Advanced Power Sources for Space Missions (1989) / Chapter Skim
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5. Approaches Toward Achieving Advances in Critical Power Technologies
5. Approaches Toward Achieving Advances in Critical Power Technologies
Pages 68-85
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From page 68... ...
In this chapter, the following subjects are discussed: advancing thermal-management techniques, advancing power-conditioning components and technologies, and materials advances required for developing power component technologies. ADVANCING THERMAL-MANAG1:MENT TECHNOLOGIES The thermal-management problem is that all heat generated on a space platform must be (a)
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From page 69... ...
Although there is no assurance that any of these concepts will prove feasible, such approaches might produce significant reductions in radiator size and specific mass, and hence warrant exploratory
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From page 70... ...
These radiators are made even more massive by the imposed survivability requirements. Two other heat rejection options are discussed below which avoid using radiators but are mass-intensive, hence they become impractical as the duration of power usage increases beyond about 1,000 s.
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From page 71... ...
Conductor mass is generally traded off against electrical losses, device efficiency, conductor temperature rise, complexity of cooling, and the amount of coolant required. Normal Conductors Practical conductors at ambient temperatures generally consist of copper or aluminum or their alloys.
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From page 72... ...
The potential availability of liquid hydrogen as a conductor coolant can have a major effect on system operating temperatures. Conductors capable of operating with liquid hydrogen should be developed either separately or as part of the component development.
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From page 73... ...
The use of superconductors in power systems generally leads to high-efficiency, compact components and subsystems. High efficiencies of power generation, power transmission, and power conditioning have direct beneficial effects on the ratings and masses of prime power sources and, in addition, a low-Ioss RF cavity reduces mass requirements for the entire system.
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From page 74... ...
Superconducting Magnetic Energy Storage Storage of energy in a magnetic field occurs when electricity flows through one or more coils. Since any electrical resistance in the circuit causes energy loss, the use of superconducting coils" which have no DC resistance is a very efficient approach to storing electrical energy for any length of time.
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From page 75... ...
The largest gas turbines generate 100 to 200 MWe per module, and specialized gas turbines operating on stored compressed air produce up to 290 MWe from a single machine (Gas Turbine World, 1987~. About 20 separate models of gas turbine power plaints currently marketed have power ratings exceeding 100 MWe.
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From page 76... ...
Advancement Potential for Alternator Technology Alternators are electrical rotating machines that convert shaft energy into AC electrical power that can then be used as generated or transformed and/or rectified as required by the load. A field winding—usually DC-energized is rotated, with the power being generated in the stationary armature.
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From page 77... ...
It also has an ambient-temperature aluminum shield that reduces external time-varying magnetic fields, which is an important design feature for space applications. Because of its Tower speeds and high-voTtage winding, the 0.045 kg/kWe machine is not directly comparable to the 3-MWe army machine.
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From page 78... ...
An alternator configuration for use in space- because of its interface with power conditioning/Ioad, thermal management, the prime mover/energy source, and the torques, magnetic fields, high voTtages, and currents it generates must be the result of a thorough, interactive systems approach. The basic advantages of the alternator in being able to generate high voltages without transformers must be traded off against the loss of flexibility in initially developing a general purpose alternator that must then be connected to a power system with transformers to provide load-specific voltage levels.
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From page 79... ...
high-temperature materials for nuclear reactors and power generation high-temperature radiators; advanced, high-temperature instrumentation and reactor control; tw~phase flow evaporation and condensation in reduced gravitational fields; electrical and thermal insulators; Tow-mass electrical conductors, including superconductors; thermal conductors; ferromagnetic and magnetic materials; survivable devices for switching, power conditioning, and generation; techniques for managing/containing high voltages, currents, and electrical and magnetic fields; and improvements In inverters, which are not presently being developed for weapons power. The comrn~ttee recognizes a clear need to make progress in materials for increasing the efficiency and compactness of power components.
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From page 81... ...
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From page 82... ...
In view of the major successes achieved in applying basic science to materials programs in high-energy-density capacitors, similar approaches should be applied to other areas of power development. This committee recommends a development strategy of this nature, pursued aggressively and funded adequately, to develop scalable power technology, particularly if success would enable selection of one weapon system over a less desirable one by removing power considerations as the principal constraint.
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From page 83... ...
Apparently Metglas~R has not yet approached the potential desirable properties achievable in magnetic materials by applying rapid quenching techniques to create new alloys. During the past year, General Electric- using ADied Signal Company MetglassR compositions built and tested a large number of commercial AC power transformers that exhibited the outstanding performance previously predicted.
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From page 84... ...
This is because only limited data are available on long-term performance in highly cyclical temperature and stress systems. A few such systems are making excellent progress, but results for these applications are emerging slowly, hence careful development of these materials for meeting specific needs wiD continue to be required.
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From page 85... ...
The development of adequate power supplies may well pace the entire SDI program. Recommendation 5: Male additional and effective investments now in technology and demonstrations leading to advanced components, including but not limited to: thermal management, including radiators; materials structural, theImal, environmental, and superconducting; electrical generation, conditioning, twitting, transmission, and storage; and long-term cryostorage of H2 and O2.
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