NASA has continued to make progress with the development of its large Space Launch System (SLS) rocket as work continued on its critical core stage throughout the partial government shutdown, and the agency is nearing critical hardware tests. However, it now seems all but certain that NASA will miss its latest launch date for the first flight of the rocket, June 2020.

Multiple sources have told Ars that while NASA is still targeting sometime later in 2020 for a test launch of the SLS rocket and Orion spacecraft, known as Exploration Mission-1, this flight is likely to slip into 2021.

This week, in response to a query about potential delays, a spokeswoman for the agency’s exploration program, Kathryn Hambleton, said the agency is not ready to discuss a new schedule yet. “NASA is still assessing impacts as a result of the shutdown, but we are still working toward a launch in 2020,” she told Ars.