{"id":25114,"date":"2016-03-04T11:00:37","date_gmt":"2016-03-04T00:00:37","guid":{"rendered":"http:\/\/www.aspistrategist.ru\/?p=25114"},"modified":"2016-03-04T16:21:19","modified_gmt":"2016-03-04T05:21:19","slug":"sea1000-the-importance-of-dived-endurance-part-2","status":"publish","type":"post","link":"https:\/\/www.aspistrategist.ru\/sea1000-the-importance-of-dived-endurance-part-2\/","title":{"rendered":"SEA1000: the importance of dived endurance (part 2)"},"content":{"rendered":"
<\/p>\n
In<\/span> part one of this series<\/span><\/a>, I examined some of the limitations of a lead acid Main Storage Battery for Australia\u2019s Future Submarines (FSM), the potential advantages offered by lithium ion alternatives now being developed and the risks attached to lithium (dramatically demonstrated by failures in some otherwise highly safety-conscious applications).<\/span><\/p>\n At stake is FSM\u2019s dived endurance\u2014a critical characteristic, particularly to meet Australia\u2019s requirements for long snort transits and patrol areas in heavily surveyed, busy littoral, tropical waters. Additional dived endurance provides increased tactical mobility and effectiveness, which improves flexibility and survivability in both transit and patrol area operations.<\/span><\/p>\n Air Independent Propulsion (AIP) offers an option to extend the dived endurance in both transit and patrol situations. There are a number of technologies available, with fuel cell systems appearing to be the future for larger submarines.<\/span><\/p>\n A submarine fuel cell typically combines hydrogen and oxygen in a chemical reaction to produce electricity (by-products are<\/span> oxygen and potable water<\/span><\/a>). But there\u2019s a downside: unlike the MSB, AIP fuel can\u2019t be recharged at sea\u2014once its fuel has been used the AIP effectively functions as additional space used and weight to be carried.<\/span><\/p>\n In low sea states or where maritime surveillance is intense during a transit or patrol, it mightn\u2019t be possible to snort to recharge the MSB at will or when planned. With a finite MSB endurance and without AIP, there\u2019s little option but to slow down and wait until the surveillance eases or to move out of the busy area on battery power\u2014accepting the impact on transit times\/time on station and battery expenditure.<\/span><\/p>\n The level of public information available on the 3 CEP contenders differs greatly; they\u2019re also offering<\/span> quite different AIP solutions<\/span><\/a> (PDF).<\/span><\/p>\n The German solution appears to be the most mature, with over 20 submarines at sea operating their fuel cell. A<\/span> methane reformer<\/span><\/a> is proposed to provide hydrogen as required by the fuel cell, avoiding the need to store the difficult to handle, expensive and dangerous gas. The reformer for FSM has yet to go to sea and is currently being tested.<\/span><\/p>\n The French propose<\/span> different fuel cell and reformer technologies<\/span><\/a>, both operating in shore-based test beds.<\/span><\/p>\n The Japanese<\/span> reportedly<\/span><\/a> intend to remove the<\/span> Stirling engine AIP system<\/span><\/a> purchased under a licence from Sweden from future Soryu-class subs with a view to replacing it with a lithium ion battery.<\/span><\/p>\n The proposed German AIP system could provide power for the Hotel Load and 5-7 knots propulsion for 21 days. At higher speeds energy is drawn from AIP and MSB, greatly extending the mobility of the submarine enabling it to evade or close a target at high speed\u2014for example, at 10 knots 50% of the power could be provided by AIP. Once the MSB reaches the minimum acceptable level the submarine can slow and still have days of AIP mobility depending on fuel remaining, without having to snort if the Commanding Officer choose not to.<\/span><\/p>\n