Value chain · CLM-0921
In plain terms
The 1978 report says the power density a solar power satellite apparently needs to make economic sense was thought to be about the same as the density at which heating starts to produce irregularities in the ionosphere. So the design was thought to sit at that threshold, not below it, and the report says understanding of the interaction was not adequate to predict the severity of all its effects.
The claim as recorded
The 1978 EMC assessment states that the minimum power densities apparently required for an economically practical SPS are thought to be approximately AT the threshold for production of ionospheric irregularities caused by intense heating. That is a statement about WHY the design sits where it does, and it is different from anything the register already holds on the origin of the 23 mW/cm2 figure. It also states that even if irregularities are not produced, systems using frequencies normally reflected by the ionosphere - low-frequency navigation and shortwave communications - would be affected, and that understanding of ionospheric interactions with radio and microwaves is not adequate to predict the severity of all effects that might result.
Evidence behind this: Government-contractor assessment read directly in the held file. The document is headed PRELIMINARY DRAFT on its own contents page. The sentence below is TRANSCRIBED rather than quoted because the scan letterspaces the page; the raw rendering is given in support.
Scope and limits
FEBRUARY 1978, MARKED PRELIMINARY DRAFT, AND IT REPORTS WHAT WAS "THOUGHT", NOT WHAT WAS MEASURED. "Apparently required" and "are thought to be" are the document's own hedges and must travel with the statement. IT DOES NOT NAME A NUMBER - no power density is given in this sentence, so the link to 23 mW/cm2 is the reader's and not the document's. AND THE LATER RECORD CUTS AGAINST IT: CLM-0420 records NASA's 1981 technical summary finding no experimental evidence at Arecibo and Platteville to support 23 mW/cm2 as an upper limit, with measured electron temperature increases a factor of two or three rather than the order of magnitude predicted. So this is a 1978 belief about a threshold that 1981 testing did not confirm. Nothing here establishes that the economic minimum and the physical threshold actually coincide - only that in February 1978 they were thought to.
What it assumes
No assumptions are recorded against this claim.
Where it comes from
TRANSCRIBED, NOT QUOTED - the page is letterspaced. Raw rendering, PDF p.26, printed -20-; earlier written as a zero-based index 25: "The situation i s complicated by the fact that the minimum power densities apparently required for an economically practical SPS are thought to be approximately a t the threshold for production of ionospheric irregularities caused by intense heating." Transcribed: "...are thought to be approximately at the threshold for production of ionospheric irregularities caused by intense heating." Same page, raw: "Even i f irregularities are not produced, systems using frequencies normally reflected by the ionosphere, including low frequency navi- gation systems and shortwave communications, would be affected." And: "interactions with radio and microwaves i s n o t adequate t o predict the severity of all effects that might result". The page also renders "might" as "~llight". This record's sentence did not match on first search and the reason was letterspacing, not hyphen-space - see SRC-111's source row, hazards 5 and 6.
Related records
- Answers question
- QST-001 not published in this release
Cite this
energyaperture.com/c/clm-0921
CLM-0921, Energy Aperture, as of 1978-02.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-111
- CLM-0918The 1978 study of what a solar power satellite would do to the radio spectrum found two things. Its transmitter NOISE would exceed what...CLM-0919In 1978 there was no rule allowing a solar power satellite to transmit power, and the industrial band everyone assumed it would use permits...CLM-0920The 1978 study says a solar power satellite cannot keep its beam entirely on the receiving station - the physics of beams forbids it - so...CLM-0959The original 1975 calculation found the satellite's radio noise would be fine for ordinary and troposcatter radio links and a problem only...CLM-0960The 1975 study found the satellite's harmonics - the multiples of its transmit frequency - would trouble radio astronomy at the second and...CLM-0961Everything in the 1975 interference analysis is for one satellite. The study itself says that a hundred of them would raise the noise and...CLM-1315The 1975 estimate of the satellite's radio noise, taken at its own frequency, is about a hundred million times above today's threshold for...