Nicdanger

Having the same issue with no mods, finally used the thermal debug tool and a very ineffective gravity turn to keep the temperature down. Now in a stable orbit and my probe is still bright yellow/orange.

The first time I played thru career mode I finished off the tech tree with a very ambitious (at least for me at the time) mission to Jool that involved 5 separate probes gathering science from Jool and 4 out of 5 of its moons. Then landed Bill and Jeb on Duna and Ike, built a few space stations, messed around with space planes, ect, ect. Then I added a bunch of difficulty mods and started over. Then added more and did it again. Currently working on a "Better Than Starting Manned" play thru and having as much fun as when I first found this game. Why? Building insanely huge things in space is pretty cool but once you've got the basics down exploring the kerbol system is (to me) less of a challenge and more a time consuming chore. Stuff like BTSM adds depth and challenge in a way that exploring the last bits of the vanilla KSP experience just won't do for me. Now I may think my way of playing KSP is better than yours, but I respect yours enough to not question your maturity just because I like rocky road and you like cookie dough. Food for thought.