Value chain · CLM-0911
In plain terms
If the steering signal from the ground stops, the 1978 design's beam does not carry on pointing somewhere. It falls apart, and the power on the ground drops by a factor of about eight thousand, to below the Soviet guideline plotted in the report. The size of that drop turns out to match the number of independently steered pieces the antenna has, which suggests the same arithmetic could give a rough estimate for other designs.
The claim as recorded
DOE/ER-0023 states that on total phase-control failure, the example given being the uplink pilot beam transmitter being shut off, the subarrays are no longer phased together, the beam defocuses, and peak ground intensity falls from 23 mW/cm2 to 0.003 mW/cm2 - which the report calls "a fail-safe feature of the phasing system", noting it is below the USSR guideline of 0.01 mW/cm2 plotted on the same figure. That collapse matches the coherent-to-incoherent loss 10.log10(N) over the design's own 7220 subarrays, 38.59 dB, to within about 1.5 dB on the figures as the report states them - or to within about 0.3 dB if the 0.003 is read off the plot it comes from. The fail-safe is therefore not a separate safety system but the same decorrelation that CALC-085 identifies as the open-loop failure mode, and its depth is set by the number of independently phased groups. A second, independent layer is also stated: sensors near the rectenna detect large changes in incident power density and signal the antenna to cease operations.
Evidence behind this: Follows the source. A DOE/NASA reference-system report, read first-hand from the held PDF at report p30 (PDF p42); the 38.59 dB comparison is arithmetic performed here on the report's own printed subarray total.
Scope and limits
THIS REPORT GIVES NO TIME CONSTANT for how fast the defocus happens. It says only that the independent sensor information "would immediately be transmitted". The programme's 1981 system definition, NASA TM-58236, lists among the features of the same retrodirective concept that "Dephasing occurs in milliseconds and diffuses the power beam to 0.003" mW/cm2, with no derivation on the page (see CLM-1020). So the speed is stated only as an order of magnitude, and speed is what matters for anything moving through the beam. A 1978 planar design, not CASSIOPeiA. THE AGREEMENT MAY NOT BE QUOTED TO TWO DECIMAL PLACES, AND 0.26 dB IS NOT A RESULT. 0.003 mW/cm2 is printed to ONE significant figure, so the true value lies in [0.0025, 0.0035) and the gap against 10.log10(7220) = 38.5854 dB runs from +1.05 dB to -0.41 dB - a span of 1.46 dB. The 0.26 is simply what the printed figure gives if treated as exact, which it is not. THE PLOT IS BETTER EVIDENCE THAN THE TEXT AND IS THE ONLY THING THAT NARROWS IT: Figure 18 rendered at 3x, its log axis calibrated on three labelled decades, places the dotted "No pilot beam present" line at 0.00296 mW/cm2, giving a gap of 0.32 dB with about plus or minus 0.2 dB from line thickness and axis residual. THERE IS NO TICK OR GRIDLINE ANYWHERE BETWEEN .005 AND .001, which is the whole basis for the caution; what rescues the comparison is that the line happens to sit where careful calibration can still place it. A READER CHECKING "23 to 0.003" IN THE TEXT CANNOT DO THAT AND HAS ONE SIGNIFICANT FIGURE. So this is a strong consistency check and not a measurement, and anything quoting it should say which of the two readings it is using. THE 38.59 dB ASSUMES 7220 EQUAL SUBARRAYS. The design's illumination is tapered, 10 dB down at the edge. For a continuous taper of that depth over a disc, the coherent-to-incoherent ratio is about 38.14 dB (CALC-144, step 5); the design's 10-step taper may differ a little from that. Against 38.14 dB the text's span runs from +0.04 to +1.50 dB and the plot reading gives about +0.77 dB. So the 0.3 dB agreement holds only for equal subarrays; the agreement to within about 1.5 dB holds either way, and the comparison stays a consistency check.
What it assumes
That the report's 23 and 0.003 mW/cm2 are the same quantity measured the same way, which Figure 18 supports since both are read from it.
