Value chain · CLM-0333
In plain terms
In one 1978 design, structure and mechanisms made up about 18% of the satellite's dry mass; a 2010 paper gives about 20% as a general rule for the main structure of aerospace systems. The two figures measure different things, so they are not two estimates of one share.
The claim as recorded
In Rockwell International's 1978 5 GW photovoltaic point design (Appendix B of the DOE/NASA reference system report), the combined "structures and mechanisms" mass of the collector array (3.825 million kg) and antenna section (1.685 million kg) totals 5.51 million kg, about 18% of the 30.47 million kg total dry mass; a 2010 NASA Langley paper separately states that primary structure is typically about 20% of dry mass for "most aerospace systems," and reports that a high-level metric of the earlier "Fresh Look Study" was a primary SPS structure of less than 3-4 kg/kW.
Evidence behind this: T3 (SRC-085); T5 (SRC-041)
Scope and limits
Neither figure is a measured result; both are paper-design assumptions or generic heuristics. The two figures (about 18% and about 20%) are not estimates of the same quantity: the first is structures plus mechanisms for one point design, the second is primary structure only, given as a generic rule of thumb for aerospace systems with no SPS derivation. Their closeness is not evidence of convergence.
What it assumes
SRC-085's figure mixes "structures" with "mechanisms" (e.g. pointing/deployment hardware), so it is not a pure structural-material fraction. SRC-041's "20% of dry mass" is stated as a generic aerospace rule of thumb, not derived from an SPS-specific mass statement.
Where it comes from
, Table R-5 (PDF p.237, printed p.B-35): "STRUCTURES AND MECHANISMS [collector array] 3.825" and "STRUCTURE AND MECHANISMS [antenna section] 1.685" [million kg], against "TOTAL SPS DRY WEIGHT 30.47" [million kg]; (3.825+1.685)/30.47 = 18.1%, computed here, not stated by the source. SRC-041 (Belvin, Dorsey and Watson, NASA Langley, "Solar Power Satellite Development: Advances in Modularity and Mechanical Systems," Online Journal of Space Communication Vol.9 Iss.16, 2010), PDF p.7, printed p.6: "A high level metric during the 'Fresh Look Study' was to achieve a structural design for the primary SPS structure at less than < 3-4 kg/KW... For most aerospace systems, the primary structure is approximately 20% of the dry mass."
Basis: structures-and-mechanisms mass as a percentage of total dry mass, excluding growth margin
Related records
- Answers question
- QST-002 not published in this release
Cite this
energyaperture.com/c/clm-0333
CLM-0333, Energy Aperture, as of 1978 (SRC-085); 2010 (SRC-041).
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-041
- CLM-0336Different design studies over four decades have each simply assumed a different working lifetime for a solar power satellite, from about 15...CLM-0343A 2010 NASA paper argues that building a solar power satellite in space is not just a robot problem: the module design, the assembly steps...
- Also from SRC-085
- CLM-0013The paper that modern UK studies rely on for the beam figure calls anything below 1 kilowatt per square metre safe, with 230 watts per...CLM-0020The original 1978 design set the beam at 230 watts per square metre in the middle of the receiving site, about one twenty-third of that at...CLM-0023In the 1978 reference design, two limits set the size of the transmitter and the receiving site: how much heat the transmitter can shed...CLM-0039The 1978 report set the figure to protect radio and navigation systems from a disturbed ionosphere, called the number theoretical and...CLM-0045The apparent conflict between 12 and 23 was not an error. The underlying study gave a range, and the figure adopted sits near the top of it.CLM-0101The 1978 contract required the researchers to report fixes if ionospheric disturbance pushed the pilot-beam phase error past 2 to 3...CLM-0137In four major space solar power studies from 1978 to 2007, none put a number on how much of the beam's energy would be lost if the beam...CLM-0138The original 1978 government design for beaming power down from space adds up all the expected energy losses to get 63% overall efficiency...More on the source page.