The Hartwell Project Open PDF Document Details Document Type Technical Report Publication Date Sep 30, 1951 Accession Number AD0103991 Entities People A.g. Hill Jerrold R. Zacharias Tags Communities of Interest Ground and Sea Platforms Weapons Technologies DTIC Thesaurus Topics Counter Countermeasures Countermeasures Depth Charges Detection Echo Ranging Identification Merchant Vessels Navy Nuclear Warfare Nuclear Weapons Ships Sonar Submarine Detection Undersea Warfare United States Warfare Weapons