U.S. inventor of prismatic and perforated-cake gunpowder that burned evenly, providing controlled expansion of gases in a gun rather than a sudden shock that might burst the barrel. He also invented a system of casting cannon around a hollow core cooled from inside, resulting in a stronger barrel as concentric layers of metal cooled and shrank one upon another.

Rodman was graduated from the U.S. Military Academy at West Point, N.Y., in 1841 and from 1845 worked out the ideas of his inventions, which were accepted by the U.S. government in 1859. During the U.S. Civil War he commanded the arsenal at Watertown, Mass. He was brevetted brigadier general in 1865. At the end of the war he was placed in command of the arsenal at Rock Island.