The RS-25 rocket engine is so complex, NASA had to burn a few before it learned how to start them.

At 4:30 PM today, NASA will test fire the RS-25, which will one day power a manned mission to Mars and other deep space destinations.

As RS-25 test project manager Ronnie Rigney explains in the video above, the RS-25 is more complicated than most rocket engines. This “Ferrari of rocket engines,” as propulsion engineer Kathryn Crow calls it, was designed to be highly efficient, with maximized thrust, thrust-to-weight ratio, and overall efficiency. It’s still a precarious process, but at least now NASA knows how to feed fluids into the engine and get it started without burning it up.

Four RS-25 engines and two five-segment solid rocket boosters will power NASA’s new rocket, the Space Launch System, which in the future will travel to an asteroid and eventually Mars.

The test will take place at the A-1 test stand at NASA’s Stennis Space Center in Mississippi, and will last for 535 seconds, the amount of time the engines will fire during an actual launch.

You’ll be able to watch it live on NASA TV here.