Value chain · CLM-1097
In plain terms
By 1976 a rectenna had delivered thirty kilowatts over a mile at 82 per cent, a certified bench system had turned DC into microwaves and back at 54 per cent, and 199 elements had run four months without a failure, which the maker converted into a 27-year mean time between failures at 90 per cent confidence.
The claim as recorded
Brown's 1977 report states the rectenna's field and life record as of 1976: the JPL Goldstone RXCV array of 17 subarrays of 270 elements converted "over 82%" of the incident microwave power at "a total DC output of 30 kilowatts" over 1.6 km, with a crowbar per subarray and a fuse per diode; the March 1975 certified test measured overall DC to DC efficiency at 54.18 per cent with a probable error of +/-0.94 per cent, with the rectenna's most probable collection efficiency 82 per cent; and a life test of 199 elements ran 2,763 hours without a failure after three infant failures in the first 150 hours, "549,837 diode hours have been accumulated without a failure or noticeable efficiency degradation", giving an MTBF of 239,059 hours or "27.3 years" at "a confidence factor of 90%" and "785,481 hours or 91 years" at 50 per cent, with the ratio of final to initial currents 0.9982; the later failures are attributed to operator error except one at 3,078 hours, which the report says is not to be confused with operator error, and the test ended on 24 March 1976.
Evidence behind this: T3-NASA contractor report, not peer reviewed: a life test with the hours, the diode-hours and the confidence level stated, and its operator errors admitted; the Goldstone and certified-efficiency figures are the contractor's own history.
Scope and limits
199 ELEMENTS FOR 2,763 HOURS IS 0.03 OF ONE ELEMENT-LIFETIME AT 30 YEARS; the MTBF is a statistical upper bound from a zero-failure run, not an observed lifetime, and the report says "The test was not a continuous life test" (normalised, PDF 82). The 82 per cent at Goldstone is collection and conversion at uniform incident density on the array, not the SPS profile; the 54.18 per cent is a bench system whose largest loss was the magnetron. The page's "91 years" for 785,481 hours is its own conversion: 89.7 years at 8,760 hours a year, the rate its 27.3 years for 239,059 hours uses; quoted as the page's words. The two 2021-2022 NRL papers restate Goldstone's power three ways - 35 kW at 1.55 km (SRC-269 PDF 2 / printed 230), 30 kW at 1.54 km at 2.388 GHz over 26.8 m2 (SRC-269 PDF 7 / printed 235) and 34 kW at 1.55 km at 2.39 GHz (SRC-270 PDF 11 / printed 38) - against this record's 30 kW over 1.6 km, none of their primaries held.
What it assumes
The MTBF is computed from zero failures in 549,837 diode-hours by the standard chi-square tables the report cites as "MTBF tables"; at 90 per cent confidence the upper bound on the failure rate for zero failures is 2.303 / T, giving T / 2.303 = 238,700 hours, which reproduces the report's 239,059 to 0.2 per cent; the report's own figures are 549,837 / 2.30 = 239,059.6 and 549,837 / 0.70 = 785,481.4, so its tables carried the factors 2.30 and 0.70.
Where it comes from
PDF 29 / printed 19, normalised: "The overall DC to DC efficiency was measured at 54" .18% with a probable error of +/- 0.94% (render reading of the digits at zoom 20; the layer prints "O. S4"); raw: "The most probable efficiency" ... "was 82%"; normalised: "The collection and conversion efficiency of this array was measured to be 82% at a total DC output of 30 kilowatts"; raw: "seventeen subarrays each" 1.22 m square and "containing 270 rectenna elements". PDF 31 / printed 21, raw: "up to 200 volts across the output load", "self-resetting crowbar", "Each diode was self-fused". PDF 30 / printed 20, Figure 1-14's estimated loss percentages: magnetron 28.3, diodes 15.0, spillover 4.0, circulator 2.6, array match 2.6, horn 1.0 (layer, column-major). PDF 82 / printed 72, normalised: "549,837 diode hours have been accumulated without a failure or noticeable efficiency degradation"; raw: "239" ,059 hours (render reading at zoom 12, the third digit damaged; 549,837 / 2.30 = 239,059.6) and "27. 3 years" and "with a confidence factor of 90%"; normalised: "785,481 hours or 91 years"; normalised: "The average ratio of the last measured currents to the initial measured currents is 0.9982"; raw: "The life test was discontinued on 24 March 1976"; normalised: elements were run "at power levels several times that anticipated in the rectenna for the SSPS and no degradation in efficiency was noted". PDF 119 / printed 109: a continuous run of 2,763 hours with 199 elements, "27.3 year MTBF with a 90% confidence factor" (layer "27. 3", squashed). SRC-269 (Rodenbeck et al., IEEE J. Microwaves 2021) PDF 7 / printed 235, read at the render, restates the certified test's breakdown as 68.87 +/- 1.0 per cent for the DC-to-RF conversion and 78.67 +/- 1.1 per cent for the RF-to-DC conversion, citing its [69] and [70]; recomputed 0.6887 x 0.7867 = 0.5418, the certified 54.18.
Basis: hours; diode-hours; years MTBF at a stated confidence; per cent
Related records
- Answers question
- QST-007 not published in this release
Cite this
energyaperture.com/c/clm-1097
CLM-1097, Energy Aperture, as of 1977-08.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-558
- CLM-1095The three harmonic numbers the register has carried since the 1978 conference paper come from one rectenna element on a bench at five...CLM-1096In 1977 one rectenna element converted 90 per cent of eight watts of microwaves to DC but only 80 per cent of fifty milliwatts, and the...CLM-1098The 1977 plan for a cheap rectenna was two flat planes, the front one doing all the work inside a metal shroud that is also the structure...