Attention, air
There is nothing new in the concept of destroying an air enemy from a submarine: artillery guns were able to do this even on submarines of World War II. However, for obvious reasons, it is easier for a submarine not to contact enemy aircraft at all and go to the depths. The emergence of anti-submarine aviation seriously complicated the situation, especially in helicopters with their ubiquitous sonar buoys. The most obvious countermeasure is a pre-emptive missile strike. The British were one of the first air defense systems on submarines.
In 1972, four Blowpipe SLAM (Submarine-Launched Air Missiles) missiles, mounted on a retractable mast, appeared on the HMS Aeneas submarine. Later, the Israelis installed the same air defense system on one of their submarines. The effectiveness of such systems for the submarine fleet is somewhat controversial: after all, the submarine has to surface to attack, exposing itself to the attack of both aviation and surface ships. But in any case, it is better than artillery pieces.
An interesting idea is offered by the French with the A3SM system (Mica SAM) from DCNS. The system is based on the MICA air-to-air missile, which is quite widespread in NATO countries, with a range of up to 20 km and a mass of 112 kilograms. MICA is mounted inside the torpedo hull and, accordingly, does not require any special rearrangement of the submarine's innards. Operators from a submerged position (depth more than 100 meters) track the appearance of hydroacoustic buoys of helicopter-hunters and launch a torpedo-anti-aircraft missile matryoshka towards the threat. Approaching the zone of the supposed hovering of the helicopter, the torpedo jumps out, and a rocket starts from it. According to a similar scheme, the submarines launch Exocet SM39 anti-ship missiles, so there are no fundamental difficulties. Anti-aircraft guidance MICA - automatic thermal imaging. The French from DCNS, in addition to an expensive missile launched from a submerged position, offer the installation of the Mistral air defense system for the submarine's cabin. The system is similar to the British Blowpipe SLAM and works only from the surface position.
Conventionally, to combat air targets, you can use the German recoilless remote-controlled gun Mauser RMK 30 with a caliber of 30 mm. The effective firing range reaches 3 km, which makes it possible to attack hovering enemy helicopters in particularly successful situations. The ammunition load includes high-explosive fragmentation, high-explosive fragmentation incendiary and armor-piercing ammunition. Targeting is carried out using a periscope and a radar station. In 2008, the installation was demonstrated as part of a MURAENA retractable mast with a height of 3 meters and a diameter of 0.8 meters. Later, the Mauser RMK 30 was mounted inside the TRIPLE-M multifunctional container, which can also store underwater drones. Initially, the Germans planned to place guns on submarines of projects 212A and 212B to combat asymmetric threats (pirates, martyrs' boats and small-sized missile boats). For the same series of submarines, the German industry supplies, perhaps, the most modern serial system for combating an air enemy - the IDAS missile system.
From the depths of the sea
The IDAS (Interactive Defense and Attack System for Submarines) anti-aircraft missile was developed by the German Diehl Defense and Howaldtswerke-Deutsche Werft GmbH with the participation of the Norwegian Kongsberg. The missile was tested for the first time in 2008 on a Norwegian submarine of the Ula type. The weapon belongs to the class of conditionally multipurpose and, if necessary, can be used not only against helicopter hunters, but also against surface ships of small displacement, boats, and even against small coastal targets. The Germans envision the use of IDAS as a support weapon for special operations forces. The system was not developed from scratch and is a deep modernization of the IRIS-T subsonic air-to-air missile. The length of the rocket is 2.5 meters, the diameter of the body is 0.8 meters, the launch weight is 120 kilograms, the maximum launch depth is 20 meters, the maximum firing range is 20 kilometers and the maximum speed is 240 m / s. Each IDAS is equipped with a 20-kilogram warhead and is used against targets from a transport-launch container weighing 1700 kilograms (each with four missiles) installed in the submarine's 533-mm torpedo tube. The start is carried out by ejection from the container using a hydraulically controlled piston. The missiles are launched from a container flooded with water, while there is no air release from the torpedo tube, that is, there is no unmasking sign by which a helicopter can detect and attack a submarine. Then, after the missile leaves the torpedo tube, the control rudders and wings are opened, the control system is turned on and the starting engine is started. A three-mode solid propellant engine is used as a power plant. The IDAS rocket, according to the developers, takes about a minute to reach the surface, launch the cruise power plant and gain the required altitude. Then there is a search and recognition of the target, if the missile is automatically guided to a pre-designated target, or it turns to the target at the command of the submarine operator via fiber optic cable. On the final segment of the flight path, the rocket is switched to gliding mode. Preliminary preparation of the inertial guidance system of the IDAS missile is carried out by the navigation equipment of the submarine. In the early stages of the development of the system, there were plans to install a cooled thermal imager on a rocket (from the original IRIS-T), but the high cost of the assembly did not allow this. Still, the weapon is positioned as multipurpose, and the expense of expensive equipment for some kind of drone or fortified coastal point would be inappropriate.
The fiber-optic guidance line, paired with the submarine's hydroacoustics, makes it possible to confidently intercept anti-submarine helicopters. In addition, the fiber-optic communication and control channel provides higher reliability and accuracy of fire, allows you to identify the target and assess the tactical situation by transmitting a digital image from the missile finder to the weapon control panel. Each rocket uses four spools of fiber optic cable to transmit control commands and receive data from the rocket camera. One coil is placed in the launch container, two are on a special compensation float, which remains on the water surface when the rocket exits from under the water, another coil is placed in the tail of the rocket. The circular probable deviation of the missile controlled by the operator via the optical communication channel is about 0.5-1 meters. There is a possibility of simultaneous launch of two IDAS missiles, which increases the likelihood of hitting a hovering helicopter to 0.85-0.9. In the future, engineers expect to detect an enemy helicopter before it drops a buoy into the water. To do this, they will adapt the sonar system of the submarine to search for a wave effect on the surface of the water from the main rotor of the helicopter. Anti-aircraft missiles are launched from a horizontal position, which creates difficulties when attacking objects directly above the submarine. German submarines of future generations (projects 214 and 216) will be equipped with vertical launchers for IDAS missiles.
At the moment, IDAS is a serial installation, but not unique. In the mid-2000s, the United States tested the launch from a submerged position of the AIM-9X Sidewinder anti-aircraft missile, developed by Raytheon. At the moment, there is no exact information about the development of such American air defense for submarines, but it is possible that the missiles are installed on nuclear missile carriers.
