Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more.
The first NASA mission to the moon since 1972 is ready for its most crucial test to date.
The 322-foot-tall (98-meter-tall) Artemis I rocket stack, including NASA’s mega Space Launch System and Orion spacecraft, began the wet dress rehearsal Friday afternoon at Kennedy Space Center in Florida. The test is expected to last through Sunday.
The results 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 powering on the SLS rocket and Orion spacecraft, 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 began with a call to stations at 5 p.m. ET Friday and will 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,” Charlie Blackwell-Thompson, Artemis launch director for NASA’s Exploration Ground Systems program, said during a news conference Tuesday.
A NASA livestream of Artemis I on the launchpad without audio commentary started at noon ET Friday and will be available throughout the weekend, but don’t expect to see all the drama of an actual launch.
The team is targeting a two-hour test window that opens at 2:40 p.m. ET Sunday, barring any delays due to inclement weather or other factors. The countdown will begin Sunday afternoon after a weather briefing, making sure all teams are a “go” for a mock launch.
Once the rocket has been loaded with more than 700,000 gallons (3.2 million liters) of propellant – the “wet” in wet dress rehearsal – the team will go through all the steps toward launch.
“Some venting may be seen during tanking,” according to the agency, but that’s about it for visible action at the launchpad.
“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 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, just before ignition and 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 it would during a real scrub.
Artemis I rolled out to the launchpad on March 18. After this rehearsal, it will be rolled back into the Vehicle Assembly Building until it’s ready to launch.
Updates of the test’s progress will be shared from the Artemis blog and a NASA Twitter account. But no audio or commentary will be provided, and there are no in-person media events surrounding the test. Additionally, some data will be kept under wraps due to security concerns.
Milestones will be shared on NASA’s site, but details such as specific timing, temperatures and how long it takes for certain tasks to be completed are “considered to be important information by other countries,” Whitmeyer said. “And so we have to be very careful when we share data, particularly for the first time, you know.”
And that’s for a reason.
“We’re really, really supersensitive 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.”
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.