At approximately 6 a.m. ET Tuesday, NASA’s Space Launch System (SLS) rocket and Orion spacecraft for the Artemis I mission arrived at the Vehicle Assembly Building (VAB) at Kennedy Space Center after a 10-hour journey from launch pad 39B that began at 7:54 p.m. ET Monday, April 25.
Over the next several days, the team will extend the work platforms to allow access to SLS and Orion. In the coming weeks, teams will work on replacing a faulty upper stage check valve and a small leak within the tail service mast umbilical ground plate housing, and perform additional checkouts before returning to the launch pad for the next wet dress rehearsal attempt.
At approximately 5:30 p.m. ET today, NASA’s Artemis I Moon rocket atop the crawler-transporter is scheduled to leave launch pad 39B and begin its 4-mile trek to the Vehicle Assembly Building (VAB) at NASA’s Kennedy Space Center in Florida.
Once inside the VAB, teams will work on replacing a faulty upper stage check valve and a small leak within the tail service mast umbilical ground plate housing on the mobile launcher while the supplier for the gaseous nitrogen makes upgrades to their pipeline configuration to support Artemis I testing and launch. Following completion, teams will return to the launch pad to complete the next wet dress rehearsal attempt.
Teams at NASA’s Kennedy Space Center in Florida are preparing the Space Launch System (SLS) rocket and Orion spacecraft for their return to the Vehicle Assembly Building (VAB) early next week. As work continues at the launch pad throughout the weekend, we will also continue working closely with our commercial crew partners to confirm a date and time. The transition is underway to move from the testing configuration to the roll back formation needed to return to the VAB. This process includes offloading hydrazine from the twin solid rocket boosters and disconnecting the rocket and spacecraft from the ground systems infrastructure at the launch pad. The core stage propellant was drained shortly after completing the last test attempt. The rocket and spacecraft remain in a safe configuration and will soon be placed atop the crawler-transporter for the 4-mile trek to the VAB.
Inside the VAB, engineers will repair a faulty helium check valve and a hydrogen leak on the mobile launcher while the supplier for the gaseous nitrogen makes upgrades to their pipeline configuration to support Artemis I testing and launch.
While most objectives associated with the wet dress rehearsal were met during recent testing, teams plan to return to the launch pad when repairs and checkouts in the VAB are complete for the next full wet dress test attempt. Following completion of the test, SLS and Orion will return to the VAB for the remaining checkouts before rolling back out to the pad for launch.
Teams concluded today’s wet dress rehearsal test at approximately 5:10 p.m. EDT after observing a liquid hydrogen (LH2) leak on the tail service mast umbilical, which is located at the base of the mobile launcher and connects to the rocket’s core stage. The leak was discovered during liquid hydrogen loading operations and prevented the team from completing the test.
Before ending the test, teams also met test objectives for the interim cryogenic propulsion stage by chilling down the lines used to load propellant into the upper stage. They did not flow any propellant to the stage because of an issue with a helium check valve identified several days ago.
When teams paused propellant loading, the rocket’s core stage liquid oxygen tank was about 49% filled and the liquid hydrogen tank had been loaded to about 5% capacity prior to the hydrogen leak.
Teams are now working to drain propellant from the rocket. They will inspect the umbilical connection, review data, and establish a go-forward plan to address the hydrogen leak.
NASA plans to host a media teleconference April 15 to provide updates on troubleshooting and next steps for the wet dress rehearsal test.
While loading liquid hydrogen (LH2) on the rocket’s core stage earlier this afternoon, engineers detected a leak on the tail service mast , which is located at the base of the mobile launcher and connects to the core stage.
Though engineers stopped loading LH2 and liquid oxygen (LOX) on the core stage, the launch director gave approval for teams to chill down the ICPS LH2 lines to collect additional data and have completed that activity. Engineers will not load LH2 or LOX into the ICPS tanks, due to an issue with a helium check valve experienced several days ago. When teams paused propellant loading earlier today, there was about 49% of LOX on the core stage and about 5% of LH2 was loaded into the core stage tank prior to the hydrogen leak.
The terminal countdown will also not occur today due to the modified configurations and delays with propellant loading. Teams are reassessing the next steps and will determine a go-forward plan following today’s test.
