NASA officials told reporters on March 29 that preparations for the SLS wet dress rehearsal (WDR) are on track. The WDR involves filling the rocket with liquid hydrogen and liquid oxygen propellant and lowering the countdown to just under T-10 seconds, just before the core stage’s four RS-25 engines ignite. Prior to the launch of Artemis 1 this summer, the WDR will test fueling and countdown processes.
According to Charlie Blackwell-Thompson, NASA Artemis launch director, the test would commence with a “call to stations” for staff at about 5 p.m. Eastern on April 1. Tanking will begin about 7 a.m. Eastern on April 3, and the countdown will end seven and a half hours later. The vehicle will be counted down to T-33 seconds initially, then recycled for a second countdown to T-10 seconds. The truck would be detanked late that afternoon, bringing the test to a close.
While technical preparations for the test continue, NASA will keep a close eye on the weather. “There’s a potential we’ll have some bad weather in this area over the weekend,” she predicted. Lightning is the main issue, with no more than a 20% likelihood of lightning within 9.3 kilometres of the pad in the first hour of tanking required.
If the test goes as planned, NASA hopes to know how the vehicle fared and when it will be ready to launch rather fast. The agency aims to host a briefing on April 4 with an initial review of the WDR data, according to Tom Whitmeyer, deputy associate administrator for common exploration systems development.
“We’re looking for two things: to see if we were able to successfully get through the timeline and the count, and get the data that we need to be able to prepare for the launch of the vehicle,” he said of that briefing, “and we’ll also look at the condition of the vehicle.”
He said NASA won’t be ready to establish a launch date for Artemis 1 during the post-test briefing because there will be more work to assess the vehicle and search for any flaws that need to be addressed before launch. “We’re hoping to be able to talk about what we’re looking for in terms of launch possibilities in about a week once we’re done with all of that,” he said.
He was adamant about not speculating on possible launch dates. The SLS has a launch window from May 7 to 21, but it is doubtful that it will be ready before that window expires since the vehicle must first travel to the Vehicle Assembly Building for final closeout work before returning to the pad for launch. June 6 to 16 is the next launch window, followed by June 29 to July 12.
While Whitmeyer and others have identified WDR as the penultimate big test before the launch of Artemis 1, NASA will give the test little attention. The agency announced on March 28 that during the test, it will give a live video feed of the pad, but no commentary or sound, including audio from launch control.
According to Whitmeyer, the lack of audio from launch control is due to export control concerns. “What they’re usually looking for is timing and sequencing data,” he explained. “As it is regarded important information by other countries, we must use extreme caution when sharing data, especially for the first time.”
Many people were surprised by this, because there were no such restrictions on controller audio during shuttle launches and tests, and the SLS uses a lot of shuttle-era technology. “Cryogenic launch vehicles of this size and capacity are extremely sensitive to us.” He described them as “quite analogous to ballistic-type capabilities that other countries are highly interested in.” However, due to the substantial time and effort required to prepare such vehicles for launch, cryogenic propellants are rarely used in ballistic missiles.
During the test, he said NASA would offer updates on social media, and he vowed to provide a thorough countdown plan to the media ahead of time. “They’re going to practice the whole thing they’re going to have for launch in parallel,” he said, so that by the time of the actual launch this summer NASA will be able “to provide the normal type of calls that you would expect to hear.”