Where it comes from
p30 verbatim: "If there is a total failure within the phase control system (for example, the uplink pilot beam transmitter is shut off), the subarrays will no longer be phased together and the total beam will be defocused. As shown in figure 18, the peak intensity of the beam drops to 0.003 mW/cm2 and the beam width greatly increases. This peak power density is significantly less than the USSR guideline indicated on figure 18." "Consequently, this is a fail-safe feature of the phasing system. In addition, there are sensors near the rectenna to detect any large changes in incident power density; this information would immediately be transmitted to the antenna to cease operations." Subarray count from p27, Figure 15, verbatim: "NUMBER OF SUBARRAYS: 7220". Figure 18 on p33 plots the failure case as a FLAT line labelled "No pilot beam present (total phase control failure)" running across the whole 0 to 20,000 m ground radius shown, against the normal curve's sidelobe structure - so the power is spread, not merely reduced. Arithmetic: 23/0.003 = 7,666.7, which is 38.848 dB; 10.log10(7220) = 38.585 dB; difference 0.263 dB. VERIFIED ON REGISTRATION, 2026-09-14. Quotation confirmed verbatim on PDF p42 with A59 controls in the same extraction - phase control 1, subarray 5, rectenna 4 on that page - and the scan renders "(for example" as "{for example" and hyphenates "guideline" across a line, both scan artefacts. Arithmetic recomputed: 23/0.003 = 7666.7, 10.log10 = 38.846 dB; 10.log10(7220) = 38.585 dB; difference 0.261 dB. The subarray count is the report's own, printed in Figure 15 as "NUMBER OF SUBARRAYS: 7220" without a comma - a search for "7,220" returns zero across all 322 pages, which is a property of the formatting and not of the document, and CLM-0871 independently records that the subarray column sums to that printed total. PRECISION, RE-DERIVED IN VERIFICATION 2026-09-14 (VER-1144). 23/0.003 = 7666.667 gives 38.8461 dB against 38.5854 dB, a gap of 0.2607 dB - but 0.003 is stated to ONE significant figure, so the true value lies in [0.0025, 0.0035) and the gap runs from +1.05 to -0.41 dB, a span of 1.46 dB. The 0.26 dB was an artefact of treating a one-figure number as exact. THE PLOT ITSELF IS BETTER THAN THE TEXT: Figure 18 rendered at 3x and the log axis calibrated on three labelled decades - 1.0, .05 and .01 fitting a straight line to within 1 pixel at 396.4 px per decade, with .005 held out of the fit and predicting to within 9 px - places the dotted "No pilot beam present" line at 0.00296 mW/cm2, within 1.5 per cent of the printed 0.003. That reading gives 38.905 dB and a gap of 0.32 dB, with about plus or minus 0.2 dB from line thickness and axis residual.
Basis: mW/cm2 (ground power density); dB (collapse depth)
Related records
- Answers question
- QST-013 not published in this release
Cite this
energyaperture.com/c/clm-0911
CLM-0911, 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.
- Also from SRC-554
- CLM-1017By 1981 the programme itself said the ionospheric limit it had designed to was probably too cautious, and worked out what relaxing it to...CLM-1018Three years of study left the efficiency chain exactly where 1978 put it, and Boeing's own version says out loud the solar constant the...CLM-1019The programme gave three reasons for choosing the klystron; the company that designed the satellite said the choice was more or less...CLM-1020By 1981 the programme was confident the beam could be pointed and formed, and named the network that carries the timing reference across...CLM-1022A loss you can make up by adding solar panels costs about 56 million dollars per percentage point; a loss at the ionospheric ceiling costs...CLM-1087When the programme wrote down why it used 2.45 GHz, its reasons were consistent: each time it named the industrial band and how the beam...CLM-1091The people running the programme said 2.45 GHz was sensible and also said, in the same breath, that nobody international had agreed to it...CLM-1478Almost everything that can go wrong with this design makes the beam fall apart and become harmless, which is the right way to fail. Two...