nuclear and non-nuclear components of weapons. This was justified on the basis that air defense warheads needed to be readily available for use, needed to be highly resistant to premature detonation, and needed to economise the use of nuclear materials. Sandia conducted research into the optimum size of an air-to-air missile warhead and, in May 1954, the Atomic Energy Commission began development of an air-to-air nuclear warhead. In May 1954, the military characteristics were specified for a warhead. It would be capable of remaining at the ready condition for 30 days, be capable of 50 hours flight time at altitudes of up to , and withstand temperatures of . The warhead would be able to withstand acceleration of along the longitudinal axis and along perpendicular axes. In June 1954, the warhead names Mark 25, Mark 30 and Mark 31 were formally adopted. The air force would be responsible for the rocket systems, including the arming and fuzing system, while the AEC would supply the warhead and associated assembly, testing and handling equipment. The rocket for the warhead was initially named Ding Dong and was optimised for carriage on the F-86 Sabre, F-89 Scorpion and F-100 Super Sabre. The rocket was to be in diameter, but excursions of up to were to be investigated. A study of yield to kill probability was published in November 1954. While higher yields increased the lethal radius of the weapon, higher yields required the launching range to be increased to allow for a safe escape by the launching aircraft. This reduced the accuracy of the weapon, eventually counteracting the advantage from the increased yield. Cost in nuclear material to kill was also studied, and it was found that the largest weapon diameter of was most efficient in nuclear material. However, larger weapons required a larger rocket and caused aircraft compatibility problems. A diameter of was eventually settled on. In January 1955, the joint study group was dissolved and reformed as the Air-to-Air Rocket Joint Project Group. By that point, the weapon weighed approximately . In March 1955, the assistant secretary for defense authorised the full development of the rocket and its warhead. In the same month, the air force expressed an urgent desire to have the weapon operational by 1957. Because of the numbers required, they requested that quantity production of the weapon begin but, because no firm production directive had been received, the AEC