Yesterday afternoon brought another big show of progress building America's next generation rocket, NASA's Space Launch System (SLS). A billowing plume of steam signaled a successful 450-second test of the RS-25 rocket engine May 28 at NASA's Stennis Space Center near Bay St. Louis, Mississippi. The hotfire test was conducted on the historic A-1 Test Stand where Apollo Program rocket stages and Space Shuttle Program main engines also were tested. RS-25 engines tested on the stand will power the core stage of SLS, which is being developed to carry humans deeper into space than ever before. The heavy-lift SLS will be more powerful than any current rocket and will be the centerpiece of the nation's next era of space exploration, carrying humans to an asteroid and eventually to Mars. Four RS-25 engines will power the SLS vehicle at launch, firing simultaneously to generate more than 1.6 million pounds of thrust. RS-25 engines are modified Space Shuttle Main Engines, which powered 135 succe...