The Big Belly modifications allowed the B-52D to carry heavy loads of conventional bombs for carpet bombing over Vietnam, while the Rivet Rambler modification added the Phase V ECM systems, which was better than the systems used on most later B-52s. The B-52D was a dedicated long-range bomber without a reconnaissance option. As all 35 B-52Cs could be fitted with the reconnaissance pod, the RB-52C designation was little used and was quickly abandoned. The RB-52C was the designation initially given to B-52Cs fitted for reconnaissance duties in a similar manner to RB-52Bs. The belly of the aircraft was painted with anti-flash white paint, which was intended to reflect the thermal radiation of a nuclear detonation. A new fire control system, the MD-9, was introduced on this model. The gross weight was increased by 30,000 pounds (13,605 kg) to 450,000 pounds. The B-52C's fuel capacity (and range) was increased to 41,700 US gallons by adding larger 3000 US gallon underwing fuel tanks. It subsequently flew as 'Balls 8' in support of NASA research until 17 December 2004, making it the oldest flying B-52B. The NB-52B was B-52B number 52-0008 converted to an X-15 launch platform. Seven B-52Bs were brought to B-52C standard under Project Sunflower. The pod required only four hours to install. Of the 50 B-52Bs built, 27 were capable of carrying a reconnaissance pod as RB-52Bs (the crew was increased to eight in these aircraft).The 300 pound (136 kg) pod contained radio receivers, a combination of K-36, K-38, and T-11 cameras, and two operators on downward-firing ejection seats. Temporary grounding of the aircraft after a crash in February 1956 and again the following July caused training delays, and at mid-year there were still no combat-ready B-52 crews. This version included minor changes to engines and avionics, enabling an extra 12,000 pounds of thrust using water injection. The B-52B was the first version to enter service with the USAF on 29 June 1955 with the 93rd Bombardment Wing at Castle AFB, California. The NB-52A, named 'The High and Mighty One' carried the X-15 on 93 of the program's 199 flights. Its first flight with the X-15 was on 19 March 1959, with the first launch on 8 June 1959. Liquid oxygen and hydrogen peroxide tanks were installed in the bomb bays to fuel the X-15 before launch. A pylon was fitted under the right wing between the fuselage and the inboard engines with a 6 feet x 8 feet (1.8 m x 2.4 m) section removed from the right wing flap to fit the X-15 tail. The last B-52A (serial 52-0003) was modified and redesignated NB-52A in 1959 to carry the North American X-15.

The tanks damped wing flutter and also kept wingtips close to the ground for ease of maintenance.

The aircraft also carried a 1,000 US gallon (3,785 L) external fuel tank under each wing. In the rear fuselage, a tail turret with four 0.50 inch (12.7 mm) machine guns with a fire-control system, and a water injection system to augment engine power with a 360 US gallon (1,363 L) water tank were added. The bubble canopy and tandem seating was replaced by a side-by-side arrangement and a 21 in (53 cm) nose extension accommodated more avionics and a new sixth crew member. The first production B-52A differed from prototypes in having a redesigned forward fuselage. Only three of the first production version, the B-52A, were built, all loaned to Boeing for flight testing. One XB-52 modified with some operational equipment and re-designated Two prototype aircraft with limited operational equipment, used for aerodynamic and handling tests The B-52 went through several design changes and variants over its 10 years of production. USAF KC135R LAGR973, USAF E8C Joint STARS REDEYE6, USAF KC10 NACHO134, NATO A330NRTT MMF18, USAF C130H HKY152, USAF KC10NACHO134, USAF B52 NOBLE42, USAF KC10 NCHO223 United States Air Force (USAF), Boeing B-52 Stratofortress

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