English: The Engine Propeller Research Building, referred to as the Prop House, emits steam from its acoustic silencers at the National Advisory Committee for Aeronautics (NACA) Lewis Flight Propulsion Laboratory. In 1942 the Prop House became the first completed test facility at the new NACA laboratory in Cleveland, Ohio. It contained four test cells designed to study large reciprocating engines. After World War II, the facility was modified to study turbojet engines. Two of the test cells were divided into smaller test chambers, resulting in a total of six engine stands. During this period the NACA Lewis Materials and Thermodynamics Division used four of the test cells to investigate jet engines constructed with alloys and other high temperature materials. The researchers operated the engines at higher temperatures to study stress, fatigue, rupture, and thermal shock. The Compressor and Turbine Division utilized another test cell to study a NACA-designed compressor installed on a full-scale engine. This design sought to increase engine thrust by increasing its airflow capacity. The higher stage pressure ratio resulted in a reduction of the number of required compressor stages. The last test cell was used at the time by the Engine Research Division to study the effect of high inlet densities on a jet engine. Within a couple years of this photograph the Prop House was significantly altered again. By 1960 the facility was renamed the Electric Propulsion Research Building to better describe its new role in electric propulsion.