The launch is scheduled for 2:17 p.m., with a two-hour launch window. Weather for a Saturday launch also could be tricky, with only a 40 percent chance of favorable conditions. But since there is a two-hour window and showers are expected to be intermittent along the Florida coast, weather officials think there could be enough time opportunity for the launch to take place.
The launch attempt Monday was scrubbed after NASA engineers were unable to lower the temperature of one of the engines to what’s required for launch. The RS-25 engines burn liquid hydrogen fuel, which is kept at minus-423 degrees Fahrenheit. To get the engines ready for such an extremely cold fluid, NASA bleeds a little bit of fuel through so that the engines won’t be shocked as the fuel starts flooding in.
Last year, NASA was able to fuel the rocket and then fire the four engines for their full eight-minute duration during a test at NASA’s Stennis Flight Center in Mississippi. But since then, the agency has struggled with getting the rocket fueled and prepping the engines for launch.
Honeycutt said Tuesday NASA engineers were uncertain whether the temperature reading was the result of a failure to cool the engine or a bad sensor not returning accurate information.
Honeycutt said that on Monday liquid hydrogen was flowing through the engines and did cool three of the engines as expected. The fourth, though, was “totally out of bed” with the others.
Honeycutt said that replacing the sensor on the pad “would be tricky.” Instead, NASA should be able to tell if the engines are at the right temperature by looking at an array of data sources instead of relying on a single sensor. Also, NASA officials said they would make a procedural change and start chilling the engines 30 to 45 minutes earlier, as they did during the successful test last year in Mississippi, to give them more time to work through any problems.
“What I’m saying is, the only thing that I know to change to replicate the success we had at Stennis is moving to test earlier in the timeline,” Honeycutt said.
During a previous fueling test, NASA never got to the point where it flowed the liquid hydrogen in because it had a leak, forcing the agency to end the test before getting to that step.
Mike Sarafin, the Artemis I mission manager, had told reporters Monday that the teams knew that could pose a problem during the launch attempt but decided to proceed anyway.
“We knew that that was a risk added into this launch campaign, and it would be the first time demonstrating that,” he said.
Jim Free, NASA’s associate administrator for exploration systems development, Monday defended the decision to proceed with the launch attempt. “There were a lot of questions of should we have rolled back and tried to do another test. We still feel like going for today was the right thing to do,” he said.
The Artemis program is an ambitious attempt by the agency to return astronauts to the moon for the first time since the Apollo era. (In Greek mythology, Artemis is the twin sister of Apollo.) The first of the Artemis missions, Artemis I, is designed to send the Orion spacecraft in orbit around the moon without any astronauts on board. The next flight, Artemis II, would send as many as four astronauts in the capsule, again to orbit but not land on the moon. If all goes to plan, a landing would come sometime in 2025 or 2026.
