South Mississippi was hotter than usual on June 25 when the fire and heat produced by the longest test firing yet of a Space Launch System (SLS) RS-25 rocket engine at NASA's John C. Stennis Space Center combined with already climbing summer temperatures.

Engineers conducted a 650-second test of a RS-25 developmental engine as part of its preparation for a return to deep-space missions aboard the new Space Launch System rocket. NASA is designing the SLS to carry humans deeper into space than ever before, to such destinations as an asteroid and Mars.

The core stage of the new vehicle will be powered by four RS-25 engines, former space shuttles main engines operated at slightly higher power levels to provide the additional thrust needed to power the SLS.

The main goal of the series is to test the engine under simulated temperature, pressure and other changes required by the SLS design. The series also supports the development of a new controller, or "brain," for the engine. The controller monitors the engine status and communicates the programmed performance needs.

The first test in the series was in January. Testing resumed in May after scheduled work was completed on the high-pressure industrial water system that provides the tens of thousands of gallons of water needed during an engine test.

[Today's] test firing, the fourth in the series, expands on the performance objectives of the first two firings, allowing engineers to better understand the engine under a range of operating conditions. Three additional tests are scheduled in July and August before the initial series is completed. Each test moves NASA a step closer to a new national era of space exploration.

As the SLS evolves, it will provide an unprecedented lift capability of 130 metric tons (143 tons) to enable missions farther into our solar system to places like Mars.