NASA is under immense pressure to succeed this weekend during its fourth attempt at a launch rehearsal for its Space Launch System. Another failed test of the gigantic rocket would be an embarrassing—and worrying—setback for the Artemis Moon program, which aims to get off the ground this year.
The towering Space Launch System (SLS), with the Orion capsule parked on top, arrived at Launch Complex 39B on June 6. NASA’s rocket had spent the past several weeks inside the Vehicle Assembly Building at Florida’s Kennedy Space Center, where it was treated to a series of fixes and inspections. The unfinished rehearsals in April were marred by a steady stream of minor issues, including a faulty helium valve on the upper stage, a problem with the third-party supplier of gaseous nitrogen, glitchy ventilation fans, and a small hydrogen leak.
These issues (apparently) resolved, NASA is ready to proceed with its fourth attempt at a wet dress rehearsal, in which both stages of the rocket are filled with supercooled liquid hydrogen and oxygen, and ground teams rehearse a countdown. The unlaunched SLS is an integral part of NASA’s Artemis program, which seeks to return astronauts to the lunar surface no earlier than 2025 and eventually maintain a prolonged and sustainable human presence on and around the Moon.
The call to stations for the fourth wet dress rehearsal is scheduled for 5:00 p.m. ET on Saturday, with propellant loading scheduled for Monday, pending a “go” from the launch director and mission management team chair. NASA is aiming to complete the practice countdown within a two-hour window that opens at 2:40 p.m. on Monday. Live coverage—including commentary this time (NASA was silent in April owing to security concerns)—of the Artemis 1 wet dress rehearsal will be made available on NASA TV and YouTube. You can also watch it at the feed below once the rehearsal begins.
Speaking to reporters on Wednesday, Jim Free, associate administrator for NASA’s Exploration Systems Development Mission Directorate, said he thinks they’ve fixed the hydrogen leak problem but that ground teams won’t truly know until “we actually flow the liquid hydrogen.” Free said the staff has worked hard to develop new loading procedures and that they’ve got an “excellent plan.”
Charlie Blackwell-Thompson, Artemis launch director for NASA, said ground teams spent the week running validation tests while working to confirm communications between the rocket’s mobile launch platform and command and control systems. The team has finished propellant preparation tests and is ready to power up all vehicle elements, she told reporters.
Blackwell-Thompson anticipates that, once the loading of cryogenic propellants is complete, the team will proceed to terminal count operations, in which the countdown will be brought down to T-33 seconds, deliberately stopped and reset (or “recycled,” in the industry parlance), and then brought down to T-10 seconds, ending the rehearsal (save for de-tanking operations).
That NASA is struggling to complete a full wet dress is not hugely alarming. SLS is an extremely complex system, and as it’s new, ground teams are having to work in uncharted waters.
But this ain’t NASA’s first rodeo, and SLS does borrow heavily from the Space Shuttle program, so it’s not complete terra incognita. A failed fourth (or fifth or sixth) wet dress would not be the end of the world, but it would be a potential sign that all is not right in NASAland. And at an estimated cost of $4.1 billion per launch, the unlaunched rocket already seems archaic—at least from a developmental perspective. Ongoing delays with SLS will only serve to propel an already burgeoning process: the space agency’s increasing reliance on the private sector.
My pessimism aside, a fully completed wet dress would mean that NASA can finally look forward to Artemis 1, the inaugural launch of SLS that will see an uncrewed Orion capsule journey to the Moon and back. Free told reporters that the early August launch window would be “very difficult,” but that the late August window is a possibility. But as Free cautioned, “we need to understand everything we can before we commit to launch.”