Atom bombardment ejects what appeared to be hydrogen nuclei. By 1920 he had accepted that the hydrogen nucleus is a distinct particle within the atom and named it proton. Neutrons have no electrical charge and have a free mass of 1,839 times the mass of the electron, or , the heaviest of the three constituent particles, but it can be reduced by the nuclear binding energy. Neutrons and protons (collectively known as nucleons) have comparable dimensions—on the order of —although the 'surface' of these particles is not sharply defined. The neutron was discovered in 1932 by the English physicist James Chadwick.
Up An' Atom Base, Texas, and was re-configured as a TB-29 trainer in April 1950 by the Oklahoma City Air Materiel Area at Tinker Air Force Base. Its subsequent assignments were to: "Up An' Atom" was dropped from the Air Force inventory in November 1956. It was transferred to the U.S. Navy and used as a target at the Naval Ordnance Test Station at China Lake, California. Up An' Atom Up An' Atom was the name of a B-29 Superfortress (B-29-36-MO 44-27304, Victor number 88) configured during World War II in the Silverplate project to carry an atomic bomb. Assigned to the 393d