Passage: During World War II, it carried President Franklin D. Roosevelt across the Atlantic to Mers El Kébir, Algeria, en route to a meeting of vital importance in 1943 in Tehran with Prime Minister Winston Churchill of Britain and Joseph Stalin, leader of the Soviet Union. When transferred to the Pacific Fleet in 1944, Iowa shelled beachheads at Kwajalein and Eniwetok in advance of Allied amphibious landings and screened aircraft carriers operating in the Marshall Islands. It also served as the Third Fleet flagship, flying Admiral William F. Halsey's flag at the Japanese surrender in Tokyo Bay. During the Korean War, Iowa was involved in raids on the North Korean coast, after which it was decommissioned into the United States Navy reserve fleets, better known as the "mothball fleet." It was reactivated in 1984 as part of the 600-ship Navy plan and operated in both the Atlantic and Pacific Fleets to counter the recently expanded Soviet Navy. In April 1989, an explosion of undetermined origin wrecked its No. 2 gun turret, killing 47 sailors.

Question: The naval ship Iowa lost how many sailors during an 1989 explosion?
47