Scope and limits

The favourable combination requires improvements "beyond the advances already assumed in the baseline assessment" in several inputs at once. Table 1 (PDF p.7, printed p.vi) changes six against the baseline: launch cost $500/kg ($425/kg with a 15% block-buy discount) against $1,000/kg ($850/kg); electric propulsion for the transfer to geostationary orbit (adding 17.2% to mass and manufacturing cost) against 12 refuelling launches; solar cell efficiency 50% against 35%; hardware lifetime 15 against 10 years; servicer and debris-removal vehicles at $100M and $50M against $1B and $500M, with the module unchanged at $1M; and learning curves of 70%, 80% and 85% against 75%, 85% and 90%. The report's written lists of the combination do not agree with each other: section 4.3 (PDF p.38 to 39, printed p.21 to 22) names the same six as Table 1, the summary list (PDF p.10, printed p.ix) names five and leaves out solar cell efficiency, and the appendix list (PDF p.92, printed p.75) names five and leaves out hardware lifetime. Table 1 and Table 3 (PDF p.39, printed p.22) print the combined result as 0.04 and 0.08 $/kWh, where the summary text (PDF p.9) and Table 26 (PDF p.94, printed p.77) give 0.03 and 0.08. The study does not assess the probability of that combination, and a sensitivity analysis showing what WOULD achieve competitiveness is not a forecast that it will be achieved.