\n A crucial test of NASA\u2019s towering Space Launch System rocket is underway \u2014 marking one of the final steps before the vehicle launches four astronauts into deep space for the first time since the Apollo program ended more than five decades ago. The mission could launch as soon as February 8.\n <\/p>\n
\n The hands-on test, called a \u201cwet dress rehearsal,\u201d involves filling up the rocket\u2019s tanks with more than 700,000 gallons of super-chilled propellants.\n <\/p>\n
\n A few hours into the test, NASA ran into issues with hydrogen leaks \u2014 a problem that also plagued the SLS rocket during its first round of dress rehearsals in 2022 ahead of the uncrewed Artemis I test flight. Ultimately, that mission took off about six months after NASA first attempted a wet dress rehearsal.\n <\/p>\n
\n Kept at minus 423 degrees Fahrenheit, the liquified hydrogen, which is the primary fuel that powers the SLS rocket, is notoriously fickle because of its tiny molecular structure that makes the substance difficult to contain.\n <\/p>\n
\n The leaks did not prevent NASA from getting the SLS rocket fully fueled on Monday, however. As of 6 p.m. ET, the space agency said the vehicle had entered \u201creplenish mode\u201d \u2014 during which the rocket is only loaded with enough fuel to top off the tanks as small amounts of the propellants boil off.\n <\/p>\n
\n The agency is now working toward the \u201cterminal countdown sequence, which includes simulated launch operations and final readiness verifications,\u201d according to NASA.\n <\/p>\n
\n Just before 10 p.m. ET, however, NASA disclosed another issue. A \u201ccloseout team\u201d \u2014 which is a group of jumpsuit-clad workers who visit the launchpad to close the hatch on the crew\u2019s spacecraft \u2014 encountered an issue with a valve that was \u201cinadvertently vented.\u201d NASA said the group still needed at least one more hour to finish their work.\n <\/p>\n
\n All told, the rehearsal is expected to include a run-through of the countdown on launch day \u2014 except that during the test run the clock will be halted with less than a minute to go. On Monday, NASA was counting down to a pretend four-hour launch window that opened at 9 p.m. ET.\n <\/p>\n
\n How this test plays out will offer hints about when NASA will be able to launch the Artemis II mission \u2014 which could occur within several launch windows between early February and late April. At launch, NASA\u2019s Christina Koch, Victor Glover and Reid Wiseman as well as the Canadian Space Agency\u2019s Jeremy Hansen are expected to ride atop the SLS rocket before their Orion spacecraft separates and begins a journey to circumnavigate the moon.\n <\/p>\n
\n NASA confirmed on January 23 that the crew members had entered quarantine in Houston in preparation for their spaceflight. Astronauts are routinely kept isolated ahead of liftoff to prevent illness.\n <\/p>\n
\n The crew is expected to arrive at their Florida launch site at Kennedy Space Center after the wet dress rehearsal is complete.\n <\/p>\n
\n Though the astronauts are not landing on the lunar surface for this mission, their trip is set to carry them deeper into the solar system than any humans have traveled, surpassing the record that Apollo 13 astronauts set in 1970.\n <\/p>\n
\n Before liftoff, NASA is looking to put the SLS rocket through a clean wet dress rehearsal. Ahead of the rocket\u2019s first flight \u2014 the uncrewed Artemis I test mission in 2022 \u2014 it took multiple wet dress rehearsals over months<\/a> to ensure the systems were ready for launch.\n <\/p>\n \n \u201cWhy do we think that we\u2019ll be successful in Artemis II? It\u2019s the lessons that we learned,\u201d Charlie Blackwell-Thompson, the Artemis launch director, noted during a January 16 news conference.\n <\/p>\n \n \u201cWe learned a lot during the Artemis I campaign getting to launch. And the things that we learned \u2026 have all been rolled in to the way in which we intend to load the Artemis II vehicle.\u201d\n <\/p>\n \n NASA, however, has cautioned that, although it expects prelaunch preparations to run more smoothly for this mission, engineers still have the option of rolling the SLS rocket and Orion spacecraft back off the launchpad and into the nearby Vehicle Assembly Building for additional work if needed.\n <\/p>\n \n Cold weather over the weekend delayed the initial date for a wet dress rehearsal.\n <\/p>\n