Value chain · CLM-0940
In plain terms
Two NASA efforts to build rectennas at much higher frequencies than the standard 2.45 GHz ended without a working device. One concluded the approach it had chosen would not work; the other simply ran out without completing anything.
The claim as recorded
Two independently funded NASA programmes to build rectennas above 2.45 GHz reported that no device was completed. The 20 GHz half of contract NAS3-22764 found the thin-film etched-circuit format unsound at that frequency, abandoned the hybrid alumina-and-beam-lead-diode route as the fabrication difficulty became apparent, and stated that performance at higher frequencies cannot be quantitatively predicted without experimental data. Separately, NASA Lewis funded a three-year high-frequency rectenna effort at 300 GHz and 28 THz, and at the termination of both grants no operational device existed.
Evidence behind this: T3-primary-report plus a second T3 agency proceedings. Both documents report on programmes their own sponsor funded, which is the relevant authority for whether a device was built.
Scope and limits
A 1987 AND 1989 JUDGEMENT ABOUT 1980s FABRICATION TECHNOLOGY, NOT A PHYSICAL BOUND, and it must not be read as one. SRC-336 still gives design targets for a 20 GHz rectenna - 30,000 diodes per square metre, 4,050 W/m2 at 60 per cent efficiency on alumina, 12.5 kW/m2 on GaAs, PDF p.76 - which are calculations and not results, and the record keeps that distinction because a target is the thing most easily mistaken for an achievement. Nothing here establishes that a high-frequency rectenna cannot be built; it establishes that three funded attempts across two programmes and three institutions did not build one, and that one of them said its chosen route was unsound. Later work is not surveyed by this record. The p.85 sentence sits in the section on the monolithic 20 GHz circuit's series resistance, so it is that design's performance the report says cannot be predicted; and the source's p.76 arithmetic does not close on its own terms (0.09 W x 30,000 = 2,700 W of heat; 4,050 W at 60 per cent would put 1,620 W into heat), quoted here as the source's figures, not vouched for.
What it assumes
No assumptions are recorded against this claim.
Where it comes from
PDF p.8, verbatim at the normalised level: "the thin-film, etched-circuit rectenna format was not a sound approach". PDF p.76: "the enormity of the task of building a large rectenna area with the hybrid technology also grew". PDF p.85: "the quantitative performance cannot be accurately predicted". SRC-417 PDF p.13, verbatim at the normalised level: "NASA Lewis Research Center has sponsored a 3-year effort to develop high-frequency rectennas. Two frequencies were chosen for development: 300 GHz by the Georgia Institute of Technology (NASA Grant NAG3-282) and 28 THz (Far-Infrared) by the University of Cincinnati (NASA Grant NAG3-532). At the termination of both grants, some encouraging results were obtained, although no operational devices were completed."
Related records
- Answers question
- QST-002 not published in this release
Cite this
energyaperture.com/c/clm-0940
CLM-0940, Energy Aperture, as of 1989.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-336
- CLM-0938A 1988 NASA paper says a rectenna built on mylar reached 85 per cent efficiency. The 1987 final report of the contract it cites says mylar...CLM-0939The 85 per cent figure that later papers quote flat was one component on a bench, in moving air, with an error bar, at one power level. The...CLM-0941In space there is no air to carry away the waste heat, so a rectenna's output is limited by how much waste heat it can radiate. The report...CLM-0969If the tubes are only 70 per cent efficient, the transmitter's own face is not big enough to get rid of the heat they make, even spread...
- Also from SRC-417
- CLM-0933In 1988 the leading experimenter listed three numbers side by side: the best efficiency physics allows for beaming power and converting it...CLM-0934In 1988 the NASA centre running the work said the solar power satellite programme did not stop because the technology failed. It stopped...
- Contradicted by
- CLM-0938A 1988 NASA paper says a rectenna built on mylar reached 85 per cent efficiency. The 1987 final report of the contract it cites says mylar...