Though NASA was optimistic about launching four astronauts on a trip around the moon as early as Friday, the space agency is now looking at March after complications during a key preflight test.
As it prepares for the Artemis II mission, NASA on Saturday evening began a wet dress rehearsal (WDR). The prelaunch exercise is designed to practice fueling the Space Launch System (SLS) rocket—the vehicle that will launch NASA’s Orion crew capsule on a 10-day mission to the moon and back—and identify any issues that might occur during the countdown to liftoff.
But the agency said engineers faced “several challenges” during the test, prompting it to require at least one more WDR before a target launch date is finalized. Teams were hoping to fly the mission during a window that opened last month and closes on February 14.
Now, Artemis II will slip to no sooner than next month, with opportunities on March 6, 7, 8, 9, and 11. Another window has openings on April 1, 3, 4, 5, and 6. Launch windows are only open about once every four weeks due to the performance requirements of SLS and Orion, the mission’s precise trajectory, and other factors.
“As always, safety remains our top priority, for our astronauts, our workforce, our systems, and the public,” Jared Isaacman, confirmed as NASA’s 15th administrator in December, wrote in a statement posted to social media. “We will only launch when we believe we are as ready to undertake this historic mission.”
The Artemis program, effectively a successor to the Apollo missions, aims to return Americans to the moon and lay the groundwork for future missions to Mars. It kicked off in 2022 with the uncrewed Artemis I mission, which marked the first integrated flight of SLS and Orion. Artemis II will be their first with crew.
The approximately 10-day mission aims to validate that vehicle systems perform as expected in a real deep space environment ahead of Artemis III, which will land a crew of four at the lunar south pole. Astronauts will conduct evaluations and practice maneuvers considered critical for that landing.
After the crew completes a few orbits around Earth, a trans-lunar injection burn will place Orion on a figure eight-shaped trajectory that at its apex extends more than 230,000 miles from the Blue Planet. On its way back, the spacecraft will rely on Earth’s gravity to pull it home naturally rather than expending additional propulsion.
What Went Wrong?
NASA began the nearly 49-hour WDR countdown on Saturday evening. Though cold temperatures forced a delayed start, engineers successfully loaded and unloaded SLS’ tanks with more than 700,000 gallons of cryogenic liquid oxygen and liquid hydrogen propellant.
A five-person closeout crew, which NASA likens to an auto racing pit crew, practiced how it would secure crewmembers in the Orion capsule during the real deal. The process on launch day is expected to take about four hours, requiring personnel to strap the astronauts into the capsule and connect them to life support, communications, and environmental control systems before closing the hatch. The closeout team will be the last to see NASA astronauts Reid Wiseman, Victor Glover, and Christina Koch, and Canadian Space Agency (CSA) astronaut Jeremy Hansen before they lift off.
However, NASA said the closeout took longer than anticipated. That was one of many obstacles engineers faced during the WDR.
On Tuesday morning, for instance, a ground launch sequencer automatically stopped the mock countdown at about T-5:15 after detecting a “spike” in the liquid hydrogen leak rate. The leak was traced to an interface of the tail service mast umbilical, which is used to load the SLS core stage with propellant.
NASA said “high concentrations” of liquid hydrogen were detected near the interface earlier in the countdown. During fueling, engineers took “several hours” to address the issue, adjusting or stopping the flow of hydrogen to the core stage and allowing the interface to warm up.
Engineers also had to “retorque” a recently replaced valve associated with pressurizing Orion’s hatch. Audio channels that facilitate ground communications suffered multiple “dropouts”—an issue teams had been troubleshooting for weeks. Though cold weather had minimal impact on the WDR, NASA said the conditions would have affected cameras and other equipment during an actual launch.
“With more than three years between SLS launches, we fully anticipated encountering challenges,” wrote Isaacman. “That is precisely why we conduct a wet dress rehearsal. These tests are designed to surface issues before flight and set up launch day with the highest probability of success.”
NASA said teams will review the WDR data and mitigate the issues before returning to testing. The crew, which entered quarantine in Houston last month, will get some fresh air before reentering isolation about two weeks before the next launch target.
Déjà Vu
NASA previously encountered some of the issues that arose during the WDR in the leadup to the uncrewed Artemis I mission in 2022.
Hydrogen leaks in the tail service mast umbilical area forced early ends to the third and fourth Artemis I WDR attempts. Both cases required NASA to roll SLS and Orion back to its Vehicle Assembly Building (VAB) for fixes.
In December, the space agency used its crawler-transporter 2 (CT-2)—the heaviest self-powered land vehicle on Earth, weighing about 6.6 million pounds unloaded—to make the approximately 4-mile, 12-hour journey from the VAB to the launch pad at Kennedy Space Center in Florida. The CT-2 is about the size of a baseball infield and can move up to 18 million pounds.
A hydrogen leak in the SLS service arm also forced NASA to scrub its second Artemis I launch attempt. It ultimately lifted off on its next try about two months later.
Artemis II will use the same heat shield that flew on the previous mission. In doing so, NASA is accepting a certain degree of risk.
The heat shield is coated in an outer layer of material designed to guard it and its occupants against temperatures that will approach 15,000 degrees Fahrenheit as Orion reenters the atmosphere. The material is designed to wear away as it heats up. But during Artemis I, charred chunks were flung off. NASA later determined this was due to gases trapped within the heat shield that caused its outer material to crack.
Though engineers managed to simulate the Artemis I reentry phase in a laboratory, an executive NASA council unanimously elected not to replace the heat shield for Artemis II. Former administrator Bill Nelson said doing so would prompt further delays to Artemis III, which will fly with a fresh heat shield. For the lunar flyby, NASA will instead alter Orion’s return to Earth to cap the buildup of gases.
Nelson cited the heat shield issue as a primary reason for Artemis III’s slide from its original 2025 launch target to mid-2027. NASA’s website now displays a 2028 target, which could continue to slip should Artemis II suffer further hiccups.