NASA Declares Megarocket Rehearsal Complete, Setting Stage for Inaugural Launch

The fourth and most recent attempt at a full launch rehearsal of NASA’s Space Launch System went reasonably well, and despite some lingering issues and uncertainties, the agency is sending the rocket back to the hangar for final preparations in advance of its first flight. That inaugural launch will represent Artemis 1, the first mission in NASA’s Artemis lunar program.

In a press release today, NASA—to my surprise—said it is done testing SLS after reviewing data from the recent launch rehearsal. That another full-blown rehearsal would be required seemed likely to me on account of an unresolved hydrogen leak linked to a faulty quick-connect fitting, which subsequently prevented ground teams from practicing the fully scheduled launch countdown on Monday. The goal was to reach T-10 seconds, but the launch controllers decided to quit the rehearsal at T-29 seconds for safety reasons.

“NASA plans to return SLS and Orion to the pad for launch in late August,” says the release. “NASA will set a specific target launch date after replacing hardware associated with the leak.”

Despite the hydrogen leak and the incomplete countdown, Monday’s wet dress did appear to go well. The ground teams finally managed to fully load SLS with propellants. Upwards of 755,000 gallons of cryogenic liquid oxygen and liquid hydrogen were supplied to the rocket’s two stages, which the teams had failed to do during the first three attempts. What’s more, all of the issues experienced during the first three wet dress rehearsals appear to have been resolved. The Orion spacecraft, currently sitting atop the rocket, also performed well during the test.

Said Tom Whitmeyer, NASA’s exploration systems manager, during a media teleconference on Tuesday: “We think that we had a really successful rehearsal,” adding that there is “relative risk” is running a fifth wet dress, with the 322-foot-tall (98-meter) rocket standing fully exposed on the launch pad.

During the Tuesday call with reporters, NASA officials said 90% of all test objectives were met, without specifying any details about the missing 10%. That said, Charlie Blackwell-Thompson, Artemis launch director, did admit to certain unknowns having to do with the late stages of the terminal count. On a positive note, the team managed to perform “several critical operations” deemed necessary for launch, including “switching control from the ground launch sequencer to the automated launch sequencer controlled by the rocket’s flight software, an important step that the team wanted to accomplish,” according to a NASA statement.

During the Tuesday teleconference, Mike Sarafin, Artemis mission manager at NASA, said the teams will have to consider “the risks of not performing another test.” Now, it seems, the space agency is satisfied with the level of risk and is ready to proceed with Artemis 1, in which the rocket will launch and attempt to send an uncrewed Orion spacecraft on a journey to the Moon and back without landing.

Following some last-minute test objectives that still need to be finalized, SLS will be transported back to the Vehicle Assembly Building for final close-outs and other launch preparations. The problem with the bleed line hydrogen leak in the tail service mast umbilical at the bottom of the rocket will also have to be fixed.

For months, NASA officials have considered at a late August launch. Very suddenly, this seems a likely target. Failing that, launch windows are available in each of the final five months of the calendar year. For Artemis 1, NASA requires launch windows in which the Moon and Earth are properly aligned, among other variables. A successful Artemis 1 mission would set the stage for Artemis 2, in which a crewed Orion will attempt the same journey (currently scheduled for May 2024).

As Hambleton pointed out, NASA will provide more information soon and meet with reporters tomorrow. I’m curious to know about those “remaining objectives” that have to be addressed before the rocket gets carted back to the VAB, and if NASA is ready to commit to an actual launch date. We’ll continue to update you on this developing story.

More: NASA’s Artemis Moon Landing Program: Launches, Timeline, and More.