HIGH VOLTAGE SYSTEMS (TUBE-TYPE MICROWAVE)/LOW VOLTAGE SYSTEM (SOLID-STATE MICROWAVE) POWER DISTRIBUTION A.A. Nussberger, Rockwell International anc| G.R. Woodcock, Boeing Aerospace Co. 12214 Lakewood Blvd, Downey, CA 90241 P.O. Box 39999, Seattle, WA 98124 This paper describes SPS satellite power distribution systems, combining the study activities of Rockwell under contract to NASA MSFC (NAS8-32475), and Boeing Aerospace Company under contract to NASA JSC (NAS9-15636). The reference satellite power system (SPS) concept (Figure 1) utilizes high-voltage klystrons (~40 kV) to convert the on-board satellite power from de to RF for transmission to the ground receiving station J The solar array generates this required high voltage and the power is delivered to the klystrons through a power distribution subsystem as represented in the simplified block diagram of Figure 2. An array switching of solar cell submodules is used to maintain bus voltage regulation. Individual klystron de voltage conversion is performed by centralized converters. The on-board data processing system performs the necessary switching of submodules to maintain voltage regulation. Electrical power output from the solar panels is fed via switch gears into feeder buses and then into main distribution buses to the antenna. Power also is distributed to batteries so that critical functions can be provided through solar eclipses. Major requirements include the klystron requirement for five basic voltages (40, 32, 23, 12, and 8 kV)—klystron body voltage (40 kV), mod anode voltage (20 kV), and low voltages for cathode heater (20 V), solenoid operation (20 V), computer (20 V) and retro-electronic (20 V)-are required in the Rockwell concept to operate 135,864 klystrons. These voltages at the required power level are provided by centralized dc/dc converters. The Rockwell point design provides 32 converters, each sized for 290 megawatts (7.19 kVA). The Boeing power distribution concept^ is similar in that conditioned power is provided for all microwave power transmission elements. The five depressed collector klystron requires conditioned power on all inputs except the two collectors which utilize power directly from the solar panel supplies (Figure 3). A section of a Boeing subarray called the integrated klystron module is shown in Figure 4. It shows the klystron mounted on the back of the slotted waveguide antenna array. The passive cooling system can be seen. Also illustrated here is the phase control system installation on the subarray, required to insure that the radiation from the modules will be in phase at the rectenna. This system will tie modules within a subarray together with waveguide and all the subarrays together with coaxial cable or an equivalent transmission link. The satellite system end-to-end efficiency chain is continuously being updated to reflect the latest values. Efficiency values used in the current studies are compared to values used in the NASA/DOE reference design for both gallium arsenide (GaAs) and silicon (Table 1),3 A major study goal has been to devise satellite approaches that use low-voltage solid-state devices for conversion from de to RF on the satellite. The desire to replace the klystrons with solid-state devices is driven by their potential for highly improved satellite reliability; klystrons probably would have to be replaced at least two and perhaps three times during the 30 year operational period. Solid-state microwave design drivers are identified as maximum breakdown voltage limits (10 to 70Vdc), junction temperatures «200°C), output power limits (<100 W), and circuit efficiencies (78% to 90%). Two basic approaches to using solid-state dc-RF converters have been evaluated: (1) power modules integrated on the solar array (sandwich concept), and (2) antenna-mounted power modules (solid-state power modules replace klystrons). A reference solid-state concept used for comparison purposes is shown in Figure 5. A two-reflector system is used to reflect sunlight onto the back of an antenna which contains GaAs solar cells integrated with the solid-state RF amplifiers in the sandwich configuration. Power is delivered directly from the solar cells at +10 volts and -4 volts to tne power amplifier. A detailed cross-section of a Rockwell sandwich antenna dipole concept is shown in Figure 6. The solar cell configuration consists of 3 rows of 18 series connected GaAs solar cells to ^Satellite Power System Concept Definition Study. Rockwell International, SSD79-0010-2-1 (March 1979). ^Solar Power Satellite System Definition Study. Boeing Aerospace Company, D180-25037 (April 1979). ^Concept Development and Evaluation Program. U.S. Department of Energy and NASA Reference System Report (October 1978).
RkJQdWJsaXNoZXIy MTU5NjU0Mg==