The two-day set of wet dress rehearsals for the Artemis 1 moon mission ended today.
The tests included fueling up Artemis 1's huge Space Launch System (SLS) rocket and performing a simulation that would take the vehicle and NASA's Orion capsule through most of the progressions they would endure on launch day. At 7:37 p.m., the simulation ended.
Things didn't go perfectly. The Artemis 1 team noticed a hydrogen leak during fueling and decided to "mask" the data associated with the issue to keep the count going. NASA officials said that such data would raise red flags. The clock was stopped at T 29 seconds before liftoff, instead of the planned 9 seconds.
Photos explain NASA's Artemis 1 moon mission.
The Artemis 1 team was still enthusiastic despite the hiccup.
Charlie Blackwell-Thompson, Artemis launch director with the Exploration Ground Systems Program at NASA's Kennedy Space Center in Florida, said that it was a great day for the team. They worked through the loading and terminal count.
The Artemis 1 stack and mobile launch platform (MLP) will need to be prepared for transport from Launch Pad 39B to the Vehicle Assembly Building (VAB) in the next few days.
The final major milestone was the wet dress. On the actual mission, the SLS rocket will launch an uncrewed Orion on a trip to the moon and back. One of the main goals of the Artemis program is to establish a permanent human presence on the moon.
Artemis 1 will be the first flight for the SLS, the realization of over a decade of research, development and manufacturing to advance NASA's human exploration plans beyond low Earth orbits. NASA plans to send astronauts to the moon in four years or so if Artemis 1 goes well.
Agency officials have expressed optimism for an Artemis 1 launch at the end of August, but only if there is a smooth wet dress rehearsal. It seems like the launch window is close to reality.
The procedures on the rocket and MLP systems at Pad 39B began on Saturday with a call to stations for ground teams at 5:00pm. The clock began to tick towards a launch time. Today's time was pushed back to 4:30 p.m. The sun rises at 2038GMT.
The first major protocol for the SLS wet dress rehearsal was to fill the water tanks for the sound suppression infrastructure. During an actual liftoff, the system dumps nearly half a million gallons of water onto the launch pad and flame trenches.
The next stage was vehicle stage startup. On Saturday night operators began to power on the systems. Next, the SLS core stage was powered up, followed by a series of checks to confirm connections between the ground infrastructure and boards in mission control.
With the rocket's first-stage systems active, final preparations for the vehicle's four engines finished on Sunday morning.
NASA officials received a weather forecast from the U.S. Space Force Space Launch Delta 45. Ground crews were performing a walk down of the rocket on Sunday to make sure it was ready for the upcoming propellant loading operations.
The teams at NASA switched on power to the upper stage of the SLS just before 2 a.m. Today's date is 0600GMT. It was by 3:20 a.m. All non- essential personnel were allowed to leave the launch pad.
The vehicle and the MLP first rolled from the VAB to the pad for a wet dress rehearsal on April 1. Three separate attempts to complete the wet dress were scrubbed due to issues with SLS fueling operations.
NASA's new moon rocket rolled to the launch pad.
After rolling the Artemis 1 stack back to the VAB, the team spent about a month making repairs and upgrades to pave the way for a wet dress try. During this morning's fueling procedures, a lot of attention was given to the systems that failed during the first wet dress.
The build-in hold was expected to last 1.5 hours. The hold was extended when operators encountered an issue with a supply valve in Pad 39B's redundant gaseous nitrogen system. The valve on NASA's live broadcast for the wet dress malfunctioned, but not with the actual valve itself, but with the controller.
They replaced the valve even though they couldn't determine the cause of the problem. Initially, the pad's redundant supply was the gaseous nitrogen line. The unaffected line was the new backup after the valve was replaced. According to the team that is out there, the manual retest of that valve is working well.
Before and after tanking, gaseous nitrogen is used to purge the fuel tanks, umbilicals and other parts of SLS. After the first wet dress attempt, Artemis 1's time back in the VAB allowed some planned improvements at the pad to move forward. Enhancement of supply capabilities for the pad's gaseous nitrogen almost doubled its capacity.
