Polaris A-1 (UGM-27A)

Polaris A-1 (UGM-27A)


The Polaris A-1 was the world’s first long-range Submarine-launched ballistic missile (SLBM) powered by solid-propellant rocket motors and the very first to be deployed on U.S. Navy submarines, equipped with a nuclear tip. Given its pioneering features and capabilities, the Polaris SLBM is often considered the most vital missile ever deployed by the U.S. Navy.

In November 1960, the USS George Washington (SSBN 598) became the first submarine to carry and deploy the Polaris A-1 missile. Although the Soviet SS-N-4 Sark, also known as the Soviet R-13, had been deployed at sea earlier, the Polaris SLBM was decidedly more advanced, making it a revolutionary weapon system that truly stood out.

Length:28 ft 6 in (8.7 m)
Diameter:4 ft. 6 in (1.37 m)
Weight:28,500 Ibs (12,927 kg)
Range:500 (926 km) - 1,200 n.miles (2222 km)
Accuracy:12,000 ft (3,658 m) C.E.P.
Propulsion:2-stage solid propellant
Warhead:1 x W-47 Y1 nuclear (600 KT)
Main contractor:Lockheed Missile and Space Coorporation (now Lockheed Martin Space Systems, Missile and Space Operations, Sunnyvale, California)

Before the inception of the Polaris SLBM, there was a collaborative effort between the Army and Navy. From November 1955 to December 1956, this joint program worked towards developing an Intermediate-Range Ballistic Missile (IRBM) that could be launched not just from land but also from ships. Following the culmination of this program, the Navy then decided to embark on the fleet ballistic missile (FBM) program, which eventually led to the development and deployment of the remarkable Polaris A-1 missile.



The A-1 Polaris missile, with its range of 1,200 nautical miles (2,220 km), emerged not as a final product, but rather as an interim weapon. Its design was rooted in a pressing need: to position a strategic deterrent on station as soon as possible. This urgency was driven by the advances in Soviet rocketry technology.

Polaris A-1 missile info

However, the Polaris Program’s objective was the delivery of a 1-megaton warhead up to a span of 1,500 miles. Therefore, when the first A-1 missiles were deployed on the USS George Washington (SSBN 598), there were plans in motion to develop variants with even longer ranges.

In its design, the Polaris was engineered as a two-stage ballistic missile. It drew its propulsion from two solid-fuel rocket motors. A standout feature of the Polaris was its self-reliant inertial guidance system. This system was designed to operate independently, without the need for any external commands or controls.

The missile itself boasted an impressive stature: it measured 8.53 meters in length, had a diameter of 137 cm, and tipped the scales at approximately 13,600 kg.

Model of USS George Washington (SSBN-598) showing the vessel launching a Polaris A-1 missile.
Model of USS George Washington (SSBN-598) showing the submarine launching a Polaris A-1 missile. (U.S. Navy photo)

Each of the missile’s motors directed its thrust via four nozzles situated at the motor’s base. To control the direction of this thrust, the design incorporated devices known as jetavators. And for durability, both the first and second-stage motor cases were crafted using steel.


For the Polaris missile, the heart of its precision laid in its guidance system: the Mk. 1. MIT’s Instrumentation Laboratory took the lead in designing and developing this innovative system.

The Mk 1 was not just any inertial system; it was a refined version, surpassing predecessors in compactness and efficiency. In fact, among early US ballistic missiles, it stood out as the most compact system. It seamlessly combined the inertial components and electronics into a single module. Despite its intricate functionality, the entire system weighed just 225 pounds.

Model of the Polaris A-1 missile displayed outside the Smithsonian Institute.
Model of the Polaris A-1 missile displayed outside the Smithsonian Institute. (U.S. Navy photo)

The electronics of the Mk. 1, having a total gate count of around 400, was on par with the complexity of a modern digital wristwatch. This might sound simple by today’s standards, but for its time, it was revolutionary.

The guidance package of the missile was a two-fold assembly. First, there was the inertial platform, a gyro-stabilized trio of accelerometers. These devices played a crucial role during the missile’s flight. Second, was a digital computer. This wasn’t just any computer; it was heralded as the first digital computer ever to be integrated into a missile.

