This is historical footage of a test drop of an unarmed AGM-86B air-launched cruise missile by a B-52H Stratofortress over the Utah Test and Training Range on September 22, 2014. Twenty nuclear tipped AGM-86B missiles can be deployed by one B-52H. The weapon has a range of 1000 miles, so no B-52 aircraft has to enter enemy territory. The ending footage is Castle Bravo nuclear test.
Corresponding Air Force fact sheet: http://www.af.mil/About-Us/Fact-Sheets/Display/Article/104612/agm-86bcd-missiles/
Film Credits: TSgt Roidan Carlson