'cluster nukes' are being developed researched - many small 1megaton nukes clustered into a larger nuke that is cased with 30mt, so it's around 37mt, and then... forget... two of those, creating power more than the Tsar Bomba. (its not all that ridiculous. the lining is the same material of matches, and it flips-inside out to light it, so that the other nukes explode.)