39 These inputs were taken by NASAOTPS and validated with another model using 87 parameters (not including separate calculations for manufacturing learning curves, first order delta v, or assembly schedule). NASA OTPS applied specific decompositions of SBSP system functions and ConOps phases. The six functions are: collect, convert, transmit, receive, convert, and deliver. The five ConOps phases are: develop, assemble, operate, maintain, and dispose. NASA OTPS further modified, decomposed, and reorganized Aerospace data into these six functions and five phases, representing 87 parameters. The functions provided key inputs to electricity generation and delivery, while the phases provided key inputs to deriving the cost of SBSP systems. To assess the SBSP systems’ GHG emissions, NASA OTPS performed an Economic Input Output Life Cycle Assessment (EIO-LCA). This method is based on aggregate sector-level economic data. By adding environmental impact data to quantified direct and indirect economic inputs of purchases, environmental implications for select economic activity is derived. We use a mix of mass- and spend-based assessments, preferring mass wherever possible. The International Aerospace Environmental Group compiles EIO-LCA data from various sources (Carnegie Melon, DoD, and more). A key limitation of the EIO-LCA method is the assumed relationship between cost, efficiency, and GHG emissions; wherever possible, we used mass-based measures. Aerospace provided data and analysis, including rationales for their methodologies, to NASA OTPS. To address the two questions in this study, we (OTPS) leveraged the data provided by Aerospace and performed an analysis to independently validate ConOps elements (such as orbital transfer and assembly times) and cost outputs for each design reference system and to estimate the GHG emissions of developing and operating each system. We also gathered data from authoritative sources on other electricity production technologies for comparison with the two design reference systems, primarily from NREL. We conclude with sensitivity analyses to explore potential effects on SBSP system costs of modifying parameters which could reasonably vary. The following sections detail our approach to cost calculations, GHG emissions, and methods to support sensitivity analyses. See Table 5 for a summary of our approach to the calculations.
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