Robert G. Sachs (May 4, 1916 â April 14, 1999) was an American theoretical physicist, a founder and a director of the Argonne National Laboratory. Sachs was also notable for his work in theoretical nuclear physics, terminal ballistics, and nuclear power reactors. Sachs was also a member of the National Academy of Sciences, chairman of the Academy's Physics Section, chairman of the Academy's Class I (Physical and Mathematical Sciences), and director of the Enrico Fermi Institute of the University of Chicago. Sachs was the author of the standard textbook Nuclear Theory (1953).