View of the "Sherwood Forest" (missile section) around 1959 on the USS George Washington (SSBN-598).
View of the “Sherwood Forest” (missile section) around 1959 on the USS George Washington (SSBN-598). (U.S. Navy photo)

Upon the missile’s launch, the digital computer took charge. Throughout the missile’s flight, the inertial platform gauged in-flight accelerations, converting them into velocities. The computer then continuously received this velocity data. With a pre-set required velocity, fed by the ship’s fire control system and stored in its memory, the computer kept comparing the two. By doing so, it ensured the missile stayed on its precise trajectory.


Aerojet Corporation, known as a top player in composite propellant production, took charge of building the rocket motors for the Polaris A1. They were responsible for both the first and second stages. The propellant chosen for these stages combined polyurethane with an ammonium perchlorate oxidizer and aluminum additives.

Polaris A-1 test missile launching.
Polaris A-1 test missile launching. (U.S. Navy photo)

The casings for these early Polaris missiles had to be robust and heavy. This strength was necessary to handle the high pressures resulting from the propellant’s combustion. To ensure the casings met these requirements and still be easy to weld, a unique low-alloy steel was developed just for the Polaris.

Thrust direction during the flight was controlled by something called jetavator rings. So, what’s a jetevator? It’s a sturdy ring with a spherical interior, positioned over the rocket’s nozzle. When this ring shifts into the exhaust’s path, it diverts the flow, allowing direction changes.

To put it simply, the Polaris A1 had two main stages, and each of these stages had four nozzles equipped with jetevators. These devices adjusted the missile’s pitch, yaw, and roll in flight. And the term ‘jetavator’? It’s a shorter version of ‘jetelevator’, which perfectly describes the device’s job: to lift and redirect jet streams.

Payload & Warheads

The Polaris A-1 missile utilized the MK 1 reentry vehicle. This same vehicle was also employed on the Polaris A2. Significantly, it was equipped with a powerful W-47 600 Kt thermonuclear warhead. However, it’s worth noting that it didn’t possess any notable penetration aids.

Model of Polaris A-1 Missile displayed at Mare Island during the launch of USS Theodore Roosevelt (SSBN-600).
Model of Polaris A-1 Missile displayed at Mare Island during the launch of USS Theodore Roosevelt (SSBN-600). (U.S. Navy photo)

The warhead’s design was such that its case also served as the outer layer for the missile’s re-entry body. Moreover, the warhead’s rear was securely closed off with a cover plate. This plate played a dual role as it acted as a barrier both inside and outside, maintaining consistent pressure levels. This pressurization was vital because it ensured that humidity levels within the warhead remained low, especially during prolonged storage periods.

A beryllium heat shield was affixed to the warhead’s front. Following this, a flared beryllium housing was attached to its rear. Interestingly, this flared structure had an essential component within it: the arming and fuzing device. This device, coupled with the housing, gave the re-entry body its distinct shape, essential for its ballistic trajectory. Altogether, with these components in place, the entire re-entry body weighed approximately 850 pounds.


World War II Origins and Initial Experiments

During World War Two, the German Navy pioneered the idea of launching strategic ballistic missiles from submarines, aiming to target American ports and coastal structures with V-2 missiles. This innovative concept was designed for submarines stationed off the eastern American coast.

After the war, inspired by this German research, the U.S. Navy embarked on its own exploration to assess the viability of missile launches from surface vessels, primarily aircraft carriers. Their efforts bore fruit on 6 September 1947, when a V-2 was successfully fired from the USS Midway (CV-41), demonstrating that a sizable missile could be launched from a ship in motion on choppy waters.

In 1947, a V-2 rocket launching from the aircraft carrier USS Midway
In 1947, a V-2 rocket launching from the aircraft carrier USS Midway (CV-41) (U.S. Navy photo)

However, the Navy’s optimism was soon tempered. The following year, in “Operation Pushover”, a V-2 missile was intentionally knocked over onto the Midway’s deck. This experiment sought to gauge the potential damage from such an accident. The aftermath was significant: a combination of fire and the extreme cold from the liquid Oxygen oxidizer severely damaged the aft deck. Consequently, the Navy discontinued its exploration into sea-launched liquid fuel missiles.

