ReflectArrays are basically RF power reflecting relays that are capable of focusing and re-directing an incoming power beam to a preferred outgoing or “reflected” direction. These devices can be designed to operate in three different modes: (1) no power gain, (2) limited gain, and (3) frequency shifted. The MEO relays are assumed to be of the first type, acting for the most part like a passive, but smart RF reflector. As described by Dick Dickinson3 who also provided Figure 3-7, the modules of the arrays are phased by receiving the information about the illumination geometry and the commanded reflected beam geometry from an array of light emitting diodes or a small laser with spread beam located in front of the array of modules on a descended fiber optic tether. The beam steering information is space fed to the individual modules where it is received by a photodiode on each antenna patch. Each module takes the beam position data and computes its own relative phase shift based upon the geometry, adds a correction factor for any calibration deduced construction placement errors, thermal warpage, gravity tides, and fabrication tolerance and environmental induced instrumental circuit phase shifts, and applies the result to the selection of the diode line switches. The diode line switches route the RF generally through binary related line lengths (180, 90,45, 22.5, 11,25 degrees, etc.) to implement the desired phase shifts. The auxiliary DC power needed to operate the ReflectArray’s beam steering computer and the diode switch bias lines have to be obtained from a rectified portion of the module RF power coupled off the antenna radiator. In-Space Infrastructure Relay satellite elements are initially deployed in LEO via multiple ETO launches. These modular elements are assembled with automated support systems and integrated with the orbital transportation vehicle that will deliver the relay satellite payload to MEO. The assumption that this assembly and deployment process can be implemented without any unique in-space infrastructure needs to be validated by design analysis. LEO-MEO Relay: Ground Segment The nominal ground receiver in this system consists of a dipole antenna type arranged in planar rectenna rows having an overall dimension of about 2 km diameter. Land-based receiver stations would be typical, although an off-shore location may be appropriate in some cases. The rectenna design may optionally be integrated with terrestrial PV systems as a dual-use, complementary power source. Because of the intermittent nature of power transmission from both the Sim Towers and the relay satellites, an energy storage system at the receiver site would be required, particularly in the early phases of system deployment. Electrical (battery) storage may be selected nominally for this function, but flywheel, fuel cell, and pressure storage techniques should be investigated as design tradeoffs. Markets and Commercial Power Utility Interface The relay satellites augment the basic Sun Tower concept to supply electrical energy markets on a global scale. With power transmission up to 100 MW, mega-towns, towns, and remote sites can be served for intermittent through baseload power demands The specific interfaces with power utilities, including direct-to-grid distribution, can be implemented in evolutionary steps as the number of Sun Towers, relays, and ground receivers grow to global constellation size. Annual revenues earned during this buildup can be used to finance additional system elements and support maintenance operations. The flexibility offered 3 Richard M. Dickinson, “RF Power Reflecting Arrays”, Personal Communication to SSP Study Team, May 7, 1996.
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