Engineers for the U.S. space agency NASA were troubleshooting several issues early Monday ahead of the planned launch of a new rocket and crew capsule designed to send humans back to the moon. 

NASA teams dealt with delays due to a thunderstorm that passed over the launch site in the southeastern state of Florida as well as a leak discovered during fueling operations. 

NASA’s assistant launch director, Jeremy Graeber, said Monday’s scheduled launch could still go forward. If it does not, another try could happen on Friday. 

The test involves the Space Launch System rocket, the most powerful in NASA’s history, which will propel the Orion capsule without any people on board for this flight. Orion is due to go around the moon and return to Earth, with the entire journey taking about six weeks.    

If successful, NASA plans to fly astronauts around the moon in 2024 and potentially put them on the lunar surface as early as 2025.     

The launch is part of NASA’s Artemis program, which aims to have humans walk on the moon for the first time since 1972, including the first woman and person of color to do so.    

NASA is also planning a moon base as part of Artemis, and says it will use what it learns to inform efforts to send the first astronauts to Mars.    

Some information for this story came from The Associated Press, Agence France-Presse and Reuters