While this RS-25 engine is the first flight article to undergo testing, Aerojet Rocketdyne racked up over 3,700 seconds of engine firing time last year. Those tests involved the first RS-25 development engine. Testing of these engines is critical as they are exposed to extreme conditions during the flight profile. Pressures inside the engine can exceed 7,000 pounds per square inch (492.15 kg/cm2). Beyond that, the engine must operate with temperature swings from –423 °F (–252 °C) to over 6,000 °F (3,315 °C). Pictured above: Engine No. 2059 arrives at the A-1 Test Stand at Stennis Space Center on Nov. 4, 2015. Photo Credit: NASA/SSC #aerojetrocketdyne #rs25 #nasasocial #nasamarsday #stennis #whoa #rocketscience