Member of the Manhattan Project, pianist, folk dancer, hiker

Robert J. S. Brown died peacefully, his five children having gathered to his bedside, on November 19. He was 95.

He was born Robert James Brown on September 7, 1924 and grew up in Lawndale, California. He graduated from Leuzinger High School before entering the California Institute of Technology in 1942.

His college years were interrupted by the war: in 1943 he joined the US Army and was sent to study electrical engineering at Ohio State University and then to Los Alamos, New Mexico, where, still a teenager, he would join the US effort to build the atom bomb.

Mr. Brown was the last person to connect the wires on the first nuclear device ever detonated, the Trinity test bomb, “The Gadget.” Along with his boss, Don Hornig, he babysat that bomb through the stormy night before it made history in the New Mexico desert at 5:29 a.m. on July 16, 1945.

After the war, and as a result of several bureaucratic mishaps arising from his too common name, he returned to Caltech as Robert James Sidford Brown. There he completed his bachelor’s degree in 1948.

He went on to earn a PhD from the University of Minnesota, and from there to take a job with the field research arm of Chevron Oil, where he pioneered techniques in nuclear magnetic well logging. He would spend his entire career with Chevron.

An avid pianist and a lifelong lover of folk dance, foreign languages and classical music, Mr. Brown enjoyed these pursuits as he retired to Claremont.

He also expanded his horizons. While his love of hiking and surfing had taken him to much of North America’s beautiful wilderness, his experience of Europe had been limited to the rigors of an oil platform in the North Sea.

His Claremont years brought regular trips to Europe, many of them devoted to exploring nuclear magnetic resonance in porous media with colleagues at the University of Bologna in Italy.

Mr. Brown is survived by his children, Erich, Dirk, Eleanor, Sidford and Kurt; 10 grandchildren; many great-grandchildren; and many friends from his years in Claremont and at Mt. San Antonio Gardens.

A memorial service is planned for 2 p.m. on Sunday, December 29, in the Assembly Room at Mt. San Antonio Gardens, 900 Harrison Ave., Pomona.