URF (Swedish Navy)

URF (Ubåts Räddnings Farkost – Submarine Rescue Vessel) is the Royal Swedish Navy’s Submarine Rescue Vessel.

History
The original design of URF had a rescue capacity of 25 submariners and included a diver lockout chamber on board the vessel to provide means for hatch-clearance and assistance. The first of three planned URFs was constructed in 1978. It was manufactured by the Kockums company of Sweden. In 1981, it was first connected successfully to a submerged submarine.

The diver lockout system was removed in 1984 in favour of longer durability and possibilities to rescue a full Swedish submarine crew of 35 in one lift. The original propulsion system with thrusters at the sides of the URF was also removed in favour of a more conventional propeller in the aft, providing more power and a reduced risk of damaging the thrusters during operation. The original trailer was replaced with on which has more axles. This, together with some minor changes of the fin, allowed transportability by air beginning in 2000.

In 2015, the original URF underwent further upgrading by marine builders JFDefence.

2015 operation
The URF to the Baltic Sea's maximum depth. It has a rescue skirt which makes it possible to mate with the submarine's emergency hatch, and can rescue a submarine crew of up to 35 submariners in a single trip, while holding them in above-atmospheric pressure if necessary until they can be transferred under pressure to a decompression chamber system to continue treatment and decompression.

The URF is a free-swimming vehicle with a pressure hull which is separated into three pressure-tight compartments. Two pilots manoeuvre the vehicle from the pilot compartment by operating one main propulsion unit and four tunnel thrusters. The third crew member is the machinery operator who also assists the pilots while docking the URF with the disabled submarine. If the submarine is pressurised, an additional rescue room operator is included in the crew.

The pressure hull is surrounded by a streamlined fibreglass plastic casing which protects auxiliary equipment placed between the pressure hull and casing, including batteries, compressed air and oxygen bottles, hydraulics and trim systems.

Although the URF can travel on its own, it is usually quicker to trailer the vessel to a nearby port and tow it to the area of the disabled submarine. In cases where its mothership, Belos, can't get it to the rescue site quickly, the URF is flown to a suitable airport, transported to port, and towed to the area of operations.