A new milestone for the Brazilian Navy’s submarine force was reached on 26 November 2025 with the christening of the fourth diesel-electric submarine, the S43 Almirante Karam (formerly Angostura), and the commissioning of the S42 Tonelero, the third of the Riachuelo-class. This was the first occasion on which two submarines were presented simultaneously.
As a derivative of the Scorpène family by Naval Group, with around five additional meters in length, the S43 is the first of its class to be entirely built in Brazil by Itaguaí Construções Navais (ICN) and marks an operational transformation with extremely modern naval assets that are essential for patrolling Brazil’s coastline, which has continental proportions.
As a direct product of the Submarine Development Programme (PROSUB), the benefits of this strategic, long-term partnership established with France in 2008 include the construction of a shipyard, a modern submarine base, a manufacturing plant, and an extensive technology transfer agreement for more than 250 Brazilians. These professionals received technical training in France in the areas of welding, boiler making, piping and electrics, enabling ICN to master the entire production process, from shaping metal plates to the integration and testing of onboard systems.
One of the highlights was the establishment of the local infrastructure in Itaguaí, in the state of Rio de Janeiro. The Brazilian Navy is now focusing its efforts on continuing the development of the SN-10 Álvaro Alberto nuclear-powered attack submarine, planned to be launched in 2034, ten years later than initially expected due to numerous delays arising from budget constraints.
Together with the SN-10, the Brazilian Navy expects to master the full nuclear fuel cycle, further enhancing Brazil’s deterrence capability through its naval arm.
Riachuelo-class Technical characteristics
Riachuelo-class submarines have a crew of eight officers and 34 ratings, a submerged displacement of 2,000 tonnes, an operating depth of up to 300 meters, a speed of 40 km/h, and an endurance of 70 days. They measure nearly 72 meters in length and six meters in diameter.
The submarines are armed with MBDA F21 heavyweight torpedoes and SM39 Block 2 Mod 2 Exocet anti-ship missiles. The sonar suite comprises the Thales TSM 2233 Eledone Sonar (DSUV-22) and two TSM 2253 flank-array sonars, integrated into the Thales S-Cube suite. Naval Group also contributes the SUBTICS tactical mission system, which provides acoustic surveillance, data and video acquisition from the optronic and attack periscopes, weapons control, damage control and continuous system monitoring, as well as transmission and acquisition via data link. The attack periscope is the Safran Series 20 (APS), and the submarine will also be equipped with the Contralto defence system.