"We went through and did a test to verify that the gaseous nitrogen upgrades supported all of our needs prior to the roll out," she said during the June 15 press call. "We went through all of the flow profiles, verified all of the pressures and also verified all the timelines with some amount of margin to make sure that our flow rates and our needs could be supported during our wet dress rehearsal."
The problem with the valve has been solved, and we're at a good configuration to pick up with cryo-loading, according to the assistant launch director. The morning's tanking procedures were given the go-ahead shortly before 9 a.m. according to Nail. The count began again at 9:28 a.m. An adjusted T0-0 of 4:58 p.m. was reached. The sun rises at 2038GMT.
Liquid oxygen and liquid hydrogen are used in the rocket's fuel. Super-cooling the propellants and chilling associated hardware are required for the process of loading. Once the umbilical connections and fuel tanks are acclimatized to the extreme cold temperatures, technicians monitor loading rates carefully, starting with a slow-fill flow. Once nearly full, transfers decrease to a "top-off" speed before reverting to a slower flow.
There is a history of rockets.
LOX slow-fill loading began at 10:00 a.m. Fifteen minutes later, fast-fill flow rates were reached. According to Nail, the core stage LOX tank can't fill past 49% until the LH2 tank's depletion sensors are complete.
For some of the morning's lost time, mission operators were able to speed up LH2 chill-down procedures. The ICPS experienced pressure spikes during the first Artemis 1 wet dress. NASA technicians added these components to the chill down procedures after the test.
The slow-fill began at 10:42 a.m. The time is 1:44 pm 10:30 a.m. After the tank was submerged, transfer rates were switched to fast-flow, and both first-stage fuel tanks were on track to reach the target time. The sun rises at 2038GMT.
The first tank to be topped off was the core stage LH2 tank, which came in at 537,000 gallons. The boil-off replenishment flow began at 12:42pm. Operators can start cooling the ICPS about 20 minutes later.
The vehicle's liquid oxygen is much denser than its liquid hydrogen catalytic counterpart, and it takes much longer to load than the first stage LOX tank.
After the core stage LOX tank was topped off, it began to replenish. The sun rises and sets at 1730GMT. Operators started fast-fill loading for the upper stage tank.
The hydrogen leak in the core stage tail service mast umbilical bleed line was reported by Nail on the NASA broadcast.
When there was a leak at the quickDisconnect for the core stage hydrogen, the hydrogen bleed was stopped.
There are every missions to the moon.
The team worked on the issue. The technicians tried to reseat the seal after warming up and cooling down. The team decided to go ahead with the dress despite the leak.
The end of the wet dress was pushed back three hours because of the leak. It changed procedures for terminal count, the final 10 minutes of the simulation, which were used to mark the end of the test. The team had to "mask" data associated with the leak so the launch computer wouldn't see it and cause a hold. Everything went on as planned.
"During the terminal count, the teams performed several critical operations that must be accomplished for launch, including switch control from the ground launch sequence to the automated launch sequence, an important step that the team wanted to accomplish," NASA officials wrote in an update tonight.
The Artemis 1 team is going to figure out how those operations went.
"Like any test we run, we will take the data," she said. We're going to look at what we have. We will look at the things that we did not get. We'll come up with a plan for the future.
There are a number of possible launch windows for Artemis 1. NASA officials have stressed the improbability of a July launch, even though earlier versions of that schedule included a window. July is no longer an option due to an updated schedule on NASA's website.
The earliest SLS can be launched is August 23, but that is a short mission. The moon's position influences the alignment of various mission parameters that are categorized by NASA. There are 38 to 42 days and 26 to 28 days in the windows.
If the VAB goes well, NASA could target the earliest long mission opportunity, which would kick off with a launch on August 29th. There is a five day mission window between Sept 2 and Sept 6. NASA isn't likely to commit to a launch date before the VAB begins its SLS inspection later this month.
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