I ran into the Kraken when running two inter-planetary rescues at one time. I had one rescue ship returning to Kerbin and I was sending a 2nd out to another planet. Once the 2nd ship entered orbit around Kerbol on it's way to my stranded science probe, I switched back to the first ship with Bill orbiting Kerbol on an intercept course with Kerbin. When Bill's ship finished loading, I got the NaN velocity and scrolling altitude landing on 666666. I was able to load a recent quicksave, but every time I tried to load either ship that was currently in orbit of Kerbol, the Kraken attacked. Luckily both ships were on course for an SOI intercept, so I thought I could just accelerate time until one of them was out of Kerbol orbit. I closed the game and called it a night, though. Then I had an idea- I installed KSP on a slightly older laptop and tried my save file. Amazingly, the Kraken did not show up, so I completed the rescue missions and exited and brought the save file back to the original computer. Kraken has stayed away since then.. so far. SO- Kraken definitely seems to be a pre-determined thing, but also random in a sense, as it seems to depend on the exact hardware running the game. Perhaps if you run into a particularly damaging Kraken attack, you could send your savefile to another player, have then open the game and load up a few ships, and if the Kraken doesn't attack, they could then send the savefile back to you and you can see if the Kraken has been dodged?