I got some explosion sounds while playing with bass and reverb the distortion makes it seem more powerful I think, you can download it if you like. I don't know how the scene plays out exactly but you could also try slowly pitching up the engine sounds as it descends to add more tension and and lower other sounds with it prior to the explosion to make it seem more powerful (like this LoTR example), Greg Russell also mentions a good point (skip to 16:35) when mixing to make an impact seem more powerful.

I got some explosion sounds while playing with bass and reverb the distortion makes it seem more powerful I think, you can download it if you like. I don't know how the scene plays out exactly but you could also try slowly pitching up the engine sounds as it descends to add more tension and and lower other sounds with it prior to the explosion to make it seem more powerful (like this LoTR example), Greg Russell also mentions a good point when mixing to make an impact seem more powerful.