The operational U.S. polar icebreaking fleet currently consists of one heavy polar icebreaker, Polar Star, and one medium polar icebreaker, Healy. In addition to Polar Star, the Coast Guard has a second heavy polar icebreaker, Polar Sea. This ship suffered an engine casualty in June 2010 and has been non-operational since then. Polar Star and Polar Sea entered service in 1976 and 1978, respectively, and are now well beyond their originally intended 30-year service lives. Coast Guard polar icebreakers perform a variety of missions supporting U.S. interests in polar regions. A Department of Homeland Security (DHS) Mission Need Statement (MNS) approved in June 2013 states that "current requirements and future projections ... indicate the Coast Guard will need to expand its icebreaking capacity, potentially requiring a fleet of up to six icebreakers (3 heavy and 3 medium) to adequately meet mission demands in the high latitudes...." The current condition of the U.S. polar icebreaker fleet, the DHS MNS, and concerns among some observers about whether the United States is adequately investing in capabilities to carry out its responsibilities and defend its interests in the Arctic, have focused policymaker attention on the question of whether and when to acquire one or more new heavy polar icebreakers as replacements for Polar Star and Polar Sea. On September 1, 2015, the White House issued a fact sheet indicating that the Administration wants to begin building a new polar icebreaker in FY2020, and that the Administration will also "begin planning for construction of additional icebreakers" beyond the one that the Administration proposes to begin building in FY2020. On October 26, 2016, the Coast Guard released a request for information (RFI) to receive industry feedback on its notional polar icebreaker acquisition approach and schedule. The summary of the RFI, dated October 25, 2016, presents a notional schedule for acquiring three heavy polar icebreakers under which procurement of long leadtime materials (LLTM) for the three ships would start in the fourth quarter of FY2019, the second quarter of FY2021, and the second quarter of FY2022, respectively, and the ships would be delivered in the fourth quarter of FY2023, the second quarter of FY2025, and the second quarter of FY2026, respectively. (Each ship would be commissioned into service a few weeks or months after it is delivered.)