The First Submarine Launched Rockets
The U-Boat Rocket Program

An Online Technical Report

with photos from the Deutsches Museum Munich Special Collection and U.S. Army

Submarine launched missiles are perhaps the strongest pillar of the "nuclear triad" that made the United States the dominant superpower at the start of the 21st Century. A mobile underwater launch platform requires vast resources to build and operate but it is difficult to detect, and a fleet of them ensures that the enemy mainland is within quick striking distance at all times. The submarine launched missile, which played such an important role in the Cold War, can be traced to a 1942 experiment conducted by the Kriegsmarine.

America's entry into WW2 prompted a discussion among German strategists seeking ways to strike the American mainland. To send weapons from one continent to another, they needed some way to circumvent the limitations on the range of bomber aircraft and the capabilities of the German surface fleet.

Various methods were available at that time, the most practical of which was inserting saboteurs by U-Boat. While at least three groups of saboteurs were successfully landed (U-202, 13 June 1942; U-584, 16 June 1942; U-1230, 30 November 1944) the plan ultimately failed due to the unreliability and ineptitude of the German agents.

Another possibility was to fly bombers to New York City, and ditch them near a waiting U-Boat in the Atlantic before the fuel ran out. Due to an understandable lack of enthusiasm by both the Luftwaffe and the Kriegsmarine, the project never proceeded past an alleged reconnaissance flight to New York City by a JU 390 of FAGr 5 in January 1944.

Yet another method became apparent during a conversation between Dr. Ernst Steinhoff, an engineer at the Penemunde rocket development facility, and his brother, Korvettenkapitan Fritz Steinhoff, Kommandant of U-511. They surmised that it would be possible to fire an artillery rocket from the deck of a sumbmerged submarine.

Tests were conducted in May/June of 1942 using a standard army issue Wurfgerat 41 launcher and rockets from 21 to 30cm. The tests proved that it was not only feasable, but that the rockets could be fired from depths up to 15 meters below the surface, without effecting the normal flight path.

The sequence of photos below show an actual launch from U-511.

In principle, Admiral Doenitz approved of the idea of launching against harbors on the American mainland, specifically the sprawling facilities in New York City. However, the plan was delayed by technical concerns. The Kriegsmarine wanted to fit specialized launchers instead of using modified army equipment, but they did not pursue the idea with urgency. Eventually, steadily improving Allied ASW capability prevented U-Boats from approaching within range and the New York bombardment was cancelled.

The project was not entirely scrapped. In the summer of 1944, three U-Boats of the Black Sea 30th flotilla were secretly equipped with rocket launchers. These were mounted midships below the waterline of U-24 and U-9 and on the deck of U-19. The weapons were allegedly deployed against Soviet harbor facilities and moored ships during the German retreat. Although the records do not mention damage sustained in the attacks, this first combat use of a submarine launched missile was an historic event.

Later experiments code named "Ursel" attempted to utilize the submarine launched rocket against a pursuing surface vessel. The accuracy required by this weapon exceeded practical technological limits and efforts were concentrated on more promising sound-guided torpedoes instead. Other research included rocket powered torpedoes, several of which were tested. Despite their unnerving tendency to explode, they showed some promise. The postwar superpowers continued this research; the Soviet Navy is alleged to have developed an operational model.

Germany's superb military engineers had greatly contributed to a rapid victory over France in 1940, and so as the war situation deteriorated, much hope and emphasis was placed on new technologies desperately needed to turn the tide. From guided missiles to night vision and jet fighters, engineers and scientists sought new ways to capitalize on technology that might give Germany a war-winning advantage over the Allies.

To overcome the transcontinental barrier that prevented Germany from attacking the United States at home, an official of the German Labor Front, Direktor Lafferenz, suggested that a watertight container be constructed, in which a V-2 ballistic missile could be brought within range of the American coast. Discussion of this novel idea reached the highest levels of the Penemunde research facility.

As it developed, the plan was to send three 500 ton displacement containers towed by a single snorkel equipped submarine. Each container, trimmed to neutral buoyancy, concealed a V2. Upon reaching the start location, the containers would be trimmed to a vertical position, and the rockets launched.

The idea was filed away until 1944, when it was given the code name Prufstand XII and Vulkanwerft secretly began work on three containers. While the records indicate that at least one such submarine launch container was completed, it was never tested with a live firing. The concept was proven sound by the Soviets in the 1950s. Using captured plans and German engineering assistance they produced the Golem submarine towed missile launcher. American engineers took the next step with the Regulus and Polaris programs, placing the missile and launcher into the submarine.

The 1942 experiments may have appeared nothing more than a stunt to an observer without the foresight to recognize the potential of such a weapon. However, in much the same way that Eugene Ely's stunt foreshadowed the Aircraft Carrier when he landed his Curtiss Pusher on the U.S.S. Pennsylvania in 1911, these experiments were the genesis of the missile launching submarine.

Weapons reseach and development in the Third Reich pointed ultimately towards a devastating confluence of advanced weapons systems. Experiments with nuclear fission proceeded along with new generations of stealth submarines, intercontinental jet bombers and missiles. Destroying Eastern Seaboard cities was exactly the sort of capability the increasingly desperate Fuhrer sought in order to win a surrender from the Allies. The intent to do exactly that was made clear by documents found after the war, such as this Luftwaffe map of Lower Manhattan showing blast damage anticipated by a rocket borne nuclear / atomic weapon. Fortunately, time ran out for the German rocket scientists.

Thanks to James Stewart, Oliver Meise and Ivan Stephens for sharing information.