Simple answer is that there's little logic to this film when it comes to traveling between the two planets. It takes a few mins to reach Kronos, yet it takes a few seconds to go back. Even stranger, they were knocked out of warp right when they reached the moon, as if they would have kept going if it weren't for the Vengeance firing at them. Crazy huh? It's simply an aspect that the film doesn't really care about because the film wants to have the climax take place in San Fransisco dammit and it wants it now!