Start Date
4-1968 8:00 AM
Description
Thermionic generators using radioisotopes as primary sources of energy are being considered for application to future space missions. The reliability of a matrix of a large number of thermionic converters has been studied by J. R. Long of the Lawrence Radiation Laboratory and found satisfactory.
In this paper, an optimization of the generator system is carried out for a thermionic generator with a power output of 300 watts* Allowance is made for the efficiency of the dcdc power conditioners that are currently available. The system chosen for the study has from 9 to 15 individual thermionic energy converters. These are interconnected to form either a flat or a three-dimensional network, and their characteristics are linearized so that each converter can be represented either by a Thevenin f s or a Norton's equivalent circuit. The system efficiency is determined from its configuration, the efficiency of the power conditioner, and from the efficiencies of the individual converters, which depend on their output power.
Degradation in the performance of the system is calculated for abrupt open- or short-circuit failures of individual converters. Gradual degradation of converters, such as that occurring when emitter temperatures or cesium reservoir temperatures change, is also considered.
A generator system of 15 individual thermionic cesium diodes was selected for detailed studies of the degradation and reliability. The system is considered realizable with the existing technology in thermionic energy conversion. The system has an adequate reliability and can fulfill a mission successfully if it is designed with a contingency factort of approximately two.
Optimization of Thermionic Generator Systems of High Reliability
Thermionic generators using radioisotopes as primary sources of energy are being considered for application to future space missions. The reliability of a matrix of a large number of thermionic converters has been studied by J. R. Long of the Lawrence Radiation Laboratory and found satisfactory.
In this paper, an optimization of the generator system is carried out for a thermionic generator with a power output of 300 watts* Allowance is made for the efficiency of the dcdc power conditioners that are currently available. The system chosen for the study has from 9 to 15 individual thermionic energy converters. These are interconnected to form either a flat or a three-dimensional network, and their characteristics are linearized so that each converter can be represented either by a Thevenin f s or a Norton's equivalent circuit. The system efficiency is determined from its configuration, the efficiency of the power conditioner, and from the efficiencies of the individual converters, which depend on their output power.
Degradation in the performance of the system is calculated for abrupt open- or short-circuit failures of individual converters. Gradual degradation of converters, such as that occurring when emitter temperatures or cesium reservoir temperatures change, is also considered.
A generator system of 15 individual thermionic cesium diodes was selected for detailed studies of the degradation and reliability. The system is considered realizable with the existing technology in thermionic energy conversion. The system has an adequate reliability and can fulfill a mission successfully if it is designed with a contingency factort of approximately two.
Comments
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