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Miniature pressure transducers with diffused, heavily doped silicon strain-gage sensor elements, operates over a wide temperature range. Small thermal mass combined with close coupling between a metallic diaphragm and sensor elements minimizes sensitivity to temperature transients.
An analysis of flight performance of the Apollo 15 cryogenic oxygen tanks was conducted with the variable grid stratification math model developed earlier in the program. Flight conditions investigated were the CMP-EVA and one passive thermal control period which exhibited heater temperature characteristics not previously observed. Heater temperatures for these periods were simulated with the math model using flight acceleration data. Simulation results (heater temperature and tank pressure) compared favorably with the Apollo 15 flight data, and it was concluded that tank performance was nominal. Math model modifications were also made to improve the simulation accuracy. The modifications included the addition of the effects of the tank wall thermal mass and an improved system flow distribution model. The modifications improved the accuracy of simulated pressure response based on comparisons with flight data.
An analysis of transient pressures in externally pressurized cryogenic hydrogen and oxygen tanks was conducted and the effects of design variables on pressure response determined. The analysis was conducted with a computer program which solves the compressible viscous flow equations in two-dimensional regions representing the tank and external loop. The external loop volume, thermal mass, and heat leak were the dominant design variables affecting the system pressure response. No significant temperature stratification occurred in the fluid contained in the tank.
There were, two different design concepts considered for the purpose of measuring heat flow as part of a Mars penetrator mission. The first of the tentative designs utilizes temperature sensors emplaced along the trailing umbilicus at regularly spaced intervals, no greater than 1m, which is thermally coupled to the adjacent regolith radiatively and possibly convectively or conductively. The second of the heat flow designs considered requires the radial deployment of two or more low thermal mass temperature sensors outward from the penetrator body over a vertical (depth) range on the order of 1m.
A curved pipe element capability for the NASTRAN structural analysis program is developed using the NASTRAN dummy element feature. A description is given of the theory involved in the subroutines which describe stiffness, mass, thermal and enforced deformation loads, and force and stress recovery for the curved pipe element. Incorporation of these subroutines into NASTRAN is discussed. Test problems are proposed. Instructions on use of the new element capability are provided.
A system used to control skin temperature in human subjects wearing water-perfused garments is described. It supplies 8 l/min at 10 psi with water temperature controlled within plus or minus 0.1 C. Temperature control is facilitated by a low circulating thermal mass and a fast responding heater based on a commercially available quartz heat lamp. The system is open so that hot or cold water can be added from the building mains to produce rates of change of water temperature exceeding 5 C/min. These capabilities allow semiautomatic control of skin temperature within plus or minus 0.1 C of desired wave forms.
A system which allows programmable temperature-time control for a 5 cc sample volume of an arbitrary biological material was constructed. Steady state and dynamic temperature control was obtained by supplying heat to the sample volume through resistive elements constructed as an integral part of the sample container. For cooling purposes, this container was totally immersed into a cold heat sink. Sample volume thermodynamic property data were obtained by measurements of heater power and heat flux through the container walls. Using a mixture of dry ice and alcohol at -79 C, sample volume was controlled from +40 C to -60 C at rates from steady state to + or - 65 C/min. Steady state temperature precision was better than 0.2 C while the dynamic capability depends on the temperature rate of change as well as the thermal mass of the sample and the container.
Thermal energy storage technology and development of building heating and cooling applications in the residential and commercial sectors is outlined. Three elements are identified to undergo an applications assessment, technology development, and demonstration. Emphasis is given to utility load management thermal energy system application where the stress is on the 'customer side of the meter'. Thermal storage subsystems for space conditioning and conservation means of increased thermal mass within the building envelope and by means of low-grade waste heat recovery are covered.
The circuit diagram for a temperature controller for use with very fast-acting (low thermal mass) furnace systems is presented and its features described. The operation of the slow response temperature controller is discussed.
Thirty-one commercially designed platinum resistance thermometers were evaluated for applicability to stagnation temperature measurements between -190 C and +65 C in the Langley Research Center's National Transonic Facility. Evaluation tests included X-ray shadowgraphs, calibrations before and after aging, and time constant measurements. Two wire-wound low thermal mass probes of a conventional design were chosen as most suitable for this cryogenic wind tunnel application.
Adhesive bonding in the aerospace industry typically utilizes autoclaves or presses which have considerable thermal mass. As a consequence, the rates of heatup and cooldown of the bonded parts are limited and the total time and cost of the bonding process is often relatively high. Many of the adhesives themselves do not inherently require long processing times. Bonding could be performed rapidly if the heat was concentrated in the bond lines or at least in the adherends. Rapid adhesive bonding concepts were developed to utilize induction heating techniques to provide heat directly to the bond line and/or adherends without heating the entire structure, supports, and fixtures of a bonding assembly. Bonding times for specimens are cut by a factor of 10 to 100 compared to standard press bonding. The development of rapid adhesive bonding for lap shear specimens (per ASTM D1003 and D3163), for aerospace panel bonding, and for field repair needs of metallic and advanced fiber reinforced polymeric matrix composite structures are reviewed.
