BNS Riachuelo (S40) is the lead ship of the emerging four-strong class of diesel-electric attack submarines for the modern Brazilian Navy. The vessel is undergoing construction at the new Itaguai Shipyard in Brazil to later be joined by her sister boats Humaita (S41), Tonelero (S42) and Ango Stura (S43). Riachuelo is expected to be commissioned into service with the Brazilian Navy around 2017.
The Riachuelo and her sisters are born from the French-originated Scorpene-class which also forms the basis of several attack boats for the Chilean, Indian and Malayian navies. The Brazilian offering will be a 75-foot long vessel capable of 21 knots when submerged (approximately 12 knots when surfaced) through a 220-cell battery propulsion and auxiliary systems arrangement. As with other hybrid diesel-electric designs, Riachuelo will utilize its diesel powerplants for surface travel and its electric system for submerged travel, surfacing (at about snorkel depth) to recharge oxygen stores, expel deadly built-up gasses and recharge its battery cells.
The propulsion system will include 4 x MTU 12V396 SE84 series diesel engines coupled with Kermount Industries 580kW generators. Sensors and processing will be made up of an acoustic surveillance system, digital-assisted attack, and dedicated analysis and monitoring hardware. The sonar system will be provided by Thales.
As an attack submarine, the boat will showcase six torpedo tubes cleared to fire the widely-accepted 21" torpedo as well as the French SM-39 "Exocet" Block 39 Mod.2 anti-ship missile. The torpedo of choice is to be the French "F21" model series, a dual-role torpedo weapon featuring high speeds (up to 50 knots) and extended ranges (up to 50 kilometers). The SM-39 missile will be initially launched within a torpedo-type body surrounding the actual missile. This body will then make its way to the surface and release the missile proper, the missile's motor then engaging and leading itself to its intended target.
The arrival of Riachuelo represents a step forward in Brazilian power projection in the South American region. Additionally, the completion of a viable shipyard for the construction of warships will assist in making Brazil a self-sustained military naval power in this part of the world.