The US Navy is buying a new breed of armed unmanned surface combat ships that will add more sensors and weapons to the current fleet. These will be 200-foot to 300-foot ships that displace 2,000 tons. The Navy plans to buy two large drone ships a year from FY2020-2024 for a total of about $2.7 billion. The corvette-sized USVs are being developed to field different types of sensors and, eventually, vertical launch system (VLS) cells for a variety of guided missiles.