12 Figure 7. Cost Calculations for SBSP Systems. Refer to Figure 6 for ConOps Phase activities. 2.2 GHG Emissions Intensity To estimate GHG emissions in carbon dioxide equivalents (CO2eq), we 1) used material decompositions of each reference design, and 2) provided a comparison to other renewable energy technologies, drawing from NREL emission data (National Renewable Energy Laboratory, 2023). We estimated the GHG emissions of each design in three steps: 1. Estimate the material composition of each design, in kilograms (kg) or square meters (m2) 2. Cite authoritative sources on the emissions intensity of delivering components and materials, in kgCO2eq per kg, m2, or thousands of dollars (kUSD). 3. Estimate the lifecycle emissions intensity using a hybrid mass and spend-based Economic Input Output-Life Cycle Analysis (EIO-LCA). EIO-LCA uses aggregate data on sectors of the U.S. economy to quantify the GHG emissions that can be attributed to specific sectors and activities. Our analysis uses the aggregated metrics provided by the International Aerospace Environmental Group (IAEG) (International Aerospace Environmental Group, 2023), including datasets from Carnegie Mellon University and the U.S. Department of Defense (DoD) on the GHG emissions intensity of activities measured in kilograms of carbon equivalents (kgCO2eq.) per kUSD, kg, or m2. This spend-based approach is used where material decomposition does not provide adequate coverage of post-processing and assembly work. It is important to remember that because the EIO-LCA model relies on aggregated economic transactions and their recorded GHG emissions, there is an assumed relationship between cost,
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