Value chain · CLM-0063
In plain terms
NASA suggested in 1981 that 550 to 600 watts per square metre might be reasonable, roughly two and a half times the figure still in use, and said the parameter decides the system size and has billions of dollars of cost impact.
The claim as recorded
NASA RP-1076 states that from a system viewpoint an ionospheric power density level of 55 to 60 mW/cm2 might be reasonable and would accommodate larger antenna and smaller rectenna systems, that determining the upper limit is one of the two most important issues in the entire SPS microwave system, and that this parameter for all practical purposes determines the size of the 2.45 GHz system and has billions of dollars of impact on electricity costs.
Scope and limits
A system-level suggestion explicitly conditional on further experiments at upgraded facilities, which the same passage says are needed. It is not an established threshold and may not be cited as one. Those upgraded experiments are not known to have been performed. A 2026 commentary (SRC-588) does not mention them either. It says later studies "have not led to any consensus about how the SBSP power beam will interact with the ionosphere" (PDF p.2) and calls for "wider experimental study of SBSP interactions with the ionosphere" (PDF p.4). That is consistent with no decisive experiment having been reported, but it does not establish that none was run.
What it assumes
No assumptions are recorded against this claim.
Where it comes from
Verbatim, SRC-107: "From a system viewpoint, an ionospheric power density level of 55 to 60 mW/cm2 might be reasonable and would accommodate the larger antenna/smaller rectenna systems proposed in Section III.A.4. However, more ionospheric experiments are needed with upgraded facilities at Platteville and Arecibo to produce the higher heating levels." Conversion: 55 to 60 mW/cm2 = 550 to 600 W/m2.
Related records
- Answers question
- QST-009 not published in this release
- Contradicts
- CLM-0018 The most recent UK government report calls 230 watts per square metre a limit to be reached...
Cite this
energyaperture.com/c/clm-0063
CLM-0063, Energy Aperture, as of 1981.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-107
- CLM-0033 (low confidence)Apart from a 1981 NASA review that found no evidence for the number and suggested a higher one, nobody was found to have revisited it, and...CLM-0060In 1981 a NASA review panel said the 230 watts per square metre figure rested on an obsolete theory with no experimental support, and made...CLM-0061The experiments were done. They found heating two or three times stronger than normal, not the tenfold effect predicted, no irregularities...CLM-0062By 1981 the theory was being revised to a steeper frequency dependence, which would raise the permitted power density.CLM-0101The 1978 contract required the researchers to report fixes if ionospheric disturbance pushed the pilot-beam phase error past 2 to 3...CLM-0160A 1978-81 NASA design study calculated that simply pointing the satellite's structure accurately enough, without any electronic correction...CLM-0420NASA's 1981 report says the experiments found nothing supporting the 23 milliwatt limit, that the measured heating was two or three times...CLM-0901Each antenna must hold its position along the line to the receiver within about three millimetres for a tenth of a decibel. The whole 1970s...More on the source page.
- Contradicted by
- CLM-0018The most recent UK government report calls 230 watts per square metre a limit to be reached because it lowers cost, and cites an earlier...