Value chain · CLM-0337
In plain terms
The 1978 study expected the satellite's mirrors to lose about a fifth of their reflectivity over 30 years in space, though the same document gives two different numbers for this in two different places.
The claim as recorded
The DOE/NASA 1978 reference photovoltaic point design assumes its aluminized-Kapton concentrator reflectors degrade from 0.90 reflectivity at beginning of life to 0.72 at end of life (a 20% relative loss) over the 30-year design life; a separate passage in the same report states a different end-of-life concentrator reflectivity of 0.83 for what it calls "the GaAlAs case."
Scope and limits
A 1978 design ASSUMPTION about material degradation in the space environment, not a measured on-orbit result. The internal inconsistency means neither number should be treated as the report's single authoritative figure without further reading of the full document.
What it assumes
The main-body figure (0.83) and the appendix figure (0.72) may describe different design iterations or concentrator variants, or may be an internal inconsistency in the report; this register has not resolved which, if either, is the report's final position.
Where it comes from
PDF p.210 (doc p.B-8, verified by image render): "Reflectivity of the reflector was taken at 0.9 BOL and 0.72 EOL... The point design solar array sizing allows for 20% reflectivity degradation over 30 years." Contrast PDF p.23 (doc p.11, verified by image render): "For the GaAlAs case, the end-of-life (30 year) concentrator reflectivity is 0.83." The first passage is in Appendix B's detailed point design section; the second is in the main body's system overview section of the same document (SRC-085).
Basis: reflectivity ratio, beginning-of-life (BOL) to end-of-life (EOL), 30-year point design
Related records
- Answers question
- QST-002 not published in this release
Cite this
energyaperture.com/c/clm-0337
CLM-0337, Energy Aperture, as of 1978.
Connected records
Other published records linked to this one. A list, not a judgement.
- 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.