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Development of an approach to the evaluation of the thermal efficiency of the process of water splitting to produce hydrogen. A way of viewing thermochemical processes - both overall and step-by-step is suggested, and some recent work on a process evaluation technique is described which provides internal checks on the thermodynamic data and calculates, in addition to the efficiency, many important process parameters.
A closed passive system independent of support from the spacecraft or its crew was developed to house five pocket mice for their flight on Apollo XVII. The reaction of potassium superoxide with carbon dioxide and water vapor to produce oxygen provided a habitable atmosphere within the experiment package. The performance of the system and the ability of the mice to survive the key preflight tests gave reasonable assurance that the mice would also withstand the Apollo flight.-
The author has identified the following significant results. Thematic maps were produced for surface water in stratum 46. The presence of large amounts of surface water, particularly during the May period, is readily apparent in the photoreduced thematic maps. Sheet water comprises much of the water detected in the May scene. Spring sheet water tends to be ephemeral and occurs as a result of an ice seal which exists within the underlying soil, temporarily preventing the percolation of water. The abundance of water in the May scene is also a result of unusually heavy precipitation which occurred during the spring and the previous fall. A qualitative analysis of the July map indicates surface water is less abundant than during the previous May; however, surface water present in the July 1975 LANDSAT scene was unusually abundant compared to other midsummer LANDSAT scenes obtained since 1972. This condition was particularly apparent for the drift plain.
The paper discusses the production concept and efficiency of two new energy transmission and storage media intended to overcome the disadvantages of electricity as an overall energy carrier. These media are hydrogen produced by water-splitting and the chemical heat pipe. Hydrogen can be transported or stored, and burned as energy is needed, forming only water and thus obviating pollution problems. The chemical heat pipe envisions a system in which heat is stored as the heat of reaction in chemical species. The thermodynamic analysis of these two methods is discussed in terms of first-law and second-law efficiency. It is concluded that chemical heat pipes offer large advantages over thermochemical hydrogen generation schemes on a first-law efficiency basis except for the degradation of thermal energy in temperature thus providing a source of low-temperature (800 K) heat for process heat applications. On a second-law efficiency basis, hydrogen schemes are superior in that the amount of available work is greater as compared to chemical heat pipes.
A model was used to study the effect of hyperthermia on a normal tissue. The model selected was the rabbit bladder and the end point measured was the changes in the micro-vasculature of the bladder wall. It was already demonstrated clinically that hot water bladder infusions produce regression in bladder tumors.
Lyman-alpha fluorescence measurements were used to study the photodissociation of water vapor to produce H(n equals 2) atoms from threshold to 500 A. The experimental threshold of 813.0 A nearly coincides with the thermodynamic limit. Excitation cross sections rise slowly from threshold to a maximum value of (1.55 plus or minus 0.12) x 10 to the -18th sq cm at about 709 A and decrease to a negligible value below 550 A. Structure in the excitation function is attributed to predissociation of Rydberg series converging to the B(overbar)B2 state of H2O(plus).
The author has identified the following significant results. Evidence of a heat sink produced by perched water tables was detected with HCMM night thermal data. The region of shallow water was not visible on HCMM visible or day IR imagery. The results are consistant with previous aircraft investigations.
Stabilization of early crust against melting by high radioactivity and against resorption into the mantle by fast convective overturn requires that water and heat producers were flushed upwards within 50 Myr of accretion. Creation of a refractory base of granulite by metamorphism associated with CO2 vapour explains CO2-rich fluid inclusions in ancient high-grade rocks, minor-element depletions and local phenomena of arrested development of charnockite in Precambrian terrains. The hot-spot and plate-tectonic models of Precambrian crustal evolution lead to different schemes for CO2 delivery to continental roots. New tectonic concepts may be needed to explain carbonic metamorphism and other features of early crustal evolution.
The magnitude and markets for applications of hydrogen produced by water-splitting through thermal or electrolytic means are projected up to the year 2025. Uses are divided into energy and nonenergy categories, with U.S. synfuels programs accounting for 65% of the increased demand for hydrogen. Applications for transportation fuel, as a natural gas supplement, in fuel cells, in refinery and synfuels industries, for synthesizing chemicals, and for manufacturing semiconductors are summarized. Electrolytic processes are noted to be more suitable for smaller scale production, where use is on-site or local. An annual growth of 8.4-9.2% is foreseen in the energy sector and 3-3.6% in the nonenergy sector, with a total contribution to the primary energy uses of 12-13% by the year 2025. Hydrogen's negligible environmental impact and the ability to interface hydrogen systems with existing equipment are seen as factors encouraging hydrogen-use growth.
