STENNIS SPACE CENTER, Miss. – In a key milestone in NASA's Space Launch System program, an RS-25 engine was installed Thursday on the A-1 Test Stand. The team at NASA's Stennis Space Center in South Mississippi will perform developmental and flight certification testing of the engine, No. 0525, a modified version of the space shuttle main engine that powered missions into space from 1981 to 2011. The SLS core stage will be powered by four RS-25 engines. Early tests on the engine will collect data on the performance of its new advanced engine controller and other modifications. (Source: NASA, 07/17/14) The core stage of the SLS is being built at Michoud Assembly Facility, New Orleans.