Submarines and autonomous UUVs
Working in tandem and the way forward
Covert mine reconnaissance has many advantages and Igor Vilnit, CEO of Rubin Design Bureau explains how submarines and UUVs would work in tandem and the way forward in the time to come.
Also : The Arrow ATBM; Nammo shoulder-launched munitions; Arrow in Apache’s quiver; Irkut’s advanced trainers; An American Air Show; Exercise Iniochos; Frisian Flag 2018; EART 2018.
We live in the creative phase of unmanned vehicles. It was not so long ago that the robot R2-D2 could exist only in the fantastic world of Star Wars. Today, we use similar robots in everyday life. Not trying to compete with Star Wars scope, let us consider the problem of interaction between submarines and underwater robotic vehicles.
A torpedo with acoustic homing can be considered the first autonomous unmanned underwater vehicle. No less an interesting example was the Granit missile deployed for the first time in the submarine of Oscar- class. These missiles had not only an advanced homing system but could interact with each other during the flight, exchanging data and coordinating their actions. This behaviour can be considered one of the first examples of interaction among unmanned vehicles in the group, which is called swarming today.
Of course, endurance of torpedoes and missiles is measured in minutes, payload is limited by the explosive charge. In contrast, modern unmanned underwater vehicles (UUVs) can operate autonomously for scores of hours, move with high accuracy along complicated trajectories, carry various types of payload and act according to sophisticated algorithms. At the same time, as compared to ‘ classic’ submarines, UUVs remain small and inexpensive.
Submarine Hunters
From the underwater warfare point of view, the most attractive mission for the unmanned underwater vehicles is to search for and trail enemy submarines. Robots, unlike classic submarines, can also use unstealthy methods for enemy’s search (for example, active sonar pings). Destruction of such a vehicle due to its small size and manoeuvrability is not only difficult but also too expensive.
However, this is not a low hanging fruit. Creation of these vehicles is full of difficulties – provision of necessary energy reserve and speed, accommodation of large antennas and processing of signals received from them, transmission of data on the detected targets, development of submarine tracking algorithms and others.
These problems can be solved in different ways. One should choose the right places for submarine hunting, use vehicles in swarms, include the vehicles in network systems of detection and data transmission. Another option is to create rather large vehicles of dozens of tonnes displacement that have a lot of energy and sophisticated detection means. Such vehicles are already being developed and tested.
Unmanned aerial vehicles UAVs can be used for above- water surveillance. As early as World War II, submarines that carried reconnaissance aircraft were developed, and German submariners used submarine-launched gyroplanes and kites for target search. However, all these aircraft were surface-launched and they
had to be recovered after the mission. Nowadays, already there is experience in launching expendable unmanned vehicles from underwater through a classic torpedo tube. Using these vehicles, submarines are capable of conducting reconnaissance beyond the horizon and even over land and availability of channel for covert reception of data from released drones considerably expands intelligence capabilities of the submarine.
Target Decoys
Enhancement of acoustic systems enables simulation of an acoustic signature of submarine with accuracy sufficient to deceive aircraft and ship sonars and in future stationary systems as well. Today, the range of offered decoy vehicles is large – from compact single-shot Mk.39 of 10 kg weight to huge vehicle MASTT with displacement over 60 tonnes.
The submarine is capable of launching only small decoys of limited endurance. However, large decoys can be delivered by other ways and move on their own to the areas where they will interact with submarines.
At the end of last year, the Rubin Design Bureau presented a concept design of the Surrogat robotic complex to be used for naval exercises. This large submarine imitator equipped with a lithium-ion battery can operate up to 1516 hours. And during that period of time it will simulate manoeuvring of enemy submarines including manoeuvres at high speed.
Appearance and evolution of acoustic decoys has led to the development and complication of torpedo homing systems because today they should differentiate between actual and false targets. Battle of the robots – torpedo and decoy– is already taking place under water!
