The Navy has been procuring Virginia (SSN-774) class nuclear-powered attack submarines since FY1998. The two Virginia-class boats requested for procurement in FY2015 are to be the 21st and 22nd boats in the class. The 10 Virginia-class boats programmed for procurement in FY2014-FY2018 (two per year for five years) are being procured under a multiyear-procurement (MYP) contract. The Navy estimates the combined procurement cost of the two Virginia-class boats requested for procurement in FY2015 at $5,288.7 million or an average of $2,644.3 million each. The boats have received a total of $1,577.0 million in prior-year advance procurement (AP) funding and $158.4 million in prior-year Economic Order Quantity (EOQ) funding. The Navy's proposed FY2015 budget requests the remaining $3,553.3 million needed to complete the boats' estimated combined procurement cost. The Navy's proposed FY2015 budget also requests $1,649.5 in AP funding and $680.8 million in EOQ funding for Virginia-class boats to be procured in future fiscal years, bringing the total FY2015 funding request for the program (excluding outfitting and post-delivery costs) to $5,883.6 million. EOQ funding is a common feature in the initial years of an MYP contract. The Navy's proposed FY2015 budget also requests $132.6 million in research and development funding for the Virginia Payload Module (VPM). The funding is contained in Program Element (PE) 0604580N, entitled Virginia Payload Module (VPM), which is line 123 in the Navy's FY2015 research and development account. DOD and the Navy are considering whether to build Virginia-class boats procured in FY2019 and subsequent years with an additional mid-body section, called the Virginia Payload Module (VPM), that contains four large-diameter, vertical launch tubes that the boats would use to store and fire additional Tomahawk cruise missiles or other payloads, such as large-diameter unmanned underwater vehicles (UUVs). The Navy estimates that building Virginia-class boats with the VPM might increase their unit procurement costs by about 13%. It would increase the total number of torpedo-sized weapons (such as Tomahawks) that they could carry by about 76%. The Navy's FY2015 30-year SSN procurement plan, if implemented, would not be sufficient to maintain a force of 48 SSNs consistently over the long run. The Navy projects under that plan that the SSN force would fall below 48 boats starting in FY2025, reach a minimum of 41 boats in FY2028-FY2030, and remain below 48 boats through FY2034.