Vault-Tec Project Manager 1 and Vault-Tec Project Manager 2 in “Unfinished Business”

This is what a five-megaton blast will look like over Los Angeles. Marketing thinks a ten-megaton blast would look better for the billboards.

But it won't be a ten-megaton blast. It will be multiple five-megaton blasts.

Obviously it would be multiple five-megaton blasts. But the design team thought it looked too busy. Just a cacophony of puff clouds.