Rear Adm. Tammen is a native of Washington Township, New Jersey.  He graduated from Rensselaer Polytechnic Institute in 1984 with a Bachelor of Science in Mechanical Engineering and earned his Master’s degree in Engineering Management from Old Dominion University.

His career as a nuclear submarine warfare officer includes assignments aboard USS Plunger (SSN 595), as a division officer; USS Nevada (SSBN 733) as the engineer officer; and USS Providence (SSN 719) as the executive officer.  Subsequent command assignments include commanding officer of USS Georgia (SSBN/SSGN 729), and commodore of Submarine Squadron 19.

Ashore, he has served as officer in charge of Combat Systems Training Team on the staff of Commander, Submarine Group 5; squadron engineer on the staff of Commander, Submarine Squadron 17; Force Nuclear Power officer for the Atlantic Submarine Force; executive assistant to the director Submarine Warfare Division (OPNAV N77); deputy division chief for Joint Capabilities Division (Joint Staff J8); section head for Platforms, Payloads, and Budget in Undersea Warfare (OPNAV N97); military assistant and chief of staff for the Assistant Secretary of Defense for Operational Energy Plans and Programs (OEPP), the Honorable Sharon Burke; and deputy director for Undersea Warfare (OPNAV N97).

As a flag officer, he served as the deputy director, Plans and Policy (J5) at U.S. Strategic Command, and Commander, Submarine Group 9, Naval Base Kitsap, Washington.

Tammen is currently the director, Undersea Warfare Division, Office of the Chief of Naval Operations (N97), Washington, District of Columbia.

His personal decorations include Defense Superior Service Medal (two awards), Legion of Merit (five awards), Defense Meritorious Service Medal, Meritorious Service Medal (two awards), Navy Commendation Medal (five awards), Navy Achievement Medal (two awards), and various unit awards.