NASA scours first attempt at SLS countdown probe

DENVER — NASA canceled the first attempt to refuel its Space Launch System rocket and conduct an exercise countdown on April 3, citing a problem with the rocket’s mobile launcher.

NASA announced just before 12 p.m. Eastern that it would be scrubbing its wet dress rehearsal (WDR) for the SLS before crews began loading liquid hydrogen and liquid oxygen propellants into the vehicle. The agency said fans in the mobile launch platform, needed to create positive pressure in confined areas of the platform to avoid a build-up of dangerous gases, were not working.

The agency said in a brief blog post that WDR could be pushed back to April 4 as reviews are scheduled later in the day. This schedule is dependent on the status of key systems, as well as the availability of Kennedy Space Center inventory and merchandise needed for the test.

Even before the fan problem, NASA was behind schedule with the test, in which the core and upper stages of the SLS are filled with propellant and run a countdown that stops at about T-10 seconds. Severe thunderstorms on April 2 delayed WDR activities at Launch Complex 39B, including multiple lightning strikes on protection towers on the pad.

NASA started WDR activities on April 3 with a delay of about an hour. according to tweets by Jeremy Parsons, associate director of the Exploration Ground Systems program at KSC. Tweets and blog posts were the primary means by which NASA provided updates about the test after claiming that export control restrictions prevented them from providing audio from the launch control center or other comments.

The countdown was halted unplanned just after 8 a.m. April 3 to synchronize pad operations with the Launch Control Center, Parsons tweeted. He later said that crews confirmed positive pressure on the mobile launcher and more than two hours after the lockdown began, NASA announced the countdown would resume, only to report a problem with fans a short time later.

The WDR is the last major test before the first launch of the SLS on the unmanned Artemis-1 mission. NASA officials said at a March 29 briefing that if the test goes well, the agency could be ready to set a launch date for the mission in about a week, likely as early as June.

While the WDR is intended to simulate a countdown, it offers greater flexibility to troubleshoot issues than crews do during an actual countdown. “We are fortunate to have this flexibility during today’s testing, but would do it differently on launch day,” Parsons tweeted just before testing ended for the day.

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