Second SLS Hot Fire Postponed

NASA is postponing the second Hot Fire test of the Space Launch System (SLS) core stage.  Last week NASA confirmed the test was scheduled for February 25, but today said an issue developed over the weekend with a valve and they need time to investigate.  A new date was not announced.

The Hot Fire test is the last in a series of “Green Run” tests of the Boeing-built SLS core stage outfitted with its four Aerojet Rocketdyne RS-25 engines that are left over from the space shuttle program.

The first test last month terminated after 67 seconds instead of 485 seconds because of the conservative test parameters that were set to ensure no damage was done during the test. This is the actual core stage and engines that will be used for the first launch, Artemis-I, not test hardware.

In a blog post this afternoon, NASA said one of eight valves, called a prevalve, that supplies oxygen to the engines was not working properly.  The agency and Boeing will “identify a path forward in the days ahead and reschedule” the test.

The first SLS launch has been delayed many times.  In 2014, NASA committed to the first launch in November 2018. That slipped to December 2019-June 2020, then to mid-late 2021.  More recently, NASA was saying November 2021, but that was premised on completing the Green Run tests and shipping the core stage to Kennedy Space Center (KSC) in mid-January 2021.

That date was not met, but NASA’s Tom Whitmeyer said last week there is still a “reasonable chance” the launch could take place this year.  That assessment seemed very optimistic last week and even more so with this latest delay.

Many months are needed once the core stage is at KSC to integrate it with the rest of the SLS rocket and conduct further tests before launch. Artemis-I is an uncrewed test flight of SLS with an Orion spacecraft as part of NASA’s effort to return humans to the Moon. Artemis-II will be the first to carry a crew.  NASA has been hoping to conduct that launch in 2023 and then send a crew to the Moon on Artemis-III in 2024.