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Life support systems for current manned missions consume material at a higher rate, typically 21 lb/man-day, than can be tolerated for long-term missions of the future; thus development of closed life support systems is underway. It appears desirable to utilize heat from thermal to electrical power systems in life support endothermic processes rather than electrical heating in order to reduce the total electrical power requirements. Consideration of waste water and urine treatment, and recovery of O 2 from CO 2 processes shows it is feasible to provide approximately 50% of the life support power requirement with heat from solar, isotope, and reactor dynamic power systems. For early capability manned orbiting systems, the life support power requirements are typically 50% of the total power requirement, so that thermal integration reduces the electrical power load approximately 25%. This is a significant reduction in such critical items as collector and radiator area and isotope inventory. For later, larger stations and manned interplanetary vehicles the life support power requirements will be a small fraction of the total electrical power requirement and there will be less incentive for thermal integration.

A thermoelectric generator has been combined with thermal energy storage to produce electricity during simulated 90-min orbits with 55 min of sunlight and 35 min of darkness. The experimental model has demonstrated the thermodynamic feasibility of converting solar energy to electric power for space application. The generator produced constant power (± 7%) during simulated orbits in a space chamber and has also operated successfully utilizing natural solar energy. Projection of the feasibility model indicates that a generator with an output of 150 w coupled with a collector-concentrator of 8-ft dia can be built. This system can operate with 0.50 orientation error with a specific power of 2.14 w/lb. Very precise orientation would reduce the area of the collector by 17.5% and increase the specific power, excluding orientation equipment, to 2.3 w/lb. Analysis of the system shows that the thermal storage feature has a significant weight advantage over electrochemical energy storage. This feature also makes the system feasible from an operational standpoint since temperature excursions and warm-up period after solar darkness are eliminated.

The results of a study of auxiliary power generating systems for a large 24-man space laboratory for the post-1970 time period are presented. Solar dynamic, nuclear Snap 8, and solar cell-battery units vere investigated as possible auxiliary power systems capable of generating 18 to 40 kw of electrical power. Tradeoffs in weight, cost, reliability, solar area deployed and/or radiator area were performed for the various systems. The power required for subsystem operation and experimentation was established at 27 kw. On the basis of the tradeoffs and the 27 kw design load, the solar dynamic Brayton system was recommended for the laboratory.

Since the original use of solar cells for electrical power generation in space, the state of the art in solar-cell arrays has experienced some significant advances. The solar cell itself has been improved in many ways. These improvements have increased silicon solar-cell efficiencies from roughly 5% to 11% in space sunlight. Material improvements have been made in silicon which have enhanced the resistance of silicon solar cells to particle radiation. The methods used to connect cells into modules as a building block for constructing large arrays have been improved also. New methods in the soldering of cells into modules have decreased the degradation of the cells resulting from handling and soldering. In addition, the successful fabrication of cells into modules has made possible the matching of cells by modules rather than by single cells. The methods used to mount the modules to the supporting structure have been improved by using better techniques and bonding agents. With the above advances, sun-oriented arrays have been built which approach 10 w/ft2 and 10 w/lb when operated in near Earth space (with no particle radiation damage). With further research and development, the watts per square foot, watts per pound, radiation resistance, and cost of solar-cell arrays may he optimized further.

Both fuel cells and batteries are electrochemical energy conversion devices. However, there is very little similarity between these devices in practice. The fuel cell is the power generating component in a fuel cell power system. Other subsystems must provide the fuel cell subsystem with reactants at the proper thermodynamic conditions, remove the products of the reaction, and carry away the cell waste heat over a range of electrical power output and environmental temperature. This paper discusses the synthesis of these ancillary subsystems and their mutual interactions in typical aerospace fuel cell powerplants.

This paper examines the mission and vehicle requirements of a space station logistics spacecraft, which influence the selection and integration of a power-generation system. A 12-man, lifting-re-entry, horizontal-landing-type logistics spacecraft is arbitrarily selected for analysis, since it imposes unique constraints on the power system. This spacecraft would have the capability of transporting cargo and personnel to and from a manned, earth-orbiting space station. A load analysis is made of all subsystems requiring electrical power to determine mission power and energy requirements and a mission power profile. The average mission power level is approximately 2 kw and the maximum total energy requirement is 101.7 kw-hr. The mission duration selected for analysis includes 24 hr for ascent, 24 hr for descent, and a 1-day postlanding period. The ascent and descent phases are separated by up to a 6-month orbital storage period. This mission represents the maximum demand from the power system since ideally it can be accomplished in considerably less time. Chemicals and possibly radioisotopes appear to be the most feasible energy sources for this mission. A variety of fluids including both monopropellants and storable hypergolic bipropellant combinations are considered. Polonium-210 and plutonium-238 are the most probable isotopes that could be utilized.

Current plans for high power level space power systems are based on the use of high-temperature, liquid-metal cooled reactors coupled to a Rankine cycle power conversion system. An alternate approach is the thermionic radiator concept in which similar reactors are used to supply thermal energy to the cathodes of radiator mounted thermionic converters* The thermionic radiator system could be a backup to dynamic conversions systems if the liquid metal cooled reactors under development are designed to satisfy the requirements of both systems* The thermionic radiator system should be considered also as the prime conversion system* Aerojet-General Nucleonics is engaged in a program to determine the feasibility of a thermionic radiator system* The primary objective of the first phase was to demonstrate the operation of a thermionic converter, using a liquid metal to supply thermal energy to the cathode. In addition, some limited systems analysis was performed. The first phase just recently has been completed, and the objectives fully were attained. Thermionic Radiator System System Considerations The nuclear thermionic space power plant will be a completely self-contained system producing electrical power in space. A high-temperature, liquid-metal cooled reactor will supply thermal energy to the radiator system* The thermionic Presented at the ARS Space Power Systems Conference, Santa Monica, Calif*, September 25-28, 1962. The work described in this paper was sponsored by the Aeronautical Systems Division, Air Research and Development Command, U. S. Air Force. *Senior Nuclear Engineer, Space Power Projects Department. 535 Purchased from American Institute of Aeronautics and Astronautics

The A discusses the possibility of obtaining mechanical and electrical power, as well as artificial cold, by expanding natural gas in a turbine prior to its further use. The process is intended to replace the usual throttling-pressure-reduction method. The paper contains: theoretical development, possible applications and figures for power and cold production, as well as an analysis of the factors on which these processes depend, i. e. initial gas temperature, ratio between initial and final pressures, and the nature of the expansion cycle. The possibility of obtaining very low temperatures by means of a multi-stage expansion plant is also mentioned.