Stuck propulsion valve delays second SLS test-firing – Spaceflight Now - Spaceflight Now

A troublesome liquid oxygen valve on the Space Launch System’s first flight-rated core stage will keep NASA from performing a second test-firing of the rocket’s four main engines this week.

NASA hoped to conduct the second hotfire test on SLS core stage Thursday, but the agency announced Monday that the engine firing will be postponed to evaluate a misbehaving valve in the rocket’s propulsion system.

One of eight “prevalves” in the core stage propulsion system was not working properly, NASA said.

All eight prevalves functioned properly during the first SLS core stage hotfire test Jan.

Engineers traced the cause of the premature shutdown to a hydraulic system parameter that tripped an overly-conservative setting for the test, the last phase of a “Green Run” test and checkout campaign for the SLS core stage at NASA’s Stennis Space Center in Mississippi.

The core stage hydraulics drive actuators that pivot, or gimbal, the four RS-25 engines to steer the rocket after liftoff.

Managers want to get at least four minutes of run time on the RS-25 engines on the second hotfire test to gather enough data to build confidence in the rocket’s performance before shipping the stage to the Kennedy Space Center in Florida for launch preparations.

Kathy Lueders, associate administrator for NASA’s human spaceflight division, said Wednesday that engineers were having trouble getting the liquid oxygen prevalve to fully open during checkouts before the second Green Run hotfire test.

The Green Run hotfire test has been delayed more than six months since the SLS core stage arrived at Stennis in January 2020.

The first SLS test launch will carry an unpiloted Orion crew capsule into space on NASA’s Artemis 1 mission.