I am not sure how you know what my intuitions are. My insights come from reading the "design trades" papers about Webb published over the last 20 years. Here i

I am not sure how you know what my intuitions are. My insights come from reading the "design trades" papers about Webb published over the last 20 years. Here is a good place to start: https://www.spiedigitallibrary.org/journals/Journal-of-Astronomical-Telescopes-Instruments-and-Systems/volume-6/issue-01/010902/Review-on-thermal-and-mechanical-challenges-in-the-development-of/10.1117/1.JATIS.6.1.010902.full?SSO=1 https://www.spiedigitallibrary.org/journals/Journal-of-Astro... Yes, insulating an RTG from the IR sensors would have been a challenge, but one that could be completely and accurately tested on earth. The lack of sufficient power directly drove the passive cooling requirement. Which in turn drove the fraught 5 layer shield requirement - which has never been and can't be "Test as you fly" tested on earth. The lack of power also drove the decision to use the experimental 26 Ghz Ka band downlink radio instead of a higher power and more robust X band radio.