The first Type 212A submarine commissioned by the German Navy, U-31 was built in two sections, and joined together before her launch in 2002. Commissioned in October, 2005, she has a highly efficient powerplant, consisting of one diesel engine and and one electric, driven by nine fuel cells. The only exhaust from the drive is distilled water, making her environmentally friendly, to boot. The ultra-quiet propulsion, coupled with a composite "stealth skin" sheathing the hull, means that the Type 212s are virtually undetectable. Her crew of twenty-seven has six 533mm (21") torpedo tubes at their disposal, capable of launching a range of torpedoes and the upcoming IDAS missile. U-31 can also carry up to twenty-four mines externally.