NASA - SLS Block 1/Orion - Artemis II - Wet Dress Rehearsa II - LC-39B - KSC - February 19, 2025

NASA continues to press ahead through the Artemis II wet dress rehearsal countdown – a fueling test of the SLS (Space Launch System) rocket. Early this morning, at approximately 3 a.m. EST, teams powered up the rocket’s core stage, which will be loaded with more than 700,000 gallons of liquid oxygen and liquid hydrogen during the tanking phase of the countdown. This will occur over a series of different propellant loading milestones to fill, top off, and replenish the tanks. The interim cryogenic propulsion stage also was powered up overnight. Around 11 a.m., or L-33 hours, 30 minutes in the countdown, operators began charging Orion’s flight batteries. Core stage battery charging is scheduled to begin this afternoon. Later today, engineers will conduct final preparations of the umbilical arms and perform a walkdown at the launch pad. 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.