Value chain · CLM-0715
In plain terms
The 2021 UK study assumed one extra fuel launch for every payload launch; NASA's 2024 study assumed twelve. The reason, which neither study states, is not that they disagree about the price of a rocket: the UK plan used chemical rockets only part of the way up, to about 5,900 km, and then switched to electric, while NASA's used chemical rockets all the way to the top. The two studies also assumed different amounts of cargo reach the top per launch.
The claim as recorded
The UK study needs ONE refuelling launch per payload launch, not twelve, and states why: its chemical tugs only travel from low Earth orbit to a 5,900 km MEO staging point, for which "the mass ratio of propellant to payload for the chemical tugs is about 1:1, allowing for an out and return journey between LEO and MEO. Thus for each launch of an SPS payload, an additional launch would be required to ferry chemical tug propellant from Earth to LEO." NASA OTPS assumes twelve refuelling launches because its chemical architecture goes the whole way to GEO. AN INFERENCE, NOT A STATEMENT BY EITHER SOURCE: the twelve against one refuel count follows from where each architecture stops using chemical propulsion, not from launch prices, since both start from a USD100M launch (NASA then applies a 15% block-buy discount to USD85M). The two also assume different mass delivered to GEO per payload launch (NASA 100 t, UK 61.3 t), so the cost-per-kilogram gap reflects staging and payload accounting together, not staging alone.
Evidence behind this: T4 (Frazer-Nash); T3 (NASA OTPS)
Scope and limits
T4 consultancy tier and a stated assumption rather than a demonstrated result. The 1:1 propellant-to-payload ratio for a LEO-to-MEO round trip is asserted without a delta-v derivation in the pages read. This does not establish that the UK architecture works, only that its refuel count follows from a different staging choice. Frazer-Nash's 2022 study for ESA, a different study and design, also pairs each payload launch with one fuel launch, but to geostationary transfer orbit, with a chemical-rocket transfer vehicle for the rest of the way, and puts 86 to 119 Starship launches on one 1.44 GW system (SRC-078, PDF p.25 and p.37).
What it assumes
that "an additional launch" means exactly one per payload launch, which is what the sentence states.
Where it comes from
PDF p.11 (index 10), verbatim and COMPLETE: "The mass ratio of propellant to payload for the chemical tugs is about 1:1, allowing for an out and return journey between LEO and MEO. Thus for each launch of an SPS payload, an additional launch would be required to ferry chemical tug propellant from Earth to LEO." One other statement on the same page bears on it and agrees: its 61.3 tonnes figure, below, takes one payload launch and one fuel launch. NASA's twelve-refuel baseline is at SRC-012 p.10, p.18 and p.49. Launch prices: SRC-019 PDF p.11, "a cost per launch comparable with the current cost for SpaceX Falcon Heavy, $100M"; SRC-012 printed p.21, "$100M or $1000/kg (with 15% block buy discount, $85M or 850/kg)". Mass to GEO per payload launch: SRC-019 PDF p.11, "61.3 tonnes can be delivered to GEO with 2 launches"; SRC-012 printed p.48, "Refueled Starship payload capacity to GEO (kg) 100,000.00".
Related records
- Answers question
- QST-040 not published in this release
Cite this
energyaperture.com/c/clm-0715
CLM-0715, Energy Aperture, as of 2021.
Connected records
Other published records linked to this one. A list, not a judgement.
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