22 • Hardware lifetime extended from 10 to 15 years • Instead of the LEO-refueling deployment scenario, ConOps uses EP for orbital transfer, adding 17.2% more mass and cost to SBSP system hardware Under these conditions, total system costs decrease by 95% and 93% for RD1 and RD2, respectively. GHG emissions decrease by nearly 86% and 89% for RD1 and RD2, respectively. These conditions would make SBSP systems highly competitive with any assessed terrestrial renewable electricity production technology’s 2050 cost projections and 2021 emissions intensity. The effects of these changes to first-order cost and emissions estimates are shown in Table 3. Table 3. Baseline versus Combined Sensitivities LCOE and GHG Emissions Sensitivity LCOE ($/kWh) GHG Emissions Intensity (gCO2eq./kWh) Baseline RD1 0.61 26.58 RD2 1.59 40.38 Combined Sensitivities RD1 0.04 3.87 RD2 0.08 4.33 4.4 Making SBSP Systems Competitive with Terrestrial Renewables As seen in Figure 11, under the baseline assumptions neither SBSP system is cost competitive with other renewables. The costs of launch for in-space assembly significantly affect the LCOE of these systems, putting them far beyond the costs of terrestrial solutions. SBSB still would not be costcompetitive with alternative renewables even if access to space were free, assuming all else remains constant. A cost-competitive SBSP solution does emerge, however, if launch costs drop to $50M/launch, solar cells achieve 50% efficiency, costs for a commercial servicer decrease to $100M, learning curves improve by 5%, hardware lasts 15 years, and EP is used for the orbital transfer of payloads to GEO. Below, we briefly discuss the likelihood of these sensitivities: • Launch cost: Launch costs per kilogram have decreased 36% over the last 10 years. If that continues, they could reach ~$60M per 100 MT (the assumed Starship payload capacity) in 2040. Note this cost is still 30 times greater than SpaceX’s desired launch cost of $2M per Starship launch. • Solar cell efficiency: According to NASA’s assessment (NASA, 2022), the state of the practice of solar cell efficiency in space today is 33%, while the state of the art is 70% (based on theoretical limits of 6-junction solar cells in laboratories today). Similarly, while state of the practice solar cell efficiency on Earth today is about 20%, laboratory solar cells can reach efficiencies of 50% (Center for Sustainable Systems, 2022) (NREL, 2023). For comparison, the highest recorded solar cell efficiency in 2011 was 27.6% (Radiative efficiency of state-of-
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