The commercialization of space will require power for everything from lights to climate control and especially for the industrial processes that are planned to take advantage of the zero-g environment. This power requirement can vary from a few kilowatts to several megewatts, depending on the particular commercial operation. This paper discusses the concepts that are available to supply this power, the different ways the power might be utilized, and some of the problems associated with development and utilization of the power source

Dearien, John A.

Martinell, John S.

English

Embry-Riddle Aeronautical University

The Space Congress® Proceedings 1988 (25th) Heritage - Dedication - Vision Apr 1st, 8:00 AM Multimegawatt Power Sources For Commercial Space Operations John A. Dearien Idaho National Engineering Laboratory John S. Martinell Idaho National Engineering Laboratory Follow this and additional works at: https://commons.erau.edu/space-congress-proceedings Scholarly Commons Citation Dearien, John A. and Martinell, John S., "Multimegawatt Power Sources For Commercial Space Operations" (1988). The Space Congress® Proceedings. 8. https://commons.erau.edu/space-congress-proceedings/proceedings-1988-25th/session-11/8 This Event is brought to you for free and open access by the Conferences at Scholarly Commons. It has been accepted for inclusion in The Space Congress® Proceedings by an authorized administrator of Scholarly Commons. For more information, please contact commons@erau.edu. Multimegawatt Power Sourcesfor Commercial Space OperationsDr. John A. Dearien and John S. Martinell Idaho National Engineering LaboratoryIntroductionThe commercialization of space will require power for everything from lights to climate control and especially for the industrial processes that are planned to take advantage of the zero-g environment. This power requirement can vary from a few kilowatts to several megewatts, depending on the particular commercial operation. This paper discusses the concepts that are available to supply this power, the different ways the power might be utilized, and some of the problems associated with development and utilization of the power source.Types of Power SourcesThere are only two types of power sources available for long term use in space - solar and nuclear. There are many variations in the systems which utilize these sources, but the ultimate source is either the sun or nuclear. For space applications, an important difference between these two sources is the energy density of the source and the manner in which this energy density affects the system. Solar energy is available, at orbital altitudes, at a flux of approximatly 200 BTU's/hr-sq. ft., whereas nuclear reactors can be constructed to generate energy at a rate of 500,000 BTU's/hr per cubic foot. Figures 1 and 2 are examples of space power sources over the rangeof100KWto5MW.Figure 3 shows the size relationship between solar and nuclear with respect to energy generation (without considering how this energy might be converted to power. This relationship does not consider the issue of what happens when the solar collector is in shadow. That effect will be discussed later.Utilization Of EnergyEfficient utilization of thermal energy in space must consider the process using the energy, a consideration not always of importance in terrestrial commercial operations.Generation of electricity in space can be very inefficient, due to lack of a good heat sink needed for most thermodynamic cycles and the use of thermal electric converters are generally in the 5% to 10% efficiency range. Direct use of the thermal energy, however, can potentially be very efficient since, theoretically, the entire energy output of the power source can be directed toward the process requiring the energy. This would lead us to think about commercial operations which involved high temperature melting or chemical processes requiring high temperatures. A melting operation through use of electrical heaters would be highly inefficient in space due to the inefficiencies associated with generating the electricity.11-2SP-100 NUCLEAR SUBSYSTEMASTRO-Spac* Division San , CAo o(D fi)3J (D D) OCQ 3REFLECTORDRIVE ACTUATORREACTOR VESSELREFLECTOR ELEMENTI ISIDOREDRIVEACTUATORCOKTWLSReactorFE2DC7UTIPAYLDASFEACTDRSystemFigure 2 5 MWe Nuclear Reactor11-4Figure 3 Area and Weights - Solar vs Nuclear100000i 13 «1000010001001010Solarn SNAP DerivativePLUTO100 1000 10000 100000 Thermal Power - KWFigure 4 System Power and Weight1II UUUUU -10000-:e i1000 -MMWe tSP-1006 B ————————— B tSNAP Derivative——————— H t10 100 1000 10000 System PowerQ Power Range e - Electricalt - Thermal10000011-5Direct use of thermal energy should be considered for operations such as gross melting of materials for the formation of special alloys, ore reduction in space or on extraterrestial surfaces, and climate control of habitation centers. Use of thermal energy in crystal formation would depend on the quantities processed since, although the temperature is high and only thermal energy is required, the amount of power required for the small masses involved may dictate going with an electrical conversion process and then using the electricity.Thus, the first consideration for a commercial power source in space is the amount and type, electrical