SLS core stage at KSC
The barge carrying the SLS core stage arrives at the Kennedy Space Center April 27. Credit: NASA/Jamie Peer

WASHINGTON — The final major element of the first Space Launch System rocket arrived at the Kennedy Space Center, but NASA’s acting administrator says it will be “challenging” to launch the rocket before the end of this year.

The barge Pegasus arrived at KSC April 27 with the core stage of the SLS on board. Pegasus transported the core stage from the Stennis Space Center in Mississippi, where it had been since early 2020 for the Green Run test campaign that culminated in a full-duration static-fire test March 18.

NASA will transport the core stage to the Vehicle Assembly Building, where workers will attach to it its two five-segment solid rocket boosters, upper stage and Orion spacecraft. It will then be rolled out to Launch Complex 39B for final tests and, ultimately, the Artemis 1 launch.

“With the delivery of the SLS core stage for Artemis 1, we have all the parts of the rocket at Kennedy for the first Artemis mission,” John Honeycutt, SLS program manager at NASA’s Marshall Space Flight Center, said in a statement.

That launch is notionally scheduled for late this year, although NASA has not provided an updated launch date for the uncrewed test flight. The NASA statement about the arrival of the core stage at KSC did not mention its launch date.

NASA Acting Administrator Steve Jurczyk, speaking at an April 27 Space Transportation Association webinar, said the plan is still to launch Artemis 1 before the end of the year. “We’re still trying our best to get that launch off by the end of this calendar year,” he said. “That will be challenging given some of the delays that we had.”

Those delays, he said, include the technical challenges suffered by the core stage during the Green Run tests, as well as those caused by weather and the pandemic. Jurczyk said later that those issues consumed nearly all of the margin in the schedule for a launch this year.

“The schedule for Artemis 1 will be really challenging,” he said. “If things go really, really well on integration of SLS and integrating Orion on the mobile launch platform and rolling out, we have a chance to launch by the end of the calendar year.”

“But this is first-time flow on a vehicle at KSC,” he added, meaning that this is the first time they have gone through the steps of assembling the vehicle components and going through prelaunch processing. “We’ll undoubtedly encounter some challenges, so we don’t have a lot of schedule reserve against launching by the end of the calendar year.”

“If we can hit those major milestones and make progress, we’ve got a shot,” he said. “If we start missing those milestones, then may have to think about whether we can make it this year or not.”

Bill Nelson, the Biden administration’s nominee to be NASA administrator, hinted at his confirmation hearing April 21 that the launch might slip to next year. “The first of the Artemis mission launches within the next year,” he stated in the written version of his opening statement, a time frame that would extend into early 2022.

“At the end of the year, perhaps early next year, you’re going to see the largest rocket ever — most powerful — launched,” he said of SLS during the hearing. “It will be the workhorse on the program of going back to the moon and then on to Mars.”

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...