The PGM-19 Jupiter was the first nuclear armed, medium-range ballistic missile (MRBM) of the United States Air Force (USAF). It was a liquid-propellant rocket using RP-1 fuel and LOX oxidizer, with a single Rocketdyne LR79-NA (model S-3D) rocket engine producing 150,000 lbf (670 kN) of thrust. It was armed with the 1.44 Mt (6.0 PJ) W49 nuclear warhead. The prime contractor was the Chrysler Corporation. The Jupiter was designed by the US Army, which needed a highly accurate missile designed to strike enemy states such as China and the Soviet Union. The US Navy also expressed an interest in the design as an SLBM but dropped the collaboration to work on their solid-fuel Polaris. Jupiter retained the short, squat shape intended to fit in submarines.
Development history
Initial concept Jupiter traces its history ultimately to the PGM-11 Redstone missile, the US's first nuclear ballistic missile. While it was entering service, Wernher von Braun's Army Ballistic Missile Agency (ABMA) team at Redstone Arsenal began to consider an upgraded version using the LR89 rocket engine being developed by Rocketdyne for the Air Force's Atlas missile project. Using the LR89 and adding a second stage would allow the new design to reach 1,000 nautical miles (1,900 km; 1,200 mi), a dramatic improvement over the Redstone's roughly 200 miles (320 km). As Rocketdyne continued working on the LR89, it appeared that it could be improved to increase thrust over the promised 120,000 pounds-force (530,000 N). In 1954, the Army asked Rocketdyne to provide a similar design with a thrust of 135,000 pounds-force (600,000 N). During this same period, the weight of nuclear warheads was rapidly falling, and by combining this engine with a warhead of 2,000 pounds (910 kg) they could build a single-stage missile able to reach 1,500–1,700 miles (2,400–2,700 km) while being significantly less complicated and easier to handle in the field than a two-stage model. This engine was continually upgraded, ultimately reaching 150,000 pounds-force (670,000 N). This last model, known to the Army as the NAA-150-200, became much better known by its Rocketdyne model number, S-3.
Navy SLBM interest
Around the same time, the US Navy was looking for ways to join the nuclear club, and had been focusing mostly on cruise missiles and similar systems. Some consideration had been given to the use of ballistic missiles on ships, but Admiral Hyman Rickover, "father" of the nuclear submarine, was skeptical that this could be done, and was worried it would take up funding needed elsewhere. Another skeptic of missiles was the Chief of Naval Operations, Robert B. Carney. Lower-ranking Navy officials became increasingly interested when the Army and Air Force began serious development of their long-range missiles. In an attempt to bypass high-ranking Navy officials, who remained uninterested in the concept, the Navy liaison to the Killian Committee championed the cause. The Committee took up the concept, and in September 1955 released a report calling for the development of a sea-based missile system. The Navy's interest in missiles had been greatly increased with the August 1955 appointment of Admiral Arleigh Burke to replace Carney. Burke was convinced the Navy had to get into the missile field as rapidly as possible, and was well aware that the Air Force would oppose any such endeavor. Instead, he approached the Army, and found that the proposed Jupiter fit the range goals needed by the Navy.
Development begins The issue of who would be given the go-ahead to build an IRBM by this time had reached the Joint Chiefs of Staff (JCS), who proved unable to reach a decision. This forced the Secretary of Defense Charles Erwin Wilson to move ahead without an official recommendation from the military. He saw the Navy interest as a reasonable argument to continue the Army project in any event, and on 8 November 1955 approved both programs. The Air Force would develop IRBM No. 1, or SM-75 (for "strategic missile"), the Army would develop their design as IRBM No. 2 or SM-78. The Navy would develop systems to launch the Army missile from ships and, later, submarines. BuShips completed a conceptual design that would take a Maritime Administration type C4-S-1a hull and convert it into a Jupiter missile launch ship, which was given the hull symbols YAG-58 then EAG-155; the conversion would later be canceled. The requirement for shipboard storage and launching dictated the size and shape of the Jupiter. The original Army design was 92 feet (28 m) long and 95 inches (2,400 mm) in diameter. The Navy stated they were not interested in anything longer than 50 feet (15 m). The ABMA team responded by increasing the diameter to 105 inches (2,700 mm). This precluded it from being carried aboard contemporary cargo aircraft, limiting it to sea and road. Even with this change, they were unable to reduce its length enough to suit the Navy. They suggested that they begin with a 60 foot (18 m) long version and then scale it down as improvements in the engines were worked into the design. This was rejected, and after briefly considering a 55 foot (17 m) version, finally settled on the 58 foot (18 m) version. On 2 December 1955, the secretaries of the Army and Navy publicly announced the dual Army–Navy program to create a land- and sea-based MRBM. In April 1956, as part of a widespread effort to assign names to various missile projects, the Army's effort was given the name "Jupiter" and the Air Force's became "Thor".
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