CALC-095
How many pieces is a solar power satellite built from in orbit
What this is
This is the project's own arithmetic, published in full so it can be checked rather than taken on trust. It is not a source. Every input it uses is cited to a record, and the conclusion it reaches only carries as far as those inputs do.
Feeds CLM-0886. Answers QST-004. Basis: count of modules assembled in orbit.
Why it was needed. VC11's depth target asks for the governing relationship of in-space assembly. Assembly effort scales with the number of things to be assembled, and that number is set by how an architecture divides its array:
N_modules = P_array / P_moduleInputs. Only architectures that state their OWN division are admitted, and the register holds exactly two.
| Quantity | Value | Source | Stated or assumed |
|---|---|---|---|
| CAST MMR-SPS array output | approximately 2.4 GW | CLM-0692, SRC-169 Table IV, image-read | STATED |
| CAST MMR-SPS solar array modules | 600 | CLM-0692, same table | STATED |
| CAST assembly sequence | modules launched to LEO, then transferred | CLM-0687 | STATED |
| CASSIOPeiA on-orbit assembly | none - "the possibility of single payload deployment requiring no on-orbit assembly" | CLM-0661 | STATED as a possibility, not demonstrated |
Working. This is an internal consistency check on CAST, not a comparison of two calculations.
2.4e9 W / 600 modules = 4.0 MW per moduleResult. 600 against 0, for systems within a factor of two in delivered power. The register holds no intermediate value.
A WITHDRAWN VERSION OF THIS COMPARISON, KEPT HERE BECAUSE THE ERROR IS INSTRUCTIVE. The first draft set CAST's 4.0 MW module against a 50 kW-class module from a Solar Electric Transfer Vehicle and reported a factor of 80 in module power and module count. A SETV IS NOT A SOLAR POWER SATELLITE. Dividing an SPS array output by a transfer vehicle's module class computes how many SETV-class modules would build a CAST-sized array - a quantity nobody proposes and no source states. The two sides were not the same kind of thing, and the arithmetic worked perfectly anyway. ASK WHETHER BOTH SIDES MEAN THE SAME THING BEFORE DIVIDING; THE DIVISION WILL NOT TELL YOU.
Cite this
energyaperture.com/calc/calc-095
CALC-095. The working above, not a source document.