NASA is another step closer to manned deep-space missions with the completion of the latest round of RS-25 rocket engine tests. Based on the engines that sent the Space Shuttle into orbit, the new power plants will form the core of the Space Launch System (SLS).

The tests, which ended on Thursday, was the seventh in a series of hot-firings of the liquid-fueled engine that will lift the Orion capsule into space on its first manned mission. During the last firing, the RS-25 ran for 535 seconds on the A-1 Test Stand at NASA’s Stennis Space Center in Bay St. Louis, Mississippi. The purpose of the firings is to test a new engine controller that monitors the engine's performance and relays telemetry to ground control. In addition, they provided data on engine materials and engine propellant inlet pressure conditions.

The RS-25 engine began life as the Space Shuttle main engine and the first flights of the SLS will use recycled engines installed on the actual Shuttle flights. These will then be replaced on later missions by simpler disposable engines based on the original design. When installed in the SLS booster, they will make it the most powerful launch vehicle ever constructed and will be used for future manned deep-space missions.

NASA says the SLS missions will require the RS-25 to run at 109 percent of its operating level. During launch, the four engines will generate 2 million pounds of thrust, while two solid-rocket boosters will be bring the total to 8.4 million pounds of thrust. This will lift the SLS in its initial 70-tonne (77-ton) configuration, as well as its later 130-tonne (143-ton) version.

The next round of tests will put the RS-25 through new paces, including lower liquid oxygen temperatures, greater inlet pressures, higher vehicle acceleration, higher nozzle heating, as well as tests of new ablative insulation and heaters. As part of this program, the B-2 Test Stand at Stennis is being refitted for the testing the SLS flight core to allow for a simultaneous firing of four RS-25 engines.

"The completion of this test series is an important step in getting SLS ready for the journey to Mars," says Steve Wofford, engines manager at NASA’s Marshall Space Flight Center. "The RS-25 engine gives SLS a proven, high performance, affordable main propulsion system. It is one of the most experienced large rocket engines in the world, with more than a million seconds of ground test and flight operations time."