NASA successfully test-fired the J2-X rocket engine on Wednesday, a key component of the Space Launch System, NASA’s giant new rocket that is slated to take cargo and crew beyond low Earth orbit. A deafening 500-second firing test at the Stennis Space Center showed the engine is ready for the next steps in building the SLS rocket.

“What you heard to today is the sound of the front end of the critical path to the future,” said Stennis Director Patrick Scheuermann, speaking at a press conference immediately after the test fire, which began at 4:04 p.m. EST (2104 GMT).

The J-2X will power the upper stage of the SLS, the $10 billion next generation heavy-lift rocket. The first flight of the new rocket won’t be until 2021, however.

“The J-2X engine is critical to the development of the Space Launch System,” Dan Dumbacher, NASA’s deputy associate administrator for exploration systems development, said after the test in Mississippi. “Today’s test means NASA is moving closer to developing the rocket it needs if humans are to explore beyond low-Earth orbit.”

Data from the test will be analyzed as operators prepare for additional engine firings. The J-2X and the RS-25D/E engines for the SLS core stage will be tested for flight certification at Stennis. Both engines use liquid hydrogen and liquid oxygen propellants. The core stage engines were developed originally for the space shuttle.

“We have 500 seconds of good data, and the first look is that everything went great. The J-2X engine team and the SLS program as a whole are extremely happy that we accomplished a good, safe and successful test today,” said Mike Kynard, Space Launch System Engines Element Manager at NASA’s Marshall Space Flight Center in Huntsville, Ala. “This engine test firing gives us critical data to move forward in the engine’s development.”