They weigh under 2 tonnes and measure 6 metres in length … Alongside airborne drones, underwater drones are attracting ever-growing interest from the world’s Navies. Less visible and attracting less media interest, their missions could turn out to be crucial in the decades to come, by increasing a submarine’s capabilities whilst improving the safety of ships and their crews. Interview with Laurent Lugherini, Naval Group underwater drone system Architect.
What Naval requirements are met by underwater drones?
Submarine operating areas are moving into ever-shallower waters, from a few metres to a few tens of metres in depth.
These are high-risk areas in which submarines are easier to detect due to the reduced bottom contrasts, and a necessity of reduced speed when close inshore, not to mention the increased risk of encountering mines or becoming trapped in an environment with no possible way of escaping.
For all that, the requirements in terms of intelligence have never been greater within Military Staffs and these requirements are often concentrated in coastal areas. In these areas however, intelligence gathered by a submarine presents a number of advantages. In fact, satellite coverage is usually intermittent and can be circumvented by the enemy if he is aware of the orbital period of the space resources. As far as long-range airborne assets are concerned, they are both few in number, costly, identifiable and are not readily available for immediate use. Moreover, cloud cover often prevents satellites, and even aircraft, from accessing the intelligence.
In order to increase the intelligence capability whilst reducing risk, submarines must be provided with drones. The submarine and its drone will be able to conduct clandestine surveillance missions, with long periods on station, and under most meteorological conditions.
An underwater drone’s intelligence missions are extremely varied, from charting ahead of the submarine in order to inform it of risks of radio interception, to observing coastlines or even taking photographs of the entrance to a port. The intelligence collected is complementary to that gathered by satellite. In a crisis situation or for a one-off operation, the use of a drone, preceding the landing of commandos in an operational theatre, also allows the mission to be better-prepared and the area in which the land forces are to be deployed to be secured.
« Having underwater drones at their disposal provides Navies with new means of gathering information and considerably increases the chances of an operation’s success »
What advantages do underwater drones bring?
Firstly, providing a submarine with a drone increases its action area whilst avoiding endangering the life of its crew or special forces. Drones can operate totally independently in order to move and return to the submarine automatically whilst gathering data and download them either directly or after each collection to the ship’s information system. By deploying a drone, a submarine can reduce the time spent at periscope depth or place itself further away from threats and, consequently, reduce its vulnerability.
How complex is it to integrate drones into submarines?
One of the technological challenges of this innovation is to be able to deploy and recover the drone automatically, whilst the submarine is underway and at a discrete depth. Naval Group has created a comprehensive, innovative solution for integrating drones on board a submarine and achieved a world-first in the Mediterranean as early as 2013. Having conducted homing operations controlling the drone’s track for its return and stowage alongside the submarine, our teams designed, produced and tested the use of a side dock (one variant consists in installing on the casing), both for receiving the drone in its cell alongside the submarine, stowing it and re-launching it.
In all cases, the operation involves adding an appendage, which requires the submarine’s hydrodynamic qualities to be reviewed and a check to be made to ensure that it does not adversely affect its stealth or its acoustic discretion.
Deploying a drone also requires the payload to operate in a fully-interactive manner with the submarine’s information system. Two complex systems therefore have to be linked. A drone, providing systems within a system, in fact carries a number of sensors useful for intelligence gathering and navigation (electronic warfare tools, video camera, telecommunication system etc.) and a supervisor who can reconfigure its mission so as to react to external events. Our solutions also have to be designed so that they can add to the capabilities of submarines already in service, or so that the complete system can be integrated at the new-build stage.
Docking: action of receiving the drone and stowing it in its cell (dock).
Homing: action of guiding and positioning the drone for its return and stowage in its dock alongside the submarine.
Payload: modular, interchangeable equipment on board the underwater drone.
Submarine hydrodynamic quality: the submarine’s geometries which characterize the manner in which it penetrates the water and affect its acoustic discretion.