The first mission for NASA’s Space Launch System (SLS) rocket and Orion capsule was originally scheduled for 2018, but it will now slip to June 2020.

An assessment by the space agency revealed manufacturing issues and tornado damage to an assembly facility are causing slow-downs. Acting NASA administrator Robert Lightfoot thinks the agency can hit an earlier launch date.

“Since several of the key risks identified have not been actually realized, we are able to put in place mitigation strategies for those risks to protect [a] December 2019 [launch] date,” Lightfoot said.

The first mission for the rocket called Exploration Mission 1 will send the Orion capsule without a crew on a trip around the moon. NASA wants the following mission to carry humans into deep space for the first time since Apollo.

Those missions will launch from Kennedy Space Center’s Launch Complex 39B, the home to a handful of Apollo missions and numerous Space Shuttle launches.

NASA says the majority of the work on the SLS rocket is on schedule and plans to fast-track the test of the launch abort system to April 2019, a critical milestone to certifying the capsule to safely carry humans.