boats designed to attack the larger capital ships of the blockading fleet as a form of asymmetrical warfare. The class of torpedo boats were steam powered with a partially enclosed hull. They were not true submarines but were semi-submersible; when ballasted, only the smokestack and few inches of the hull were above the water line. CSS Midge was a David-class torpedo boat. CSS Squib and represented another class of torpedo boats that were also low built but had open decks and lacked the ballasting tanks found on the Davids. The Confederate torpedo boats were armed with spar torpedoes. This was a charge of powder in a waterproof case, mounted to the bow of the torpedo boat below the water line on a long spar. The torpedo boat attacked by ramming her intended target, which stuck the torpedo to the target ship by means of a barb on the front of the torpedo. The torpedo boat would back away to a safe distance and detonate the torpedo, usually by means of a long cord attached to a trigger. In general, the Confederate torpedo boats were not very successful. Their low sides made them susceptible to swamping in high seas, and even to having their boiler fires extinguished by spray from their own torpedo explosions. Torpedo misfires (too early) and duds were common. In 1864, Union Navy Lieutenant William B. Cushing fitted a steam launch with a spar torpedo to attack the Confederate ironclad . Also the same year the Union launched , a purpose-built craft with a number of technical innovations including variable ballast for attack operations and an extensible and reloadable torpedo placement spar. Self-propelled torpedo A prototype self-propelled torpedo was created by a commission placed by Giovanni Luppis, an Austrian naval officer from Rijeka, then a port city of the Austro-Hungarian Empire, and Robert Whitehead, an English engineer who was the manager of a town factory. In 1864, Luppis presented Whitehead with the plans of the Salvacoste ("coastsaver"), a floating weapon driven by ropes from the land that had been dismissed by the naval authorities due to the impractical steering and propulsion mechanisms. Whitehead was unable to improve the machine substantially, since the clockwork motor, attached ropes, and surface attack mode all contributed to a slow and cumbersome weapon. However, he kept considering the problem after the contract had finished, and eventually developed a tubular device, designed to run