Hopes of a launch of NASA's Space Launch System (SLS) in 2021 have been dealt a further blow by an admission that a second Green Run hot fire test is required for the SLS core stage.
The Boeing-led core stage for NASA's monster Moon rocket arrived at the Stennis Space Center, Mississippi, over a year ago and was mounted in the B-2 test stand for a succession of check-outs known as the Green Run. These culminated in a firing of all four Shuttle-derived RS-25 engines in order to simulate a launch.
Things did not go well. "Intentionally conservative" test parameters resulted in a premature pfffft and the run only lasted for 67.2 seconds. That's quite some way from an actual launch, although the agency was quick to point out that the scenario would not have happened on the launch pad. The abort left the hardware "in excellent condition."
At the time, engineers were set the unenviable task of working out if enough data had been collected to justify shipping the stage to Kennedy Space Center. That assessment has been done, and the result was... nope. At least four minutes of data was needed in order to verify the stage was ready for flight and barely a minute simply wasn't going to cut it.
Therefore engineers are to press ahead with a second run, and once again aim for the eight minutes needed to simulate a launch. Those pesky parameters will be tweaked, and the engines refurbished. The faulty electrical harness that triggered the Major Component Failure instrumentation notification on Engine 4 has already been repaired.
The problem for mission managers is one of schedule. Once the second hotfire is performed, which could be "as early as the fourth week in February" according to the agency, it will take a further month to refurbish the stage and engines once more before shipping it to Kennedy Space Center by barge. It will then be mated with the other components of the system ahead of an Artemis launch "later this year."
Based on performance to date, it is difficult to see how a launch in 2021 is possible even if managers find a way of performing tasks in parallel to make up the time lost by the Green Run problem. A failure to launch the first (uncrewed) test flight in 2021 will put further pressure on the already slim chance of a landing in 2024. ®