JWST app "where is webb" just started displaying vehicle temperatures. It is said in the background info that these temperatures were predicted from thermal modeling. I would like to know how well the actual measured temperatures are comparing with the predictions. A reference to any published papers on the predictions would also be interesting.

In my youth, some time ago, on the Apollo project, I was involved in spacecraft thermal control and modelling efforts. At that time, the thermal analysis software was new and evolving as was the application of the software. Engine fuel components for the Service Module, for example, could not get too hot (would vaporize the storable fuel and/or oxidizer) or too cold (would freeze the fuel and oxidizer). Either situation could jeopardize the entire mission. Thermal control approaches were evolved to meet predicted problems. Our analytical thermal modelling predictions were found adequate (but not great) as verified through a thermal simulator wherein various radiation sources were applied to a full scale vehicle and later through actual data.

I'd be interested to see how well the current state-of-the-art predictions compare with the actual data. Should be better than in the distant past.

tom kosvic

  • $\begingroup$ Right now(30 dec) the hotside is 80C cooler, and the coldside is about 170C hotter than the optimal. This is expected, of course, as the heatshield is not even close to deployed yet. Additionally, much of the deployment process involves electrical heating strips to get structural and mechanical elements to the desired deployment temperature. Even once fully deployed, the coldside will take (literally, no exaggeration) months to reach the correct equilibruim temperature. This question will need to sit until april or so before it can be answered honestly. $\endgroup$ Commented Dec 30, 2021 at 6:30
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    $\begingroup$ @CuteKItty_pleaseStopBArking the question mentions that the current numbers on the site are modeled, not measured. That doesn't seem unreasonable considering that the temps haven't changed in hours. Additionally, it's a request to the papers/data used to predict those numbers. So most of that should be answerable today, if it's available. And even though it won't be at equilibrium soon, we should still be able to compare cooling curves predicted (I believe I've seen a chart of this) to what the spacecraft is measuring, and that also doesn't have to wait, though the answer can be updated $\endgroup$ Commented Dec 30, 2021 at 12:26
  • $\begingroup$ @fyrepenguin "doesn't seem unreasonable considering that the temps haven't changed in hours". The site does say "These temperature observations are reported daily from actual spacecraft telemetry data." so not changing is several hours is expected. (click on the word Cold Side>, 4th paragraph, 4th sentence) $\endgroup$ Commented Dec 30, 2021 at 13:31
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    $\begingroup$ @CuteKItty_pleaseStopBArking ah, I'd missed that bit. Even better, since that means we currently have data that can can start to be fit to whatever predicted values there were $\endgroup$ Commented Dec 30, 2021 at 13:36
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    $\begingroup$ My question would be "how do the current measured temperatures compare with the preditions made for vechicle temperatures at the physical ponts of the measured data for the vehicle in it's current state of deployment". The measured temps must be being compared with predictions to analyze for any anomalies of concern. $\endgroup$
    – tckosvic
    Commented Dec 31, 2021 at 7:52


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