The Shift Towards a Solid-Fuel IRBM

As the 1950s progressed, the landscape of missile technology underwent substantial shifts. The initial years after Operation Pushover witnessed major breakthroughs in solid-fuel rocket motor designs. Responding to these advancements, the Navy initiated the construction of “Big Stoop” in 1950. This 51-foot, two-stage, solid-fuel missile was crafted to evaluate the feasibility of a solid-fuel, nuclear-capable missile.

After three triumphant flights, the Navy deduced the concept had merit. Yet, while Big Stoop marked a pivotal step, it merely highlighted the possibility of solid-fuel missiles. The practical application demanded far superior solid-fuel rocket motor performance.

The Jupiter was the first US intermediate-range ballistic missile to be successfully launched
The Jupiter was the first US intermediate-range ballistic missile to be successfully launched. (U.S. Air Force photo)

The game-changer arrived two years post-Big Stoop, with Thiokol’s invention of a 5,000lb. thrust solid fuel motor. Distinguished by its internal burning star design, this motor set a precedent in high-performance solid fuel mechanisms. Bolstered by this innovation, in 1955, the Navy presented a proposal to the Department of Defense for a sea-launched solid-fuel IRBM.

Yet, the journey was far from smooth. In September 1955, President Eisenhower greenlit the development of a sea-launched ballistic missile, but to the Navy’s dismay, the endorsement was for a liquid-fueled missile. Matters further tangled when, in November, Defense Secretary Wilson instructed the Navy to modify and use the Army’s liquid fuel Jupiter IRBM.

The Birth of the Polaris Program

Recognizing the associated safety risks for crews on deploying liquid fuel Jupiter on vessels, the Navy, in February 1956, embarked on creating a solid-fuel variant of the Jupiter. This endeavor received a nod from the Office of the Secretary of Defense Ballistic Missile Committee in March.

By April, contracts were awarded to Lockheed and Aerojet for the Jupiter S (Solid). Intriguingly, on the same day, Lockheed bagged another contract for a smaller solid-fuel missile, aimed to leverage an anticipated breakthrough in designing compact, high-yield thermonuclear warheads.

Rear Adm. William F. Raborn, named the first director of the Navy Special Projects Office (SPO), responds to inquiries regarding SPO's objective and the progression of the Polaris A-1 missile.
Rear Adm. William F. Raborn, named the first director of the Navy Special Projects Office (SPO), responds to inquiries regarding SPO’s objective and the progression of the Polaris A-1 missile. (U.S. Navy photo)

When this technological leap was verified in September 1956, the focus shifted to this smaller missile. The culmination came in December 1956, with Defense Secretary Wilson permitting the Navy to abandon the Jupiter initiative in favor of the compact solid fuel IRBM. This decision marked the inception of the Polaris program.


The testing of the Polaris A-1 missile encompassed an array of venues and vehicles. The mainstay of flight testing was undertaken at the Atlantic Missile Range, complemented by additional tests at the Pacific Missile Range.

In these endeavors, the USS Observation Island (EAG-154), originally a post-World War II Mariner class cargo ship, underwent significant modifications to serve as a missile firing test platform. Meanwhile, the USS Compass Island (EAG-153), served as a navigation system test ship.

Polaris A-1 missile ready for launch at Cape Canaveral test site.
Polaris A-1 missile ready for launch at Cape Canaveral test site. (U.S. Navy photo)

The initial Polaris component test vehicle was set into the air from Point Mugu, California, on 11 January 1958. Following this, on 23 March 1958, there was a significant achievement: a dummy Polaris was cold launched from an underwater setup at San Clemente Isle. This was a precursor to the more intricate tests that would come.

On 24 September 1958, the first Polaris AX, a propulsion test vehicle, was launched. While this marked a milestone, it was during the fifth launch on 20 April 1959 that a successful flight was recorded.

