Who was in the bubble at the bottom of the b52 in World War 2?

B-52's were not developed until the late 1940's and didn't see operational service until 1955, and therefore were not used in a major conflict until the Vietnam War. The "bubble" you refer to is called a "ball turret" and was operated often by the flight engineer, or possibly the smallest person on the crew, as it was a tight fit. It was seen on the B-17 and the B-24 bombers of World War 2. B-52 bombers do not have a ball turret, but there was a small rear-facing tail gunner position under the vertical stabilizer (also on B-17 and B-24s) on early B-52 models that was operated by a crewman. That was later replaced by an automatic system.