The Rotary Vee is similar in configuration to the elbow steam engine. Watt was also concerned with fundamental research on the functioning of the steam engine. "Rocket" was built at a time of rapid development of steam engine technology. Applied science lead to the development of the steam engine. These attempts at imitating the principle of a steam engine were very inefficient. It manufactured the first portable steam engine. James Watt used a butterfly valve in his steam engine prototypes. Smeaton was the first to develop a rigorous theory of steam engine design of operation. This was based on a successful steam engine design. These ploughs date back to the days of the steam engine and the horse. A steam car is a car (automobile) propelled by a steam engine. Smeaton also made mechanical improvements to the Newcomen steam engine. In this drill, the drill bit passed through the piston of a steam engine. Compound steam engine powered ships enabled a great increase in international trade. Steam locomotives are locomotives with a steam engine that provides adhesion.