Trevor Mahlmann
After completing a review of the data collected during a hot fire test of its Space Launch System rocket in mid-December, NASA has decided it should retest the large vehicle. Full firing of the engine is planned as early as the fourth week of February.
During the December 16 test, when NASA planned to run the rocket’s four main engines for eight minutes, the test was aborted after just 67.2 seconds. NASA said the engine firing was stopped due to a strict limit on the hydraulic pressure in the thrust vector control mechanism used to gimbal or steer the engines.
In the days following the mid-December test firing, NASA and Boeing officials were cautious about whether to test the missile a second time. While it would be helpful to gather additional data, they said, there were concerns about the core stage, with its four main space shuttle engines and large tanks for liquid oxygen and hydrogen, due to the stress of repeated testing. (The SLS missile is replaceable, so it’s only meant to be launched once.)
According to the agency, the original hot fire test completed 15 of the 23 targets. Four other targets got the most data searched, three had partial data and one no data. The latter was a test of how the tank pressure would react with liquid oxygen if most of the liquid oxygen had been used up and the tank was emptied. Because the test goals were not met, engineers within the agency prompted NASA and Boeing leadership to conduct a second test to reduce the risk of failure during launch.
On Friday, NASA made it official. After evaluating the data from the first hot fire and the previous seven Green Run tests, NASA and core stage prime contractor Boeing decided that a second, longer hot fire test should be conducted that would pose minimal risk to the Artemis I- core phase and at the same time valuable data to help certify the core phase of flight, “the space agency said in a blog post.
NASA said that running the engines for four minutes during this second test should provide enough data to give confidence in core performance, but the main engines would fire for up to eight minutes if all goes well.
After the second hot fire test – assuming NASA and Boeing get the necessary data – it will take about a month to refurbish the nuclear stage and its engines. The vehicle will then be loaded onto a barge, shipped across the Gulf of Mexico and the Atlantic Ocean, and delivered to the Kennedy Space Center in Florida. It is now unlikely to happen before the end of March or April.
In its blog post, NASA says that once in Florida, the SLS core stage will be assembled with its solid rocket boosters and docked with the Orion spacecraft in preparation for its first launch “later this year.” However, given that a 2021 launch date was based on the nuclear stage shipping from Stennis Space Center in January, a 2021 launch of the SLS rocket now seems highly unlikely.