KENNEDY SPACE CENTER, Fla.—Five days after NASA’s first attempt to fly the massive Space Launch System rocket ended with technical problems, the space agency is ready to try again.

A launch team began fueling the rocket on Saturday morning shortly before the Sun began rising over the Atlantic Ocean waters that encircle the spaceport. The SLS rocket, which is launching the Artemis I mission around the Moon, has a two-hour launch window that opens at 2:17 pm ET (18:17 UTC).

A successful launch would mark the beginning of a 42-day mission that will send the Orion spacecraft into lunar orbit, and test critical technologies such as a heat shield that will protect the spacecraft during a fiery reentry through Earth’s atmosphere. If the mission goes well, Artemis II would follow in a couple of years, carrying humans around the Moon. A lunar landing is planned for later this decade.