RB-47B was the designation initially given to a proposed photo-reconnaissance version of the B-47B Stratojet. It was designed to replace the RB-29 and RB-50 aircraft which were serving in the long-range photo-reconnaissance role but which were rapidly approaching obsolescence.
The design of the RB-47B began in March of 1951. Shortly before October 1952, it was decided that the plane would feature the A-5 fire control system as well as the still-experimental J47-GE-25 engines. Since it was projected that the RB-47B would not be ready before 1954, and by the time that the RB-47B was completed it would more closely resemble the B-47E than the B-47B, the reconnaissance version of the Stratojet was redesignated RB-47E.
What actually became known as the RB-47B were 24 B-47Bs that were converted to reconnaissance configuration in 1953-54 by adding a special 8-camera heated pod in the forward bomb bay. Unlike the later RB-47E, the RB-47B could only provide daylight photographic coverage.
The YRB-47B was a later conversion of the B-47B specifically intended for the training of crews for RB-47Es. The 91st Strategic Reconnaissance Wing (Medium) received its first YRB-47B in April of 1953, the 26th 3 months later.
In 1953 a decision was made to also equip 320th BW at March AFB with YRB-47Bs. The conversions were carried out by Douglas and by the Grand Central aircraft companies. Between July and November, 1953, the 320th received 44 YRB-47Bs. In November of '53, the Wing began to restore all of these planes back to bomber configurations, completing all re-conversions by March, 1954. Eventually, these were exchanged through "High Noon" and other programs.