Following the completion of slow fill for liquid hydrogen (LH2), teams encountered an issue when they started fast fill operations for LH2. After fast fill on LH2 began, a surge in pressure automatically stopped the flow of liquid hydrogen. Teams are working to troubleshoot this issue and the rocket is in a safe configuration. In the meantime, liquid oxygen flow was paused on the core stage to ensure the tanking operations for LOX and LH2 remain synchronized.
After fast fill resumes for liquid hydrogen to the core stage, teams will load minimal cryogenic propellants on the interim cryogenic propulsion stage. Because of an issue with a helium check valve found several days ago, teams will chill down the lines used to load propellant into the upper stage but not flow any actual propellant to the stage.
The clock is continuing to count down for now, and the team will work to re-synchronize the operations timeline and clock during a planned T-10-minute hold at which point the launch team will establish a new T-0.
After troubleshooting an issue with the temperature of liquid oxygen during early stages of propellant loading into the rocket’s core stage, launch controllers have resumed operations. Teams performed chill down operations again before liquid oxygen began flowing into the tank and adjusted pump speeds as necessary during flow to help ensure temperatures remain below limits. They also opened valves to bleed off any warm liquid oxygen.
Earlier in the count, teams began slow fill operations for liquid oxygen, but were automatically halted when temperature readings on the propellant showed it was warmer than intended. The liquid oxygen is an extremely cold, or cryogenic, propellant that is maintained at minus 297 degrees Fahrenheit and must be kept at super cold temperatures. As the super cold liquid oxygen fills the core stage main propulsion system, some venting may be visible.
Teams have now progressed to fast fill for core stage liquid oxygen and slow fill for liquid hydrogen.
Liquid oxygen loading into the core stage was automatically halted near the beginning of slow fill operations when temperature readings on the propellant showed it was warmer than intended. The rocket is in a safe configuration while teams troubleshoot and determine a path forward.
Engineers believe they understand the issue and are working a solution that will allow operations to continue. Teams saw a similar issue during the wet dress rehearsal attempt on April 4, but at a slightly different point in propellant loading operations.
The slow fill process involves slowly filling the core stage with propellant to thermally condition the tank until temperature and pressure are stable before beginning fast fill operations, which is when you fill the tank at a quicker pump speed.
The launch control team has begun chill down operations and resumed the countdown clock ahead of flowing super cold liquid oxygen (LOX) into the core stage tank. The new T-0 time for today’s test is 3:57 p.m. EDT for the first of the two terminal count runs for the wet dress rehearsal.
The process for the chill down, or cooling, uses the propellant lines to load the Space Launch System rocket’s core stage liquid oxygen in preparation for tanking. The liquid oxygen tank holds 196,000 gallons of liquid oxygen, cooled to minus 297 degrees Fahrenheit. Venting from the super-cold propellant may be visible during this time.
Liquid oxygen will soon flow into the rocket. Teams will fill the tank slowly at first and then will begin filling it more quickly. As the super cold liquid oxygen fills the core stage tank, some venting may be visible.
The next blog update will be provided when core stage liquid hydrogen loading begins.
At approximately 8:05 a.m. EDT, the launch director gave the “go” to start tanking operations. The countdown will resume at 8:47 a.m. EDT at T-6 hours, 40 minutes.
Tanking begins with chilling down the liquid oxygen lines for the core stage. In sequential fashion, liquid oxygen (LOX) and liquid hydrogen (LH2) will flow into the into the rocket’s core stage tank and be topped off and replenished as some of cryogenic propellant boils off. The team also will conduct leak checks to ensure propellant loading is proceeding as expected. Only minimal cryogenic operations are being conducted on the interim cryogenic propulsion stage because of an issue with a helium check valve found several days ago which cannot be fixed at the launch pad. Teams will chill down the lines used to load propellant into the upper stage but not flow any actual propellant to the stage.
NASA is streaming live video of the rocket and spacecraft at the launch pad on the Kennedy Newsroom YouTube channel. Venting may be visible during tanking operations. NASA is also sharing live updates on the Exploration Ground Systems Twitter account.