Value chain · CLM-0883
In plain terms
NASA puts the level at which internal charging starts causing failures at twenty billion electrons per square centimetre over ten hours, and designs to half that. It says no safety margin beyond that is specified.
The claim as recorded
NASA's internal charging guidance states an anomaly threshold of 2x10^10 electrons per square centimetre accumulated over a 10-hour period, equivalent to a 5x10^5 per square centimetre per second average, and states that no additional safety factor is specified in the NASA Handbook; the same document's design guidance protects to 10^10 electrons per square centimetre per 10 hours, a factor of two below that threshold.
Evidence behind this: Same held document as CLM-0882. Read from a rendered page because this scan's text layer corrupts the digits: it gives "2x101" for 2x10^10.
Scope and limits
THE THRESHOLD IS INFERRED FROM ANOMALY EXPERIENCE, NOT MEASURED AS A FAILURE POINT. The document's own words are that it is implied by on-orbit anomaly analysis of various satellites together with CRRES experimental data, and it opens the section by saying it is not an easy answer. It is a threshold for internal charging anomalies in conventional spacecraft, not a qualification limit, and no SPS-scale structure is in evidence behind it. Dated 2000. THE FACTOR OF TWO IS THE DOCUMENT'S TWO NUMBERS SET SIDE BY SIDE, NOT A MARGIN THE DOCUMENT CLAIMS, and it says explicitly that no additional safety factor is specified.
What it assumes
That the anomaly threshold and the design protection level refer to the same accumulated quantity, which the document states in the same units but does not explicitly relate.
Where it comes from
Read on the rendered page 2 of the held file: "These sources imply that the internal charging anomaly threshold is 2x10^10 electrons per square centimeter accumulated over a 10-hour period (equivalent to 5x10^5/cm2-s average). An additional safety factor is not specified in the NASA Handbook." The design level is on page 3: "protect dielectrics and circuits to the level of 10^10 e/cm2 per 10 hours".
Basis: GEO internal charging environment
Related records
- Answers question
- QST-043 not published in this release
Cite this
energyaperture.com/c/clm-0883
CLM-0883, Energy Aperture, as of 2000.
Connected records
Other published records linked to this one. A list, not a judgement.