USS Observation Island (EAG-154) launching a "Polaris A-1" test missile
USS Observation Island (EAG-154) launching a “Polaris A-1” test missile. (U.S. Navy photo)

Later, on 27 August 1959, the USS Observation Island marked the first seaborne launch of a Polaris test missile, this event took place off Cape Canaveral. Another noteworthy event occurred on 21 September 1959 when the first Polaris A-1 tactical round was dispatched from a flat pad at Cape Canaveral.

By the end of 1959, the missile had made successful flights spanning 700 miles. Furthermore, shipborne launches from the USS Observation Island were also accomplished.

On July 20, 1960, the USS George Washington (SSBN-598) launched its first test Polaris missile.
On July 20, 1960, the USS George Washington (SSBN-598) launched its first test Polaris missile. (U.S. Navy photo)

Fast forward to January the following year, and the first all-inertial flight of the Polaris was achieved on 7 January 1960. Shortly after, on 14 April, the first limited burn flight was observed at the San Clemente launcher.

On 20 July 1960, the USS George Washington made history by launching two A-1 missiles while submerged near Cape Canaveral, Florida. These missiles traveled more than 1,150 miles down the Atlantic test range with an interval of 2 hours and 53 minutes. Following this achievement, the USS George Washington embarked on its first war patrol on 15 November 1960.

Operative Service

The USS George Washington (SSBN-598) departed from Charleston, South Carolina, on 15 November 1960 on the Navy’s initial Polaris deterrent patrol. It was equipped with 16 of the Polaris A-1 missiles. By 21 January 1961, it reached New London, Connecticut, concluding a submerged voyage of 66 days and 10 hours. At the time, this journey set a new record as the lengthiest submerged submarine operation in U.S. history.

USS George Washington (SSBN-598) launching ceremony
USS George Washington (SSBN-598) launching ceremony. The submarines of the George Washington class were the only ones deployed with the Polaris A-1 missiles. The next class, the Ethan Allen, was equipped with A-2 missiles. (U.S. Navy photo)

Interestingly, a mere two days post the commencement of the USS George Washington (SSBN-598)’s patrol, testing of the Polaris A-1 ceased. The Navy received its last Polaris A-1 on 7 December 1961. Subsequent efforts focused on the Polaris A-2 missile variant.

The George Washington class, consisting of five nuclear-propelled submarines, was the only class armed with the Polaris A-1 missile. Each of these submarines carried a total of 16 missiles. These vessels were initially operational between 1960-1961. However, later, they transitioned to being equipped with the Polaris A-3 missile.

In 1960, at Port Canaveral, the USS George Washington (SSBN-598) loads a Polaris Missile in preparation for submerged launchings on the Atlantic Missile Range.
In 1960, at Port Canaveral, the USS George Washington (SSBN-598) loads a Polaris Missile in preparation for submerged launchings on the Atlantic Missile Range. (U.S. Navy photo)

In terms of operational duration, the A-1 remained in service from 15 November 1960 to 14 October 1965. On the latter date, the USS Abraham Lincoln (SSBN-602)made its way back to a U.S. harbor after the last Polaris A-1 patrol. The USS Abraham Lincoln (SSBN-602) was then slated for its first major overhaul and transition to the Polaris A-3 missile system.

Further reading


  • Nuclear Weapons of the United States: An Illustrated History by James N. Gibson, 1997
  • The U.S. Nuclear Arsenal: A History of Weapons and Delivery Systems since 1945 by Norman Polmar Robert & S. Norris, 2009
  • Jane’s Strategic Weapons Systems, Issue 38, Jane’s Information Group, UK, 2003
  • The Fleet Ballistic Missile System: Polaris to Trident by R. A. Fuhrman, 1978
  • From Polaris to Trident: The Development of US Fleet Ballistic Missile Technology by Graham Spinardi, 2008


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Javier Guerrero
Javier Guerrero
Javier is the editor @ Nuclear Companion and loves to investigate and write about the cold war.

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