3. Candidate System Concepts and Architectures 3.1. Space Solar Power Architectures - Overview A total of six notional SSP concepts/architectures came out of the Phase I study effort, extracted from a broad and diverse set of new system concepts, architectures, applications and technologies considered by the study team. About 30 such new ideas were submited by participants at the first SSP Technical Interchange Meeting hosted by the Advanced Concepts Office of NASA/OSAT. Several more concepts were gathered in follow-up submissions by the Meeting participants and by study team attendance at the Wireless Power Transmission Conference in Kobe, Japan. After combining concepts with strong similarities, the total number of candidate concepts reached 37 and covered a broad spectrum of ideas ranging from full SSP architectures to very specific subsystem technologies. The study team carefully evaluated these candidates through a structured decision process, fully described in the Phase I study report, and selected the (1) Sun Tower, (2) SolarDisc, (3) LEO - MEO Relay, (4) LEO - GEO Relay, (5) GEO Millimeter Wave, and (6) Planetary Power Web concepts for further assessment in Phase IL The Phase I report provided summary descriptions of the six selected concepts, as well as most of the other candidates, in their early stage of definition. For reference purposes, these Phase I descriptions have been included as an Appendix to this Final Report. In Phase II, the selected concepts (except for Planetary Power Web) were given added definition and further refined with respect to their architectural elements in order to proceed with the more detailed evaluations required. These refinements led to the addition of two new augmentations to concepts in the Phase II study - the MEO Sun Tower and the ReflectArray - that seemed to offer potential performance benefits for the Sun Tower and the two relay architectures respectively. Also, several other concept elements were modified in response to new ideas from the study members and inputs from concept reviewers at the Phase II Technical Interchange Meeting hosted by the Advanced Space Analysis Office at NASA/LeRC. These modifications include: • Re-design of the SolarDisc transmitting array to a dual system to counter regular periods of occultation/interference by the solar collector • Re-design of the Sun Tower configuration for non sun-synchronous, inclined orbits, which requires enhanced guidance and control to maintain continuous roll operation at one rotation per orbit and continuous sun-tracking by the individual solar collectors • Recommendation to minimize drag and debris damage of LEO Sim Tower relay transmitters by constraining their transmitting arrays to a fixed, non-rotating alignment in the orbital plane (with transmitting axis normal to the plane) and using electronic beam-steering as the sole means of directing power to the relay satellites. • Replacement of dual frequency relay satellites, with high frequency uplinks and lower frequency downlinks, with single frequency ReflectArray systems to achieve higher system efficiency and potentially lower cost. • Suggested employment of a combined High-Temperature Super Conductive (HTSC) power transmission line in a Hoytether configuration to provide low transmission losses and reduced susceptibility to both structural and electrical damage or failure.
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