably controlled by a light valve. This device is valuable for systems requiring temperature regulation.
Bimetallic thermostatic fins for spacecraft skin temperature control in space and solar radiation simulated environment
Rankine cycle technology programs noting use of stainless steel bimetallic systems, boiler and condenser problems, turbine operation, etc
Shear modulus effect on stress distribution of planar array of screw dislocations near bimetallic welded half-planes interface
Tantallum-stainless steel bimetallic joints tested to determine overall strength of brazed joint
Technical report is presented on sodium and lithium cells using fused salt electrolytes. It includes a discussion of the thermally regenerative galvanic cell and the secondary bimetallic cell for storage of electricity.
Converting electric power into powerful linear thrust without generation of magnetic fields is accomplished with an electrothermal linear actuator. When treated by an energized filament, a stack of bimetallic washers expands and drives the end of the shaft upward.
Electrical resistance of a carbon-pile resistor is controlled by the compression or relaxation of a pile of carbon disks by a thermally actuated bimetallic spring. The concept is advantageous in that it is direct-acting, can cover a wide range of controllable characteristics, and can handle considerable power directly.
Valve concept has been devised which offers lightweight, simplified mechanism capable of automatic control of large number of fluid flow ports. Valve control is achieved with valve stem which is bimetallic device activated by heating coil to open or close selected supply port. Number of controlled ports is limited only by desired physical size of system.
The thermal heliotrope is a passive solar-array orientation device containing a bimetallic helix that rotates when activated by solar energy. The rate and extent of the rotation depends upon the properties of the two metals and the temperature of the helix. An energy-balance analysis is performed to determine the temperature distribution in the helix. By initially restricting the analysis, a simplified equation governing the response of the heliotrope is obtained. In order to gain insight into the response of the heliotrope, a series of experiments were performed. The results of these tests and the implications are presented.
A test program was carried out to demonstrate an igniter motor initiation system utilizing the bimetallic material Pyrofuze for a solid propellant rocket with controlled low rate of thrust buildup. The program consisted of a series of vacuum ignition tests using a slab burning window motor that simulated the principal initial ballistic parameters of the full scale igniter motor. A Pyrofuze/pyrotechnic igniter system was demonstrated that uses a relatively low electrical current level for initiation and that eliminates the necessity of a pyrotechnic squib, with its accompanying accidental firing hazards and the typical basket of pyrotechnic pellets. The Pyrofuze ignition system does require an initial constraining of the igniter motor nozzle flow, and at the low initiating electrical current level the ignition delay time of this system was found to be quite sensitive to factors affecting local heat generation or loss rates.
Studies and experiments on the use of bimetallic lattice structures for determining and controlling thermal expansion characteristics are discussed.
A passive solar array orientation device, called a thermal heliotrope, is described, and several terrestrial applications are illustrated. The thermal heliotrope consists of a bimetallic helical coil that serves as the motor element, producing torque and angular displacement. A control mechanism in the form of one or more shades completes the basic device. In comparison with electromechanical tracking systems, the thermal heliotrope is electrically passive, has relatively few parts, and is low cost. After describing the principle of operation and several models built for space applications, the design considerations for several terrestrial thermal heliotrope units are presented. It is suggested that the use of the thermal heliotrope for solar array orientation could significantly reduce array cost, thereby increasing the competitive economic posture of solar arrays for terrestrial applications. The thermal heliotrope modified for terrestrial use is readily adaptable to orient solar energy concentrators, such as furnaces and stills.
Nickel foils of nominal thickness 0.1 and 1 micron have been resistively evaporated onto copper-foil substrates of thickness 25 and 2.5 microns. In depositions in which the pressure was as high as 0.00001 torr, the deposited nickel was not shiny and appeared granular in a 100x microscope. Foils evaporated in higher vacuums were shiny, but became granular if heated to 500 C in oxygen at pressures greater than 0.000005 torr, or in carbon dioxide at pressures greater than 0.0000005 torr. This phenomenon has been interpreted as recrystallization. Foils heated to 500 C at pressures of hydrogen above 0.0003 torr exhibit cracking characteristic of hydrogen embrittlement. The bimetallic foils curled concave toward the nickel during evaporation, consistent with a connected-island form of film growth.
Device is constructed of bimetallic stock material formed into segments of small diameters and fastened together by metal strips. Coil is useful in various types of actuators, such as temperature controls.
The performance characteristics of a bimetallic coil actuated thermal control louver system were simulated using a multinode mathematical computer model. There is satisfactory agreement between space chamber data and calculations by the methods discussed.
By adding an extra layer to multilayer beams or plates of different isotropic materials, it is possible to prevent the thermal bending of these materials. With the proper selection of thermoelastic properties the curvature produced prior to this addition would be eliminated. Several numerical examples are presented for various temperature distributions. A simple experiment was conducted, involving the addition of a brass strip to a bimetallic strip made of aluminum and steel at room temperature. The trimetal strip was placed in a furnace and remained straight for varying temperatures.
Bimetallic contacts utilizing palladium and aluminum, gold, silver, or chromium, are used in reduction of series resistance in GaAlAs/GaAs solar cells, thereby improving cell reliability.