 The Tsar Bomba is the single most physically powerful device ever deployed on Earth.For comparison, the largest weapon ever produced by the U.S., the now-decommissioned B41, had a predicted maximum yield of .The largest nuclear device ever tested by the U.S. (Castle Bravo) yielded because of an unexpectedly high involvement of lithium-7 in the fusion reaction; the preliminary prediction for the yield was from .