LIVE: Artemis II Wet Dress Rehearsal Coverage

Live updates for the Artemis II wet dress rehearsal will be published on this page. Live views of the launch pad and test are available online. All times are Eastern.

3:32 p.m.

Now in a 1-hour, 10-minute hold during today’s wet dress rehearsal countdown, all stages of the SLS rocket remain in replenish mode.

NASA’s pad rescue and closeout crew teams are moving to their staging area before heading to Launch Complex 39B. These teams ensure safety and readiness during the critical fueling operations and play a vital role in protecting personnel and hardware throughout the countdown.

2:41 p.m.

NASA teams have transitioned all cryogenic tanks on the SLS (Space Launch System) rocket to replenish mode. This includes both liquid hydrogen and liquid oxygen tanks for the core stage and the interim cryogenic propulsion stage.

Cryogenic propellants naturally warm and evaporate over time, even in insulated tanks. Replenish counteracts this by continuously adding small amounts of liquid hydrogen and liquid oxygen to maintain proper levels and pressure. This ensures the rocket remains fully fueled and stable as the countdown progresses toward terminal count.

Following all stages replenish, teams will perform final system checks and verify valve and sensor performance before transitioning to the terminal countdown sequence, which includes simulated launch operations and final readiness verifications.

With all stages in replenish, the Artemis II wet dress rehearsal is now in its final fueling configuration, bringing this test wet dress rehearsal operations closer to terminal count.

1:50 p.m.
NASA teams have completed the fast fill of the upper stage liquid hydrogen tank on the SLS rocket. Liquid oxygen fast fill continues on the upper stage. On the rocket’s core stage, both the liquid oxygen and liquid hydrogen tanks are in replenish mode. Replenish keeps the tank at flight-ready levels by replacing any liquid hydrogen lost to boil-off.

1:23 p.m.

NASA teams transitioned to fast fill of the interim cryogenic propulsion stage liquid oxygen tank. After completing chilldown, this phase rapidly loads super-cold liquid oxygen, chilled to minus 297 degrees Fahrenheit, into the upper stage tank.

Fast fill is a critical step that ensures the stage is fully fueled and ready to pair with liquid hydrogen for the RL10 engine burn. This engine will provide the in-space boost needed to send Orion into high Earth orbit before its lunar flyby. During this process, teams closely monitor tank levels, pressure, and valve performance to maintain system integrity.

1:07 p.m.

NASA teams have transitioned the SLS rocket’s core stage liquid hydrogen tank to replenish mode. This marks an important milestone in the test, as teams reached this step without exceeding the ground safety limit of the hydrogen leak concentration, as was observed during the first Artemis II wet dress rehearsal.

After completing fast fill and topping, replenish keeps the tank at flight-ready levels by replacing any LH2 lost to boil-off. Replenish is essential for maintaining stable pressure and temperature in the tank as the countdown continues. Cryogenic propellants like liquid hydrogen naturally warm and evaporate over time, even in insulated tanks. Replenishing the tanks counteracts this by continuously adding small amounts of liquid propellant to maintain the correct volume and pressure. This phase ensures the core stage remains fully fueled and ready to power its four RS-25 engines at liftoff, providing the thrust needed to send Orion and its crew on their journey around the Moon.

12:43 p.m.

NASA teams have begun chilldown for the liquid oxygen lines on the interim cryogenic propulsion stage. This critical step cools the hardware ahead of loading super-cold liquid oxygen, chilled to minus 297 degrees Fahrenheit, into the SLS (Space Launch System) rocket’s upper stage tank.

Once complete, teams will transition to slow fill and then fast fill of liquid oxygen, pairing with liquid hydrogen to power the RL10 engine that will send Orion into high Earth orbit before its lunar flyby.

12:30 p.m.

As teams continue to fuel the SLS rocket’s core stage with liquid oxygen and liquid hydrogen, teams began loading liquid hydrogen into the rocket’s interim cryogenic propulsion stage or upper stage.
 
The core stage liquid hydrogen and liquid oxygen tanks, meanwhile, are currently in fast fill.

12:12 p.m.

Teams began chilling down the liquid hydrogen lines for the interim cryogenic propulsion stage of NASA’s SLS rocket. This critical step cools the propellant lines ahead of loading super-cold liquid hydrogen, chilled to minus 423 degrees Fahrenheit, into the SLS’s upper stage tank.

The chilldown process ensures the hardware is properly conditioned for cryogenic temperatures, reducing thermal shock and safeguarding system integrity. Once complete, teams will transition to fast fill of liquid hydrogen, followed by liquid oxygen operations later in the countdown.

The interim cryogenic propulsion stage, powered by an RL10 engine, will provide the in-space boost needed to send the Orion spacecraft into high Earth orbit before its lunar flyby.

