Value chain · CLM-0885
In plain terms
A normal communications satellite spends about 50 metres per second of velocity change a year holding its slot. Working backwards from the 1978 design's own fuel budget, that design would spend about 360 a year against the push of sunlight on its very large area - seven times a normal satellite's entire budget - because it is vast and light.
The claim as recorded
Inverting the rocket equation against the 1978 reference design's own stated propellant budget shows that solar radiation pressure, not gravitational perturbation, governs station keeping for that design: the design's 9.98 per cent 30-year propellant mass fraction at 13,000 s specific impulse implies 447 m/s per year of total station-keeping delta-v, of which the 8.12-point solar radiation pressure term alone implies 360 m/s per year - 7.2 times the approximately 50 m/s per year that a conventional geostationary satellite requires for its entire station-keeping budget. The residual non-SRP term comes out at 80 m/s per year, the same order as that conventional figure, which is the check passing.
Evidence behind this: Arithmetic performed here over four held claims. Inverts the rocket equation against a published mass fraction rather than restating it.
Scope and limits
THE RELATIONSHIP IS REPRODUCIBLE; ITS DOMINANT INPUT IS HELD FOR EXACTLY ONE ARCHITECTURE. Solar radiation pressure delta-v scales with area-to-mass ratio, and the register holds an SRP propellant figure only for the 1978 DOE/NASA 5 GW point design. It does NOT transfer to any other concept. CASSIOPeiA proposes passive photon-pressure balance instead of propulsive counteraction, and CLM-0441 records that the paper quantifies no residual propellant for it, so the two cannot be compared in kg per year at all. A CONVENTION IS IN PLAY AND IT MATTERS AT THE 9 PER CENT LEVEL: the 80 m/s/yr residual is computed from its own stated mass fraction, not by subtracting delta-v, because mass fractions referenced to a common initial mass do not subtract under the rocket equation; the subtraction route would give 87 m/s/yr. That 9 per cent is not the CLM-0330 against CLM-0331 cross-check and must not be read as it. All inputs are 1978 paper-design estimates apart from the 2019 comparator.
What it assumes
That the 9.98 and 8.12 per cent figures are fractions of the same initial mass, which CLM-0330 states. That the 13,000 s ACS specific impulse applies to the station-keeping propellant the budget covers, which the 1978 design implies by using one ACS for both but does not state separately.
Where it comes from
This is the project's own working, shown in full:
m_p/m_0 = 1 - exp(-dv/(Isp x g0)), g0 = 9.80665. With Isp 13,000 s from CLM-0332 and T 30 years from CLM-0330: 9.98 per cent gives 13,403.7 m/s; 8.12 per cent gives 10,796.4 m/s; 1.86 per cent gives 2,393.6 m/s. Divided by 30: 446.8, 359.9 and 79.8 m/s/yr. Comparator 50 m/s/yr from CLM-0441. Cross-check from a different table of the same report: CLM-0331's 93,000 kg/yr over 30 years against 30.47e6 kg is 9.16 per cent against CLM-0330's 9.98.
Basis: dimensionless mass fraction, and m/s of delta-v
Related records
- Answers question
- QST-022 not published in this release
Cite this
energyaperture.com/c/clm-0885
CLM-0885, Energy Aperture, as of 2026-09.