 After leaving active duty in 1974, Herdt enlisted in the United States Navy Reserve, serving in various Selected Naval Reserve units while attending Kansas State University.Returning to active duty in 1976, he served as a Naval Reserve Recruiter in Milwaukee, Wisconsin, and in 1978 rejoined the regular navy.Herdt served aboard , , and on the staff of the Nuclear Power School in Orlando, Florida, prior to his tour as Chief of the Boat aboard .