NASA has added another feather to its cap. On March 10, the space agency successfully test-fired its rocket engine No. 2059 on A1 Test Stand at Stennis Space Centre. The engine was tested for 500 seconds straight, thus marking a major milestone for NASA's deep space exploration. The engine will power NASA's Space Launch System (SLS) which is expected to be ready for launch by 2018. The engines that will power the SLS have been previously used on 135 space shuttle missions between the period 1981-2011. NASA said that out of these, four engines - that have a combined thrust of 2 million pounds - will be used to power the SLS. Also, for their first SLS flight, the engines will fire at 109 per cent thrust level. NASA's SLS is touted to become the most powerful rocket ever built by the agency since Saturn V - the rocket that was used to launch Apollo missions. "What a great moment for NASA and Stennis. We have exciting days ahead with a return to deep space and a journey to Mars, and this test is a very big step in that direction," said Rick Gilbrech, director of NASA’s Stennis Space Center in a statement.