The planned launch of the Artemis 1 moon rocket was cleared on Monday, NASA officials announced, before later vowing that “it’s not going to fly until it’s ready.” The rocket was to take off on a mission to put a crew capsule with three test dummies into orbit around the moon. The decision to cancel the launch comes after crews working on the project “encountered a problem with the cooling of engine number three,” among other factors, according to Artemis mission manager Mike Sarafin. “We need the engine to be at a cryogenically cool temperature so that when it starts it doesn’t get shocked with all the cold fuel flowing through it. We needed a little extra time to evaluate that,” Sarafin told reporters Monday afternoon. “When the team started working, they also saw a problem with a vent valve in the inner tank,” he continued. NASA CLEARS BLUE ORIGIN, SIERRA SPACE’S ORBITAL ROOF STATION, FOR PLANNING PHASE NASA canceled the launch of the Artemis 1 moon mission on Monday after a series of delays. (NASA) “So the combination of not being able to cool engine three and the vent valve issue they saw in the inner tank really caused a pause today and we felt like we needed a little more time,” added Sarafin. “There were also a number of weather issues throughout the window.” The next launch attempt won’t be until noon Friday, but Sarafin suggested the crew working on the mission need time to assess where things stand. “We will give the team time to rest, first of all, and then we will come back fresh tomorrow and reassess what we learned today,” he said. “And then develop a number of options – it’s too early to say what the options are … and then we’ll come back and talk about where we are tomorrow afternoon.” Vice President Kamala Harris was among those in attendance Monday for the planned launch at Florida’s Kennedy Space Center and was “pumped up the whole time,” NASA Administrator Bill Nelson said. “This is a brand new rocket, it’s not going to fly until it’s ready,” he added. “There are millions of components to this missile and its systems, and needless to say, the complexity is daunting when you bring them all into the focus of a countdown.” BUZZ ALDRIN’S MOON-FLOWN APOLLO 11 JACKET SOLD FOR RECORD $2.8 MILLION NASA’s New Moon rocket sits on Launch Pad 39-B hours before liftoff Monday, Aug. 29, in Cape Canaveral, Fla. (AP/Chris O’Meara) As the precious minutes ticked away Monday morning, NASA repeatedly stopped and restarted refueling the Space Launch System rocket due to a leak of highly explosive hydrogen, eventually managing to reduce the leak to acceptable levels. The leak occurred in the same spot that saw a leak during a dress rehearsal in the spring. Fueling had already been delayed nearly an hour due to storms. “The fear now is that the problem is in motor 3. If so, it cannot be replaced at the pad, but will have to go back to the [vehicle assembly building]Homer Hickham, a former NASA engineer, told FOX Business. “The delay will not be days but weeks. We’ll see. There is too much data for engineers to study before they can come to any conclusions about today’s effort and whether [Space Launch System] the rocket can stay on the cushion and try for friday. The 322-foot-long rocket is the most powerful rocket ever built by NASA, surpassing even the Saturn V that carried the Apollo astronauts to the moon. No astronauts were inside the rocket’s Orion capsule. Instead, three test dummies were strapped in for the six-week mission, which was scheduled to end with the capsule’s descent into the Pacific in October. NASA’s moon rocket is ready less than 24 hours before it is scheduled to launch at Pad 39B for the Artemis 1 mission into lunar orbit at the Kennedy Space Center, Sunday, Aug. 28, in Cape Canaveral, Fla. (AP Photo/ John Raoux ) (AP Newsroom) CLICK HERE TO READ MORE ABOUT FOX BUSINESS The launch is the first flight in NASA’s 21st century lunar exploration program, named Artemis after Apollo’s mythological twin sister. Assuming the test goes well, astronauts will board the craft for the second flight and fly around the moon and return as soon as 2024. A two-person lunar landing could follow by the end of 2025. Editor’s note: This article has been updated for clarity and to reflect information Artemis mission manager Mike Sarafin conveyed during NASA’s press conference Monday. Heather Lacy of Fox News and The Associated Press contributed to this report.