14 The total GHG emissions for each system are: RD1, 14B kgCO2eq.; and RD2, 21B kgCO2eq. A breakdown of emissions by ConOps phase and cost elements is shown in Figure 10. As is the case with costs, Maintain, represents over half of each system’s GHG emissions, with Assemble accounting for one quarter of the total. Similarly, the largest emissions across the SBSP lifecycle are attributable to the thousands of launches required, again highlighting launch’s disproportionate impact on SBSP systems. Access to space comprises 64% and 72% of total emissions for RD1 and RD2, respectively. In descending order, Develop, Operate, and Dispose produce the most emissions after Maintain and Assemble. The largest contributors in these segments is large-scale manufacturing of SBSP spacecraft, servicers, and launch vehicles. The activity with the next largest emissions is associated with the ground support infrastructure and staff, including R&D and operations. Figure 11 depicts the LCOE and GHG emissions of the SBSP reference systems alongside other forms of renewable energy. The baseline costs, estimated using the assumptions described in the methodology overview, are significantly higher than those for current renewables, while GHG emissions are comparable. This remains true even when storage requirements to achieve a similar “power on demand” – also known as “baseload power” – for solar and wind are taken into account. Energy storage must be considered for solar and wind because they cannot deliver power consistently throughout the day or year. The LCOE for space-based systems is significantly higher as terrestrial systems do not face the high costs of launch and assembly in space, and this first-of-akind system’s costs include R&D.
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