Communication and Navigation
Communication systems for submarines must be robust and high-speed, but first of all they must be discreet to preserve submarine’s overall stealth. Use of satellite communication systems has increased considerably the security of radio channel itself, however has not solved the problem totally. To use the satellite communication system, the boat should come to the periscope depth and raise creates masts. This discloses and puts in a disadvantaged tactical position. Similar problems arise when it is necessary to use GPS.
One of the solutions allowing the submarine to maintain a two- way communication and receive data from space navigation systems ‘keeping speed and depth’ is a radio communication system with buoy antennas, for example, Calisto and RTOF (recoverable tethered optical fibre) systems. These systems give greater freedom to act but the submarine still remains tethered to the surface although with a looser leash.
A number of problems can be solved when the UUV is used as a gateway between the underwater and air environment. The ability of such communication vehicles to manoeuvre on their own practically lifts all the constraints of the submarine.
Moreover, the vehicle can be preprogrammed to transmit the information only after a certain period of time or after moving to the specified area. In the same way, the R2-D2 robot delivered the message on the Death Star plans to the Rebels. During this process, the vehicle is able to receive and transmit data to the submarine with the help of high-frequency underwater acoustic or even laser channel, i. e. it is unnecessary to launch and recover UUV.
Assessment of Environmental Parameters
As the theatre of submarine operations passes to coastal and shallow zones, mapping of bottom terrain becomes more and more important. Information on terrain is necessary not only for safe manoeuvring near the bottom but may also give tactical advantages allowing the submarine to appear in a place where it was not expected.
Ship and aircraft sonar systems are constantly being improved, and this factor requires more meticulous account for hydrological parameters. Firstly, to facilitate functioning of own detection sensors they will already have preset information on the underwater environment and, secondly, to evade detection by enemy sensors. New requirements appear as well. Thus, for laser communication the water transparency should be known. Such information can be collected with onboard sensors but it takes a lot of time that may not be available under certain circumstances. Instead of this, UUVs can evaluate hydrology comparatively fast and safely. Such vehicles are being developed by Indian universities.
Launch of these vehicles from submarines has also been implemented: they can be launched from lock-in/lockout chamber installed on the submarine hatch. Launch of these UUVs from missile containers is also being developed.
Mine Detection
Today, many types of mine countermeasures unmanned vehicles have been developed and are being manufactured – from light man-portable of less than 40 kg to rather large ones with weight up to one tonne. Indian companies also offer such vehicles. There are even larger vehicles, for example, UUV RMMV with weight about 6 tonnes, which is used within the AN/ WLD- 1 system on board the ships like US Navy LCS. Single-shot underwater vehicles are used for mine sweeping.
However, all these vehicles are intended for employment from surface ships. Hence, they can be used only in own coastal waters or in the areas controlled by one’s own navy.
Near the enemy’s littoral, in hostile conditions, covert intelligence is required. And covertness can be ensured only when a vehicle is delivered by a submarine. Moreover, it is the submarine that more often comes to the area of future operations for ISR purposes and therefore it needs reliable and up-to-date information on the mine threat. It is faster and safer to gather the information using UUV than to survey the area with submarine onboard sensors. In addition, autonomy of UUV allows the submarine to solve other tasks while the vehicles survey the area in order to detect mines.
However, even an UUV launch from the submarine is a serious challenge and UUV recovery is manifoldly difficult. Though the difficulties are not insurmountable; Swedish submarines operate the UUV AUV-62MR. Since 2007, the US Navy submarines have been using the AN/BLQ-11 system earlier known as LMRS (Long-term Mine Reconnaissance System).
The Rubin Design Bureau has also developed technology for employing autonomous UUVs and remotely operated vehicles from underwater moving objects. Of course, this method requires not only UUV with suitable capabilities but adaptation of the submarine itself and relevant training of the crew. Experience shows that the development of mine countermeasure complex comprising UUV and submarine makes high demands on both time and budget and even after all efforts it may not meet customer’s requirements. However, covert mine reconnaissance has so many advantages that leading navies continue activities in this direction.