Including astronauts would have also required significant work, like adding a fully operational life-support system to the Orion crew capsule, where the astronauts would have been seated.
Even without that additional work, Mr. Lightfoot announced that the launch date has slipped again, to 2019 from the previous target of November 2018, because of various technical challenges and some bad luck. In February, a tornado struck the Michoud Assembly Facility in Louisiana, where pieces of the rocket are being built, damaging the roof and equipment.
“That really set us back in a big way,” said William H. Gerstenmaier, the associate administrator for the human exploration and operations directorate at NASA.
This month, a big dome-shaped piece at Michoud was badly damaged while being moved; it was to become the bottom of a liquid oxygen tank that will be used for testing. “It’s probably not repairable,” Mr. Gerstenmaier said. But there are additional domes, and Mr. Gerstenmaier said he did not expect that to add much to the delay.
The construction of the European Space Agency’s contribution to the rocket — a service module that will provide propulsion, power and supplies for the Orion capsule — is also behind schedule.
NASA will now follow its original plan. For the first flight, Orion is to fly thousands of miles beyond the moon during a three-week trip. Mr. Gerstenmaier said one advantage of a crewless mission is that it will allow more thorough testing, closer to the edge of the capabilities of the spacecraft. “We will push as hard as we can,” he said.
The second flight, the first with astronauts, will come about three years later. It is scheduled for August 2021, but will also likely be delayed.
The delays will add to the skepticism of those who think the Space Launch System and Orion will be obsolete by the time they get to the launchpad.
SpaceX, the rocket company started by Elon Musk, is planning to finally launch this summer its long-delayed Falcon Heavy rocket. The Falcon Heavy is not as powerful as the Space Launch System, but with a $90 million price tag, far cheaper. The Space Launch System, which would launch only about once every two years, is…