Thomas Jackson Rodman Thomas Jackson Rodman ( July 31 , 1816 – June 7 , 1871 ) was an American artillerist , inventor , ordnance specialist , and career United States Army officer . He served as a Union Army general during the American Civil War , in which he was noted for his many improvements and innovations concerning the artillery used by the Union forces . He is especially remembered for developing the Rodman gun , which in various sizes saw extensive use in coastal defenses , and was called the " strongest cast iron cannon ever made . " General Rodman also discovered the use of shaped gunpowder grains , in which properly compressing and shaping the gunpowder into pre - designed grain shapes allowed the control of gas production by the burning gunpowder . This resulted in increased muzzle velocities with lower maximum pressures when compared to performance with conventional ball powder . The Rodman seven perforation grain was named after Rodman , and similar propellant grain shapes are still in use today in artillery , rockets , and automotive airbag inflators . After the conflict Rodman remained with the U . S . Army in his chosen profession , and is also noted for his alleged controversies while in command of the Watertown Arsenal . Early life and career . Thomas Jackson Rodman was born in 1816 on a farm near Salem in Washington County , Indiana . He was a son of James Rodman and his wife Elizabeth Burton , who was originally from Virginia . In 1837 Rodman entered the United States Military Academy in West Point , and graduated four years later , standing seventh out of 52 cadets . On July 1 , 1841 , He was appointed a brevet second lieutenant in the U . S . Army Ordnance Department . On December 13 , 1843 , Rodman married Martha Ann Black ( 1823 – 1908 ) , and the couple would have seven children together . His two daughters were named Florence ( born 1849 ) and Ella Elizabeth ( born 1856 ) , and his sons were named : John B . ( 1844 – 1909 ) , Edmund B . ( born 1846 ) , Thomas Jackson Jr . ( 1852 – 1919 ) , Robert S . ( born 1855 ) , and Addison B . ( born 1858 . ) Two of Rodman ' s sons also attended West Point . Addison Burton Rodman was admitted on July 1 , 1877 , but resigned on December 18 that same year . John Black Rodman was admitted on September 1 , 1863 , graduated on June 15 , 1868 , served initially with the 20th U . S . Infantry , and rose to the rank of colonel before retiring . Rodman also saw limited military action in 1846 – 48 during the Mexican – American War . The Rodman gun and Civil War service . Starting in 1844 , Rodman began running experiments to overcome the size limitations of cast iron cannon due to the way they were made . Up to that time , all cannon barrels made of iron were cast solid and then cooled only on their outside , resulting in uneven cooling when the metal contracted toward the barrel ' s outer surface . This process also " created internal strains and structural irregularities , " and these problems were even more prevalent in large bore castings , especially on any actual openings in the cannon that were designed . Made in this way , the cannons could crack during the cooling process , break apart during shipment , or worse burst as they were fired . Although it took him years , Rodman developed a way to solve these drawbacks . He found that if the cast the iron around a hollow core and then applied a steady stream of water within the barrel for cooling , a much more reliable and stronger product was made . His method , and the result , has been described as : " Water circulating through the tube cooled the bore while coals were piled against the mold to keep the outer surface hot . Rodman ' s manufacturing method , now known as the ' wet chill process ' , forced the impurities outward while the outer metal shrank against the hardened interior . " Doing this forced the thickest material toward the center of the barrel , and Rodman would then patent this invention . On March 3 , 1847 , Rodman was promoted to first lieutenant , and was promoted to the rank of captain on July 1 , 1855 . Rodman experimented for almost a decade at the Fort Pitt Foundry in Pittsburgh , Pennsylvania , testing his theory and performing trial runs of his cannon barrels . After viewing the results , the U . S . War Department approved construction of a fifteen - inch smoothbore columbiad of Rodman ' s design in 1859 . On December 23 a prototype was cast , and it test fired 509 times without incident . The following year he supervised its construction at the foundry , and once complete it was shipped for testing to Fortress Monroe at Old Point Comfort on the Virginia Peninsula . It tested successfully there in March 1861 , but due to its size and weight it would be destined for permanent , fixed positions , and not suitable for field service nor naval use . The specifications of this gun were : overall length of fifteen feet , ten inches long ; and a bore length of thirteen feet , nine inches ; total weight around 50 , 000 pounds . This design , capable of firing either shell or shot , would be the base for most of the Rodman guns that followed . Rodman also addressed the effectiveness of the gunpowder used in cannons . During 1856 his experiments showed that using powder compressed into hexagon el - shaped grains with several holes cut lengthwise into them caused the grains to burn outside as well as in , unlike their predecessors . This resulted in a longer and more consistent burn time in the bore , increasing the muzzle velocity of the round fired , thereby increasing the range of the weapon . As a result of his work , on April 17 , 1861 , Rodman reported to the U . S . War Department that he could now produce reliable cannon in almost any size using the methods he