Radio astronomical observations of Uranus show that the radio emission spectrum is evolving in time. Ammonia vapor must be depleted in the Uranian atmosphere as Gulkis et al. (1978) previously suggested. Since 1965, ammonia either has been decreasing in time or is a decreasing function of latitude, or both, provided that the radio emission is atmospheric in origin. If Uranus has an observable low-emissivity 'surface', these trends may be reversed. The microwave observations made in 1965, at the time when the spin axis of Uranus was nearly perpendicular to the sun-Uranus line, are consistent with an atmospheric opacity profile that would be produced by saturated ammonia vapor in a predominantly hydrogen atmosphere. At the present time, when the spin axis of Uranus is nearly aligned with the sun-Uranus line, the measurements require an opacity that would be produced by saturated water vapor. A large thermal gradient between the pole and equator is ruled out.
The engineering costs and performance of a nominal 25,000 scmd (883,000 scfd) photochemical plant to produce dihydrogen from water were studied. Two systems were considered, one based on flat-plate collector/reactors and the other on linear parabolic troughs. Engineering subsystems were specified including the collector/reactor, support hardware, field transport piping, gas compression equipment, and balance-of-plant (BOP) items. Overall plant efficiencies of 10.3 and 11.6% are estimated for the flat-plate and trough systems, respectively, based on assumed solar photochemical efficiencies of 12.9 and 14.6%. Because of the opposing effects of concentration ratio and operating temperature on efficiency, it was concluded that reactor cooling would be necessary with the trough system. Both active and passive cooling methods were considered. Capital costs and energy costs, for both concentrating and non-concentrating systems, were determined and their sensitivity to efficiency and economic parameters were analyzed. The overall plant efficiency is the single most important factor in determining the cost of the fuel.
The engineering costs and performance of a nominal 25,000 scmd (883,000 scfd) photochemical plant to produce dihydrogen from water were studied. Two systems were considered, one based on flat-plate collector/reactors and the other on linear parabolic troughs. Engineering subsystems were specified including the collector/reactor, support hardware, field transport piping, gas compression equipment, and balance-of-plant (BOP) items. Overall plant efficiencies of 10.3 and 11.6 percent are estimated for the flat-plate and trough systems, respectively, based on assumed solar photochemical efficiencies of 12.9 and 14.6 percent. Because of the opposing effects of concentration ratio and operating temperature on efficiency, it was concluded that reactor cooling would be necessary with the trough system. Both active and passive cooling methods were considered. Capital costs and energy costs, for both concentrating and non-concentrating systems, were determined and their sensitivity to efficiency and economic parameters were analyzed. The overall plant efficiency is the single most important factor in determining the cost of the fuel.
The anticipated increase in rendezvous and docking activities in the various space programs in the Space Station era necessitates a renewed interest in manual docking procedures. Ten test subjects participated in computer simulated docking missions in which the influence of initial velocity was examined. All missions started from a resting position of 304.8 meters (1000 feet) along the space station's +V-bar axis. Test subjects controlled their vehicle with a translational hand controller and digital auto pilot which are both virtually identical to their space shuttle counterparts. While the 0.1 percent rule (range rate is equal to 0.1 percent of the range) used by space shuttle pilots is comfortably safe, it is revealed to be extremely inefficient in terms of time and not justifiable in terms of marginal safety. Time is worth money, not only because of training and launch costs, but because the sooner a pilot and spacecraft return from a mission, the sooner they can begin the next one. Inexperienced test subjects reduced the costs of simulated docking by close to a factor of 2 and achieved safe dockings in less than 4 percent of the time the baseline approach would entail. This reduction in time can be used to save lives in the event of an accident on orbit, and can tremendously reduce docking costs if fuel is produced from waste water on orbit.
