Spaceflight Now by Stephen Clark February 24, 2021
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.
The space agency said Monday that engineers identified the problem over the weekend. One of eight “prevalves†in the core stage propulsion system was not working properly, NASA said.
The prevalve supplies liquid oxygen to one of the rocket’s four RS-25 main engines. The engines are left over from the space shuttle program, and consume liquid hydrogen fuel in combination with super-cold liquid oxygen. All eight prevalves functioned properly during the first SLS core stage hotfire test Jan. 16, officials said.
“NASA and the core stage lead contractor Boeing will identify a path forward in the days ahead and reschedule the hot fire test that was originally scheduled for Feb. 25,†NASA said Monday.
The Jan. 16 hotfire test was supposed to last more than eight minutes, but the four RS-25 engines shut down a little more than a minute after ignition. 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.
More:
https://spaceflightnow.com/2021/02/24/stuck-propulsion-valve-delays-second-sls-test-firing/
