Today is one small step for NASA's future Space Launch System, which could later form part of a giant leap in getting mankind back into space and hopefully, all the way to Mars.
The Space Launch System is the proposed new "heavy launch" rocket that will be used for getting people deeper into space than the International Space Station. Derived from the engines that were used on the now-retired Space Shuttle, the hope is that four RS-25 engine will deliver 512-thousands pounds of thrust each. According to PopSci this is even more thrust than the cumbersome Shuttle, which 'only' delivered 491-thousand pounds of thrust per engine.
Today's test is all about seeing what actually happens when you fire up an RS-25. NASA is going to set one of the massive engines to burn for nine minutes to monitor what happens if the engine is switched on for the same amount of time it would be during a real launch.
Here's an earlier test, from back in January:
If it is successful, the hope is that the SLS will take off for real some time in 2018. The test tonight will be streamed on NASA TV, and you can tune in at about 9:30pm tonight UK time if you want to watch. [PopSci]