Forgive my ignorance, but what is a “gravity” nuclear bomb? Drop one from an airplane and gravity does the rest. I thought all nuclear bombs were “gravity” bombs.
Yes they are gravity bombs. I loaded the B-61, MK-61 back then, when it first came out in the late sixties. Obviously this is a newer generation of the same. Tactical fighters such as the F-16 (F-100 in my case to show my age) actually release the weapon on an upward arc of a climb. not straight over and dump. Easy weapon to load compared to it predecessors.
I don’t know but I assume it doesn’t detonate until it penetrates the ground after so many feet. Just a guess...
Gravity weapons are dropped from aircraft. There are other weapons that are delivered by missiles, and once we even had artillery delivered, and man-portable weapons. Those are not considered gravity weapons.