11:45 a.m.

Normal communications have been restored, and NASA teams have made the decision to transition to fast fill of the SLS rocket’s core stage with super-cold liquid hydrogen. Core stage liquid oxygen remains in fast fill.

Fast fill rapidly loads hundreds of thousands of gallons of liquid hydrogen and liquid oxygen into their core stage tanks. During this process, teams also monitor for leaks and conduct engine bleed procedures to thermally condition the RS-25 engines for launch. Once fast fill is complete, operations will move to topping and replenish phases.

Up next, teams will start chilling down the liquid hydrogen tank on the interim cryogenic propulsion stage – or the upper stage – of SLS.

11:11 a.m.

Teams in the firing room at NASA’s Kennedy Space Center are experiencing an issue with ground communications and have moved to backup communication methods to maintain safe audio command and control. The launch director has decided to maintain the current vehicle state, continuing the liquid oxygen fast fill, but delaying moving into liquid hydrogen fast fill, while engineers troubleshoot the issue.

10:43 a. m.

Teams have transitioned from slow fill to fast fill for liquid oxygen on the core stage of the SLS rocket. Liquid hydrogen remains in slow fill for the core stage.

10:30 a.m.

Following successful chilldown of the liquid hydrogen and liquid oxygen lines, teams have started slowly filling the SLS rocket’s core stage with super-cold liquid hydrogen, chilled to minus 423 degrees Fahrenheit, then with liquid oxygen chilled to minus 297 degrees. This marks the official start of propellant loading for the Artemis II wet dress rehearsal.

Slow fill is a deliberate process that allows the tanks and associated hardware to thermally condition before transitioning to fast fill. This step minimizes thermal stress and ensures the integrity of the system as hundreds of thousands of gallons of cryogenic propellant flow into the core stage.

9:40 a.m.
Teams have started chilling down the liquid hydrogen and liquid oxygen lines for the SLS rocket’s core stage. This critical step cools the propellant lines ahead of loading super-cold liquid hydrogen and liquid oxygen into the core stage tank, which will eventually hold more than 700,000 gallons of liquid hydrogen and liquid oxygen.

The chilldown process ensures the hardware is conditioned for the extreme temperatures of cryogenic propellants, reducing thermal shock and safeguarding system integrity. Once complete, teams will transition to slow fill of liquid hydrogen and liquid oxygen, followed by fast fill later in the countdown.

9:35 a.m.
At approximately 9:27 a.m., the Artemis launch director gave the “go” to begin loading cryogenic liquid propellant into the SLS rocket.

NASA teams have completed final preparations and closeouts of the umbilicals connecting the mobile launcher to the SLS rocket and Orion spacecraft. The umbilicals provide power, communications, and fuel to different parts of the rocket and spacecraft, while additional accessories provide stabilization. During launch, each umbilical releases from its connection point, allowing the rocket and spacecraft to lift off safely.

Teams will begin slowly filling cryogenic propellant into the rocket beginning at L-9 hours 45 minutes in the countdown. Liquid hydrogen and liquid oxygen will flow into the rocket’s core stage and interim cryogenic propulsion stage tanks, topped off and replenished as some cryogenic propellant boils off. The team will also conduct leak checks to ensure loading proceeds as expected.

7 a.m.

The Artemis II wet dress rehearsal countdown continues as teams at NASA’s Kennedy Space Center in Florida began configuring the SLS (Space Launch System) rocket with gaseous nitrogen, an important step to mitigate fire hazards, protect spacecraft systems, and ensure mission safety ahead of fueling operations.

Technicians are replacing the ambient air with gaseous nitrogen, which is an inert gas that does not support combustion. By replacing air – which contains highly-combustible oxygen – with nitrogen, engineers can remove the oxidizer needed to sustain fire and dramatically reduce flammability risks in a launch environment filled with high-energy systems and propellants.

The step also includes an inerting purge that removes oxygen and prevents contaminants like moisture or particulates from entering sensitive systems on the rocket. This keeps propulsion and life-support hardware clean and stable and creates a non-reactive environment that protects hardware and minimizes chemical reactions during countdown and ascent.

Overnight, teams prepared fueling lines on the mobile launcher and powered up the SLS upper stage and boosters. In the next few hours, teams will activate the ground launch sequencer used for command and control during the countdown, and verify several systems are ready for fueling operations. NASA’s Artemis launch director, Charlie Blackwell-Thompson, will poll whether to give a “go” for tanking operations to begin.

While there won’t be a launch today, teams are targeting 8:30 p.m. EST as the opening of a simulated launch window. Following a first run through the countdown to 33 seconds before the simulated launch time, teams will recycle the clock to T-10 minutes and will resume until stopping at approximately T-30 seconds.