The first Space Launch System rocket is currently undergoing testing inside the Kennedy Space Center's Vehicle Assembly Building. A mass simulator on top of the rocket will soon be replaced by the Orion spacecraft. Credit: NASA/Frank Michaux

WASHINGTON — NASA expects to roll out the Space Launch System rocket for the first time in mid-March for a dress rehearsal of a launch that could come as soon as May but more likely some time in the summer.

NASA officials said Feb. 24 that workers had completed the last in a series of tests of the rocket in the Vehicle Assembly Building (VAB) at the Kennedy Space Center and were now closing out work on the vehicle to prepare for rollout to Launch Complex 39B.

That rollout is scheduled to begin at 6 p.m. Eastern March 17, Mike Bolger, Exploration Ground Systems program manager, said in a call with reporters. It will take about an hour for the vehicle and its mobile launch tower to move out of the VAB on a giant crawler-transporter vehicle, then 11 hours to the pad.

SLS will spend about a month at the pad undergoing tests, highlighted by a tanking test and practice countdown called a wet dress rehearsal about two weeks after rollout. The core stage will be filled with liquid hydrogen and liquid oxygen propellants and then go through a practice countdown that will stop at T-9.34 seconds, just before the core stage’s four RS-25 engines would ignite during an actual launch.

“We’re going to get very late in the count, purposefully, and demonstrate all the interfaces,” said Mike Sarafin, Artemis 1 mission manager.

At the end of the wet dress rehearsal, the vehicle will roll back the VAB for final launch preparations. That includes resolving any issues found during the test as well as charging batteries on the Orion spacecraft and updating flight computer software on SLS. “There’s a fair amount of work still to go, but it’s all things I think we understand well, and we’ll look to turn around pretty quickly,” Bolger said.

NASA expects that final work in the VAB to take about a month, although managers admitted some uncertainty in that schedule. “I wouldn’t want to say whether 30 days is conservative or not,” Bolger said. “I do acknowledge there’s a lot of work.”

The agency doesn’t plan to set a launch date for the Artemis 1 mission until after the wet dress rehearsal. “We recognize that is a period of time that could be very challenging,” said Tom Whitmeyer, NASA deputy associate administrator for exploration systems development.

He did confirm, though, that a launch in April is no longer feasible. “We’re still evaluating the tail end of the May window,” he said, which runs from May 7 to 21. Future launch windows, governed by orbital mechanics and other mission constraints like a splashdown during daylight hours, are June 6 to 16 and June 29 to July 12, with a “cutout” of July 2 to 4 when a launch would not be possible.

He added that he was unaware of any components of the vehicle that come from Russia or Ukraine and whose availability could this be affected by Russia’s invasion of Ukraine. “A lot of this is shuttle-heritage hardware,” he said, developed decades ago. The only major non-U.S. component is the service module for the Orion spacecraft, provided by the European Space Agency.

Processing of future SLS launches should be faster as they work through first-time issues on this vehicle. “For every first flow of a major NASA mission, we’ve always recognized that we’re going to learn some things and it’s going to take longer than the follow-on flows,” Bolger said. “We’re pretty optimistic that the lessons learned that we’re collecting as we go through this are going to enable us to process these faster the second time and then even faster the third and the fourth time.”

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...