Value chain · CLM-0891
In plain terms
The 1978 design says the size of its transmitting antenna was set by how much heat the array could shed, and elsewhere gives that limit as about 22 kW/m2 of radio power at the centre of the array. Working through the design's own numbers puts the centre at about 21.9 kW/m2, right at the limit, so the limit did set the size. Counted instead as waste heat from the transmitter tubes, the design would produce only about a fifth of the limit, but the report gives the number as radio power, not heat.
The claim as recorded
The 1978 reference design states that a thermal dissipation limit of approximately 21 kW/m2 sized its transmit antenna, and its own figures put the design point at that limit when the limit is read as the same report states its value elsewhere, as RF power density at the array centre (22 kW/m2 rf, CLM-0204): 6.72 GW through a 1 km aperture with a 10 dB Gaussian taper gives a peak RF density of 21.9 kW/m2 at the array centre. Read instead as conversion waste heat, the same figures give 3.9 kW/m2 at the report's own 0.85 DC-to-RF conversion efficiency, about a fifth of the limit, and the two figures would agree only at a conversion efficiency of 0.51; the report's statement of the value as RF density does not support that reading.
Evidence behind this: Arithmetic performed here over held figures, against a relationship the source states in its own words.
Scope and limits
THE REPORT GIVES THE LIMIT'S CAUSE AS WASTE HEAT AND ITS VALUE AS RF DENSITY. CLM-0204 quotes SRC-085 PDF 37 [printed 25] for the cause (the limit is "due to waste heat" from the converter tubes) and PDF 281 [printed B-79] for the value at the centre of the array ("22 kw/m2rf"). Read as RF density, the design point sits at the limit (21.89 against 21 to 22 kW/m2) and the limit binds. Read as conversion waste heat, the design point is 3.86 kW/m2, about a fifth of the limit. The report's figures fit the first reading; that its 22 kW/m2 rf was set to cap tube waste heat at about 3.9 kW/m2 is our inference, not stated. Also read 2026-10-02 by the ON-292 drafter, not via a cited record: SRC-085 PDF 40 [printed 28], Figure 15, lists power density levels of 22 kW/m2 at the centre and 2.4 kW/m2 at the edge of the transmit antenna, and PDF 222 [printed B-20] gives "21 KW/m2 radiation at center". The peak-to-average factor is modelled; its agreement with the stated centre density is a check on it, not a source for it. A post-tolerance reading of 6.72 GW raises the peak 3.6 per cent, to 22.68 kW/m2, about 3 per cent above 22.
What it assumes
That a 10 dB Gaussian taper gives a peak-to-average of 2.5584, modelled here as a truncated Gaussian with 10 dB edge illumination - CLM-0015 states the taper, not a peak-to-average; the result, 21.89 kW/m2, agrees with the 22 kW/m2 rf at the array centre that CLM-0204 quotes. That 6.72 GW is aperture RF rather than a figure already reduced by the 0.9653 pointing and tolerance factor.
Where it comes from
This is the project's own working, shown in full:
SRC-085 PDF p.124 (printed A-25), via CLM-0023: "Thermal dissipation limits set a heat density value on the transmit antenna of approximately 21 kW/m2... With these two limits, and a desired value of power output at the rectenna, transmit antenna size and rectenna size can be traded." SRC-085 PDF p.281 (printed B-79), via CLM-0204: "The thermal loading in the center of the array (22 kw/m2rf) permits a design for a 1 km diameter array which provides roughly 5 GW of dc power on the ground per antenna." Aperture 1 km, 2.45 GHz, 10 dB Gaussian taper, 6.72 GW beamed (CLM-0015); DC-to-RF 0.85 from the same report's Figure 25 (CLM-0138). Area 785,398 m2, average 8.56 kW/m2, peak/average 2.5584, peak 21.89 kW/m2 RF against the 22 kW/m2 rf stated; waste heat at that peak 3.86 kW/m2.
Basis: kW/m2 of RF power density at the array centre, and the waste heat it implies
Related records
- Answers question
- QST-018 not published in this release
Cite this
energyaperture.com/c/clm-0891
CLM-0891, Energy Aperture, as of 2026-09.