Adhesive bonding in the aerospace industry typically utilizes autoclaves or presses which have considerable thermal mass. As a consequence, the rates of heatup and cooldown of the bonded parts are limited and the total time and cost of the bonding process are often relatively high. Many of the adhesives themselves do not inherently require long processing times. Bonding could be performed rapidly if the heat was concentrated in the bond lines or at least in the adherends. Rapid Adhesive Bonding concepts are developed to utilize induction heating techniques to provide heat directly to the bond line and/or adherends without heating the entire structure, supports, and fixtures of a bonding assembly. Bonding times for specimens can be cut by a factor of 10 to 100 compared to standard press or autoclave bonding. The development of Rapid Adhesive Bonding for lap shear specimens (per ASTM D1002 and D3163), for aerospace panel or component bonding, and for field repair needs of metallic and advanced fiber reinforced polymeric-matrix composite structures is reviewed. Equipment and procedures are described for bonding and repairing thin sheets, simple geometries, and honeycomb core panels.
The application of refrigeration at low temperatures ranging from production of liquid helium for medical imaging systems to cooling of infrared sensors on surveillance satellites is discussed. Cooling below about 15 K with regenerative refrigerators is difficult because of the decreasing thermal mass of the regenerator compared to that of the working material. In order to overcome this difficulty with helium gas as the working material, a heat exchanger plus a Joule-Thomson or other exponder is used. Regenerative magnetic refrigerators with magnetic solids as the working material have the same regenerator problem as gas refrigerators. This problem provides motivation for the development of nonregenerative magnetic refrigerators that span approximately 1 K to approximately 0 K. Particular emphasis is placed on high reliability and high efficiency. Calculations indicate considerable promise in this area. The principles, the potential, the problems, and the progress towards development of successful 4 to 20 K magnetic refrigerators are discussed.
Coefficients of viscosity of various types of gas mixtures, including simulated natural-gas samples, have been measured at atmospheric pressure and room temperature using a modified capillary tube method. Pressure drops across the straight capillary tube section of a thermal mass flowmeter were measured for small, well-defined, volume flow rates for the test gases and for standard air. In this configuration, the flowmeter provides the volumetric flow rates as well as a well-characterized capillary section for differential pressure measurements across it. The coefficients of viscosity of the test gases were calculated using the reported value of 185.6 micro P for the viscosity of air. The coefficients of viscosity for the test mixtures were also calculated using Wilke's approximation of the Chapman-Enskog (C-E) theory. The experimental and calculated values for binary mixtures are in agreement within the reported accuracy of Wilke's approximation of the C-E theory. However, the agreement for multicomponent mixtures is less satisfactory, possible because of the limitations of Wilkes's approximation of the classical dilute-gas state model.
The development history of solid amine/water desorbed (SAWD) CO2 control systems is reviewed. The design of the preprototype SAWD I CO2 system on the basis of a three-man metabolic load at the 3.8 mm Hg ambient CO2 level, and the functions of the CO2 removal, CO2 storage/delivery, controller, and life test laboratory support packages are described. The development of a full-scale multiple canister SAWD II preprototype system, which is capable of conducting the CO2 removal/concentration function in a closed-loop atmosphere revitalization system during zero-gravity operation, is examined. The operation of the SAWD II system, including the absorption and desorption cycles, is analyzed. A reduction in the thermal mass of the canister and the system's energy transfer technique result in efficient energy use. The polyether foam, nylon felt, nickel foam, spring retained, and metal bellows bed tests performed to determine the design of the zero-gravity canister are studied; metal bellows are selected for the canister's configuration.
The objectives of Phase 1 were to evaluate analytically and experimentally the operation, performance, and lifetime of arcjet thrusters operating between 0.5 and 3.0 kW with catalytically decomposed hydrazine (N2H4) and to begin development of the requisite power control unit (PCU) technology. Fundamental analyses were performed of the arcjet nozzle, the gas kinetic reaction effects, the thermal environment, and the arc stabilizing vortex. The VNAP2 flow code was used to analyze arcjet nozzle performance with non-uniform entrance profiles. Viscous losses become dominant beyond expansion ratios of 50:1 because of the low Reynolds numbers. A survey of vortex phenomena and analysis techniques identified viscous dissipation and vortex breakdown as two flow instabilities that could affect arcjet operation. The gas kinetics code CREK1D was used to study the gas kinetics of high temperature N2H4 decomposition products. The arc/gas energy transfer is a non-equilibrium process because of the reaction rate constants and the short gas residence times. A thermal analysis code was used to guide design work and to provide a means to back out power losses at the anode fall based on test thermocouple data. The low flow rate and large thermal masses made optimization of a regenerative heating scheme unnecessary.
Method of deadweight loading for vacuum-furnace brazing improves quality of joint, increases yield, and reduces costs. In improved method, plates weighted with heavy stainless-steel blocks. Blocks act independently and are immune to distortion. Besides being uniformly distributed, force applied to plates larger and repeatable from one brazing operation to next. Larger blocks used on edges of plates, where more thermal mass needed to reduce differences between temperatures of interior and edge as temperature of furnace varied.
The fabrication of the first Z-technology module with 128 active layers of readout electronic circuitry is being pursued. Several issues which will be investigated regarding the 128-layer module build, such as photolithographic processing at the edge of the module (edge effects) and module buttability, are discussed in this paper. Other topics which are covered apply to future applications of fully populated HYMOSS modules. These topics include possible reductions of thermal mass for quick cool-down time applications and improvements of end-to-end yield for low-cost applications.