Your explosions look very good!
If you want to make them more realistic here some things i miss:

- in outer space there is not much fire because there is nearly no O² (only the one from the ship). So there is nearly no smoke.
I think spaceships better explode with an energy flash and a shockwave

- on earth the smoke moves up or is blown by the wind, expanding not radial and dissapear but growing randomly and vanish.


But thats just my ideas and your explosions look realy good!