Electrical power systems for space - Achievements and issues
Electrical power systems for spacecraft, reviewing solar cells, batteries, fuel cells and radioisotope thermoelectric generators
Miller, P. R.↗
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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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Pioneer-class mission capabilities
Pioneer Jupiter spacecraft, noting low weight, radioisotope thermoelectric generators and gyroscopic stabilization by spinning with antenna pointed at earth
Jackson, R. W.↗
Review of long life performance of lead telluride and silicon germanium RTG technologies
Long life performance predictions for lead telluride and silicon germanium radioisotope thermoelectric generators for deep space missions
Caputo, R. S.↗
Nuclear radiation sources on board outerplanet spacecraft
Nuclear characteristics of plutonium fuel for thermoelectric generators and required shield thicknesses for sensitive radiation experiment in outer planet spacecraft
Anno, G. H.↗
Reentry thermal protection from Pioneer F RTG insulation material
Ablation tests were performed on the insulation material used in the Pioneer F radioisotope thermoelectric generator (RTG) in the Ames Arc-Heated Planetary-Gas Wind Tunnel. Test results indicate that the material, trade name Min-K 1301, should experience little ablation for heat transfer rates below 40 BTU/sq ft-sec. If the current design were to be changed so that the various pieces of Min-K were fastened or interlocked together the total amount of heat delivered to the RTG heat source during an earth orbital decay reentry would be reduced by at least 22.7%.
Vorreiter, J. W.↗
Design considerations for combined radiation effects facilities for twelve year outer planet spacecraft voyages
The design considerations influencing the choice and utility of environmental simulation methods and facilities are described, insofar as they relate to the requirements imposed on outer planet spacecraft because of radiation environments to be expected. Possible means for duplicating the radioisotope thermoelectric generator radiation environment, and for duplicating the effects of the trapped radiation belt environment are described, together with an assessment of radiation levels to be expected in the vicinity of an environmental testing chamber when in use.
Miller, C. G.↗
The program at JPL to investigate the nuclear interaction of RTG's with scientific instruments on deep space probes
A major concern in the integration of a radioisotope thermoelectric generator (RTG) with a spacecraft designed to explore the outer planets is the effect of the emitted radiation on the normal operation of scientific instruments. The necessary techniques and tools developed to allow accurate calculation of the neutron and gamma spectrum emanating from the RTG. The specific sources of radiation were identified and quantified. Monte Carlo techniques are then employed to perform the nuclear transport calculations. The results of these studies are presented. An extensive experimental program was initiated to measure the response of a number of scientific components to the nuclear radiation.
Truscello, V.↗
Spacecraft Radiation Analysis
The radiation interface in spacecrafts using radioisotope thermoelectric generators is studied. A Monte Carlo analysis of the radiation field that includes scattered radiation effects, produced neutron and gamma photon isoflux contours as functions of distance from the RTG center line. It is shown that the photon flux is significantly depressed in the RTG axial direction because of selfshielding. Total flux values are determined by converting the uncollided flux values into an equivalent RTG surface source and then performing a Monte Carlo analysis for each specific dose point. Energy distributions of the particle spectra completely define the radiation interface for a spacecraft model.
Harris, D. W.↗
The effects of radiation on the outer planets grand tour
A handbook is presented which was designed to accompany an oral presentation on the effects of radiation on the outer planets grand tour (OPGT). A summary of OPGT radiation environments expected from natural sources and the radioisotope thermoelectric generators and basic radiation effects and processes are reviewed, and ionization and displacement effects are examined. The presentation summarizes the effects of radiation on miscellaneous spacecraft materials and devices. The annealing and hardening of electronics are described. Special emphasis is placed on microcircuits. Mathematical modeling of circuits affected by radiation and radiation environmental testing are discussed. A review of means of evaluating the performance and correcting failures of irradiated devices is also presented.
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Previous design restraints and radiation damage effects of low energy particles
Spacecraft design fluences and damage by low energy electrons and protons are summarized. For electron energies 5 MeV, the design fluence is 10 to the 11th power electrons/sq cm; for energies 5 MeV, the integral spectrum is assumed to go as 1/E sq. The design fluences for proton energies 30 MeV is 1.5 x 10 to the 9th power protons/sq cm; for energies 100 MeV, it is 5 x 10 to the 14th power protons/sq cm. The radioisotope thermoelectric generator gamma and neutron radiation constraints are listed. Damage due to electron energies 0.5 MeV and proton energies 10 MeV are summarized for effects on spacecraft thermal surfaces, reflective surfaces, and refractive materials. The high frequency noise figure for field effect transistors may increase markedly, and another effect is the buildup of charge on insulating surfaces, resulting in large electric fields.
Trainor, J. H.↗
The electrical power subsystem of the Pioneer F/G spacecraft.
The Pioneer F/G spacecraft is the first to use radioisotope thermoelectric generators (RTG's) for a long duration interplanetary mission. This paper describes the design of the spacecraft power subsystem which meets the unique requirements of such a mission. The primary power source consists of four SNAP 19 RTG's. The 4.2 volt dc outputs of the RTG's are inverted to higher voltage ac by four inverters which are connected in parallel at their outputs. A power control unit (PCU) regulates the ac output of the inverters such that the RTG's are operated at near maximum power voltage throughout the mission. The PCU also contains charge and discharge controls for a silver cadmium battery which supplements the RTG's if load requirements temporarily exceed RTG power output. Battery reliability is enhanced by overcharge and cell reversal protection electronics which are provided for each cell. Multiple, low voltage, regulated dc outputs which supply power to the spacecraft subsystems are provided by a central transformer-rectifier-filter unit (CTRF). The CTRF operates directly from the regulated ac bus.
