SLS on LC-39B
The Space Launch System rocket and Orion spacecraft at Launch Complex 39B after the fourth wet dress rehearsal test in June. NASA is targeting dates in late August and early September for the Artemis 1 launch: Credit: NASA/Kim Shiflett

WASHINGTON — NASA has reserved three days in late August and early September for the first launch of its Space Launch System rocket to send the Orion spacecraft to orbit around the moon and back.

At a July 20 briefing, NASA officials announced that they had target launch dates of Aug. 29, Sept. 2 and Sept. 5 for the Artemis 1 mission, an uncrewed test flight of the Orion spacecraft and the first launch of the SLS. Orion will spend up to six weeks in cislunar space before splashing down off the coast of San Diego.

“We think we’re on a good path to get to attempts on those dates,” Jim Free, NASA associate administrator for exploration systems development, said on the call.

Crews have been working on SLS and Orion since it returned to the Vehicle Assembly Building (VAB) July 2 after the fourth wet dress rehearsal test, where the rocket was loaded with liquid oxygen and liquid hydrogen propellants and put through a practice countdown. That included work to fix a liquid hydrogen leak on the core stage found during that test.

During that work, technicians discovered a loose fitting, called a collet, where the liquid hydrogen umbilical connects to the rocket. That required going into the rocket’s engine section to tighten the fitting. “That actually gave us a little pause of wondering if we were going to be able to make a launch date on those three dates,” Free said. With those repairs complete, he said he was more confident about being ready for those dates.

Free and other NASA officials on the call cautioned they still had work to perform on both SLS and Orion to get the vehicles ready for launch. If those preparations remain on schedule, the vehicle would roll back out to Launch Complex 39B around Aug. 18, although a final decision on proceeding with a launch attempt would come only after a flight readiness review about a week before launch.

The three launch dates have different launch windows and mission durations:

  • The Aug. 29 launch window opens at 8:33 a.m. Eastern for two hours, and would result in a 42-day mission ending with a splashdown Oct. 10.
  • The Sept. 2 launch window opens at 12:48 p.m. Eastern for two hours, and would result in a 39-day mission splashing down Oct. 11.
  • The Sept. 5 launch window opens at 5:12 p.m. Eastern for 90 minutes, and would result in a 42-day mission splashing down Oct. 17.

All three are considered “long-class” missions by NASA, while launch opportunities on other days instead support shorter missions lasting about four weeks. “We don’t have a strong preference of whether it’s a short- or long-class mission,” said Mike Sarafin, NASA Artemis mission manager. Both support all the mission objectives of testing the launch vehicle and spacecraft, with a particular emphasis on demonstrating Orion’s heat shield on a reentry at lunar return velocities.

One complication for launch planning is the batteries for the rocket’s flight termination system (FTS). That includes conducting a launch no more than 20 days after a final test of the system. “With our three attempts, we do have issues with that timing,” said Cliff Lanham, senior vehicle operations manager in NASA’s Exploration Ground Systems program. NASA is working with the Eastern Range to see if there are ways to address that issue.

Another issue is that the FTS batteries are located on portions of the SLS not accessible at the pad. That means that, if the vehicle rolls out to the pad in August but does not launch by Sept. 5, it would have to return the VAB for additional testing and reset of the clock.

That would make it difficult to have the vehicle ready for the next launch period, which runs from Sept. 20 to Oct. 4. “That would be a real challenge for us, to be honest with you,” Lanham said of launching during that timeframe. “But we would certainly give it our best shot.” The following launch period runs from Oct. 17 to 31.

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...