A maritime version of Project E, known as Project N supplied US Navy weapons. Providing American atomic bombs for Royal Navy ships would have involved similar dual key arrangements and detachments of US Marines on board Royal Navy ships, which was deemed impractical even for ships and weapons dedicated to use in European waters. However, RAF Coastal Command acquired Mk 101 Lulu nuclear depth bombs (with the W34 nuclear warhead) for its Avro Shackleton and Hawker Siddeley Nimrod maritime patrol aircraft from 1965 to 1971 under Project N. These were later replaced by the more capable Mark 57, which was stockpiled at RAF St Mawgan and RAF Machrihanish.