NASA formally announced today that the Wet Dress Rehearsal of the Space Launch System rocket and Orion spacecraft for the Artemis I flight test is complete. The stack will be rolled back to the Vehicle Assembly Building next week to get ready for launch. Officials were not willing to commit to a launch date today, but the next window is at the end of August and early September.
The fourth try at the Wet Dress Rehearsal – “wet” because the tanks are loaded with propellant – on Monday got as far as T-29 seconds into the practice countdown to launch. That wasn’t as close as planned, T-9.3 seconds, but NASA officials indicated yesterday enough of the test objectives were met to declare success. Today they made it official.
Tom Whitmeyer, NASA Deputy Associate Administrator for Common Exploration Systems Development, told reporters that “we’ve determined that we’ve successfully completed the evaluations and the work we intended to complete for the dress rehearsal.”
During a briefing earlier in the week, Launch Director Charlie Blackwell-Thompson read from the list of two primary and five secondary test objectives explaining what had or had not been achieved. NASA did not have a public version of that list at the time, but published it today.
As with the first three attempts in April, there were problems with the supply of gaseous nitrogen (GN2) needed to purge propellant lines, another hydrogen leak was discovered, and several other hiccups were encountered, but they achieved two major milestones – filling the liquid hydrogen and liquid oxygen tanks on both the core stage and the upper stage, and getting far into the countdown just past the point where ground computers hand off to automated computers on the rocket, T-33 seconds. That’s a critical point in the terminal count, although the goal had been to get all the way to T-9.3 seconds, just before the four Aerojet Rocketdyne RS-25 engines would ingite. Engineers were able to hide or “mask” the hydrogen leak from the ground computers, but not the Automated Launch Sequencer on the rocket, which halted the countdown.
Not all of the objectives were met. In primary objective one, for example, they did not “perform a recycle to T-10 minutes” or “a second terminal countdown.” In addition, engineers at Marshall Space Flight Center wanted to test the hydrazine-powered turbines for the Solid Rocket Boosters, a step that would have happened at T-28 seconds. NASA decided to perform that one test today.
NASA Associate Administrator for Exploration Systems Development Jim Free had said last week that if the rehearsal encountered any issues his instinct would be to delay committing to launch until every problem was “run to ground.” He was not on the media call today, but Whitmeyer said Free has been throughly briefed and agrees the test is complete.
NASA now has checked off all but one of the boxes on its integrated testing list.
SLS / Orion now will be rolled back to the Vehicle Assembly Building to fix that hydrogen leak and other anomalies as well as finalizing other work. All of that is expected to take 6-8 weeks.
If weather cooperates, roll back is scheduled to begin just after midnight Friday, July 1, with the stack firmly in place (“hard down”) in the VAB later that day. First movement of the Crawler-Transporter with SLS / Orion and the Mobile Launcher on top is scheduled for minutes after midnight in order to avoid thunderstorms that are common this time of year in Florida.
Artemis I is an uncrewed test flight of SLS / Orion around the Moon. It can launch only during roughly two-week windows each month to meet test criteria such as returning to Earth in daylight. The launch windows for the rest of 2022 are the following.
- August 23- September 6, but not August 30, 31 or September 1
- September 20-October 4but not September 29
- October 17-31but not October 24, 25, 26 or 28
- November 12-27but not November 20, 21 or 26
- December 9-23but not December 10, 14, 18 or 23