The countdown to launch of NASA’s Artemis moon rocket ticked smoothly into its final 24 hours Friday as engineers prepared the giant booster foron a delayed test flight to send an unpiloted Orion crew capsule on a .
If all goes well, engineers will begin pumping 750,000 gallons of cryogenic liquid oxygen and hydrogen fuel into the Space Launch System rocket at 6 a.m. EDT Saturday, setting up a launch attempt at 2:17 p.m., the opening of a two-hour window.
Forecasters predicted a 60% chance of good weather, improving to 80% “go” toward the end of the window. Storm clouds and rain swept over the spaceport Friday afternoon, but engineers were hopeful nature would be more cooperative Saturday.
A launch attemptwhen engineers were unable to confirm all four of the SLS rocket’s RS-25 first stage engines had been cooled enough by circulating liquid hydrogen to ensure a safe startup.
A detailed post-scrub data analysis confirmed the engines were, in fact, receiving the correct thermal conditioning, a requirement to prevent possible bearing damage when powerful turbopumps begin spinning up for takeoff.
“We’re on track for a 2:17 p.m. launch,” said Jeremy Parsons, deputy manager of Artemis ground systems at the Kennedy Space Center. “The team has really just done a fantastic job getting us out of launch attempt number one, repairing all the issues and getting us into a safe configuration to proceed into a tomorrow’s launch attempt.”
Along with the engine cooling issue, the launch team also dealt with a leaking seal in a hydrogen umbilical line that feeds propellant into the base of the SLS core stage and concluded that a vent line quick-disconnect fitting that also briefly leaked what acceptable for flight as is.
Likewise, a post-scrub analysis showed a crack in the core stage spray-on insulation, likely caused by thermal stress during fueling Monday, did not pose any significant risk to the rocket.
But engineers will be paying close attention to the engine cooling procedure, known as a “kickstart bleed,” that diverts liquid hydrogen to the engines and their turbopumps to condition them to the low temperatures of cryogenic propellants — minus 423 degrees Fahrenheit for hydrogen.
While the data review showed all four RS-25 engines were being sufficiently chilled Monday, the kickstart bleed was moved up in the countdown for Saturday’s launch try to allow more time for the hardware to cool down. Temperature data from a suspect sensor on engine 3 will be ignored and engineers will rely instead on readings from other sensors.
Assuming an on-time launch, the SLS rocket’s upper stage will boost the Orion capsule out of Earth orbit about an hour-a-half after takeoff, sending it on a trajectory to loop around the moon and into a distant orbit.
After extensive tests and checkout, the spacecraft will be directed back to Earth for a high-speed re-entry and splashdown in the Pacific Ocean on Oct. 11.
If the flight goes well, NASA will press ahead with plans to launch four astronauts on a looping flight around the moon in 2024. That mission will be followed by the first Artemis astronaut landing in the 2025-26 timeframe.