Launch day arrives for NASA's Artemis I mission that will journey around the moon
(CNN) -- Launch day has finally arrived for the uncrewed Artemis I mission to liftoff on a journey around the moon.
It's a sight to behold as the 322-foot-tall (98-foot-tall) stack, consisting of the Space Launch System rocket and Orion spacecraft, glows in the early morning darkness at NASA's Kennedy Space Center in Florida.
The stack is sitting on historic Launchpad 39B, where Apollo 10 and shuttle missions previously lifted off. Tune in to NASA's website and TV channel to watch the final preparations and witness the launch.
Weather conditions remain 80% favorable for a launch at the beginning of a window that opens at 8:33 a.m. and closes at 10:33 a.m. ET, according to the latest forecast.
But several issues have cropped up since the rocket began fueling after midnight. The Artemis team is evaluating the delays to determine how it impacts the launch.
Offshore storms with the potential for lightning prevented the team from beginning the fueling process, due to start at midnight, for about an hour.
The hold was lifted at 1:13 a.m. ET, and the tanking process began to load the rocket's core stage with supercold liquid oxygen and liquid hydrogen.
The team stopped filling the tank with liquid hydrogen twice due to an initial leak as well as a pressure spike, but tanking resumed for the core stage and began for the upper stage, or the interim cryogenic propulsion stage.
Now, the launch team has discovered an issue with an engine bleed in one of the rocket's four engines and are working to reconfigure it. So far, their efforts haven't been effective.
During engine bleeds, hydrogen is cycled through the engine to condition it for launch. Three of the four engines are performing as expected, but engine #3 is experiencing an issue.
The team also discovered a line of frost on the inner stage flange. The frost may indicate the presence of a crack.
Engineers are also working to find out what has caused an 11-minute delay in communications between the Orion spacecraft and ground systems. The issue could impact the beginning of terminal count, or the countdown that begins when 10 minutes remain on the clock before liftoff. But engineers feel good about figuring out the issue ahead of the terminal count, according to NASA.
Vice President Kamala Harris and Second Gentleman Doug Emhoff are expected to visit Kennedy Space Center Monday.
Appearances by celebrities like Jack Black, Chris Evans and Keke Palmer and performances of "The Star-Spangled Banner" by Josh Groban and Herbie Hancock and "America the Beautiful" by The Philadelphia Orchestra and cellist Yo-Yo Ma are also part of the program.
Orion's journey will last 42 days as it travels to the moon, loops around it and returns to Earth -- traveling a total of 1.3 million miles (2.1 million kilometers). The capsule will splash down in the Pacific Ocean off the coast of San Diego on October 10.
While the passenger list doesn't include any humans, it does have passengers: three mannequins and a plush Snoopy toy will ride in Orion.
The crew aboard Artemis I may sound a little unusual, but they each serve a purpose. Snoopy will serve as the zero gravity indicator -- meaning that he will begin to float inside the capsule once it reaches the space environment.
The mannequins, named Commander Moonkin Campos, Helga and Zohar, will measure deep space radiation future crews could experience and test a new suit and shielding technology. A biology experiment carrying seeds, algae, fungi and yeast is tucked inside Orion to measure how life reacts to this radiation as well.
Cameras inside and outside of Orion will share images and video throughout the mission, including live views from the Callisto experiment, which will capture a stream of Commander Moonikin Campos sitting in the commander's seat. If you have an Amazon Alexa-enabled device, you can ask it about the mission's location each day.
Expect to see views of Earthrise, similar to what was shared during Apollo 8 for the first time, but with much better cameras and technology.
Science experiments and technology demonstrations are riding in a ring on the rocket. The 10 small satellites, called CubeSats, will detach and go their separate ways to collect information on the moon and the deep space environment.
The inaugural mission of the Artemis program will kick off a phase of space exploration that lands diverse astronaut crews at previously unexplored regions of the moon and eventually delivers crewed missions to Mars.
The rocket and spacecraft will be tested and put through their paces for the very first time before they carry astronauts to the moon on Artemis II and Artemis III, slated for 2024 and 2025 respectively.
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