NASA said late Thursday it is still planning to launch Artemis I from Florida to loop around the Moon and back at 2:17 p.m. EDT Saturday within a two-hour window.
Officials confirmed a temperature sensor on engine 3 was indeed not functioning properly when Monday’s attempt was scrubbed.
“We know we had a bad sensor,” said John Honeycutt, Space Launch System rocket program manager, during a news conference. Since the scrub on Monday, crews have had time to look at data and compare with independent analysis and see there was a bad sensor and “good quality propellant through the system.”
It turns out the sensor on engine 3 was not necessary and crews can take observations from other sensors and data needed to confirm that the mission’s four RS-25 engines are chilled down sufficiently for a launch.
“It is conclusive that the sensor was not a witness for what we’re looking for,” said John Blevins, SLS chief engineer.
The funky sensor was working at one point, but its reading disagreed with other temperature sensors later in the launch sequence showing a reading up to 40 degrees warmer than the other three engine temperature sensors. It was designed to provide engineering data and is not a flight instrument, Blevins said.
Crews must cool down all the engines to minus-420 degrees F to allow a launch sequence to continue and will begin that process earlier Saturday by up to 45 minutes than they did on Monday. Crews supply liquid hydrogen from tanks to the engines in a bleeding process that that brings them to minus-420.
Crews detected other problems since the scrubbed launch on Monday, including a hydrogen leak on the tail service mast umbilical quick disconnect, sometimes called a purge can. That leak was repaired, while an event valve leak was determined not to be a problem.
They also found a crack in the foam on the core stage, the large orange colored rocket underneath the Orion spacecraft. If some of the foam broke free at launch it would hit other equipment, with only a “low likelihood” of causing damage, said Mike Sarafin, Artemis I mission manager.
Sarafin also said crews have been able to confirm they can chill all four of the core stage engines. With the minor problems detected, he gave an “incremental risk assessment” and said there is about a 1 in 125 risk of damage to the Orion spacecraft atop the SLS stack.
“We’re comfortable with our risk posture,” Sarafin said. “There’s no guarantee we’ll get off Saturday, but we’re going to try.”
There is a 70% chance weather will look good for the Saturday launch, officials said. The mission is expected to last 37 days with splashdown in the Pacific Ocean off the coast of San Diego on Oct. 11.
Streaming coverage of the launch is available starting at 12:15 p.m. EDT Saturday on NASA TV.
If Saturday’s launch is scrubbed, a launch window is available for Monday beginning at 5:12 p.m. EDT and lasting for 90 minutes. Tuesday is also a possibility. It normally takes 72 hours to prepare for a turnaroud, putting Tuesday in play.
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