The Russians tested a 50 megaton bomb in 1961.
They dropped it from 34,000 feet, over a cluster of Russian islands, north of the Arctic Circle.
It descended for three minutes with a parachute, then detonated at 12,500 feet.
The thermal pulse burned off a coat of protective white paint on the bomber and the chase plane, which were 30 miles away and 4 miles above the explosion.
Andrei Sakharov helped design the bomb. Soon after the test, he resigned from weapons research and became a human rights activist.
Tsar Bomba. Atmospheric reflection blew out windows 400 miles away.