In the 1950s, the US Navy studied the “Diamondback”, a Sidewinder-derived nuclear air-to-air missile with liquid propulsion and dual-mode guidance.

In the mid-1950s, the US Navy initiated the “Diamondback” project, aimed at developing a nuclear-tipped air-to-air missile derived from the Sidewinder. This missile was to feature liquid-fuel propulsion and a dual-mode guidance system, combining infrared seeker and passive radar guidance. Despite significant advances, the project was abandoned in the late 1950s, as the navy preferred other air defense solutions.

Diamondback” project background

In 1956, the Naval Ordnance Test Station (NOTS) in China Lake, California, launched studies to improve the AAM-N-7 air-to-air missile, known as the Sidewinder. The aim was to create a longer-range, nuclear-capable version, initially called “Super Sidewinder”, then renamed “Diamondback” in reference to a species of rattlesnake, following the tradition of naming missiles after vipers.

Technical specifications

The “Diamondback” was to measure 3.75 meters in length, with a diameter of 30 centimeters and a wingspan of 1 meter. Weight was estimated at 385 kilograms. The propulsion system envisaged was a dual-pulse liquid-fuel rocket engine, derived from the NOTS Liquid Propellant Aircraft Rocket (LAR) project. This type of propulsion, using a hypergolic mixture of RFNA and hydrazine, was to enable the missile to reach a speed in excess of Mach 3 (i.e. over 3,675 km/h) and a range of between 24 and 32 kilometers. The operational ceiling was estimated at 24,000 meters, well above the flight altitude of aircraft at the time.

Innovative guidance system

The “Diamondback” was to be equipped with a dual-mode guidance system, combining an infrared seeker and passive radar guidance. This approach was intended to improve the probability of target destruction by enabling the missile to track its target even if one of the guidance systems failed. At the time, air-to-air missiles generally used a single guidance mode, making this dual approach particularly innovative.

Nuclear weapons

Among the armament options, a low-yield 0.75-kiloton nuclear warhead was considered for the “Diamondback”. This approach was in line with the doctrine of the time, which saw nuclear weapons as an effective solution for neutralizing enemy bomber formations. Other nuclear air-to-air missiles, such as the US Air Force’s GAR-11 (later AIM-26A “Nuclear Falcon”), were also developed along these lines

Abandonment of the project and its consequences

Despite significant advances, the “Diamondback” project was abandoned around 1958. The U.S. Navy felt that the missile did not meet its operational needs, preferring to concentrate on other air defense systems. This decision led to the subsequent development of longer-range missiles, such as the AIM-54 Phoenix, which equipped the F-14 Tomcat and became a mainstay of the fleet’s air defense for many years.

Diamondback” heritage

Although the “Diamondback” was never put into service, it represents a milestone in the evolution of long-range air-to-air missiles. The concepts explored, such as dual-pulse propulsion and dual-mode guidance, influenced subsequent developments in the missile field. Today, the US Navy continues to seek solutions to long-range air threats, with projects such as the AIM-174B, an air-to-ground variant of the SM-6 missile, designed to meet the challenges posed by potential adversaries such as China.

The “Diamondback” project illustrates the US Navy’s technological innovation efforts in the 1950s to improve its air defense capabilities. Although the missile was never deployed, the lessons learned from its development helped shape the air defense strategies and technologies of the following decades.

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