The Drass SDV DS4 is a highly effective, insidious and stealthy warfare submersible craft for sabotage and intelligence covert missions. The Drass DS Class SDV is designed to transport its offensive equipment and commandos/combat divers, from the operational base (such as a ship or submarine) to the target (such as a moored/ anchored ship, a harbor or coastal installation), and to transport them back to the base once the mission is complete.
It provides great support to commandos in terms of speed, endurance, comfort, carried volume and operation flexibility; it usually comes in two main configurations:

  • Standard Configuration, DS4: for up to 4 divers with standard payloads;
  • Heavy Load Configuration, DS4 Mine Option: for up to 2 divers with additional payloads (Bottom Mines).


  • Pilot Control Module
  • Co-Pilot Control Module
  • GPS – Global Positioning System
  • DVL – Doppler Velocity Log
  • Echo Sounder
  • Obstacle Distance Measurement System
  • INS – Inertial Navigation System
  • Wireless Underwater Communication System
  • Wired Underwater Communication System
  • Salvage buoy
  • Underwater camera

The payload’s overall volume is about 250 litres in the standard configuration; in heavy load configuration Mine Option, 4 neutrally buoyant mines must be added reducing the crew capabilities from 4 pax to 2 pax.

The hull consists of a resistant structure in GRP covered with hydrodynamic GRP fairings, shaped to gain the best efficiency and achieve the required longitudinal and transversal strength in accordance with regulations. The main pressure-resistant parts are aluminum or stainless-steel containers and all of them are watertight and pressure-resistant up to a depth of 100 metres in transit condition.

The compressed air system stores 528 litres of air at 300 bar and supplies both the breathing and ballast tank blowing sub-systems.

A Trim & Buoyancy System is installed. The purpose is to maintain the best craft status and to provide a suitable solution for positive and negative buoyancy and longitudinal trim.

The propulsion is extremely silent thanks to the propeller’s dedicated design. The propeller is directly connected with the electric motor without any reduction gear, thereby eliminating propulsion noise. The maneuvering system consists of a hydraulically-controlled rudder with bow and stern planes that drive the craft both horizontally and vertically. Both pilot and co-pilot can perform the maneuvers or engage the auto-pilot system.

The main electric power source is latest generation lithium batteries divided in two redundant sections (or subbattery packs) in accordance with the applied design philosophy in terms of redundancy.

A hydraulic system is provided to supply hydraulic power to the maneuvering actuators such as the rudder, ballast tanks’ vent valves, TV camera mast, etc. Hydraulic oil is supplied by a pressure-resistant HPU (Hydraulic Power Unit) in the stern of the craft.

There are two communication systems – one is a personal wireless system for each diver, and the other is an onboard wired communication system. During navigation, the fixed on-board system provides an excellent solution as it minimizes the risk of interception without using the batteries required by the wireless system. This means that these remain fully charged and ready for use when the operators leave the SDV.

Drass provides a structured training scheme which comprises of both Operations and Maintenance courses. The aim of Operations training is to provide the crews with a comprehensive knowledge of the SDV systems and equipment, and preparation to use the craft in any foreseeable situation. This part of the training includes theoretical classroom sessions, as well as practical sessions in the water on board the craft.
The Maintenance training is directed to the client’s maintenance engineers and technical personnel, and includes focused sessions in the following areas:

  • Preventive Maintenance
  • Troubleshooting
  • Corrective Maintenance
  • Integrated Logistic Support

Dedicated software is available for the integrated logistic support (spare parts and preventive maintenance). Such programs can be tailored to, and interfaced with, the customer’s data management system.

Drass staff are available to help the end user with the design of the SDV base, where the crafts are recovered during its normal operational life and maintenance activities.