Value chain · CLM-1448
In plain terms
In 1979, the planners of a space solar power programme expected launch to low orbit to cost about 140 dollars a kilogram in today's money, on a large rocket they planned to fly hundreds of times. A 2026 study puts the average cost over all launches in 2025 at about 3,900 dollars a kilogram in today's money, about 28 times as much. The two numbers are different kinds of figure: one is a forecast for one planned rocket, the other an average over every rocket that flew that year.
The claim as recorded
The 1979 cost data book of the US space solar power programme put a flight of the heavy-lift rocket the programme planned at USD 10.1 million in 1977 dollars, for a net payload of 374 t: USD 27.0 per kg to low Earth orbit. In 2024 dollars that is about USD 140 per kg. A 2026 peer-reviewed study puts the average cost per kg in 2025, across launches to all orbits standardised to low Earth orbit, at USD 3,868 in 2024 dollars, about 28 times the 1979 estimate.
Evidence behind this: T0: a price-year restatement computed from published records and held US consumer price index files (CALC-137); not a figure any source publishes.
Scope and limits
The two figures differ in kind. The 1979 figure is a parametric estimate from a proprietary cost model for one planned vehicle, at 100 per cent reliability, with no reserve vehicles and no launch facilities, for a fleet flying 11,606 flights to build 60 satellites (CLM-1024, CLM-1028). The 2025 figure is an average over all vehicles that flew, built partly from imputed costs, with payload to other orbits converted to a low-orbit equivalent by coefficients given in the dataset notes, not in the paper (CLM-1389). Both are costs, not prices, and the study notes that a near-monopoly supplier has an incentive to charge more than cost (CLM-1389). The comparison does not show that the 1979 cost could have been reached, nor how today's cheapest vehicle compares, since one vehicle can cost well below an average over all of them. It says nothing about why the programme stopped. The payload chosen moves the multiple from 26.6 to 31.4 times (CALC-137). The data book used its own factor of 1.15 from 1977 to 1979 dollars, where CPI-U gives 1.197, and the page does not say which index gave 1.15 (CALC-137). Even the 1979 plan's average transport cost per kg all the way to geostationary orbit, about USD 279 in 2024 dollars, is about one fourteenth of the 2025 average to low orbit; that figure leaves out development, launch facilities and some support costs (CALC-137, CLM-1028).
What it assumes
The 374 t net payload is the mass each flight delivers, as CLM-1024 assumes. A consumer price index stands in for launch and aerospace costs, because no US producer price index or GDP deflator is held (CALC-137).
Where it comes from
This is the project's own working, shown in full:
CALC-137, working and result: 27.0 USD per kg x (313.689 / 60.608) = 139.7 USD per kg in 2024 dollars, and 3,868 / 139.7 = 27.7. The price index is US CPI-U, all items, series CUUR0000SA0: the 1977 value is the mean of the 12 monthly values in SRC-771, and the 2024 value is the annual average in SRC-773 (CALC-137, as in CALC-124). CLM-1024: a flight cost of USD 10.1 million in 1977 dollars over a 374 t net payload. CLM-1389: USD 3,868 per kg in 2025, in 2024 dollars, standardised to low Earth orbit.
Basis: USD 2024 per kg to low Earth orbit. The 1979 figure is a cost per flight of one planned vehicle over its net payload, moved from 1977 dollars with US CPI-U annual values; the 2025 figure is an average over all launches, standardised to low Earth orbit (CALC-137).
Related records
- Answers question
- QST-003 not published in this release
Cite this
energyaperture.com/c/clm-1448
CLM-1448, Energy Aperture, as of 2026-10.