NASA reschedules moon launch for Saturday as it checks data from first attempt

A screenshot of the launch pad shows the underside of NASA’s Space Launch System rocket, including the four RS-25 main engines in its core stage. (NASA via YouTube)

A day after the first launch of NASA’s Space Launch System heavy-lift rocket had to be scrubbed due to an engine cooling problem, mission managers announced they will try again on Saturday.

In the meantime, engineers will work out the details of a go/no-go plan in case they encounter problems similar to those that forced Monday’s scrub.

Saturday’s two-hour launch opportunity opens at 2:17 p.m. ET (11:17 a.m. PT) at NASA’s Kennedy Space Center in Florida. If all systems go, liftoff will mark the start of NASA’s Artemis 1 mission, an uncrewed test flight that aims to set the stage for sending astronauts to the lunar surface in the mid-2020s.

Some aspects of the countdown will change for Saturday’s effort. For example, mission managers plan to conduct the engine cooling process at an earlier stage of the fueling process. This process involves “bleeding” some of the rocket’s liquid hydrogen fuel to cool the core’s four main engines to the desired temperature of 420 degrees Fahrenheit below zero.

When the cooling system was tested in March during a “Green Run” at NASA’s Stennis Space Center in Mississippi, the process was successful, early in the fueling process. But when the hydrogen leak occurred later in Monday’s countdown, a sensor indicated that one of the engines — the No. 3 engine — wasn’t cold enough.

Mission managers decided to repeat the process used at Stennis.

John Honeycutt, NASA’s SLS program manager, suggested that the problem might be with the sensor rather than the hydrogen venting system itself.

“We understand the physics of how hydrogen works,” he told reporters. “The way the sensor behaves doesn’t match her physical condition.”

Honeycutt said he and his team were working on a plan to verify that the engines are cooling properly, based on a wider range of data. He said the team preferred to avoid having to get into the rocket and work directly on the sensor, which might require rolling the rocket off the launch pad.

“What I intend to do, with the help of the team, is put us in a situation that gives us the data we need to know that we’ve properly cooled the engines and are flying, using the data we’ve got access to today,” he said. Honeycutt.

Engineers will also look into other concerns raised during Monday’s countdown — for example, a leaking vent valve in the intermediate tank area of ​​the SLS. Launch manager Charlie Blackwell-Thompson said the leak was apparently a consequence of troubleshooting the hydrogen venting system.

Forecasters say there is a 40% chance of acceptable weather for a launch on Saturday. If weather forces another postponement, Blackwell-Thompson said another attempt could be made Monday at the end of the Labor Day weekend.

For the Artemis 1 mission, the SLS rocket will send an uncrewed Orion spacecraft on a test flight that orbits the moon and heads back to Earth for a crash in the Pacific Ocean. NASA’s current plan calls for Artemis 2 to send an Orion crew on a lunar orbit in 2024 and Artemis 3 to carry astronauts to the lunar surface in the 2025-2026 timeframe.

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