In late 2020 the French navy successfully tested the MdCN (Missile de Croisière Naval) cruise missile fired from one of its new Barracuda Class SSNs (nuclear attack submarines). These missiles cost about $5 million each and are built to be launched under water. MdCN is actually the Scalp cruise missiles modified for use by a submerged submarine. Back in 2007 France ordered fifty Scalp missiles for the Barracuda SSNs.
Noting the American success with submarine fired cruise missiles, more navies are equipping their SSNs and other nukes to do the same. The big advantage of sub launched cruise missiles is that the nukes can get to where they might be needed faster than any surface ship and do it undetected. The sub can then wait for weeks or months until needed and then quickly launch a barrage of very accuratecruise missiles. The timing of such attacks usually comes as a surprise to those on the receiving end and that increases the effect of the attack.
Scalp was first developed as an air launched missile. Britain uses the same missile, but calls it the Storm Shadow. The design was based on the older French Apache airfield-attack missile, and built largely to British specifications. The basic Scalp design is stealthy and allows for the quick upgrade of guidance and target detection systems. The MdCN variant is a 6.5 meter (21.3 feet) foot long missile weighing 1.4 tons and uses inertial guidance, GPS and terrain following to find the target. With a range of over a thousand kilometers, it can carry a variety of 220 kg (480 pound) warheads. Terminal guidance can use infrared (heat) imaging for greater accuracy. The long range and high accuracy make it an ideal weapon to taking out heavily defended targets. Development was rather quick, as it began in 1997 and the missile entered service in 2002 as Scalp and 2012 as MdCN.
And then there is the submarine launcher. In mid-2019 the first of six new French Barracuda class SSN's, the SNA Suffern, was launched. This first one entered service on schedule, in 2020. All six will enter service in the 2020s. Back in 2006, France decided to buy six new Barracuda class SSNs for about $1.5 billion each. The 4,700-ton (surface displacement) boats are smaller than America's new 7,300-ton Virginia class subs. These larger boats cost about $2.8 billion each. A new class of Russian SSNs will displace 6,000 tons. The older American Los Angeles class boats were about 7,000 tons. Size does matter, as it indicates how much space you have available for sensors and weapons. Larger boats are better equipped and more heavily armed. New Russian SSN construction was delayed by shortages of cash and qualified shipyard personnel. The U.S. already had two Virginia's in service by 2006 and now there are 19 in service with 11 under construction. Two Virginia's a year are entering service, for an eventual total of about 60 subs.
Construction on the first Barracuda began in 2007 and it was supposed to be launched by 2012. That launch date was tentative because the development of the Barracuda nuclear power plant began in 2003 and soon ran into problems. Problems with the power plant were no surprise because France, unlike Britain, did not license the American submarine power plant. Using the U.S. tech would make it more difficult to export French nuclear subs and so on. The French chose a different design that used commercial (not weapons) grade nuclear fuel. This meant French nuclear subs had to be refueled more often but this was made easier by building the hull with special large hatches that could be quickly opened for the once every 7-10 refueling. France is the only nation using this type of ship power plant and has to handle development and maintenance procedures itself. With a small fleet of nuclear subs, this drives up the cost per sub. Britain, by licensing the American tech, gets the benefit of a much larger American nuke fleet and the larger budget for work on the power plants. Ever since the first Barracuda began construction, the delays have come from power plant problems. By 2012 it was believed that launch date could be 2017 but delays perfecting the power plant continued. The sub could not be launched until the power plant was completed and the hull made watertight
The Barracudas relies on a lot of automation and has a crew of sixty, plus berths for 12 passengers. These will usually be commandos and their gear will be stored in a pod attached to subs sail. The Barracuda design emphasized silencing, making it more difficult to detect. The Barracuda's have four 533mm (21 inch) torpedo tubes which can also be used to launch missiles, mines or torpedoes. Twenty weapons are carried, the mix of torpedoes, mines and missiles depends on the mission. French SSNs have two crews which each having the boat for three months. Enough food is carried to sustain the crew for 70 days. Two more Barracudas are under construction.