Mark 28 nuclear bomb

The Mark 28 series of bombs are the oldest nuclear weapons in the United States arsenal with first deployment in 1958. It can be assembled and deployed in five different configurations. "The first Mk-28 drop shapes were the Internal, or IN, version; the External, or EX, version; and the Retarded External, or RE, version."

Mk-28 EXTERNAL

The EX version of the Mk-28 was designed for use on both bombers and fighter-bombers in attacking strategic targets. High kiloton to megaton yield.

Mk-28 INTERNAL

The IN version of the Mk-28 was designed for bomb-bay equipped aircraft, including F-105s, for strategic targets. High kiloton to megaton yield.

Mk-28 RETARDED EXTERNAL

The Retarded External, or RE, version of the Mk-28 was a Mk-28EX equipped with a parachute system (4 ft. pilot, 28 ft. ribbon chute). High kiloton to megaton yield.

Mk-28 FULL FUSING INTERNAL

The FI, or Full Fusing Internal Mk-28, was developed to adapt to new low-level delivery techniques of the Air Force in the 1960s, and is the only model of this bomb equipped for air, ground, and delayed action burst. High kiloton to megaton yield.

Mk-28 RETARDED INTERNAL

The RI, or Retarded Internal, was the fifth and final variants of the Mk-28 deployed. Although externally identical to the Mk-28FI, it only carried fusing for air and contact burst. For low altitude drop, a different, larger parachute system was used. High kiloton to megaton yield.