First, it's a very precise spell, it requires the ashes of their heart, so unless we have the right vampire, it won't matter much. Second, dropping a bomb might not do the job. To make sure it's permanent you have to subject them to direct sunlight so they burn, or cut off their head and stake their heart then burn the head and body separately, or use an incantation that's incredibly dangerous to you and I, so that's out.