CAPE CANAVERAL (CBSMiami/CNN) -- NASA's Artemis I mission is another step closer to its lunar launch.
The massive 322-foot-tall stack, which includes NASA's Space Launch System rocket topped by the Orion spacecraft, is being rolled for its testing debut at Kennedy Space Center on Thursday.
The integrated stack, which sits on a mobile launcher, began its slow-moving crawl into launch position Thursday afternoon.
The 4-mile ride aboard one of the Apollo-era giant NASA crawlers from the assembly building to the launchpad could take up to 11 hours, according to NASA.
Artemis I will ride on top of Crawler Transporter-2 for its trip to the launchpad, just like the shuttle missions and Apollo Saturn V rockets once did. The 6.6 million-pound crawler will carry the towering rocket stack and its mobile launcher at a top speed of 1 mile per hour.
The iconic crawler is one of two that have operated for more than 50 years at Kennedy Space Center. They were first operated in 1965 and can each transport 18 million pounds, or the weight of more than 20 fully loaded 777 airplanes, according to NASA. They are so wide that a professional baseball diamond could sit on top of each crawler.
"Rolling out of the (Vehicle Assembly Building) is really an iconic moment for this vehicle," said Tom Whitmeyer, associate administrator for exploration systems development at NASA Headquarters during a Monday press conference. "Thursday is going to be a day to remember."
Following a couple weeks of tests at the pad, the vehicle will be ready for its wet dress rehearsal the weekend of April 1 -- the final test before launching the first uncrewed Artemis mission beyond the moon and back to Earth. NASA is collecting names to be put on a flash drive and sent into space on the Orion spacecraft.
The wet dress rehearsal includes running through the full set of operations to load propellant into the fuel tanks and a launch countdown -- basically everything necessary for a launch without actually launching. During the hours of prep leading up to the wet dress rehearsal, more than 700,000 gallons of cryogenic propellants will be loaded into the rocket
If the test is successful, the stack will go back into the assembly building until it's ready to launch.
"Artemis I is such an important mission for us," said Howard Hu, manager of the Orion program at NASA's Johnson Space Center in Houston, during the Monday press conference. "It's gathering very critical engineering data and validating our performance capability as spacecraft for our next mission and beyond -- Artemis 2 with the crew and future missions as we go further and expand our capabilities in the solar system."
The Artemis program has experienced a multitude of delays. The mission was originally scheduled to launch in November 2021, but the pandemic, storms like Hurricane Ida and other factors have drawn out the mission time line.
Artemis I is the first step of NASA's ambitious program to land the first woman and the first person of color on the moon later in the 2020s. It's all in preparation to establish a long-term lunar presence and to prepare for exploring Mars. Depending on the results of the wet dress rehearsal, the uncrewed mission could launch in May, June or July.
During the flight, the uncrewed Orion spacecraft will launch atop the SLS rocket to reach the moon and travel thousands of miles beyond it -- farther than any spacecraft intended to carry humans has ever traveled. This mission is expected to last for a few weeks and will end with Orion splashing down in the Pacific Ocean.
Artemis I will be the final proving ground for Orion before the spacecraft carries astronauts to the moon, 1,000 times farther from Earth than where the space station is located, said Cathy Koerner, former Orion program manager, in October. Koerner is now NASA's deputy associate administrator for exploration systems development.
After the uncrewed Artemis I flight, Artemis II will be a crewed flyby of the moon and Artemis III will return astronauts to the lunar surface. The time line for the subsequent mission launches depends on the results of the Artemis I mission.
(©2022 CBS Broadcasting Inc. All Rights Reserved. Cable News Network, Inc., a Time Warner Company, contributed to this report.)
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