The 322-foot-tall (98-meter-tall) Artemis I rocket stack, including NASA’s mega SLS rocket and Orion spacecraft, will begin the wet dress rehearsal Friday. The test is expected to last through Sunday.
The results of the test will determine when the uncrewed Artemis I will launch on a mission that goes beyond the moon and returns to Earth. This mission will kick off NASA’s Artemis program, which is expected to return humans to the moon and land the first woman and the first person of color on the lunar surface by 2025.
The wet dress rehearsal simulates every stage of launch without the rocket actually leaving the launchpad. This includes loading supercold propellant into the rocket’s tanks, going through a full countdown simulating launch, resetting the countdown clock and draining the rocket tanks. The test will begin with a call to stations on Friday at 5 pm ET and end Sunday evening with the final countdowns.
The call to stations, which is a check-in with every team associated with a launch, “is a big milestone because it is the time in which we are calling our teams notifying them that the wet dress rehearsal test is officially underway,” said Charlie Blackwell-Thompson, Artemis launch director for NASA’s Exploration Ground Systems program, during a news conference Tuesday.
Trial run includes countdown
Once the rocket has been loaded with more than 700,000 gallons (3.2 million liters) of propellant, the teams on Sunday will go through all of the steps toward launch.
“Liquid hydrogen is at a negative 450 degrees Fahrenheit (negative 268 degrees Celsius), liquid oxygen is negative 273 (negative 169 degrees Celsius), so it’s very cold substances,” said Tom Whitmeyer, deputy associate administrator for common exploration systems development at NASA Headquarters during the news conference. “I used to participate in this back in the Shuttle Program and it’s like watching a ballet. You’ve got pressure, volume and temperature. And you’re really kind of working all those parameters to have a successful tanking operation.”
The team members will count down to within a minute and 30 seconds before launch and pause to ensure they can hold launch for three minutes, resume and let the clock run down to 33 seconds, and then pause the countdown.
Then, they will reset the clock to 10 minutes before launch, go through the countdown again and end at 9.3 seconds before launch would occur. This simulates what is called scrubbing a launch, or aborting a launch attempt if weather or technical issues would prevent a safe liftoff.
At the end of the test, the team will drain the rocket’s propellant, just as they would during a real scrub.
Some steps will be classified
While milestones will be shared on NASA’s site, details like specific timing, temperatures and how long it takes for certain tasks to be completed are “considered to be important information by other countries. And so we have to be very careful when we share data, particularly for the first time, you know,” Whitmeyer said.
And that’s for a reason.
“We’re really, really super sensitive to cryogenic launch vehicles that are the size and capability that are very analogous to ballistic-type capabilities that other countries are very interested in,” Whitmeyer said. “And what they’re specifically looking for is timing sequence flow rates, temperatures, anything that would help them or other folks to potentially be used to help other people do similar things.”
The complex interaction of loading propellants and the sequence of events to prevent stress on the vehicle are the kinds of specific data that would be of particular interest, he said.
Whitmeyer stressed that the agency was being conservative and exercising an abundance of caution, “particularly in the environment that we’re in nowadays.”
Summer launch anticipated
The space agency is expected to provide an update about the results of the test on Monday.
Depending on the outcome of the wet dress rehearsal, the uncrewed mission could launch in June or July.
During the flight, the uncrewed Orion spacecraft will launch atop the SLS rocket to reach the moon and travel thousands of miles beyond it — farther than any spacecraft intended to carry humans has ever traveled. This mission is expected to last for a few weeks and will end with Orion splashing down in the Pacific Ocean.
Artemis I will be the final proving ground for Orion before the spacecraft carries astronauts to the moon, 1,000 times farther from Earth than where the International Space Station is located.
After the uncrewed Artemis I flight, Artemis II will be a crewed flyby of the moon and Artemis III will return astronauts to the lunar surface. The time line for the subsequent mission launches depends on the results of the Artemis I mission.