CAPE CANAVERAL—Problems with a helium isolation check valve on the upper stage of the Space Launch System (SLS) rocket prompted NASA on April 9 to revise plans for a full tanking test and to delay a modified wet dress rehearsal (WDR) to April 14.
Instead of filling the SLS core and Interim Cryogenic Propulsion Stage (ICPS) with 755,000 gallons of cryogenic liquid oxygen and liquid hydrogen on April 11, the revised WDR three days later will focus on SLS core stage operations, with minimal propellant operations on the upper stage.
The change is due to a faulty helium purge valve in the ICPS’s Aerojet Rocketdyne RL10 engine, which uses helium to purge the system and to activate upper-stage valves during the WDR. The valve, which is about 3-in. long, prevents the helium from flowing back out of the rocket.
In a blog post on the agency’s website, NASA said it modified the WDR operations to “ensure safety of the flight hardware.”
The valve issue surfaced on April 7 after technicians replaced a regulator on the SLS mobile launcher following a WDR attempt on April 4.
After the modified WDR, the SLS and Orion capsule, currently located at Kennedy Space Center’s Launch Complex 39B, will be rolled back to the Vehicle Assembly Building as planned for prelaunch preparations during which the faulty valve will be inspected and replaced, if necessary.
The two-day countdown for the modified WDR is scheduled to begin on April 12. It will mark the third time the SLS launch team gathers for what is intended to be the final key test ahead of the rocket’s debut launch on the Artemis I mission to send an uncrewed Orion capsule on a flight test around the Moon.
WDR operations were scrubbed on April 3 during the initial stages of propellant loading and again on April 4 during the loading of liquid oxygen and ahead of the liquid hydrogen loading.
NASA said it plans to brief reporters on Monday about the modified WDR.
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