Certain part of render taking too long

Hi, so I have been using blender for about two months now and have done a few small projects, but I decided to try something alittle bigger. I took a simple spaceship that I had modeled during a tutorial and added some burner effects to it, as well as an animation of it shooting and blowing up an asteroid. I added a quick explode and a quick smoke modifier to the asteroid to make it blow up. I’ve never really worked with these effects before, so I’m unsure how they effect render times.The part of the animation with the spaceship renders relatively quickly, however any frame with the asteroid in it (frame 166 on) takes AT LEAST two hours to render, and doesn’t seem to have the material I added to it ( a simple brown diffuse). I’m unsure if the render times are because of the added effects, or if I messed up something with my project. I’ve gone through and turned down any of the quality settings that I thought I could afford to so that I could render faster. I’m using cycles render, but I don’t have a GPU that supports GPU rendering. I was wondering if someone could take a look at my .blend file and see if I’ve done something wrong, or if it’s just my computer.
Here’s a link to the .blend file


Thank you so much!!!