had developed . In November 1861 the first U . S . Government order was made for Rodman ' s fifteen - inch cannon , " . . . the largest in the U . S . arsenal . " During the conflict around 130 fifteen - inch , 445 ten - inch , and 213 eight - inch Rodman guns were purchased by the U . S . Government , and an unknown number made after the conflict . Another innovation Rodman developed was a replacement for the rear knob of cannons ( a part of the area called a cascabel ) which is used for fitting the gear that lifted and lowered the gun . Older designs had a knob that were small and round , which were found to easily break on the larger barrels being cast at the Fort Pitt Foundry . Rodman gave his cannon a short knob nearly as wide as the base of the barrel , a distinctive and easily recognizable feature of Rodman ' s guns . He also created instruments capable of measuring the internal pressure of his cannons . Rodman ' s contributions and the extent his work was utilized had been described as : Throughout the American Civil War , Rodman was commander and superintendent of the Watertown Arsenal , located along the Charles River in Watertown , Massachusetts . He also served on the army ' s Fortification Board during the war , and on June 1 , 1863 , Rodman was promoted to the rank of major . He would spend about three years designing a twenty - inch cannon ( the largest he would create ) and the work finally began on February 11 , 1864 . Using several of the arsenal ' s furnaces , about 160 , 000 pounds of molten iron were cast into four separate molds , then a week of cooling followed , and the cannon was finished on a huge lathe specially built for this task . A railroad flatcar capable of holding the gun , and its large carriage weighing 36 , 000 pounds itself , were also made under Rodman ' s supervision at the arsenal . While awaiting shipment to Fort Hamilton in New York Harbor , the large cannon drew spectators . On July 23 , 1864 , the " Pittsburgh Gazette " newspaper reported " Juveniles , aged from ten to fifteen years , were amusing themselves today in crawling into the bore on their hands and knees . A good sized family including ma and pa , could find shelter in the gun and it would be a capital place to hide in case of a bombardment . . . " As the American Civil War ended in 1865 , Rodman was rewarded for his service with three brevet promotions in the U . S . Army , all occurring on March 13 , making him a brevet brigadier general . Later career , controversy , and death . After the war ended , Rodman chose to remain in the U . S . Army . His actions while in command of the Watertown Arsenal drew the attention of the powerful Congressional Committee on the Conduct of the War , who investigated allegations of Rodman ' s possible disloyalty , improper management of the facility , and misuse of government resources , among other items . In particular he was charged with the following : Almost 100 witnesses were called to testify before the Committee on this matter , however Rodman was not permitted to cross - examine any of them ; instead he was only allowed to refute these charges in a letter to his own commander , Brig . Gen . Alexander B . Dyer , the army ' s Chief of Ordnance . To the accusations concerning his personal loyalty , Rodman answered " that he had given much attention to the loyalty of his men , and he showed his vigilance in pointing out that there had been no accidents at the Arsenal during his tenure there . " To the charge he failed to properly celebrate the Union victory and mourn Lincoln , he stated " that he had not fired a salute in recognition of the end of the war and of the President ' s death because he had never received official orders to do so . " The issue investigated most heavily by the Committee , however , concerned the building of the post commander ' s residence at the Watertown Arsenal . Speculation and rumor as to its total cost ranged up to $ 100 , 000 to $ 150 , 000 US $ , and that such extravagance was only to benefit Rodman himself . To the second claim Rodman stated that he had received orders to construct the residence ( along with specifications and plans for it ) by his superiors in the Ordnance Department , but the first claim required further testimony . Rodman stated that " every economy possible was being observed in constructing the house " and other witnesses testified that the cost ( estimated to be between $ 40 , 000 and $ 60 , 000 ) was reasonable for its completion ; the final total would come to $ 63 , 478 . 65 . The investigation itself developed its own controversy . Believing the Committee was hearing only " one - sided testimony " the civilians of Watertown wrote affidavit s praising Rodman ' s performance , asking he remain commander of the arsenal , and demanding he receive a fair trial . The hearings were described as " More than 90 witnesses were examined by Honorable Mr . Gooch of the Congressional Committee , who appears to have carefully selected for testimony those persons who advocated Rodman ' s removal ; and to have asked leading question s to any witnesses who may have been in sympathy with the commanding officer . " Although the investigation was completed , the results of the charges against him were never revealed , and in July 1865 Rodman was sent to Rock Island , Illinois , to supervise the construction of a new arsenal . This facility would become the Rock Island Arsenal , where Rodman would spend the rest of his life and career at , as well as building an even larger commander ' s residence . On March 7 , 1867 , Rodman was promoted to the permanent rank of lieutenant colonel in the U . S . Army . He died on duty at Rock Island on June 7 , 1871 , and was buried on June 17 in the arsenal ' s National Cemetery .