Reppucci, G. M.↗
Nuclear radiation interference and damage effects in charged particle experiments for extended space missions.
Demonstration that meaningful galactic and solar cosmic radiation measurements can be carried out on deep space missions. The radioisotopic thermoelectric generators (RTGs) which must be used as a source of power and perhaps of heat are a problem, but with proper separation from the experiments, with orientation, and with some shielding the damage effects can be reduced to an acceptable level. The Pioneer spacecraft are crucial in that they are targeted at the heart of Jupiter's radiation belts, and should supply the details of those belts. The subsequent Grand Tour opportunities can be selected for those periods which result in larger distances of closest approach to Jupiter if necessary.
Trainor, J. H.↗
An evaluation of some special techniques for nuclear waste disposal in space
A preliminary examination is reported of several special ways for space disposal of nuclear waste material which utilize the radioactive heat in the waste to assist in the propulsion for deep space trajectories. These include use of the wastes in a thermoelectric generator (RTG) which operates an electric propulsion device and a radioisotope - thermal thruster which uses hydrogen or ammonia as the propellant. These propulsive devices are compared to the space tug and the space tug/solar electric propulsion combination for disposal of waste on a solar system escape trajectory. Such comparisons indicate that the waste-RTG approach has considerable potential provided the combined specific mass of the waste container - RTG system does not exceed approximately 150 kg/kw sub e. Several exploratory numerical calculations have been made for high earth orbit and Earth escape destinations.
Mackay, J. S.↗
Standardization and economics of nuclear spacecraft: Executive summary
Feasibility and cost benefits of nuclear-powered standardized spacecraft were investigated. The study indicates that two shuttle-launched nuclear-powered spacecraft should be able to serve the majority of unmanned NASA missions anticipated for the 1980's. The standard spacecraft include structure, thermal control, power, attitude control, some propulsion capability and tracking, telemetry, and command subsystems. One spacecraft design, powered by the radioisotope thermoelectric generator, can serve missions requiring up to 450 watts. The other spacecraft design, powered by similar nuclear heat sources in a Brayton-cycle generator, can serve missions requiring up to 2200 watts. Design concepts and trade-offs are discussed. The conceptual designs selected are presented and successfully tested against a variety of missions. The thermal design is such that both spacecraft are capable of operating in any earth orbit and any orientation without modification.
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Design point characteristics of a 500 - 2500 watt isotope-Brayton power system.
An analytical study was conducted to investigate the potential performance characteristics of an isotope-Brayton space power system at electric power levels from 500 to 2500 W. Utilization of the Pu 238 heat source, or capsule, being developed for the Multi-Hundred Watt Radioisotope Thermoelectric Generator was assumed. A single-loop system design concept was selected. The design concept and results of first-order tradeoff studies of the effects of major system parameters on system performance are presented. Results of the study indicate the potential for high system efficiency and high specific power over the entire power range.
Barna, G. J.↗
Silicon-germanium technology program of the Jet Propulsion Laboratory.
The outer planetary exploration missions studied by the Jet Propulsion Laboratory require silicon-germanium radioisotope thermoelectric generators (RTGs) in which the factors of safety are as low as is compatible with the reliable satisfaction of the power needs. Work on silicon germanium sublimation performed at the Jet Propulsion Laboratory is presented. Analytical modeling work on the solid-diffusion process involved in the steady-state (free) sublimation of silicon germanium is described. Analytical predictions are made of the sublimation suppression which can be achieved by using a cover gas. A series of accelerated (high-temperature) tests which were performed on simulated hardware (using four SiGe couples) to study long-term sublimation and reaction mechanisms are also discussed.
De Winter, F.↗
Isotope Brayton electric power system for the 500 to 2500 watt range.
An extensive study was conducted at the Lewis Research Center to evaluate an isotope Brayton electric power system for use in the 500 to 2500 W power range. The study emphasized overall system simplicity in order to reduce parasitic power losses and improve system reliability. The study included detailed parametric cycle analysis, conceptual component designs, and evaluation of system packaging. The study has resulted in the selection of a single-loop system (gas) with six major components including one rotating unit. Calculated net system efficiency varies from 23 to 28% over the power range. The use of the Pu-238 heat source being developed for the Multi-Hundred-Watt Radioisotope Thermoelectric Generator program was assumed.
Macosko, R. P.↗
The evolution of power systems for unmanned interplanetary spacecraft in the 70's.
The power subsystems planned for missions in the 70s have relied heavily on earlier hardware technology and represent an extension of technology conceived in the 60s. Solar panels and primary rechargeable silver-zinc batteries were used throughout the series as power sources. However, because of the increase in battery discharge-charge cycles required, subsequent spacecraft beginning with the Mariner Mars 1971 will use nickel-cadmium batteries. Spacecraft missions to Mars and Venus will continue to use the solar panel and the battery as primary and secondary power sources. The use of the radioisotope thermoelectric generator as the primary power source appears mandatory for missions to the outer planets.
Swerdling, M.↗