A faulty sensor may have scrubbed the launch of NASA’s massive SLS rocket

After scrubbing a launch attempt of the Space Launch System rocket on Monday, NASA officials said they're working toward a second attempt to fly the Artemis I mission on Saturday, September 3.

NASA flight controllers halted first launch attempt after they were unable to verify that one of SLS rocket's 4 main engines—engine no. 3—had been properly cooled to temp of -420° F prior to ignition.

The engines must be chilled to very cold temperatures to handle the injection of very cold liquid hydrogen and oxygen propellants.

NASA's program manager, John Honeycutt, said his team believed engine had actually cooled down from ambient temp to the required level but it was not properly measured by faulty temperature sensor.

Accordingly, NASA's current plan involves some work at the launch pad today, including the inspection of an area where there was a small hydrogen leak during Monday's countdown.

Then, if officials are satisfied with those inspections and their flight rationale for dealing with the faulty temperature sensor, the agency will start counting down on Thursday. 

Fueling operations would begin on Saturday, ahead of 2:17 pm ET opening of 2hr launch window. To give the launch team more time, the process known as "conditioning" the engines would begin on Monday.