From the start, the B-47 bomber had been designed with the capability of delivering nuclear weapons. The hydrogen bomb program, whose development began during the late 1940s and was pressed to completion during the early 1950s, promised to increase the destructive power of nuclear weapons by almost a hundredfold. However, the thermonuclear bomb did present a special problem not encountered by the less-powerful atomic bomb--it was expected to deliver such a lethal blast that it would destroy any aircraft releasing it in the conventional manner.
In 1949, the Air Force began work on a super-secret program to develop an effective delivery system for the upcoming hydrogen bomb. At first, it was thought that only missiles would be suitable for the delivery of the hydrogen bomb. However, in 1949 was estimated that it would take at least three years before any of the missiles that were then under development could be ready. In search of a delivery option that would be available sooner, the Air Force settled on the use of an unmanned aircraft. At the time, only three aircraft could meet the basic load and range requirements--the B-36, B-47, and B-49. Of these, the B-47 seemed to be the most suitable.
Early in 1950, it was decided that one of the ten B-47As expected to be delivered by 1951 would be converted into a drone director aircraft under the designation DB-47A. In support of the program, two future B-47Bs would be modified to unmanned hydrogen bomb carrier (MB-47) configuration. The Air Force was still uncertain about the details of how the MB-47 would operate--one possibility was that it might dive onto its target like a conventional missile, with another option being to release its bomb in the normal fashion and then be destroyed by the blast.
In April of 1951, the program was given the code name Brass Ring. Unfortunately, very little information was available about the size and weight of the future H-bomb, but it was expected to be large and heavy. Consequently, it was assumed that the B-47 drone would have to be refuelled in midair several times in order to reach its target. This meant that the drone would have to carry a crew until the very last refuelling operation. The crew would then bail out over friendly territory and the deserted MB-47 would proceed on to its target guided by autonomous stellar tracking systems or by auto-navigation. The design of a fully-automatic, non-jammable guidance and bombing system provided a major challenge, so the Air Force started to consider the possibility of using a director DB-47 that would accompany the MB-47 drone all the way to the target.
Boeing subcontracted North American Aviation to develop the autonavigation equipment. The Sperry Gyroscope Company was to supply the automatic flight control equipment, and the Collins Radio Company would supply the guidance equipment.
None of these schemes ever reached fruition, because it was found that it was perfectly feasible to deliver hydrogen bombs the old-fashioned way. It was found that a B-36 could release a parachute-equipped H-bomb over a target with an adequate margin of safety for escape. The Brass Ring program was officially canceled on April 1, 1953.