For all people who have problems with missiles that don't make enemie explode: after a week I finally solved it! You have to make sure that the name of your 'ship' is exactely filled in the codes, and it must be different from the class name. So I called it 'ShipInstance' and it only worked after I filled in this:
for(var i in _root.ShipInstance.enemies)
{
if(this.hitTest( _root.ShipInstance.enemies[i] ) )
{
this.removeMovieClip();
_root.ShipInstance.enemies[i].explode();
}
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