At this time the United States Navy committed to the construction of several steam vessels, and Haswell, who had watched their earlier experimental steam vessels in New York Harbor, applied to supervise the engineering of , under construction. Although at first his role was only quasi-unofficial, there being no rank structure for engineers in the Navy at the time, when he was finally officially nominated and confirmed in 1851 to the rank of chief engineer, the appointment was to date from the start of his service in July 1836.Journal of Executive Proceedings of the United States, Washington: Government Printing Office, 1887, vol. 8, pp. 274, 288. Thus began a Naval career during which he would supervise the design of engines for ten warships.Burr William McIntosh, "People of Note", Burr MacIntosh Monthly, August 1907, vol. 14 (no. 53) In 1839, he served on a naval board responsible for the construction of the steam frigates Missouri and Mississippi, for which he was relieved of his duties to the Fulton. After work on the Michigan, he became chief engineer on the Missouri, but a dispute over a plan to replace its one smokestack with two earned him a two-year suspension, during which time he was involved in the construction of the boilers for the Allegheny and several revenue cutters."New York has Oldest Practicing Engineer", The New York Times, 13 May 1906 He was also instrumental in the Navy's creation of a corps of engineers, and he was named the first engineer-in-chief in October 1844. He subsequently designed the engines of Powhatan and San Jacinto. A public dispute over the design of the latter led to his removal as Engineer-in-Chief, and he was instead made chief engineer of the San Jacinto, having had responsibility for the design of its propulsion system, advocating his preferred propeller over a sidewheel, but being overruled.George W. Baird, "Charles H. Haswell, M.E.", Marine Engineering, vol. 5 (1900), p. 538-540 One of his innovations while with the navy was the use of zinc lining to the boilers to reduce corrosion.
