HMS Rattler was a 9-gun steam screw sloop of the Royal Navy, and one of the first British warships to be completed with screw propulsion. She was originally ordered as a paddle wheel 4-gun steam vessel from Sheerness Dockyard on 12 March 1841. She was reordered on 24 February 1842 as a propeller type 9-gun sloop from HM Royal Dockyard, Sheerness, as a new vessel. William Symonds had redesigned the ship as a screw propeller driven vessel.

The Experimental Squadrons also known as Evolutionary Squadrons of the Royal Navy were groups of ships sent out in the 1830s and 1840s to test new techniques of ship design, armament, building and propulsion against old ones. They came about as a result of conflict between the "empirical" school of shipbuilding, the "scientific" school led by the first School of Naval Architecture, and the "traditional" school led by master shipwrights from the royal dockyards.