The submarine S-81 Isaac Peral is undergoing its final tests before its delivery to the Spanish Navy.

Next November, the Spanish Navy will receive the S-81 Isaac Peral, the first submarine of the S-80 class, one of the best non-nuclear submarines in the world. In approximately one month, the handover will take place. Navantia has shared a video with images of the S-81's sea trials, adding to those conducted in recent months. In June, it submerged for the first time to the seabed and tested the diver's lock, and early in the same month, it completed its first static immersion in the bay of Cartagena.

The submarine already carried out its initial test dive on March 30th, although it was not a complete immersion. During the operation, the Navy's rescue and salvage ship Neptuno closely monitored it, along with the Salvamento Marítimo tugboat Clara Campoamor. In July, authorization was granted for the transition to the next phase, during which the submarine will conduct all its submerged navigations, including dives to maximum depth, before its scheduled handover at the end of November.

The Submarine Base in Cartagena continues its remodeling process to accommodate the S-80 submarines, involving the demolition of buildings, construction of new facilities, dredging, modification of submarine berths, and the construction of a new dock.

The S-80 represents a technological leap for the Spanish submarine force, featuring an integrated platform control system, a combat system, and an armament system capable of launching tactical missiles, a unique capability among non-nuclear submarines in NATO. It has a submerged displacement of 2,965 tons, a length of 81 meters, and a resilient hull diameter of 7.3 meters. Its surface speed is 10 knots, and its submerged speed is 19 knots.

The submarine is equipped with a primary propulsion system based on a 3,500 kW electric motor (MEP) and a diesel engine composed of three 1,200 kW generator groups that provide power to the MEP. The Air-Independent Propulsion (AIP) system allows the vessel to remain submerged for up to three weeks without the need to surface and snorkel to recharge its batteries.

The submarine's crew consists of 32 sailors, although it has the capacity to accommodate eight additional personnel for special operations. High automation of equipment and systems has reduced the crew size by half compared to the S-70 series submarines. The weapon system includes six torpedo tubes and the capacity to carry 18 weapons, including missiles, torpedoes, and mines.

In addition to the S-81 Isaac Peral, set to be delivered to the Navy this year, the next in line for service is the S-82 Narciso Monturiol in December 2024. The S-83 Cosme García will be delivered in October 2026, and the S-84 Mateo García de los Reyes in 2028.

The S-83 and S-84 will be the first in the series to incorporate the Air-Independent Propulsion (AIP) system as standard, allowing them to generate their own electrical power and navigate for weeks without surfacing, making them less vulnerable and detectable. The S-81 and S-82 will be delivered to the Navy without this system, which will be installed during their first major overhaul.