Why is Israel's new submarine different from most modern submarines?

Experts believe the future INS Drakon submarine will house and launch nuclear-tipped cruise missiles in its turret. If so, the sea-based nuclear missiles would be part of Israel’s secret nuclear arsenal, which the Middle Eastern nation has never officially acknowledged.

The Israeli Navy is famous for the secrecy surrounding its submarine force. They have five Dolphin-I/II class submarines that are believed to carry nuclear-tipped missiles. Now, the newest submarine, INS Drakon, has been quietly launched in Kiel, Germany. It appears to have new missiles, and is larger. Drakon also represents a significant increase in Israel's submarine capabilities.

A variant of the highly successful Dolphin-II class, the Drakon's unique lines reflect Israel's fiercely independent naval thinking. INS Drakon is larger than any previous Israeli submarine and much longer than the first two Dolphin-IIs. Even more notable is its massive tower.

The curious big tower

The INS Drakon submarine was spotted in several photos last week as it was unveiled in Kiel, Germany. Submarine expert HI Sutton said the submarine is an improved Dolphin II class, with a hull several metres longer than previous submarines. Like previous Dolphin IIs, the new submarine will also have an air-independent propulsion system, allowing it to stay submerged for much longer than other non-nuclear submarines.

Sutton and naval analyst Matus Smutny believe it is likely that the large tower will conceal cruise missiles, including nuclear-tipped cruise missiles. The missiles will be stored vertically in the tower, and a booster will launch the missile straight out of the submarine. When the cruise missile reaches subsonic speeds, the control fins will retract and the missile’s turbine engine will take over. This is a common technique for submarine-launched cruise missiles, from NATO’s Tomahawk land-attack cruise missile to Russia’s Kalibr.

Most submarine-launched cruise missiles are launched from torpedo tubes or vertical launch silos along the submarine’s hull. However, torpedo tubes have a fixed diameter of 533mm, which limits the diameter of the cruise missile. If the cruise missile is larger than the torpedo tube, designers must choose another launch method.

One possibility is to store them in tubes along the bow, like the submarine-launched ballistic missiles of the US, Russian, French and British navies. However, the Drakon is significantly smaller than the US Navy’s submarines, with a lower hull height that would make it difficult to fit a large cruise missile. Adding a pod behind the fin, like the Ohio-class submarines, would likely require a long-term redesign.

In 2016, North Korea unveiled its Sinpo-class ballistic missile submarine (SSB). The Sinpo is famous for its retrograde missile storage system: storing missiles in turrets similar to the old Golf-class submarines of the Soviet Navy. The Golf class can hold three RF-11 nuclear-tipped missiles in turrets, partly due to the size of the submarine and partly due to the functionality of earlier, more primitive missile technology.

Why Israel needs new submarines, carrying new missiles

Israel’s Drakon may have a similar arrangement. Previously, Israeli submarines lacked large turrets and launched cruise missiles only from torpedo tubes. This begs the question: Why would Israel build cruise missiles that are larger than torpedo tubes?

Answer: Iran, a major political rival of Israel. The Block IV version of the sea-based Tomahawk missile, the most common in Israel’s service, has a range of nearly 1,500km. But from a launch site off the coast of Israel in the Mediterranean, a cruise missile would have to have a range of up to 2,700km to ensure that all of Iran would be within range.

Israel may not launch a preemptive strike against Iran, but it must ensure that any Iranian nuclear facilities are within range of Israeli weapons. A cruise missile capable of doing so would have to carry twice the amount of jet fuel as a Tomahawk cruise missile, making it too large to be launched through a torpedo tube.

Israel is one of nine states with nuclear weapons and the only one that has not publicly declared itself a nuclear power. Israel maintains a policy of "nuclear ambiguity" intended to keep its enemies uncertain about its capabilities, and thus reduce their confidence in a successful surprise attack. The Arms Control Association estimates that Israel possesses 90 nuclear weapons. Israel and South Africa are believed to have conducted a joint nuclear test in 1979 over the South Atlantic, an event known as the "Vela Incident".

Israel's weapons could be spread across air, land and sea forces, with nuclear gravity bombs for F-16 fighters and nuclear warheads for cruise missiles on existing Dolphin I-class submarines among its possible nuclear forces. Israel also maintains Jericho II and III missile forces.

The inclusion of both a torpedo tube for a nuclear-armed cruise missile and a vertical launch tube may surprise analysts, suggesting the new missile is not a direct replacement for the cruise missile, according to Naval News.

One explanation is that the new weapons will not be ready until the submarine is operational. Indeed, the Drakon could be used to test new missiles. So retaining the torpedo tubes would allow for continued nuclear deterrence during the transition. It is possible that one missile battery would be armed with conventional weapons and the other with nuclear weapons. This would allow for land attack missions while maintaining a nuclear deterrent.

A more common answer is that the vertical launch tubes were added late in the design, perhaps even after construction had begun. It would have been cheaper and easier to keep the extra torpedo tubes.

It may take some time, perhaps years, to decipher the submarine’s capabilities. The Israeli navy keeps some aspects of its existing submarines secret, so we may never know everything. Observers can only decipher some of the new images that have emerged.