Since the RMS Lusitania wasn't a US flagged vessel and the Cunard Steamship Company wasn't a US company, there aren't records relating to her daily operations in the US National Archives. You may be better served by looking into records at the UK's National Archives (Home - The National Archives ). There appears to be records of the Cunard Line both at the UK's National Archives and at Liverpool University (SC&A - Liverpool University Library). It may also be worth your while to the contact's the UK's National Maritime Museum (National Maritime Museum Cornwall). There are also a great many secondary sources available relating to the Lusitania and her sinking. These may prove to be valuable resources for finding primary sources of information on the duties of the officers aboard the vessel.