A comparison between the Phase Doppler Particle Analyzer and the combined measurements from Particle Measuring Systems' Forward Scattering Spectrometer Probe and the Optical Array Probe was conducted in an icing wind tunnel using NASA Icing Research Tunnel spray nozzles to produce the supercooled water droplet cloud. Clouds having a range of volume median diameters from 10 to greater than 50 microns were used for the instrument comparisons. A volume median diameter was calculated from combining the droplet distributions of the Optical Array Probe and the Forward Scattering Spectrometer Probe. A comparison of the combined volume median diameters and the Phase Doppler Particle Analyzer volume median diameters showed agreement from 10 microns up to 30 microns. Typical drop size distributions from the Phase Doppler Particle Analyzer, the Forward Scattering Spectrometer Probe, and Optical Array Probe are presented for several median volume diameters. A comparison of the distributions illustrates regions of the distributions where there is good agreement and other regions where there are discrepancies between the Phase Doppler Particle Analyzer and the Particle Measuring Systems' droplet size instruments.
A concept is developed for interrelated optimizations in space missions that utilize extraterrestrial resources. It is shown that isolated (component) optimizations may not result in the best mission. It is shown that substantial benefits can be had through less than the best propellants, propellant combinations, propulsion hardware, and actually, some waste in the traditional sense. One ready example is the possibility of discarding hydrogen produced extraterrestrially by water splitting and using only the oxygen to burn storable fuels. The gains in refrigeration and leak-proof equipment mass (elimination) outweigh the loss in specific impulse. After a brief discussion of this concept, the synthesis of the four major components of any future space mission is developed. The four components are: orbital mechanics of the transportation; performance of the rocket motor; support systems that include power; thermal and process controls, and instruments; and in situ resource utilization plant equipment. This paper's main aim is to develop the concept of a figure-of-merit for the mission. The Mars Sample Return Mission is used to illustrate the new concept. At this time, a popular spreadsheet is used to quantitatively indicate the interdependent nature of the mission optimization. Future prospects are outlined that promise great economy through extraterrestrial resource utilization and a technique for quickly evaluating the same.
The environmental fatigue crack propagation behavior of advanced Al-Li-Cu based alloys and metal matrix composites is being characterized. Aqueous NaCl and water vapor, which produce atomic hydrogen by reactions on clean crack surfaces, are emphasized. The effects of environment sensitive crack closure, stress ratio, and precipitate microstructure are assessed. Mechanistic models are sought for intrinsic crack tip damage processes to enable predictions of cracking behavior outside of the data, metallurgical improvements in material cracking resistance, and insight on hydrogen compatibility.
The difference between the temperature of the ocean at 4-cm and 2-m depth was continuously monitored during a cruise to the coastal transition zone off Point Arena, California, during June 1987. The two temperatures were coincident most of the time but diverged during one nearshore leg of the cruise where large temperature differences of up to 4.7 C were observed between the 4-cm and 2-m sensors, in areas which were separated by regions where the two temperatures were coincident as usual. The spatial scale of this 'patchy' thermal structure was about 5-10 km. A mixed layer model (Garwood, 1977) was used to simulate the near surface stratification when forced by the observed wind stress, surface heating, and optical clarity of the water. The model produced a thin strongly stratified surface layer at stations where exceptionally high turbidity was observed but did not produce such features otherwise. This simple model could not explain the horizontal patchiness in the thermal structure, which was likely due to patchiness in the near-surface chlorophyll distributions or to submesoscale variability of the surface wind stress.
A model is presented of thermal emission from a canopy/soil surface, where the soil and the leaves are at different temperatures, Tg and Tc, respectively. The temperature Tm corresponding to a radiometer reading is given by B sub lambda(Tm) = chi-B sub lambda(Tg) + (1-chi)B sub lambda(Tc), where B sub lambda denotes the Planck blackbody function at wavelength lambda, chi specifies the fraction of the field of view occupied by the soil at a given view direction, and an emissivity of 1.0 is assumed for the plants and the soil. It is observed that at large view zenith angles, only the plants are effectively seen, and therefore Tc can be determined from the observations a large zenith angles, to the extent that such observations are practical. Water stress can produce an increase of chi and thus tends to produce an exaggerated increase in the observed temperature compared to the actual increase in canopy temperature. These effects are analyzed for a simulated soybean canopy.