NASA counts down to within 29 seconds of launching the large SLS rocket - Ars Technica

NASA tried three times during April to complete a critical fueling test of its large Space Launch System rocket.

And so NASA made the difficult decision to roll the large rocket back into the Vehicle Assembly Building for repairs, adding a couple of months of delays to a program already years behind schedule.

Over the course of more than 14 hours on Monday, NASA largely succeeded in completing this fueling test, loading hundreds of thousands of gallons of liquid oxygen and hydrogen into the first and second stages of the SLS rocket.

She and other NASA officials joined a conference call with reporters on Tuesday to discuss the results of the fourth "wet-dress rehearsal" test, which is intended to work out the kinks of counting down the rocket to liftoff before launch day.

NASA got to within T-29 seconds of liftoff during the test, near its intended target of T-9.3 seconds, before ending the test just prior to igniting the rocket's four main engines.

During the teleconference, NASA officials declined to answer specific questions about whether a fifth test was going to be needed—to bring the count down to T-9.3 seconds—or when the rocket may be ready for its debut launch.

From their comments, however, it sounded like the officials may be leaning against a fifth test.

A handful of technical problems occurred during Monday's test, the most significant of which was a hydrogen leak in a quick disconnect at the bottom of the mobile launch tower that supports the SLS rocket during fueling.

This fueling test is the final major obstacle between the SLS rocket and a launch attempt later this year.