A/N: I haven't written in the Superman fandom before, and this is both a) not very generous towards Jor-El and b) completely unreviewed (I'm such a hypocrite), but I just wanted to get the premise out on Word.
Peer Review (It's There For a Reason)
Jor-El paced through his lab, agitatedly typing into one terminal here, another there. The calculations he was performing were complex and time-consuming, and he didn't think when he called Zor-El over that he would have this much trouble convincing his own brother.
Across the lab from him, Zor-El was talking. "Jor-El, this is madness. As a member of the Science Council and on my own, I've been over your calculations, and you're wrong. The sun will not explode!"
Jor-El turned to his brother. "You just don't understand, do you?" he fumed as he shoved a packet into Zor-El's face. "Read it. It's right. It's undeniable."
Zor-El slapped the papers away from his face, annoyed. "I did it myself, Jor-El. Double checked it, too and-"
He broke off as he saw two rockets inside the lab: one small, only fit to transport a baby, and one gigantic, almost too big for the lab to contain – and Jor-El's personal lab was the largest in all of Krypton, greater even than the labs allotted to the entire Science Council.
"What is this?" Zor-El asked, amazed despite himself.
"My plan," Jor-El's expression changed from shadowed to bright, "to save our people."
"Explain." Zor-El was nervous. "Now."
Jor-El laid out his plot.
Zor-El listened, and refrained from commenting that his brother was clearly a madman.
In order to save the planet, Jor-El was going to attach a gigantic mass driver onto the pole, and literally push Krypton behind the cover of one of the other orbiting planets, which Jor-El had long ago fitted with heat shields for this specific purpose. After the sun had gone nova, the drivers would provide heat for the planet until Jor-El could get it settled in another system.
It was insanity. Assuming the sun did not blow up, the way everyone's calculation other than Jor-El's said, this maneuvering of the planet would lead it directly into the sun's orbit, flash frying everyone on Krypton and blowing chunks of the planet into the solar wind.
But there was no way to stop him. Jor-El's plan was almost done - the crystal technology had been building on the pole unnoticed for years now, and the rocket would arrive by force of arms if not by peaceful acclamation. Jor-El was going to win, one way or another.
"And the other rocket?" Zor-El asked, stalling for time.
Jor-El's gaze grew cold once again. "That is my contingency. My son Kal was just born, and in the event that I am unable to save the planet, he will enter the rocket and be blown by the solar wind to a planet where he will be accepted. I have prepared crystals enough for him that he will be safe."
Zor-El nodded. Of course; Jor-El would protect his son from even his own foolishness. He swallowed, making his decision.
"Go ahead, Jor-El. I'll make one for Kara, too. No matter what, they must be safe."
He saw a gleam of understanding in his brother's eyes.
A/N: Sorry for all the canon I'm sure I mutilated.
And that's how Krypton really died.