or thermal, of energy required.Electrical Energy: Generation of electrical energy from a thermal source, solar or nuclear, can be through many different processes, with the most efficient process depending on the amount of power required. For space applications, one of the most important factors in a power source selection is the weight. Figure 4 shows different power sources and the weights of the systems.Considerations that must be given in selecting a system are, for solar, the weight of batteries or an energy storage device to supply power during the shadow portion of the orbit and the drag associated with a large solar collector. For a nuclear system, the radiation field around the reactor must be considered if the operation is going to be manned or the commercial operation in process is sensitive to radiation.Both solar and nuclear systems will have large radiators to dump the waste heat associated with thermodynamic cycle power generation. The location and orientation of these radiators with respect to the commercial operation and their survivability to space debris must be considered.Thermal Energy: Direct use of the thermal energy generated by a power source has the potential for being the most efficient utilization of energy in space. Solar collectors have the potential for concentrating sunlight and obtaining extremely high temperatures (5000+F) and nuclear reactors can sustain a temperature of 2000+F foryears.Solar power systems have the disadvantage with respect to nuclear of requiring back up power during the shadow portion of the orbit and a back up system, plus its recharging system can become very heavy and very complex. This would not be a problem if the process in operation could go through a "non-powered" time during the dark side of the orbit. Operations such as crystal growth could probably not take such a transient, but other operations involving gross melting of materials might stand such an on-off period.The second consideration for a power source in space is the duty cycle required for the source. If it can be intermittent, one type of system will be most efficient, it it must be continuous and tightly controlled, another system will be required.Process Power RequirementsIt requires 1000 BTU's to melt a pound of Silicon or 100 KW to melt 300 Ibs/hr. This is the electrical power output of the SP-100 reactor presently under development by DOE/NASA/DOD. With the efficiency of the SP-100 reactor being around 10%, the thermal power output of the reactor is approximatly 1 -1.2 Megawatts. If the thermal power of the reactor were to be utilized for the above melting process, one could process 3000 Ibs/hr or do the same process, 300 Ibs/hr, with a reactor of 1/10 th the power. In addition, all the weight (80% - 90% of total weight) associated with heat transport and power conversion could be eliminated.Table I gives some typical process energy requirements in electrical and thermal power. A system developed for a commercial operation in space will most likely be a hybrid system utilizing both electrical and thermal energy. Even if the commercial process consists totally of high power thermal energy usage, there will be a certain amount of electricity required for controls, mass transport, environmental control (if manned), and communications. The optimum system will thus require a great deal of planning and coordination with the development of the commercial process.11-6Table I Energy Requirements of Industrial Processes Process Thermal ElectricalMeltingSilicon AluminumDecompositionAluminum ore Iron ore (asteroids) Water11000BTU/lb 400 BTU/lbTemperature2600 F 1000F400 BTU/lbllmenite (for oxygen)2 17500 BTU/lb-mole Chemical Vapor DepositionCarbon filiments6.2 kw-hr/lb 0.3 kw-hr/lb2800 F 1300 F2450 FSummaryThere is a great deal of interest in commercial operation in space today, but very little consideration of where the power to run such an operation is to come from. This is not surprising, considering the way commercial ventures are planned and developed in the United States and other advanced societies. When you are ready for power, you call the local power company and ask them to "hook you up". It will not be this way in space for a long, long time. For any commercial operation in space, the power source, especially those involving kilowatts and megawatts of power, must be considered at the very onset of the venture.The Multimegawatt Space Reactor Program at the Idaho National Engineering Laboratory is working this problem in conjunction with the development of Strategic Defense Initative needs. The same type of up-front power development program needs to be considered in all discussions associated with commercial ^lopment in space.ReferencesIdaho National Engineering Laboratory and the University of Idaho, (1987), Lunar And Other Extraterrestrial Materials Processing Concept, Topical ReportSimon, Michael C., (1985), A Parametric Analysis of Lunar Oxygen Production, Lunar Bases and Space Activities of the 21st Century (W. W. Mendell, Ed.),pp. 531, Lunar and Planetary Institute, Houston, Tx.11-7

Multimegawatt Power Sources For Commercial Space Operations

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Multimegawatt Power Sources For Commercial Space Operations

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