Steam blasts out of the A-2 Test Stand at Stennis Space Center on Oct. 22 as engineers begin a certification test on engine 2061, the last space shuttle main flight engine scheduled to be built. Since 1975, Stennis has tested every space shuttle main engine used in the program - about 50 engines in all. Those engines have powered more than 120 shuttle missions - and no mission has failed as a result of engine malfunction. For the remainder of 2008 and throughout 2009, Stennis will continue testing of various space shuttle main engine components.