Practice makes… better, although not perfect.
On Thursday night, NASA successfully completed a countdown rehearsal for the Artemis II moon mission, experiencing only a few small glitches along the way.
That was a marked improvement from the agency’s first try a couple of weeks ago, which was cut short because of leaks of hydrogen, the fuel used by the rocket.
“Proud of the @NASA team as this was a big step toward America’s return to the lunar environment,” Jared Isaacman, the NASA administrator, wrote on X on Friday morning. “We are going.”
Unless a review of data reveals a subtle showstopper, the almost flawless rehearsal should pave the way for a launch attempt for Artemis II in a couple of weeks.
“We don’t have any indications of anything that we’re worried about,” John Honeycutt, the chairman of the mission management team for Artemis II, said during a news conference Friday morning. “But we’re just getting started.”
Lori Glaze, the acting associate administrator for NASA’s exploration systems development mission directorate, said the agency was aiming to hold a rigorous review of the data late next week to determine if the mission was ready to fly.
If the mission passes muster, NASA officials can then announce a launch date. The agency is currently targeting March 6, Ms. Glaze said. “For right now, that’s the direction that we’re headed,” she said.
There are additional launch opportunities on March 7, 8, 9 and 11. If Artemis II misses those, it will have to wait for the next set of possible launch dates in April.
The crew of four — three NASA astronauts and one from the Canadian Space Agency — will enter quarantine on Thursday, a precaution to ensure that they remain healthy.
“The excitement for Artemis II is really, really starting to build,” she said.
That launch will send the astronauts on a 10-day journey that will swing around the moon and return to Earth. The astronauts will not land on the moon, but they will be the first to leave low-Earth orbit since the end of NASA’s Apollo program more than 50 years ago.
The two-day countdown test at NASA’s Kennedy Space Center in Florida included filling up the tanks of the giant Space Launch System rocket with millions of pounds of liquid hydrogen and liquid oxygen.
The S.L.S. design is, in large part, a remix of decades-old technologies from NASA’s space shuttles. The rocket on the launchpad includes leftover engines and other parts from the retired shuttles.
Like the shuttles, S.L.S. has been bedeviled by hydrogen leaks at the launchpad.
Because hydrogen is the lightest element, it is efficient, providing the most energy per pound of any fuel. But hydrogen molecules, which consist of pairs of hydrogen atoms, are also small and notoriously difficult to contain.
During the first attempt, sizable hydrogen leaks occurred at the interface between the rocket and the launchpad. The tanks were eventually filled, but hours behind schedule.
But in the final part of the countdown, the hydrogen leak reappeared, and the rehearsal was ended with about five minutes left in the countdown.
Technicians have since replaced the seals at the junction.
On Thursday, the hydrogen remained well behaved throughout the countdown, with concentrations near the connection at 1.6 percent or less, far below the 16 percent limit.
“Really no leakage to speak of,” said Charlie Blackwell-Thompson, the launch director.
Minor issues included a problem with ground communications in the launch control center and a “voltage anomaly” in the measurement of a battery that briefly paused the countdown with 90 seconds left.
The countdown resumed and ticked down to 33 seconds, and then stopped as planned. The countdown clock was then reset to 10 minutes as systems were reconnected.
That allowed NASA to practice how to reset a launch attempt to fix a last-minute problem instead of scrubbing the attempt.
The reset, which included replenishing hydrogen and oxygen in the rocket’s propellant tanks, was expected to take about an hour. “We did it in 57 minutes,” Ms. Blackwell-Thompson said.
The countdown then resumed, again ending as planned — this time with 29 seconds left.
It was a busy night in Florida. As the Artemis II rocket sat on the pad, a SpaceX Falcon 9 rocket launched from a nearby launchpad at the Cape Canaveral Space Force Station, carrying a load of Starlink satellites to orbit.