Value chain · CLM-0953
In plain terms
The rectenna was squashed to fit its container, which spoiled the impedance match between it and the incoming beam. The report accepts this on two grounds: the mismatch protects the circuit from high power, and efficiency was not being measured anyway.
The claim as recorded
The flown rectenna's spacing was cut to fit the package, this caused an impedance mismatch, and the report then treats the mismatch as a protective feature. Verbatim: "The spacing between the rectenna plane and the reflecting plane is normally 2 to 2.5 cm. This spacing was reduced to 1.1 cm as mandated by the package contents." The reduction is stated to cause a mismatch between free space and a dipole input impedance given as 120 ohms, against a theoretical dipole input impedance of approximately 25 ohms at 0.11 wavelengths above a reflecting plane. The report's own justification is two-part and both parts are about something other than performance: "the transmitted power from the mother section is predicted to be 800 W, and this impedance mismatch will help to protect the rectenna circuitry from large power densities", and "Because rectenna efficiency will not be considered, the impedance mismatch works for the rectenna."
Evidence behind this: T3-primary-report. The report is the only document that can say why its own hardware was built as it was, which is the whole of this record.
Scope and limits
THIS IS A DEFENSIBLE ENGINEERING TRADE AND IS NOT RECORDED AS A CRITICISM. The METS payload was a physics experiment about ionospheric effects, not a power-delivery demonstration, and a designer who is not being measured on efficiency has no reason to spend package volume on it. THE RECORD EXISTS BECAUSE IT EXPLAINS CLM-0943'S NUMBERS, not because the decision was wrong. NOTHING HERE QUANTIFIES THE EFFICIENCY COST OF THE MISMATCH - the report gives no figure for what the 1.1 cm spacing cost against 2 to 2.5 cm, and this record does not infer one. THE PROTECTION ARGUMENT IS THE REPORT'S OWN AND IS NOT TESTED IN IT: no measurement is offered showing the circuitry would have been damaged without the mismatch.
What it assumes
No assumptions are recorded against this claim.
Where it comes from
All four spans read from SRC-340 PDF p.15 and verified at the normalised level on registration. The impedance values are reported rather than quoted: the text layer renders them as "(120 _2)" and "approximately 25 f_ when spaced 0.11 _," - ohms and the wavelength symbol are both corrupted - and a rendering is not repaired and then presented as verbatim. The reading is secure from context rather than from the glyphs.
Related records
- Answers question
- QST-002 not published in this release
Cite this
energyaperture.com/c/clm-0953
CLM-0953, Energy Aperture, as of 1993.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-340
- CLM-0946A rectenna under test emitted a spurious signal. The cause was the resistor they hung on its output, not the rectenna itself, and swapping...CLM-0948The "space ready" rectenna was tested for surviving the rocket launch and fitting into its container. Its report describes no vacuum or...