Scope and limits

Authors Xinyang Che (King's College London; Xi'an Jiaotong University), Lijun Liu (Xi'an Jiaotong University), Wei He (King's College London, corresponding author), verified from the paper's own title page. This is an academic energy-systems-modelling paper, not an ESA or EU institutional publication, and it does not independently re-derive SBSP hardware costs. It should not be read as independent verification of NASA's or any other study's launch-cost or capex assumptions; it inherits them without checking them. READ AGAINST THE JOULE VERSION OF RECORD, 2026-10-10. The figures here are the same in the preprint and in Joule: Joule's Table 2 repeats the preprint's Table 1 SBSP rows and adds an FOM column, and Joule's Table 1 is the preprint's Table 2. The wording differs in three places: the preprint's "economically unattractive" for the planar design is "uneconomical" in Joule's Summary; Joule keeps the sentence giving 6.4-9.7 and 9.5-14.3 times solar (PDF p.4) and adds, in its Context & Scale, that system costs fall 7-15% if the heliostat design delivers at six to nine times the 2050 cost of ground PV (PDF p.2); and Joule cites the exchange rates to its reference 48, where the preprint cited 46. The published title is "...for European-scale..."; this claim carried "in". WHICH NASA CASE, AND THE BASIS OF THE MULTIPLES (our arithmetic, 2026-10-09, from Table 1 and Table 2 of the preprint; the same figures are Joule's Table 2 and Table 1). Dividing Joule Table 2's annual fixed cost (fixed O&M included, marginal cost 0) by the hours of output at the stated capacity factor gives 0.561 and 1.463 EUR/kWh for the "baseline" rows, which are NASA's 2050 baseline LCOEs of 0.61 and 1.59 USD/kWh (CLM-0123) times 0.920 for both designs, and 0.031 and 0.075 EUR/kWh for the "2050" rows, which match NASA's combined-improvements 0.03 and 0.08 USD/kWh (CLM-0124), whose likelihood NASA did not assess. So the paper's "near-term (2020)" baseline is NASA's 2050 baseline result, and its "2050" case is NASA's favourable case. The paper states no euro price year; it takes exchange rates from its reference 48 (46 in the preprint). The common 0.920 is consistent with a currency conversion, but the year is not stated. The multiples of solar (6.4-9.7 and 9.5-14.3 times, Joule PDF p.4) are of annual fixed cost: they reproduce as Joule Table 2's 2050 annual fixed cost over Table 1's high and low solar figures (267.87 / 41.74 = 6.4, 267.87 / 27.68 = 9.7, 396.59 / 41.74 = 9.5, 396.59 / 27.68 = 14.3). The 14x, 9x and 6x thresholds are stated in Joule's text on the same basis, annual fixed cost against the 2050 solar PV cost (PDF p.6); Figure 4 itself was not read.