NASA’s wet dress rehearsal for its new “mega Moon rocket,” the Space Launch System (SLS), is officially over — at least for now. A series of problems, mostly with ground equipment, drove a stake into getting the dress rehearsal done this week. The test run was initially slated to begin on April 1 and intended to last about 48 hours.
The latest problems to crop up were NASA’s inability to locate a leak in a hydrogen supply line, a faulty valve, and the need to improve the flow of nitrogen to the pad where the SLS has been sitting for days. The goal of the wet dress rehearsal was to test the operations, procedures, and equipment needed for the maiden launch of the world’s most powerful rocket, which is still planned for later this year.
For the Artemis 1 mission, the first in a series of incremental steps that will take humans back to the lunar surface, the SLS is tipped with an uncrewed Orion capsule and a handful of cubesats. In the not-so-distant future, nearly 50 years after the last Apollo mission, the SLS aims to successfully deliver these payloads to lunar orbit.
Artemis 1 takes a step back
With the wet dress rehearsal on hold, NASA now plans to roll the rocket back to the massive Vehicle Assembly Building (VAB) on April 26. While there, workers will attempt to remedy the hydrogen leak, as well as address a tetchy valve that prevented fueling of the rocket’s upper stage. NASA will then evaluate whether it wants to do additional work on the SLS while they have it in the shop, which will inform their next step.
One possibility is that NASA will get the SLS flight-ready, roll it back out, conduct a successful wet dress rehearsal, then leave the vehicle on the pad to launch when celestial mechanics cooperate. The earliest optimistic launch window is probably this summer, from June 29 to July 12. However, given the extensive history of the SLS delays, making that window could be a challenge.
Despite the problems, the wet dress rehearsal achieved most — but not all — of its objectives, NASA officials say. The team accomplished partial loading of the SLS’s cryogenic fuels while also verifying the health and safety of the Orion crew capsule, command and communications, and range safety checkouts. The launch team also gained fluency in start-and-stop countdown procedures and troubleshooting, and they even quickly came up with new fueling procedures.
Notable missed objectives for the Artemis 1 dress rehearsal include a complete fuel loading of the upper stage and the testing of three commands for that operation, according to Artemis Launch Director Charlie Blackwell-Thompson.
Issue after issue
Even before this week, the Artemis 1 wet dress rehearsal, which began in early April and was scheduled to last one weekend, has had several fits and starts.
Early on, fans on the mobile launcher that are used to prevent the build-up of dangerous gases failed. That meant personnel could not load the rocket’s super-cold propellants — liquid oxygen and liquid hydrogen — into its core stage and interim cryogenic propulsion stage. Technicians were forced to wait for the equipment to thaw before resuming. Also related to the mobile launcher, someone mistaken left a fuel-loading valve switch closed instead of open. These early problems prompted the dress rehearsal team to temporarily give the right-of-way to the launch of Axiom-1, the first all-private mission to the International Space Station.
Another valve problem also cropped up on the rocket itself, the only equipment issue on the vehicle. A helium check valve wasn’t working to specifications, which meant the upper stage of the rocket could only be partially loaded with fuel. That problem can’t be corrected until the SLS returns to VAB. But the good news is, once there, it should be an easy fix.
Driving the final dagger into the dress rehearsal, on April 14, one of the umbilicals that attach to the rocket sprung a hydrogen leak, grinding progress to a halt again.
Artemis 1 presses on
“We will be ready when we get through the test program…We are putting in some long hours,” Artemis Mission Manager Mike Sarafin told reporters.
History shows us that launching rockets capable of carrying crews to the Moon isn’t easy. As CBS’s William Harwood pointed out, the first simulated countdown of the Apollo Saturn V rocket took nearly three times as long as originally planned, clocking in at 17 days instead of six.