After replacing faulty seals that resulted in the second scrubbed SLS launch attempt on September 3, NASA is ready to proceed with a full-scale cryogenic tanking test of its megarocket on Wednesday, which you can watch live right here.
The tanking test starts bright and early on Wednesday, September 21, with the launch director expected to get the ball rolling at around 7:00 a.m. (all times Eastern). Should everything go smoothly, the test will conclude at around 3:00 p.m. NASA’s live coverage of the test is scheduled to start at 7:15 a.m., which you can watch at NASA TV, NASA’s YouTube channel, or at the feed provided below. A brief interruption of the tanking test will occur at 9:00 a.m., as NASA TV is planning to switch coverage to the Soyuz MS-22 crewed launch to the International Space Station.
This test is in preparation for Artemis 1, an uncrewed Moon-orbiting mission to demonstrate the new Space Launch System rocket and NASA’s Orion crew spacecraft. A successful test on Wednesday could set the stage for an SLS launch attempt on September 27, with NASA targeting a launch window that opens at 11:37 a.m. and ends 70 minutes later. Failing that, NASA could try again on October 2.
Importantly, NASA has not yet received flight permission from the Eastern Range, a branch of the Space Force that oversees launches from Kennedy Space Center. Should the Range not grant the requested waiver, NASA would have to transport SLS from its current position on Launch Pad 39B to the nearby Vehicle Assembly Building. There, engineers would inspect and reset batteries associated with the rocket’s launch abort system—the focus of the Range’s concern.
NASA is calling it a cryogenic demonstration test, but let’s call it for what it essentially is—the seventh wet dress rehearsal of SLS (the previous six being the four formal wet dress rehearsals and the two failed launch attempts). NASA officials are steadfastly refusing to call it a wet dress, saying teams won’t go into the terminal count phase of the launch countdown, nor will they power the Orion spacecraft or the side boosters. That said, the teams will attempt to fully load propellants into both the core stage and upper stage tanks, and also cool the rocket’s four RS-25 engines down to their required ultra-cold temperatures. Certainly smells like a wet dress rehearsal to me.
So, for this distinctly not-a-wet-dress, the teams will attempt a “kinder, gentler” propellent loading process, as Jeremy Parsons, deputy manager of NASA’s Exploration Ground Systems (EGS) Program, told reporters during a Monday media call. Through this tempered approach, ground teams will attempt to minimize pressure and temperature spikes, which they’ll do by slowly increasing the pressure within the liquid hydrogen tank, Parsons explained. This tanking strategy should slowly bring components down to ultra-cold temperatures and mitigate chances of thermal shock, and it shouldn’t add more than 30 minutes to the tanking process, he said.
Fingers crossed, this approach will prevent the kind of hydrogen leak that caused the second scrub in early September (the first scrub, on August 29, was the result of a faulty sensor that gave erroneous engine temperature readings). Following the second scrub, engineers replaced two seals on the rocket’s quick disconnect, an interface that connects the liquid hydrogen fuel line to the rocket’s core stage. The engineers performed the required fixes while the rocket stood on the Florida launch pad. Tom Whitmeyer, deputy associate administrator for common exploration systems development at NASA, said the primary objective of Wednesday’s test is to “look at the two new seals.”
Analysis of the 8-inch seal showed a potential indentation mark that could have resulted in the hydrogen leak, but as Artemis mission manager Mike Sarafin told reporters, no foreign object debris (FOD) was recovered. The indentation was tiny—under 0.01 inches—which “doesn’t sound like a lot,” Sarafin said, but hydrogen is the “smallest particle on the atomic chart.” As a propellant, pressurized hydrogen has a propensity to leak, but it’s valued for its power and efficiency.
Parsons clarified that the true cause of the indentation is not known, citing thermal or pressure shock as other possible causes. And indeed, an inadvertent command briefly raised the pressure within the system during the second launch attempt. The team is currently working through its fault tree in an attempt to source the problem, but Parsons said he has “no technical concerns” going into Wednesday’s test, and that the “kinder, gentler” tanking approach should prevent further hydrogen leaks. His biggest concern right now is the weather, but with a 15% chance of problematic lightning on Wednesday, the test is looking good to proceed as planned, Parsons said.
As for the potential launch on September 27, that’s still in the hands of the Eastern Range. John Blevins, SLS chief engineer, said NASA’s launch dates are pending and for planning purposes, and that “we are internally marching ahead” as some of preparatory activities “require longer lead times than what we’ve got available.” The goal is to have the teams ready once the Range’s decision comes, he added. Blevins said he’s “impressed” with the questions being asked by Space Force and that it’s “up to us to provide the information they’re asking for.” NASA is still having technical discussions with the Range, but the space agency is “being respectful” of the process, Blevins said. Space Force is aware of the cryogenic tanking test, according to Sarafin, and NASA will perform the demonstration “whether we fly or not” on September 27.
A successful launch of SLS would kickstart the Artemis era and our return to the Moon. NASA and its international partners are planning a series of missions over the coming years to build a sustainable human presence both on and around the Moon. Artemis is also serving as a precursor program for eventual crewed missions to Mars.