NASA’s moon megarocket is facing yet another testing delay ahead of the vehicle’s expected first flight for the Artemis program.

For months, NASA personnel have been conducting a series of tests called a “green run” on the first core stage of the agency’s massive new rocket, the Space Launch System (SLS). The tests are occurring at the NASA Stennis Space Center in Mississippi ahead of being shipped to Florida for the uncrewed Artemis 1 launch from the NASA Kennedy Space Center, near Orlando.