WHAT DOES UNDERWATER NUCLEAR TEST 'UMBRELLA' MEAN?

This leads to the blast bubble in no way to get beautifully spherical. Instead, The underside from the bubble is flatter, and during contraction, it even has a tendency to "arrive at up" toward the blast center.“The underwater nuclear assault drone, which was deployed for any drill from the coast of Riwon County of South Hamgyong Province on Tues