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CAPE CANAVERAL, Fla. (WHNT) – The latest attempt by NASA to complete a mock launch and countdown has ended.

The SLS has been in development since 2011 and has never flown to space. The purpose of the wet dress rehearsal is to fully fuel the rocket and take it through a launch countdown up until 10 seconds before liftoff. The rocket will not be launching during the test.

The launch team arrived at their stations inside the Launch Control Center at the Kennedy Space Center around 4 p.m. Saturday and the countdown began at 4:30 p.m. The team spent the night filling the water tank for the sound suppression system, powering up all of the rocket’s components and preparing the connections between the mobile launcher and the rocket.

The three previous attempts at a wet dress rehearsal were stopped early due to issues with the ground systems at the launch pad, a faulty helium valve in the upper stage of the 322-foot rocket and a hydrogen leak.

A faulty valve for the backup nitrogen gas supply paused the countdown at T-6 hours, 40 minutes just before 6:30 a.m. Monday. However, the valve was repaired shortly before 6:45 a.m. and crews resumed the countdown around 8:30 a.m.

When the countdown resumed teams started the process of chilling the core stage and the fuel lines that will carry liquid oxygen into the tanks.

The launch team began slowly fueling the core stage with liquid oxygen around 9 a.m. and the fast-fill began 15 minutes later. The SLS oxygen tank holds 196,000 gallons of propellant cooled to -297 degrees Fahrenheit.

At 10:10 a.m. liquid hydrogen started to flow into the rocket after the crew took some extra time to chill the fuel lines, according to Derrol Nail with NASA’s communication department. During the last wet dress rehearsal attempt, it was during this stage of the test that NASA teams discovered a hydrogen leak and decided to end that test.

Liquid hydrogen reached 98% full just after 11:35 a.m., and the tanks were topped off by 11:42 a.m. Liquid oxygen tanks were 80% full at that point. The core stage tanks were filled just after 12:30 p.m., with the upper stage liquid hydrogen moving into fast-fill mode.

While filling the upper stage with liquid oxygen, crews were alerted to a pressure warning and fueling was paused for about 30 while crews worked on a solution. They decided to manually adjust the liquid oxygen pressure in the upper stage to get back to fueling.

The hydrogen tank can hold 537,000 gallons of liquid hydrogen chilled to -423 degrees Fahrenheit. The tank is also one of the largest components of the core stage, standing at 130 feet tall.

Launch crews have also been made aware of a small grass fire that is burning near the Hydrogen Flare Stack. The excess hydrogen from the test is vented to this stack and then burned off, according to Nail. He said the fire appears to be heading towards a dirt road where it should go out on its own.

With T-10 minutes left in the countdown, NASA entered a scheduled hold. The clock was stopped so crews could catch up on any tasks that needed to be finished and work through any remaining issues, including a hydrogen leak where one of the lines connected to the mobile launcher refused to properly seal.

Teams created a temporary solution to the seal issue before proceeding with the test. All four tanks in the rocket were fully fueled and launch teams took the rocket through a countdown until T-29 seconds.

The wet dress rehearsal ended at 6:37 p.m.

This rocket will be used for the first mission of the Artemis program, which will fly an uncrewed mission to orbit the moon and return the Orion capsule home safely.

If everything goes well in the two-day test, NASA officials said they hope to launch Artemis I sometime in August.

NASA will stream live footage of the rocket on Launch Pad 39B throughout the test and is scheduled to have commentary during fueling operations on Monday, June 20 at 5 a.m.

News 19 will continue to update this article as the countdown continues.