mixture of Gould Mark 48 Mod 4 torpedoes and UGM-84C Sub-Harpoon anti-ship missiles; previously carried by the Oberon-class boats. In 2006, the Mark 48 torpedoes were upgraded to the Mod 7 Common Broadband Advanced Sonar System (CBASS) version, which was jointly developed with the United States Navy. Waller was the first vessel of either navy to fire an armed Mod 7, sinking the decommissioned destroyer on 16 July 2008, during RIMPAC 08. Some or all of the torpedo payload can be replaced with up to 44 Stonefish Mark III mines. During the construction phase, consideration was given to acquiring submarine-launchable Tomahawk cruise missiles; giving the boats the capability to attack land targets after minor modifications. Plans to acquire Tomahawk or similar land-attack missiles remained under consideration until 2009, when the Defending Australia in the Asia Pacific Century: Force 2030 white paper was released; stating that land-attack missiles will instead be incorporated into the armament of the Collins-class replacement. The Collins class was not designed to support special forces operations providing a limited capability similar to the Oberon class. In 2005, Collins received a special forces upgrade to provide three capabilities of multi swimmer release, float on/float off and exit and reentry. However, there were issues with exit and reentry during sea trials. Originally only one submarine was planned to receive the upgrade. In 2014, Dechaineux was upgraded and the issue with exit and reentry was rectified. Collins is scheduled on its next maintenance docking to receive the safety upgrade for exit and reentry. However, the full special forces upgrade is yet to be reached with outboard stowage of equipment, such as for inflatable boats, still in the design phase. Propulsion Each submarine is equipped with three Garden Island-Hedemora HV V18b/15Ub (VB210) 18-cylinder diesel engines, which are each connected to a 1,400 kW, 440-volt DC Jeumont-Schneider generator. The combined electrical generation capability of each submarine is 4.2 megawatts. The Hedemora diesels were chosen because of modular construction, which made servicing easier; they could be installed three across in the available space, while other contenders required at least two banks of two; and they had turbochargers driven by the exhaust gas. Fifteen fuel tanks are located throughout the submarine: they must be used in specific sequences to preserve the submarine's buoyancy and trim. Electricity is stored in four lead-acid battery packs, totalling 400 tonnes, assembled by Pacific Marine Batteries, a joint venture